NUCLEUS

INTRODUCTION:

Nucleus as a cell organelle was first described by Robert Brown as early as 1831. Later the material of the nucleus stained by the basic dyes (Acetocarmine was given the name chromatin by Flemming.

"Nucleus is double membrane bound dense protoplasmic body, which controls all cellular metabolism and encloses the genetic information of cell".

Nucleus is consider as controller or director of cell. Importance of nucleus in control of heredity. growth and metabolism was Largest alga). experimentally proved by Hammerling Experiment was an Acetabularia a single cell

Generally eukaryotic cell contain at least one nucleus but nucleus is absents in mature phloem sieve tube elements and mature RBCs of mammals.

Dikaryotic (Paramoecium) and multikaryotic cells are also known.

STRUCTURE OF INTERPHASE NUCLEUS :

i) Interphase nucleus : Nucleus of cell when it is not dividing

ii) Nuclear membrane or karyotheca.

iii) Nuclear matrix/Nucleoplasm/Karyolymph/Sarcoplasm.

iv) Chromatin net

v) Nucleolus/little nucleus/Ribosome factory

i) Nuclear membrane : 

• Electron microscope has revealed that the nuclear envelope, which consists of two preme ne n a space between (10 to 50 um) called the perinuclear space. These actors a s a batter between the material present.inside the nucleus and that the cytoplasm.

• The intermembrane usually remains continuous with the endoplasmic reticulum and also beschloss

• At a number of places the nuclear envelope is interrupted by minute pores, which ats lormed bu the Son of two membranes These nuclear pores otet passages through which movement END and protein molecules takes place in both directions between the nucleus and the cytoplasm.

• The nucleus he nuclear pore, is guarded by a octagonal discold structure of nucleoplasmin protein.

• The inner side of Inner nuclear membrane is lined by nuclear lamina This structure is formed by filaments of lamin protein.

ii) Nucleoplasm or Karyolymph :

Nucleoplasm or Nuclear sap is a ground substance of nucleus, which is a complex number of chemicals in nucleotides, nucleosides. ATP proteins & enzymes Chromatin net and nucleolus are components of nucleoplasm.

A) Chromatin net :- (Term Given by Fleming)

•  Interphase ucles has a loose and indistinct network of nucleoprotein fibers called chromatin, which Embedded in nucleoplasm. Chromatin net is mainly formed of DNA and histone per complexes.

• Chromatin fibres contain genetic information and condensed to form chromosomes during cell division.

•  During different stages of cell division cells how structured chromosomes in place of nucleus.

•  Chemically chromatin consists of DNA, RNA Histone protein (asic proteins, rich in arginine and in and non histone proteins:

Chromatin net has two type of chromatins:

A) Euchromatin : This is lightly stained and diffused part of chromatin. Which is transcriptionally or genetically more active.

B) Heterochromatin : This is dark stained thick and condensed part genetically less active or inactive chromatin.

i) Constitutive heterochrómatin:- Occurs in all cells in all stages eg. centromeric region.

ii) Facultative heterochromatin :- Occurs in some cells in some stages ag barr body in females,

B) Nucleolus :-

The nucleoli are spherical and membraneless structure so that the content of nucleous is continuous with the rest of the nucleoplasm.

It is a site for active ribosomal RNA (r-RNA) synthesis.

Nucleolus usually attached to chromatin (or chromosomes) at specific site called Nucleolar organiser region/NOR.

Nucleolus is called Ribosome factory of cell.

• Larger and more numerous nucleoli are present in cells actively carrying out protein synthesis.

Plastids

Plastids are found in all plant cells and in euglenoides. These are easily observed under the microscope as the sone specific pigments, thus imparting specific colours to the plants. Based on the presence or absence and type of pigments plastids can be classified into chloroplasts, chromoplasts and leucoplasts.

TYPES OF PLASTIDS 

Chromoplasts : In chromoplasts fat soluble carotenoid pigments like carotene, xanthophylls and others are present. This gives yellow, orange or red colour to the part of the plant. Chlorophyll either absent or occur in very less amount Chromoplasts occurs mainly in pericarp and petals. Red colour of tomatoes is due to the red pigment "Lycopene" of chromoplasts.

• Chromoplasts occur in petals but colour in petals is mainly due to water soluble pigments which are found in cell sap. eg. Anthocyanin

Chloroplasts :- The chloroplasts contain chlorophyll and carotenoid pigments which are responsible for trapping light energy essential for photosynthesis.

Leucoplasts:- The leucoplasts are the colourless plastids of varied shapes and sizes with stored nutrients.

Amyloplasts store carbohydrates (starch), e.g. potato: elaioplasts store oils and fats whereas the elaioplasts store proteins. Pigments and lamellar structure absents in Leucoplasts Generally occurs in non green and underground plant cells.

• Different types of plastids may transform from one form to another. Because genetic material is similar

Number, Shape & Size of chloroplasts :

• Majority of the chloroplasts of the green plants are found in the mesophyll cells of the leaves.

• Number varies from 1 per cell of the Chlamydomonas a green alga.to 20-40. T cell in the mesophyll.

• These are lens-shaped, oval spherical discoid. or even ribbon shaped,

• Length and width are also variable.

          Length= 5-10 m

           Width= 2-4 um

STRUCTURE OF CHLOROPLAST

Membrane : Like mitochondria the chloroplast are also double membrane bound Out of the two, the inner membrane is relative less permeable (Outer membrane contain porins

• The space limited by the inner membrane is caled the stroma.

Components of stroma:

(a) Thylakoids : In the stroma a number of organised flattened membranous sacs are present called thylakoids.

Thylakoids are arranged in stacks like the piles of coins called grana (singular granum or the intragranal thylakoids.

Each chloroplast! contains about 40-60 granum.

Stroma lamellae or Fret channel or Stroma thylakoids are flat membranous tubules connecting the thylakoids of the different granum.

The membrane of the thylakoids enclose a space called lumen.

Chlorophyll (photosynthetic pigments) are present in the thylakoids membrane.

A photosynthesis functional unit (Located in thylakoids membrane) contains of about 250 to 400 molecules of various pigments (Chl-a, Chl-b. Carotenes, Xanthophylls etc.) is called as Quantasome.

(b)Enzymes :  The stroma of the chloroplast contains enzymes required for the synthesis of carbohydrate. die enzymes of Calvin cycle or Dark reaction and protein synthesis.

(c) DNA :Stroma contain small double-stranded circular DNA molecules.

(d) Ribosome The Ribosome of the chloroplast are smaller (70s) than the cytoplasmic ribosOmes (80s) Chloroplasts have their own genetie system & complete protein synthesis machinery (ds - DNA, RNA, Ribosome, Enzymes Amino acids) but enzymes for photosynthesis are synthesised by nucleus and chloroplast thus chloroplasts are also called as semi autonomous organelle of the cell

FUNCTION :

Photosynthesis : The chloroplasts trap the light energy of sun and transform it into the chemical energy in the form glucose.

BIOGENESIS 

(1)From Proplastid

(2)  From binary fission of pre-existing plastids.

 ORIGIN : Endosymbiotic origin by a cyanobacterium.

FLOWER, FRUITS AND SEEDS

A flower is a modified shoot where in the shoot apical meristem changes to floral meristem. Internodes do not elongate and the axis gets condensed. When a shoot tip transforms into a flower, it is always solitary. 

Generally flower has a short or long stalk which is called pedicel. The upper part of pedicel is swollen which is called thalamus. Floral leaves are present on it 

There are 4 types of floral leaves

(1) Sepal

(2) Petal

(3) Stamen

(4) Carpel

• A typical flower has flour different kinds of whorls arranged succession thalamus. These are.com corolla, androecium and genoclom.

• Calyx and corolla are accessory organs or accessory whorls while androecium and gynoecium are reproductive organs or reproductive whorls of essential whorls.

• complete flower All four whorls are present

• Incomplete flower Any whorl is absent eg. Unisexual flower

• Bisexual flower perfect flower

• Unisexual flower Imperfect flower

A flower may be trimerous, tetramerous or pentamerous when the floral appendages me in multiple or 5, respectively. In dicots flowers are usually pentamerous while in monocots flowers are trimerous.

SYMMETRY OF FLOWER

Actinomorphic/Radial/Regular - When a flower can be divided into two equal radial halves by any vertical plane or radial plane passing through the centre, then it is said to be actinomorphic flower eg. Mustard,Datura, chilli.   

Zygomorphic/Bilateral - When a flower can be divided into two equal (similar halves only by one particular vertical plane then it is said to be zygomorphic flower. eg. Pea, bean, gulmohur. Cassia.

Asymmetrical/Irregular - When a flower cannot be divided into two equal (similar halves from any vertical plane passing through the centre, then it is said to be asymmetrical flower eg. Canna.

• The part of flower which lies near to the mother axis is posterior part while the part which is far from the mother axis is anterior part of flower. The position of the mother axis with respect to the flower is represented by a dot on the top of the floral diagram.

TYPES OF FLOWERS ON THE BASIS OF INSERTION OF FLORAL LEAVES

The relative position of gynoecium changes with respect to floral parts. Based on the position of calyx, corolla and androecium in respect of the ovary on thalamus the flowers are divided into three types.  

 

Hypogynous flower - When gynoecium occupies the highest position while the other parts like petals sepals and stamens are situated below the ovary, then the flower is called hypogynous and in this condition ovary will be superior eg. Mustard, china rose, brinjal, mango. 

Perigynous flower - In it thalamus grows upwardly and form a cup shaped structure. On the margin or rim of thalamus floral parts are attached except gynoecium, which lies at the basal part or in the centre. So in this condition gynoecium is situated below the other floral parts. But ovary in this condition is said to be half inferior Eg. Rose, plum. peach,

Epigynous flower - When the margin of thalamus grows upward enclosing the ovary completely  and getting fused with it and other parts of flower like petals, sepals & stamens are situated above the Ovary then, the ovary is said to be inferior the rayflorets of sunflower. and rest of the floral parts superior Eg. Guava apple, cucumber, sunflower.

BRACT

Bract is a reduced leaf found at the base of the pedicel of flower.

Bracteate flower - The flower with bract is called bracteate flower.

Ebracteate flower - Flower without bract is known as ebracteate flower.

Involucre - The whorl of bracts is called involucre.

Spathe - When large bract completely encloses whole inflorescence, then it is called spathe.

Eg. Banana, maize 

Petaloid bract When the size of bract is greater than the size of flower and it is of various coloured like petals, then it is called petaloid bract. In. Bougainvillea.

Glumes - Small dry, scaly bracts are called glures. Eg. Wheat, grass (Gramineae family)

CALYX

The outermost whorl of flower is called calyx. Each member of this whorl is called sepal, when all the sepals are free from each other, then it is called polysepalous condition eg. Mustard, radish. When the sepals are fused (united) with each other then this condition is called gamosepalous condition. Eg. Cotton, Datura, brinjal.

• Sepals are green leaf like and protect the flower in the bud stage
• In calyx of Mussaenda, one of sepal enlarged and forms a leaf like structure. it may be brightly  coloured. It attracts the insects and thus acts as advertisement flag/advertising flag.

• In Trapa. Calyx is modified into spines and helps in protection of fruits

• In the family of sunflower (compositae) sepals are modified into hairy structure which is known as pappus. The pappus is modified calyx and helps in dispersal of fruit by parachute mechanism.

• If sepals do not fall and remain attached to fruit then they are called persistent sepals Eg. Tomato, chilli, brinjal, cotton. Datura

COROLLA

The second whorl of flower is called corolla and each member of corolla s called. petal. When all the petals are free, then it is called polypetalous condition and when petals are fused, then it is called gamopetalous condition

Petals are usually of brightly coloured to attract insects for pollination.

FORMS OF COROLLA -

(A) Actinomorphic Polypetalous Corolla

(1) Cruciform In cruciform corolla 4 petals are found. These petals are arranged crosswise. The lower narrow part of petal is called claw while the upper broad part is called limb. Eg. Radish, mustard (Cruciferae)

 (B) Actinomorphic Gamopetalous Corolla

 

Campanulate/Bell shaped In this type of corolla 5 fused petals are present. It's shape is similar to bell. Eg Tobacco, raspberry, Campanula

Tubular - In this type 5 fused petals form tubular (tube like) or cylindrical structure Eg. Disc florets of sunflower

Funnel shaped or infundibuliform - In this type 5 fused petals are found. It's shape is similar to funnel. Eg. Datura, railway creeper. Petunia

Wheel shaped/Rotate - In this type 5 gamopetalous petals are found and the fused parts fom small tube and the petals are arranged in a whorl above the tube. Eg. Brinjal.

ZYGOMORPHIC POLYPETALOUS COROLLA -

Papilionaceous (Butter fly shaped corolla) - In this type of corolla five petals are found. Posterior petal is largest and is known as standard or vexillum. Vexillum covers two lateral petals which are called wings or alae and the innermost anterior petals are united to forma keel or carina. Both lateral petals cover the keel. Eg. Pea, bean gram, (Papilionatae).

ZYGOMORPHIC GAMOPETALOUS COROLLA

Bilabiate - The petals of gamopetalous corolla are divided into two lips. The place between two lips is called corolla mouth Eg Ocimum (holy basil = tulsi), Salvia (Labiatae family) 

Ligulate-  The upper part of corolla is long flattened tongue like which is attached with short narrow tube. Eg. Ray florets of sunflower

AESTIVATION

The mode of arrangement of sepals or petals in floral bud with respect to the other memben of the same whorl is known as aestivation. It is of following types :-

1. Valuate - When the petal of a whorl lie adjacent to other petal and just touch one another at the margin without overlapping then it is known as valvate aestivation. Eg. Calotropis plant. Cruciferae, Solanaceae & Liliaceae family.

2. Twisted - In this type one margin of a petal covers adjacent petal and the other margin is covered by another petal. One margin of the petal overlaps that of the next one, and the other margin is overlapped by the another one. Eg. Cotton ladyfinger. china rose (Malvaceae family).

3. Imbricate - When both margins of the one petal are covered by the other two petals and both margin Children of another one, covers other. Rest are arranged in twisted manner. OR ! the margins of sepals or petals overlap one another but not in any particular direction, then it is known as imbricate aestivation.

Eg. Cassia, gulmohur (Delonix regia).

4. Vexillary or Papilionaceous or Descending imbricate - The posterior petal is outermost and largest and is known as standard or vexillum which overlaps the two lateral petals wings or alae These two laterals petals.overlaps two smallest anterior petals ie keel or carina Vexillary arrangement is found in pea family. Eg. Pea bean (Papilionaceae subfamily of leguminosae family).

5. Quincuncial :- Out of the five petals, two are completely internal two are completely external und in the remaining petal, one margin is internal and the other margin is external.

Eg. Murraya

ANDROECIUM

It is composed of stamens. When the stamens of an androecium are free from one another, then it is called polyandrous condition.

COHESION OF STAMENS :

When the floral parts of similar whorl are fused, then it is called cohesion

1) When stamens are united by their filaments only, then it is called adelphi. It is of following types:

a) Monadelphous - In this type of cohesion all the ligaments are united into a single bundle or one bunch but anthers remain free. In this type of cohesion a tube is formed around the gynoecium which is called starinal tube Eg. China rose (Malvaceae family).

b) Diadelphous - In this type of cohesion filaments are united into two bundles but the anthers remain free Eg. Pea (Papilionatae).

In these plants out of 10 stamens, 9 stamens are united into a bundle while 1 stamen remains free

c) Polyadelphous - Filaments are united into more than two bundles. Eg Citrus.

2) Syngenesious - Only anthers are united in bundle, but filaments remain free eg Compositae family.

3) Synandrous Anthers as well as filaments of stamens are united through their whole length.

Eg. Colocasia, Alocasia, Cucurbitaceae family

ADHESION OF STAMENS -

When the stamens are attached to other parts of flower, then it is called adhesion of stamens.

1) Epipetalous - Stamens are attached to the petals. Eg. Brinjal (Solanaceae) 

2) Epiphyllous or Epitepalous - Stamens are attached to the tepals (perianth (3) Eg. Lily (Liliaceae) 

3)Gynandrous - Complete stamens or only anthers are attached to the gynoecium. Eg. Calotropis, Aristolochia

LENGTH OF STAMENS -

There may be a variation in the length of filaments within a flower, as in Salvia and mustard.

Didynamous - f four stamens are present and out of them two are long and two are short, then it is called didymus condition. Eg Lamiaceae/Labiatae family (Salvia), 

Tetradynamous - When there are six stamens and they are arranged in two whorls. In outer whorl, there are two short stamens while in inner whorl, there are four long stamens, this condition is called tetradynamous Eg. Cruciferae family (Mustard, radish, turnip)

GYNOECIUM

• Gynoecium is female reproductive organ of the flower and is made up of one or more carpels.

•  If only one carpel is present in gynoecium then this condition is called monocarpellary condition:
• If more than one carpel is present in gynoecium then this condition is called polycarpellary.

• When all the carpels in polycarpellary/multicarpellary condition are free, then this condition is called apocarpous eg. lotus, rose, Michelia,

• When all the carpel are fused, then this condition is called syncarpous eg. Papaver, Hibiscus, mustard, tomate.

PLACENTATION

The Ovules are attached on ovary walls on one or more cushion like structure called placenta. The manner in which placenta or ovules are arranged on ovary wall is known as placentation or The arrangement of ovules within the ovary is known as placentation. It is of following types.

Marginal : This type of placentation is found in monocarpellary gynoecium. In this type of placentation placenta forms a ridge along the ventral suture of the ovary and the ovules are borne on this ridge forming two rows, as in pea. There is no true placenta. Eg. Pea (Leguminosae family

Axile This type of placentation is found in multicarpellary, syncarpous gynoecium.Ovary is multilocular and the ovules are borne on the central axis. Number of chambers are equal to the number of carpels fused. Eg. china rose. lemon. tomato.

 Parietal : This type of placentation is found in unilocular syncarpous ovary. The ovules, develop on the Inner wall of the ovary or on peripheral part. Eg. Mustard and Argemone.

• In some plants, ovary is one chambered but it becomes two chambered due to formation of false septum or replum. Cruciferae family (Eg Mustard. Capsella) and Argemone.

Free central/Central This type of placentation is found in syncarpous gynoecium. In it, the ovary is unilocular (septa are absent) and the ovules are borne on the central axis eg. Primrose, Dianthus

Basal: The ovary is unilocular and the placenta develops at the base of ovary and single ovule is attached at the base of ovary. Eg. marigold, sunflower (Asteraceae Compositae family), Gramineae / Poaceae family.

Superficial - This type of placentation is found in multicarpellary, syncarpous, multilocular gynoecium.

The ovules  are attached on the entire inner surface or walls of loculii Eg. Nymphaea (water lily).

FRUIT 

The fruit is the characteristic feature of the flowering plants. It is the mature or ripened ovary, developed after fertilization. If a fruit is formed without fertilization of ovary, it is called a parthenocarpic fruit. In some fruits like grapes, banana seeds are not found and such type of fruits  are called parthenocarpic or seedless fruits. Parthenocarpy can be induced through the application of growth hormones.

PERICARP (Fruit wall) :After ripening, the ovary wall changes into pericarp. This pericarp may be thick and fleshy or thick and hard or thin and soft.

In fleshy fruits pericarp (fruit wall) is made up of 3 layers:

(1) Outermost layer- Epicarp

(2) middle layer- mesocarp 

(3) innermost layer- Endocarp

Epicarp - It is the outermost layer, it may be thick or thin and hard or soft. It forms outermost layer of fruit which is also called rind.

 Mesocarp: It is the middle layer which is thick and fleshy in mango, peach and date palm. In coconut this layer is made up of fibres which is also called coir. Endocarp: It forms the innermost layer, It may be thin membranous (eg. Orange, Date Palm) or thick and hard (eg. Mango, Coconut)

TRUE FRUIT OR EUCARP

When the fruit is developed only from the ovary then the fruit is called true fruits. eg. mango, coconut, zizyphus.

FALSE FRUIT OR PSEUDOCARP

In some fruits, in place of ovary, some other parts of flower like thalamus, calyx and inflorescence are modified into fruit or a part of fruits. Eg Apple. Strawberry, Pear, Mulberry, Fig, Cashew nut. 

• In apple, strawberry, cashew, etc. the thalamus also contributes to fruit formation Such fruits are called  false fruits.

CLASSIFICATION OF FRUITS :

Fruits are divided into 3 types :

SIMPLE FRUITS

These fruits develop from ovary of monocarpellary gynoecium or multicarpellary, syncarpous gynoecium and only one fruit is formed by the gynoecium, Simple fruits are of two types :

(a) Fleshy fruits

(b) Dry fruits 

(a) FLESHY FRUITS In fleshy fruits, fruit wall (pericarp) is differentiated into epicarp, mesocarp and endocarp. these fruits are indehiscent

Fleshy fruits are of following types:

DRUPE FRUITS. These fruits develop from monocarpellary, superior ovaries and are one seeded. In these fruits endocarp is hard and stony, so these fruits are also called stony fruits. Eg Mango coconut, almond, peach. walnut, plum. In mango the outermost cover or thin rind is called epicarp. Middle edible fleshy part is mesocarp and the inner story hard endocarp. In plum (Ber), epicarp and mesocarp both are edible while endocarp is stony.

The hard covering of almond and walnut is endocarp and their edible part is seed. In coconut epicarp is hard and thin while mesocarp is thick and fibrous. The endocarp is hard and seed is proteced in it.The sweet water and edible part of coconut are liquid and solid.endosperm respectively.

 BERRY: These fruits develop from mono or multicarpellary syncarpous ovary. Ovary may be superior or inferior. Placentation is axile. Generally epicarp is thin membrane like and seeds are embedded in fleshy part. Initially seeds are attached with placenta of fruit but after maturation these seeds are detached from placenta and are spread randomly in fleshy part. eg. Tomato, grapes, brinjal guava, banana (date palm and betelnut are single seeded berry).

 PEPO : These fruits develop from inferior ovaries. They have parietal placentation but looks like axile due to swelling of placenta. Eg fruits of cucurbitaceae family like cucumber (khira), water melon (tarbooz). Cucurbita maxima (pumpkin), bitter gourd (karela), muskmelon (kharbuja).

 POME This fruit develops from inferior ovary and having enlarged thalamus Eg Apple, pear. These are false fruits. Fleshy swollen thalamus of these fruits is edible part.

HESPERIDIUM They have axile placentation. This fruit is specially found in the plants of Rutaceae family. Eg, Orange, lemon.

Epicarp of these fruits is made up of thick rind which is having many oil glands. Mesocarp is the white fibrous structure which is attached with epicarp. Membranous endocarp projects inward and forms many chambers. Many glandular hairs are present on the inner side of endocarp These glandular juicy hairs are edible.

BALAUSTA This fruit, develops from inferior ovary. Calyx is persistent which is arranged in the form of crown. Testa of seed is fleshy and juicy. Testa is the edible part. Eg. Pomegranate (Punica granatum) - anar

DRY-FRUITS

Pericarp (fruit wall) of simple dry fruits is not differentiated into epicarp, mesocarp and endocarp.

In some dry fruits, pericarp dehisces/ruptures after ripening and seeds are dispersed, such fruits are called dehiscent fruits. In some fruits, pericarp breaks/splits into one or more seeded segments, such fruits are called schizocarpic fruits. In some fruits, pericarp does not dehisce even after maturing/ripening, Such fruits are called indehiscent fruits.

Simple dry fruits can be divided into following three groups :

(1) Indehiscent

(ii) Dehiscent

(ii) Schizocarpic

1.INDEHISCENT FRUITS These fruits do not dehisce/rupture. These simple dry fruits are general of small sized and single seeded.

(1) CYPSELA This is a small, one seeded dry fruit which develops from bicarpellary, syncarpous, Inferior ovary. In cypsela fruit pericarp (Fruit wall) and seed coat are free from each other and a bunch of hair is attached with the fruit which is known as pappus. Pappus helps in fruit dispersal. Pappus is modification of calyx. Eg Compositae family (Sunflower, marigold).

(2) CARYOPSIS: These are small, one seeded dry fruits, which develop from monocarpellary, superior Ovary In these fruits Pericarp is fused with the seed coat and form a joint surface These fruits are present in family Gramineae. Eq wheat, rice, maize etc.

(3) ACHENE In these fruits pericarp is free from the seed coat & pappus are absent. Eg. Ciemats,Mirabilis, Boerhaavia.

(4) NUT : This is a single seeded fruit, its pericarp is hard. eg. cashewnut,tarpa (water chest-nut), litchi.

• In litchi epicarp and mesocarp is fused and give leathery appearence. Endocarp is membrane like thin. An additional coat arround the seed is formed which is called aril. Actually it is a sort of third integument. In mature fruit, this aril is fleshy and is only edible part. 

SAMARA : These are dry indehiscent one seeded winged/feathery fruit. The main character of the fruits is that wing like structure develops from pericarp which helps in dispersal of fruits. Eg. Holoptelia (chil-bil). Dioscorea.

DEHISCENT FRUITS Pericarp of these fruits gets ruptured after ripening and seeds dispersed outside. These fruits are mainly of 5 types:

LEGUME OR POD. These fruits develop from monocarpellary, unilocular, superior ovary with marginal placentation They Are generally long and multi seeded fruits. Dehiscence of fruit occurs at both sutures i.e. dorsal  and ventral suture. Dehiscence starts from apex/tip and reaches to basal part. Eg Pea, beans, gram.

 SILIQUA: This fruit develops from bicarpellary, syncarpous, superior ovary and ovary has parietal placentation. Dehiscence occurs from both dorsal and ventral suture, Dehiscence starts from lower part and proceeds upward (from base to the apex). Initially ovary is unilocular but due to formation of false septum replum ovary becomes bilocular later on. On false septum seeds are attached. This type of fruit is found in Cruciferae family Eg Brassica (mustard).

SILICULA : Small, broad siliqua is known as silicula. It is reduced form of siliqua.

Eg. Candytuft (iberis amara), Capsella

CAPSULE-Dehiscence occurs by various methods. Poricidal (Porous), loculicidal, septifragal, septicidal.

Eg Papaver (poppy-opium plant), Gossypium (cotton), Datura, Abelmoschus (lady finger), onion

SCHIZOCARPIC FRUITS - SPLITTING FRUITS : After ripening, they break/split and divide into mericarps and after destruction of pericarp seed comes out: Each mericarp contains one or two seed (usually one seed).

Schizocarpic fruits are of five types:

LOMENTUM : These fruits are splitted in one seeded many mericarps, after maturity mericarps get separated with each other. Eg Tamarind, Cassia fistula, Mimosa pudica, Arachis hypogea (ground nut/ pea nut), Desmodium, Acacia (babool).

CREMOCARP . It is generally found in umbelliferae family. On maturation, it splits from apex to the base in such a way that two mericarps are formed and catch mericarp contains one seed. These mericarp are attached with carpophore. Carpophore is the extended part of thalamus. Eg Coriander (dhania), Daucus (carrot), Cuminum (jeera = cumin), Foeniculum (saunf-fennel)

REGMA : In it 3 to 5 locules are present and it breaks/splits into 3 to 5 one seeded parts.Each part is known as coccus. At the outer side of pericarp, spines are found. Eg, Euphorbiaceae family (arand-castor Ricinus) has three cocci and Geranium has 5 coccus.

CARCERULUS It divides into four one seeded mericarps / locules & spines are absent. Eg Ocimum tulsi). Salvia

AGGREGATE FRUITS

These fruits develop from multicarpellary, apocarpous gynoecium. In apocarpous condition each carpel is free from each other and it forms a fruitlet. Aggregate fruits are made up of a bunch of fruitlets which is known as etaerio.

Etaerio of achenes In this type of aggregate fruit, each fruitlet is an achene. Eg. Rananculus, strawberry rose, lotus.

In lotus, thalamus becomes spongy and some achenes are embedded in it. In strawberry, thalamus is fleshy and small achenes are found on its surface. In rose, many achenes are present on a saucer (cup) like inner surface of fleshy thalamus.

Etaerio of berries. It is an aggregation of small berries. Eg. Polyalthia, Annona squamosa (custard apple-sitaphal). In etaerio of Anona all the berries are arranged densly on thalamus.

Etaerio of drupes : In this type of fruit, many small drupes develop from different carpels. Eg. Raspberry, blackberry

COMPOSITE FRUITS

All composite fruits are false fruits.

In composite fruits, generally whole inflorescence is modify into fruit. These are of two types 

SOROSIS: This fruit develops from spike, spadix or catkin inflorescence.Eg. Pineapple (annanas) jack fruit (kathal). mulberry (shahtoot)

SYCONUS OR SYCONIUM This fruit develops from hypanthodium inflorescence. Many achene develop from the pistillate flowers. Eg Ficus species like Fig anjeer (Ficus carica), peepal (Ficus religiosa).

Dispersal of fruits and seeds :

We know that most of the plants do not move from one place to another. They grow, produce flower and fruits while remaining fixed at one and the same place. The seeds falling directly under the mother plant have to germinate and develop under limited food supply and space. To overcome this problem, the fruits and seeds have developed several special devices for wide dispersal. The natural agents like wind, water and animals and even mechanism of dehiscence in some fruits, help the seeds and fruits to disperse from one place to another, and to long distances from the parent plant.

Wind -In the species where the seeds are light in weight or have some accessory part to help dissemination, are dispersed by the air current. The seeds of Drum-stick and Cinchona, and fruits of yam, maple and sal tree, are provided with one or more appendages in the form of thin, flat and membranous wings, which help them to float in the air and be carried away to long distances. In the members of Asteraceae, the calyx is modified into hair-like structures called pappus. They persist in fruit and open out like umbrella, helping the seeds to float in the air. In poppy and prickly poppy (Argemone), the fruit dehisces and seeds are thrown out to a distances away from the parent plant. The seeds of Calotropis. Alstonia and cotton are provided with hair and cover sufficient distances alongwith the wind. The seeds of orchids and some grasses are very small and light in weight and may be easily carried away by wind to far off places.

Water -The fruits and seeds with specialised devices which may be in the form of spongy and fibrous outer walls as in coconut and spongy thalamus as in lotus, and small seeds with airy aril as in water lily. float very easily in water and are carried away to long distances with the water current.

Animals -The fruits and seeds with hooks, spines, bristles, stiff hair etc., get attached to the body of hairy and woolly animals and are carried away by them to distant places. For instance fruits of Xanthium and Urena bear curved hooks, spear grass has a bunch of stiff hair, Tribulus has sharp and rigid spines Boerhaavia has sticky hair, which help their dispersal by animals. The edible fruits like guava, grape, fig and phum are dispersed by birds and even human beings, either by feeding on them and passing out undigested seeds with faeces or by carrying them to other places for later feeding.

Defense mechanism in plants :

Plants have developed special organs or devices to repulse or avoid the attack of their enemies. Some plants Hke lemon, pomegranate and Duranta have thorns : pineapple, date palm, Agave and Yucca have sharp pointed spines at the leaf ends, silk.cotton tree and rose have prickles Opuntia and other cacti have spines for their protection from animals. The stinging hair with sharp and siliceous apex occur on all parts of the body in nettles (Laportea spp) and Urtica dioica. Glandular hair with sticky substances are present in jatropha, Boerhaavia and tobacco. The dense coating of hair or stiff hair which are always repulsive to animals are found in cudweed (Gnaphalium) and in many cucurbits.

There are other defense devices like the presence of poisonous and irritating substances in the plants. These are in the form of latex in Ficus. Nerium and Euphorbia alkaloids in poppy, Datura and tobacco, and irritating substances in Colocasia and other aroids. The plants of neem and karela have a bitter taste. Production of tannin, resin, essential oils, etc., in some plants and the geophilous habit in others leg zinger, turmeric, colocasia and onion) are protective measures Some plants like guava, mange and litchi have a habit of harbouring ants (myrmecophily), which save the plant from damage by other animals. Mimicry is a habit of imitating the general appearance, colour, shape of other plants or animals, generally disliked by attackers. The aroids (Caladium) and Sansevieria resemble spotted snakes and are thus able to scare away plant-eating animals

LEAF

The leaves develop from the nodes. The main function is to carry out photosynthesis or food formation. axillary buds are found in the axil of leaves. The axillary bud may develop into a branch. Leaves originate from shoot apical meristems and are arranged in an acropetal order.

Leaf Is a lateral outgrowth of stem developed exogenously at the node

Leal (Phyllopodium) is divided into 3 main parts :

(1) Leaf base (Hypopodium) - The part of leaf which is attached to stem is known as leaf base. Sheathing leaf base is found in monocots. In monocots, the leaf base expands into a sheath covering the stem partially or wholly. Pulvinus leaf bases are found in some legume plants Swollen leaf base is known as pulvinus leaf base.

(2) Petiole (Mesopodium) - The part of leaf connecting the lamina with the branch or stem is known as petiole. Petiole or stalk containing leaves are known as petiolate leaves and when petiole or stalk is absent then leaves are called sessile. In Eichhornia petiole swells up and in Citrus it is winged. The petiole helps hold the blade to light Long thin flexible petioles allow leal blades o flutter in wind, thereby couling the leaf and bringing fresh air to leaf surface.

(3) Lamina (Leaf blade-Epipodium) - It is a broad and green flattened part of leaf . Its main functions are photosynthesis and transpiration.

Stipules :

Leaves of some plants have two lateral appendages on either side of leaf base, known as stipules., Leaf with stipule is known as stipulate leaf. eg Fabaceae Leaf without stipule is called ex-stipulate leaf eg. Solanaceae, Liliaceae

Stipules are of various types -

1. Free lateral-They are independently present on both sides of leaf base Eg. Hibiscus rosa sinensis (China rose)

2. Foliaceous - These type of stipules are leaf like. Eg. - Pea

3. Spiny - Stipules modified into spine like structures. Eg. Ziziphus (ber) 

4. Ochreate - When both stipules of a leaf combine together and form a tube like structure, then it is called ochreate. Eg. Polygonum 

5. Tendrillar - Stipules are modified into tendrils like structure. Eg. Smilax

Types of Leaves -

Bracts - These are leaf like structure which may present at base of pedicel of flower.

Bracteoles - These are leaf like structures found on pedicel.

VENATION OF LAMINA

The arrangement of veins and veinlets in leaf lamina is known as venation. It is of 2 - types

(1) Reticulate It is found in dicots. Exception - Calophyllum (It has parallel venation) 

(2) Parallel. It is found in monocots. Exception - Smilax (It has reticulate venation)

1. Reticulate venation - In this type of venation lateral veins are divided into various branches (veinlets) and vein lets form a net like structure.

Reticulate venation is of 2 types:

(a) Unicostate or pinnate - This type of venation is having only one principal vein or midrib that gives off many lateral veins which proceed towards margin and apex of lamina of the leaf and form a network

(b) Multicostate or palmate - In this type of venation many principal veins arising from the tip of petiole and proceed upward, this is again of two types.

2. Parallel venation - In this type of venation, all veins run parallel to each other and they donot form network.

They are of 2 types: 

(a) Unicostate or pinnate This type of pattern is having only one principal vein, that gives off many lateral veins, which proceed toward the margin of leaf blade in a parallel manner but they donot have veinlets.

(b) Multicostate or palmate: This type of pattern is having many principal veins arising from the tip of the petiole and proceeding upwards.

MODIFICATION OF LEAVES

When leaves are modified into different structures then it is called modification of leaves.

• Leaf tendril - In some plants whole leaf is modified into a wire like structure which is called leaf tendril Tent helps is climbing. Eg. Lathyrus aphaca (wild pea) Peas 

• Leaf spine - Leaves are modified into pointed spines. Eg Opuntia Cacti. Argemone

• Leaf pitcher - Leaves of some plants are modified into pitcher shaped structure. Eg. Nepenthes (pitcher plant) (Only lamina is modified into pitcher). Water is stored in the pitcher of Dischidia (complete leaf is modified into pitcher). In Nepenthes insectivorous pitcher while in Dischidia - non insectivorous pitcher is formed.

• Leaf bladder - In some plants, leaves are modified into bladder like structure Eg. Utricularia (bladder wort)

• Phyllode - In some plants petiole becomes flat leaf like green. Synthesises food and functions as normal leaf. Eg. Australian acacia, Parkinsonia. 
•  Leaflet tendril - When leaflet is modified into tendril like structure then it is called leaflet tendril. Eg.: Pisum sativum (garden pea), Lathyrus odoratus (sweet pea).

Note: Dionaea venus flytrap, is insectivorous plant and also has modified leaves

• Leaflet hook - eg. Cat's nail (Bignonia unguis cati)

SIMPLE AND COMPOUND LEAF

Simple Leaf : A leaf is said to be simple, when its lamina is entire or may be incised to any depth. but not up to the midrib or petiole. Eg. :-Peepal, mango, radish,

Compound leaf A leaf in which the leaf blade (lamina) is incised up to the midrib and petiole, thus dividing it into several small parts, i.e. leaflets.

It has two types :

(A)Pinnately compound leaf : In this type of leaf, leaf blade (lamina) is incised upto the mid rib and mid rib is known as rachis. A number of leaflets are present on a common axis, the rachis.

Eg. Neem

(B) Palmately compound leaf: In this type incisions of leaf are directed from leaf margins to apex of the petiole and all leaflets are attached at a common point i.e. at the tip of the petiole. Rachis is absent in palmately compound leaf. Eg. Silk Cotton (Bombax)

• A bud is present in the axil of petiole in both simple and compound leaves, but not in the axil of leaflets of the compound leaf.

PHYLLOTAXY

Phyllotaxy is the pattern of arrangement of leaves on the stem or branch.

This is usually of three types.

Alternate : In this type a single leaf arises at each node at alternate manner. Eg. Mustard, china rose, sunflower.

Opposite : In this type of phyllotaxy a pair of leaves arise at each node and lie opposite to each other. eg. Guava, Calotropis, Ocimum (tulsi)

Whorled: If more than two leaves arise at each node and form a whorl. then it is called whorled phyllotaxy.

Eg. Alstonia (devil tree), Nerium

Function and structure

The principal function of leaves is to absorb sunlight need ed to manufacture plant sugars through a process called photosynthesis. Leaf surfaces are flattened to present a large area for efficient light absorption. The blade is the expanded thin structure on either side of the midrib and usually is the largest, most conspicuous part of a leaf.

A leaf is held away from its stem by a stem-like appendage called a petiole, and the base of the petiole is attached to the stem at a node. Petioles vary in length or may be lacking entirely, in which case the leaf blade is described as sessile or stalk less. A celery stalk is a leaf petiole.

The node where a petiole meets a stem is called a leaf axil. The axil contains single buds or bud clusters, referred to as axillary buds. They may be either active or dormant. Under the right conditions, they will develop into stems or leaves.

A leaf blade is composed of several layers. On the top and bottom is a layer of thick, tough cells called the epidermis. Its primary function is to protect the other layers of leaf tissue. The arrangement of epidermal cells determines the leaf's surface texture. Some leaves, such as those of African violets, have hairs (pubescence), which are extensions of epidermal cells that make the leaves feel like velvet.

The cuticle is part of the epidermis. It produces a waxy layer called cutin, which protects the leaf from dehydration and disease. The amount of cutin on a leaf increases with increasing light intensity. For this reason, when moving plants from shade into full sunlight, do so gradually over a period of a few weeks. This gradual exposure to sunlight is referred to as hardening off. It allows the cutin layer to build up and protect the leaves from rapid water loss or sun scald. Transplants produced indoors should be hardened off before planting outdoors.

The waxy cutin also repels water. For this reason, many pesticides contain a spray additive (sticker, spreader, etc.) to help the product adhere to, or penetrate, the cutin layer.

Special epidermal cells called guard cells open and close in response to environmental stimuli such as changes in weather and light. They regulate the passage of water, oxygen and carbon dioxide into and out of the leaf through tiny openings called stomata. In most species, the majority of the stomata are located on the undersides of leaves.

Conditions that would cause plants to lose a lot of water (high temperature, low humidity) stimulate guard cells to close. In mild weather, they remain open. Guard cells also close in the absence of light.

Located between the upper and lower epidermis is the mesophyll. It is divided into a dense upper layer (palisade mesophyll) and a lower layer that contains lots of air space (spongy mesophyll). Located within the mesophyll cells are chloroplasts, where photosynthesis takes place.

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STEM

Stem develops from the rule of the embryo of germinating seed. The stem bears nodes and internodes. The region of the stem where leaves are bone are called nodes while the portions between two nodes are called internodes. Stem shows negatively geotropic growth. Stems, support buds and leaves and serve as conduits for carrying water, minerals and food (photosynthetic). Stems place the leaves in favorable positions for exposure to light. The vascular system inside the stem forms a continuous pathway from the root through the stem, and finally to the leaves It is through this system that water and food products move.

Forms of stem :

(1)Caudex/Columnar :- it is unbranched,

erect, cylindrical stem and marked with scars of fallen leaves.

eg - Palmi.

(2) Culm :- Jointed stem with sülid nodes & hollow internodes eg :- Bartaco Gramineae

Modification of stems :

A-sub-aerial modification of stem. These are creeping stems.

(1) Runner - In these stems roots develop at lower side and leaves at upper side from the nodes eg Cynodon dactylon (doob grass), Oxalis, Strawberry.

(2) Stolon - In it branches develop from the lower part of the main stem and grow for some distance like arch and finally touch the ground to give rise to new shoot Eg. Fragaria (Wild strawberry), jasmine. peppermint 

(3) Sucker - In it the main stem grows in the soll but branches deselop bra basal mad underaround nodes and comesout from the soil. Eg Mint, pineapple, Chrysanthemum, banana.

(4) Offset - Generally these occur in aquatic plants which have fragile stem. Internodes of offset ate small & mid each node bears a rosette of leaves and a tuft of roots It is ako known as aquatic runner. Eg Pistia Eichhomia.

B - Underground modification of stem

This type of modification occurs generally for food storage and vegetative propagation

(1) Tuber - The tips of branches become swollen in the soil. Eyes are found on tuber which are axillary buds and axillary buds are covered with scaly leaves. Eg. Potato

(2) Rhizome - It is fleshy stem which grows horizontally in the soil. Nodes and small internodes are found which are covered by scaly leaves. Eg. Ginger, turmeric, canna, water lily, banana.

(3) Corm - It is condensed structure which grows vertically under the soil surface. Eg. Colocasia, Alocasia, zaminkand, saffron, Colchicum > Lillace

Organ of perennation - Underground stems of potato, ginger. turmeric. Colocasia, zaminkand are modified to store food in them. They also act as organ of perennation to tide over conditions unfavourable for growth.

(4) Bulb - Stem is highly reduced and disc like and surrounded by numerous fleshy leaves. Many roots arise from its base. Eg. Onion, garlic. The fleshy leaves of onion and garlic store food.

Note : Type of stem in banana is rhizome and modification is sucker. Banana propagates through thiome. Aerial part of banana plant which looks like stem is pseudostem (leaf bases).

C- Aerial modification of stem

(1) Stem tendril - In this type of modification axillary bud forms tendril in place of branches aıd helps in climbing of those plants which have weak stem. Eg. Grapes/Grape Vines. Passiflora, gourds (cucumber, pumpkins, watermelon).

(2)Stem thorn - Thom develops from axillary bud of the stem. It may bear leaves, flowers

Eg. Carissa (karonda), Bougainvillea pomegranate, Citrus. 

• Thom protects plant from browsing animals It is a woody pointed structure.

(3) Phylloclade - Stem is modified into a fleshy flat (Opuntia) or fleshy cylindrical (Euphorbia) and green leaf like structure and carries out photosynthesis like leaf The leaves are modified into spines Eg. Opuntia, Euphorbia, cactus, Casuarina (cylindrical).

Structure

Vascular system The vascular system consists of xylem, phloem and vascular cambium. It can be thought of as a plant's plumbing. Xylem tubes conduct water and dissolved mineral also, phloem tubes carry food such as sugars.

The cambium is a layer of meristematic tissue that separates the xylem and phloem and continuously produces new xylem and phloem cells. This new tissue is responsible for a stem's increase in girth.

The vascular cambium is important to gardeners in several ways. Xylem and phloem tissues on a grafted scion (top wood) and rootstock need to line up, if the graft is to take. Careless weed trimming can strip the bark off a tree, injuring the cambium and girdling the tree and causing it to die. This often occurs when string weed trimmers are used to remove grass from around the trunk of trees. Stem boring insects are attracted to cuts made by weed trimmers.

The vascular systems of monocots and dicots differ. Although both contain xylem and phloem, these structures are arranged differently in each. In a monocot, the xylem and phloem are paired in bundles dispersed throughout the stem. The vascular system in dicots is said to be continuous because it forms rings inside the stem. The phloem forms the outer ring and eventually becomes part of the bark in mature woody stems. The xylem forms the inner ring. Sapwood is newer xylem that is still conducting and heartwood is older xylem that is crushed in the center of the stem and is no longer conducting, Heartwood is filled with waste materials such as gums, resins tannins and oils.

The difference in the vascular systems of monocots and dicots is of practical inter est to gardeners because some herbicides affect only one group. For example, 2, 4-D kills only plants with a continuous vascular system (dicots). Non selective herbicides, on the other hand (eg.. glyphosate), kill plants regardless of their type of vascular system.

Nodes:  A node is an area on a stem where buds are located. It is a site of great cellular activity and growth where small buds develop into leaves, stems or flowers. When pruning, it is important to locate a plant's nodes. Generally, you want to cut just above, but not too close to, a node. Pruning in this manner encourages the buds at that node to begin development and ultimately form new stems or leaves.

The area between nodes is called the internode. Its length depends on many factors, including genetics. Other factors also can influence internode length:

• Reduced soil fertility decreases inter node length, while an application of high-nitrogen fertilizer can increase it.
• Lack of light increases internode length causing spindly stems. This situation is known as stretch, or etiolation, and often occurs in seedlings started indoors and in houseplants under low light conditions. Internode length varies seasonally.
• Early-season growth has long inter nodes; late-season growth has shorter internodes.
• Plant energy divided among three or four side stems, or diverted into fruit growth and development, shortens inter node length.
• Plant growth regulator substances and herbicides also can influence internode length.

Types of plants and their stems:

fig: Types of plants and their stems

 Trees generally have one main trunk, usually more than 12 feet tall when mature. In contrast, shrubs have several main stems, less than 12 feet tall when mature.

Most fruit trees, ornamental trees and shrubs have woody stems. These stems con tain relatively large amounts of hardened xylem tissue (heartwood) in the central core. The sapwood is the light colored living xylem near the outside just under the bark of a tree.

Herbaceous or succulent stems contain only a little xylem tissue and usually live for only one growing season. In perennial plants, new herbaceous stems develop from the crown (root-stem interface) each year.

Canes are stems with relatively large pith or central strength-giving tissues. They usually live only 1 or 2 years.

Examples of plants with canes include roses, blackberries and raspberries. For fruit production, it is important to know which canes to prune. how to prune them, and when to prune them. For example, two-year old raspberry canes are pruned at the ground. One-year old canes are left to produce the following Season.

A vine is a plant with long, trailing stems. Some vines grow along the ground, while others must be supported by another plant or structure. Twining vines circle a structure for support. Some circle clockwise (e.g. hops and honeysuckle), while others circle counterclockwise (e.g., pole beans). Climb ing vines are supported either by aerial roots (e.g., English ivy and poison ivy), by slender tendrils that encircle a supporting object (e.g., cucumbers, gourds, grapes and passion flowers) or by tendrils with adhesive tips (e.g., Virginia and Japanese creeper).

Stems as food :

The edible tuber of a potato and the Jerusalem artichoke are both fleshy under ground stems. Asparagus and kohlrabi are enlarged, succulent stems. A ginger "root" is actually a rhizome or underground stem. Sugarcane and bamboo shoots are stems.

The main function of the stem is spreading out branches bearing leaves, flowers and fruits. it conducts water, minerals, photosynthates (food). some stems performs the function of storage of food (potato, ginger, zaminkand and colocasia,) support, protection and of vegetative propagation.

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ROOT

Roots are (+) vely geotropic. (+) vely hydrotropic. (-) vely phototropic.

TYPES OF ROOTS :

Tap roots - In most of the dicot plants, the direct elongation of the radicle leads to the formation of primary root It bears lateral roots of several orders that are referred to as secondary. tertiary roots, etc.

The primary roots and its branches constitute the tap root system. Eg. : mustard plant

Adventitious roots :- In some plants, like grass, Monstera and the banyan tree roots develop from parts of the plant other than the radicle and are known as adventitious roots.

Fibrous roots :- In monocot plants, the primary root is short lived and.is replaced by a large number of roots. These roots originate from the base of the stem and constitute the fibrous root system. Eg.: wheat plant.

Functions of the root system - Absorption of water and minerals, provide a proper anchorage to the plant parts, storage of reserve food material (Carrot, radish, turnip sweet potato and Asparagus and synthesis of PGR (plant growth regulators).

MODIFIED ROOTS

1. Modified tap root for storage :

(i) Fusiform roots/Spindle roots These root are thicker in the middle and tapering on both ends.

eg. - Radish

(ii) Conical roots These roots are thicker at their upper side and tapering at lower side eg. Carrot

(iii) Napiform roots These roots become swollen and spherical at upper end and tapering (like a thread) at their lower end. Eg. Turnip sugarheet - beetroot Beta vulgaris

(vi) Tuberous roots - These roots do not have regular shape and any portion of roots become swollen & fleshy. Eg. Mirabilis.

(v) Nodulated roots - Nodules are formed on branches of roots by nitrogen fixing bacteria (Rhizobium

Eg. Plants of Papilionatae sub family of leguminosae family - Pea, gram, bean

2. Tap root modification for respiration

 In marshy/swampy areas, scarcity of OXYgen is found. Some branches of tap root of the plants which grow in this region grow vertically upward and comes on the surface These roots are called pneumatophores which have minute pores called pneumathodes or lenticels by which air enters in the plant and plant gets oxygen for respiration Pneumatophores are negatively geotropic. 

Eg. Rhizophora, Heritiera, (Mangrove plants)

Modification of adventitious roots :

(i) Fasciculated roots. These are adventitious roots occuring in clusters and all of them are swollen.

Eg Asparagus, dahlia

(ii) Beaded or moniliform roots - Root swells up like a bead at different places altes a regular interval.

Eg. Vitis(grapes), Momordica (bitter gourd, Portulaca.

(iii) Tuberous adventitious roots: The food is stored in these roots therefore they become swollen and irregular. These roots have no definite shape Eg. Sweet potato (Ipomoea batatas)

(iv) Stilt roots or brace roots - These roots arise from lower node and enter in the soil. These roots are Supporting roots. Eg. Maize, sugarcane. Pandanus (screwpine).

(v) Prop roots or pillar roots. These hanging roots arise from branches of plant and gmw downward forwards the soil. These roots support the tree. Eg. Banyan (Ficus benghalensis)

(vi) Climbing roots - These roots arise from nodes and help in climbing. Eg.Money plant (Pothos), Monstera, betel (Piper betel, black pepper

(vii) Foliar roots or Epiphyllous roots :- When roots arise from leaf then they are called foliar roots.

Eg. Bryophyllum, Begonia.

(viii) Sucking roots or Haustorial roots or Parasitic roots :- In parasitic plants, roots enter in the host plant to absorb nutrition from the host. Eg. Dendrophthoe, Cuscuta. Viscum.

(x) Annulated roots : In these roots swelling occurs in a series of rings on the roots. Eg. Ipecac.

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mitochondria

fig : Mitochondria

Number of mitochondria depends upon physiological activity of cell.

• One in Microasterias, Chlorella fusca (alga)
• All the mitochondria present in a cell are collectively called chondriome.
• Usually plant cells have fewer mitochondria as compared to animal cell.
• In higher animals maximum mitochondria are found in flight muscles of birds.
• Mitochondria are differ in size and shape and can make its shape sausage or cylindrical.
• Diameter 0.2-1.0 um (average 0.5 um), length 1.0-4.1 uum

Mitochondria is also named as - 

• Power house of cell or ATP-mill in cell
• Cell within cell
• Most busy and active organelle in cell Semi autonomous cell organelle,
• Endosymbionts of cell

STRUCTURE

• Mitochondria unless specifically stained are not easily visible under the microscope. Mitochondria are stained by Janus green B.
• Mitochondria is covered by double unit membrane, the outer membrane is smooth and inner one folds into several cristae. Outer membrane has more phospholipids (Phosphatidyl choline) and cholesterol as compared to inner membrane. Phospholipid in inner membrane is mainly phosphatidyl glycerol and Inner membrane have more protein
• The outer membrane and the inner membrane dividing its lumen distinctly into two aqueous.compartments.ie.. the outer compartment and the inner compartment. The inner compartment filled with a dense homogenous substance is called the matrix. The outer membrane forms the continuous limiting boundary of the organelle
• The two membranes have their own specific enzymes associated with the mitochondrial function
• Both membrane are separated by a space called peri mitochondrial (Intermembrane) space
• Inner membrane is folded into a number of finger like cristae.
•  In metabolically active mitochondria number of cristae is higher Many electron carrier cytochromes are arranged in a definite sequence in Inner membrane of mitochondria, which forms Electron transport system (ETS).
• Inner membrane is studded with pin head particles called oxysomes or elementary particles on particles or ATP Synthase. These particles first described by Fernandez Moran.
• Head of Oxysomes or F, is concerned with Oxidative phosphorylation (formation of ATP by energy of oxidation).
•  Mitochondrial matrix have enzyme for Krebs cycle (Aerobic respiration). Beside these enzymes matrix have a complete protein synthesis apparatus (Ribosome (70-s), DNA, few RNA's & enzymes) so mitochondria called as semi autonomous cell organelles.
• Single double stranded and circular naked DNA present in mitochondrial matrix.
•  Mitochondrial DNA is 1% of total DNA in a cell. It is rich in GC content
• Mitochondrial DNA can code the synthesis of some types of proteins. Rest of the proteins and enzymes of mitochondria are synthesized under the control of nuclear genes.
• Enzymes for replication and transcription of DNA like DNA- polymerase and RNA- polymerase are found in mitochondrial matrix.

FUNCTION OF MITOCHONDRIA:

Mitochondria are site of aerobic respiration and ATP production.

 

Biogenesis of mitochondria -

• New mitochondria arise from division of pre-existing mitochondria (Mitochondria divide By binary fission
• Endosymbiotic origin from prokaryotic cells.
• Type of DNA (DNA sequences, double stranded, circular, G-C rich).
• Type of ribosome (70s).
• Divide by binary fission.