Neha Singh Parihar

B.SC. – 2nd- year.

SSTUDY OF BOTANY

CONSERVATION & MANAGMENT OF NTURAL

RESOURCE, BIODIVERSITY

SUBJECT-BOTANY B.SC.–IIND-YEAR

NEHA SINGH PARIHAR

BOTANY TABLE OF CONTENTS

• TOPIC – Ist ( TYPES OF VESCULAR BUNDLES )

• TOPIC – IInd ( ANATOMY OF MONOCOAT & DICOT STEM )

• TOPIC – IIIrd ( INTERNALSTRUCTURE OF MONOCOAT & DICOT LEAF )

• TOPIC – IVth ( POLLINATION )

• TOPIC –Vth ( DOUBLEFORTELLIZATION )

• TOPIC –VI th ( FOOD CHAIN )

• TOPIC –VIIth ( PLANT SUCCESSION )

• TOPIC –VIII-th ( IN SITU & EX SITU CONSERVATION )

• TOPIC –VIxth ( PHYSICAL & CHEMICAL PROPERTIES OFSOIL )

• TOPIC – X ( CONSERVATION & MANAGMENT OF NTURAL RESOURCE )

TOPIC – Ist (Types of Vascular Bundles in Plants)

Types of Vascular Bundles in Plants

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Neha Singh Parihar

TOPIC – IInd ( ANATOMY OF MONOCOAT & DICOT STEM )

ANATOMY OF MONOCOAT & DICOT STEM

Monocot stems have scattered vascular bundles. Dicot stems have their vascular bundles in a ring

arrangement. ... Dicot stems have bundles in a ring surrounding parenchyma cells in a pith region.

Between the bundles and the epidermis are smaller (as compared to the pith) parenchyma cells making

up the cortex region.

Angiosperms, flowering plants, are divided into two groups: monocots and dicots.

Monocot seeds have one "seed leaf" termed a cotyledon (in fact

monocot is a shortening of monocotyledon). Dicots have two

cotyledons. Both groups, however, have the same basic architecture of

nodes, internodes, etc.

Comparison of monocot (left, oat) and

dicot (right, bean) gross anatomy. Image

from W.H. Freeman and Sinauer

Associates, used by permission.

Monocots have their flower parts in threes or multiples of three; example the tulip and lily (Lilium ). Dicots have

their flower parts in fours (or multiples) or fives (or multiples). Examples of some common dicot flowers include the

geranium, snapdragon, and citrus.

Monocot and Dicot Stems (With Diagram) | Plants

The following points highlight the top four types of monocot and dicot stems. The types are: 1. Normal Monocot Stems 2. Monocot Stem with Secondary Thickenings 3. Normal Dicotyledonous Stems 4. Anomalous Dicotyledonous Stems.Monocot and Dicot Stems: Type # 1.

Normal Monocot Stems:

I. Zea mays-Stem: T.S. of the material shows following tissues from outside within: It is circular in outline with a well-defined epidermis, hypodermis, ground tissue and many scattered vascular bundles

Epidermis:1. It is the outermost layer of stem.2. The outer wall of cells is covered by a thick cuticle.3. The continuity of the layer is broken by few stomata.4. Epidermal hair are absent.Hypodermis:5. It is two to three cells thick, sclerenchymatous and present just below the epidermis.6. Cells are polygonal is shape.Ground tissue:7. It is not differentiated into cortex, endodermis, pericycle and pith.8. The cells are parenchymatous and extend from below the sclerenchyma up to the centre.9. The cells are small and compactly arranged below the hypodermis but they are large, round and loosely arranged in the centre.Vascular Bundles:10. Vascular bundles are many and scattered in the ground tissue with no definite arrangement.11. They are small and more in number towards the periphery than the centre of the section.12. Each vascular bundle is conjoint, collateral, closed and endarch.13. A well-developed sclerenchymatous sheath surrounds each vascular bundle which is more prominent at its upper and lower faces.14. Xylem and phloem constitute the vascular bundle.

15. Xylem:(i) Consists of vessels (protoxylem and metaxylem), tracheids and xylem parenchyma.(ii) Vessels are in the form of ‘Y’.(iii) Metaxylem is present at the divergent ends of ‘ Y’ in the form of two big oval vessels.(iv) Protoxylem is present at the lower arm of’ Y’, consisting of two small vessels.

(v) Protoxylem is surrounded by tracheids and xylem parenchyma.

(vi) Inner protoxylem vessel and parenchyma break down and form a Water-containing cavity called lysigenous cavity.

16. Phloem:

(i) Consists of only sieve tubes and companion cells.

(ii) Phloem fibres and phloem parenchyma are absent.

(iii) The outer parts of the phloem, which is broken and disorganized, is called protophloem.

(iv) Inner phloem contains sieve tubes and companion cells, and called metaphloem.

Special Points:1. Scattered vascular bundles.2. ‘Y’-shaped vasels.3. Presence of protophloem and metaphloem.II. Canna-Stem:T.S. reveals the following tissues from outside within:It is circular in outline with a well-defined epidermis, hypodermis, ground tissue system and many scattered vascular bundles.Epidermis:1. It consists of many small, flat and tangentially elongated cells.2. A thick cuticle covers the outer wall of the cells of epidermis.3. Epidermal hair are absent.Ground Tissue System:4. It consists of cortex, chlorenchyma, patches of sclerenchyma and ground tissue.5. Just below epidermal layer are present two layers of cortex, consisting of large polygonal cells.6. Chlorenchyma is present immediately below the cortex in the form of one or two layers.7. Sclerenchyma patches remain attached with the chlorenchyma.8. Rest of the portion is filled with may large, thinwalled, parenchymatous cells which form ground tissue.9. Large intercellular spaces are present in the ground tissue.

Vascular Bundles:10. Many vascular bundles are scattered in the ground tissue.11. Vascular bundles are of different size.12. Each vascular bundle is conjoint, collateral, closed and endarch.13. Each vascular bundle is covered by incomplete, sclerenchymatous bundle sheath. It is rarely complete.14. Bundle sheath is present in the form of a large patch on the outer side and a small strip on the inner side of vascular bundle.15. Each vascular bundle is made up of phloem and xylem16. Phloem is situated towards the outer side in the vascular bundle and consists of companion cells and sieve tubes.17. Xylem is situated towards the inner side in the bundle, and consists of few large and small vessels and xylem parenchyma.Identification:(a) 1. Presence of vessels in the xylem……………. Angiosperms(b) 1. Vascular bundles are conjoint, collateral and endarch. Stem(c) 1.Well-developed ground tissue.2. Scattered vascular bundles.3. Vascular bundles are closed.4. Absence of secondary growth………………………. MonocotSpecial Points:1. Incomplete bundle sheath.2. Presence of sclerenchymatous patches in the ground tissue.

Monocot and Dicot Stems: Type # 2.Monocot Stem with Secondary Thickenings:Dracaena-Stem:T.S. is circular in outline and reveals the following tissues from outside with-in:Epidermis:1. Single-layered epidermis, consisting of rectangular cells, is present in the younger stages but at maturity it gets ruptured due to secondary growth and replaced by cork.2. Some lenticels are also present.Periderm:3. In old stems is present the periderm which consists of cork, cork-cambium and secondary cortex. These are also known as phellem, phellogen and phelloderm, respectively.4. Cork cambium is one-to few cells deep and consists of barrel-shaped, thin-walled cells. It cuts off cork towards outer side and secondary cortex towards inner side.5. Cork consists of rectangular and dead cells.6. Secondary cortex is either parenchymatous or chlorenchymatous. It is many cells deep.Vascular System:7. Primary structure consists of numerous, scattered vascular bundles which are closed and collateral.8. In the later stages the stem shows secondary growth.9. At the time of secondary growth many-layered cambium (meristematic tissue) develops outside the primary bundles in the parenchyma.10. Cambium or meristematic tissue cuts many secondary vascular bundles only towards inner side.

11. A small amount of thin-walled parenchyma is cut off on the outer side by the cambium (meristematic zone).12. Primary bundles are central in position, scattered and large.13. Secondary bundles are peripheral in position, small in size, oval in transection and amphivasal, i.e., phloem is surrounded by xylem.14. Phloem consists of sieve tubes, companion cells and phloem parenchyma.15. Xylem consists of tracheids and xylem parenchyma.Ground Tissue:16. It is well-developed, thin-walled and parenchymatous.Secondary Growth:The meristematic tissue, instead of cutting separate vascular tissues, cuts individual vascular bundles. Primary bundles are large and collateral whereas these secondary bundles are small and amphivasal. This meristematic zone stops functioning after sometime. It originates near leaf primordia.

Identification:

(a) 1. Presence of vessels in the xylem.

2. Vessels have perforated end walls with scalariform and regularly arranged holes ……….Angiosperms

(b) 1. Vascular bundles are conjoint and collateral.

2. Well-developed ground tissue……………………. Stem

(c) 1. Vascular bundles are closed.

2. Scattered vascular bundles…………………… Monocot

Monocot and Dicot Stems: Type # 3.Normal Dicotyledonous Stems:Luff a-Stem:T.S. exhibits following details:It is wavy in outline, usually with five ridges and five furrows, and ten vascular bundles remain arranged in two rings of five each.Epidermis:1. Single-layered epidermis consists of many barrel- shaped cells covered with cuticle.2. Some of the epidermal cells protrude out as multicellular shoot hair.Cortex:3. It consists of collenchymatous hypodermis. chlorenchyma and an innermost layer of endodermis.4. Collenchyma is present just below the epidermis, in the form of six to ten or more layers in the ridges and only a few layers or none in the furrows.5. Chlorenchyma is present in the form of two to three layers in between the collenchyma and endodermis. Its cells are filled with chloroplasts.6. Endodermis is the innermost layer of cortex. It is wavy in outline. The cells are filled with starch grains and lack casparian strips.Pericycle:7. It consists of four to five layers of thick- walled, lignified sclerenchymatous zone present just below the endodermis.

Ground Tissue:8. The space between sclerenchyma and the central pith cavity is filled with many thinwalled, parenchymatous cells of ground tissue, in which the vascular bundles remain embedded.Vascular Bundles:9. Ten vascular bundles are arranged in two rows of five each.10. Five vascular bundles of outer ring are present opposite the ridges whereas the remaining five of the inner ring face the furrows.11. Vascular bundles are conjoint, bicollateral, open and endarch.12. Each vascular bundle consists of centrally located xylem, surrounded on its outer and inner faces by strips of outer and inner cambia. Outside the outer cambium is present a patch of outer phloem, and inner to the inner cambium is present the inner phloem, thus representing the open and bicollateral condition of vascular bundles.13. Xylem consists of wide vessels present on the outer side representing the metaxylem and narrow vessels present towards inner side representing the protoxylem. Xylem also contains certain tracheids, wood fibres and xylem parenchyma.14. Cambium is present in the form of strips on both the sides of the xylem. It consists of thin-walled, rectangular cells arranged in radial rows.(i) Outer cambium is flat and many-layered.(ii) Inner combium is curved and only few-layered.15. Phloem is situated in the form of patches of outer phloem and inner phloem. It consists of companion cells, thin-walled cells of phloem parenchyma, and well-developed sieve tubes.

Pith:16. Thin-walled parenchymatous cells of ground tissue form the pith.Identification:(a) 1. Presence of vessels in xylem …….Angiosperms(b) 1. Vascular bundles are conjoint, bicollateral, open and endarch.2. Multicellular epidermal hair ………..Stem(c) 1. Vascular bundles are arranged in rings.2. Presence of cambium.3. Well-differentiated cortex and well-developed pith. ………Dicot.

Special Point:

Presence of bicollateral, open, vascular bundles.

Monocot and Dicot Stems: Type # 4.Anamalous Dicotyledonous Stems:I. Bougainvillea-Stem:It is circular in outline and exhibits following tissues from outside with-in:Epidermis:1. Single-layered epidermis consists of compactly arranged thin-walled cells and is covered by thick cuticle.2. It bears many multicellular hair when young.3. In the mature stems showing secondary growth, cork cambium is present which cuts cork towards outer side and secondary cortex towards inner side.Cortex:4. It consists of collenchyma, parenchyma and endodermis.5. Collenchyma in young stems is present in patches but in old stems it remains in the form of a continuous ring of few layers, present just below the epidermis.6. Next to the collenchyma is situated the region of parenchyma, consisting of many thin-walled, oval to spherical cells with intercellular spaces. Sometimes they develop chlorophyll.7. Endodermis is the innermost layer of the cortex the cells of which are barrel-shaped and contain starch grains. In old stems, however, it is not a conspicuous layer.Pericycle:8. It is represented by thick, sclerenchymatous stone cells forming a discontinuous layer.

Vascular System:9. It consists of phloem and xylem.10. In the young stem are present many vascular bundles arranged in ring. Bundles are conjoint, collateral, open and endarch. Many medullary bundles are also present.11. The old stem shows secondary growth.12. Just below the pericycle are present the patches of primary phloem.13. Secondary phloem is present inner to the primary phloem.14. Phloem consists of sieve tubes, companion cells and phloem parenchyma. Phloem fibres are absent.15. Cambium is present in between secondary phloem and secondary xylem.16. Secondary xylem, which forms the major part of the section, consists of tracheids, vessels, fibres and prosenchyma.17. Primary xylem is present near the pith facing its protoxylem towards the centre of stem.Interxylary Phloem:18. Many groups of secondary phloem are embedded in the region of secondary xylem and called interxylaryphloem or included phloem.Medullary Bundles:19. Many conjoint, collateral, open and endarch bundles are present in the pith. These are called medullary bundles.

Pith:20. It is parenchymatous and its cells are rounded with intercellular spaces.Anomalous secondary growth is due to the formation of successive rings of collateral vascular bundles. These bundles get embedded in the thick prosenchyma and their phloem appears as included or interxylary phloem. Medullary bundles are innermost secondary bundles.Identification:(a) 1. Presence of vessels in the xylem…………….. Angiosperms(b) 1. Vascular bundles are conjoint, collateral, open and endarch……………….. Stem(c) 1. Multicellular epidermal hair.2. Vascular bundles are arranged in ring.3. Presence of cambium…………………………… DicotAbnormality:Interxylary phloem and medullary bundles are present.

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Neha Singh Parihar

TOPIC – IIIrd

( INTERNALSTRUCTURE OF MONOCOAT & DICOT LEAF )

Monocot Leaf Vs. Dicot Leaf: Leaf is the main place where photosynthesis occurs.

Most leaves are usually green, due to presence of chlorophyll in the leaf cells. However, some leaves may have different colors, caused by other plant pigments that mask the green chlorophyll. In this article, learn the difference between monocot and dicot leaves. The basis of comparison include: Stomata, Shape, leaf orientation, Upper and lower surface color, intellectual spaces, Bundle Sheath, Mesophyll differentiation, venation pattern, the hypodermis of the midrib.

Monocot Leaf

Monocot leaves are leaves which appear on plants produced from seeds with single cotyledon like maize, rice, grass, wheat etc. The monocot leaves are usually described as isobilateral leaves because the both the upper and lower surfaces have the same color.In a monocot leaf equal number of stomata is present on both surfaces of the epidermis. This condition is normally described as amphi stomatic condition.

Anatomy of a monocot leaf

Upper Epidermis

The upper epidermis is a single layer made up of cubical shaped cells with no intercellular spaces in between them. The outer surface of the upper epidermis cell is covered by a thin cuticle. A few cells present in the upper epidermis are enlarged to form motor cells referred to as bulliform cells. These cells help the leaf to roll over themselves in order to reduce the surface area exposed to sunlight during hot seasons.

Mesophyll

Mesophyllis a green tissue between upper epidermis and lower epidermis. In monocot leaf, the mesophyll tissue is not differentiated into palisade parenchyma and spongy parenchyma with chloroplast and chlorophyll. The mesophyll is usually involved in photosynthesis process in the leaves of these plants.

Vascular Bundles

Vascular bundles represent the veins of the leaves. Each vascular bundle consists of phloem and xylem tissues surrounded by abundle sheath. Bundle sheath layer of the vascular bundle is made up of large barrel shaped endodermal cells. Xylem is usually responsible for conduction of water and dissolved minerals whereas phloem is responsible for conduction of dissolved food materials.

Dicot Leaf

Dicotyledons commonly known as dicots include mango, peanut, peas, oranges, cashews, beans, apples, oak trees etc.Anatomy of a dicot leafJust like a monocot leaf, the main internal structures of a dicot leaf include: epidermis, mesophyll and vascular bundle.

Epidermis

The epidermis is usually made up of a single layer of cells that are closely packed. A dicot leaf consist of a lower and upper epidermis with small openings referred to as stomata. The upper epidermis is thicker than the lower epidermis. More importantly,the lower epidermis has more stomata than the upper epidermis. The main function of the epidermis is to give protection to the inner tissue known as mesophyll.

Mesophyll

The mesophyll usually has two regions the spongy and palisade parenchyma. The palisade parenchyma cells contain more chloroplasts than the spongy parenchyma cells and thus its function is photosynthesis. On the other hand, spongy cells are irregularly shaped and loosely arranged so as to facilitate the exchange of gases within the air spaces.

Vascular bundles

The vascular bundles of a dictot leaf are surrounded by a compact layer of paranchymotous cells known as border parenchyma. The xylem consists of metaxylem vessels and protoxylem vessels. Phloem consists of sieve tubes, companion cells and phloem parenchyma.

The Key differences

1.The main characteristic feature that differentiates a monocot and a dicot leaf is that, the guard cells of stomata are kidney-shaped in dicot leaf and dumb-bell shaped in a monocot leaf.2.The orientation of a dicot leaf is dorsiventral while that of a monocot leaf is isobilateral. A dorsiventral organ is one that has two surfaces differing from each other in appearance and structure. Isobilateral orientation is whereby plant leaf surface parts (upper and lower) are identical to each other.3.The upper surface of a dicot leaf is dark green while the lower surface is light green in color. On the other hand, the upperand lower surfaces of a monocot leaf are equally green.4.The vascular bundle is large in dicot leaf whereas in monocot leaf, both small and large vascular bundles are present.5.In a dicot leaf stomata are usually present on the lower surface of the leaf, a condition referred to as hypostomatic. On the contrary, the leaves of monocot plant have stomata on both surface of the leaf, a condition referred to as amphistomatic.6.The intercellular spaces of a dicot plant leaf are relatively large due to presence of loosely packed mesophyll cells. In monocot plant leaf, the intercellular spaces are relatively small due to compact arrangement of mesophyll cells.7.The walls of epidermal cells of a dicot leaf do not have silica deposition whereas; the walls of epidermal cells of a monocotplant leaf have heavy deposition of silica.8.The stomata are arranged randomly on the epidermis of a dicot plant leaf whereas in monocot leaf, the stomata are arranged in parallel rows and are uniformly present on both the leaf surfaces.

The Key differences

9.The bundle sheath of a dicot plant leaf generally has a single layer and formed of colorless cells. On the contrary, the bundle sheath of a monocot plant leaf may have a single or double layer and formed of colored cells due to presence of chloroplasts.10.The mesophyll of a dicot leaf is differentiated into two parts, the lower spongy mesophyll and upper palisade. On the contrary, the mesophyll of a monocot plant leaf has no such differentiation.11.The venation pattern in a dicot plant leaf is reticulate (veins are interconnected and form a web like network). In contrast,the venation pattern of a monocot plant leaf is parallel (whereby the secondary veins run parallel to each other off a central, perpendicular primary vein).12.The shape of a dicot plant leaf is broader and relatively smaller whereas a monocot plant leaf is slender and long in shape.13.The hypodermis of the midrib region of a dicot plant leaf is collenchymatous while in a monocot plant leaf, the hypodermis of the midrib region is sclerenchymatous.14.In monocot leaf, large vascular bundles may show differentiation into protoxylem and meta-xylem elements whereas; in dicot leaf large vascular bundles do not show differentiation into protoxylem elements.15.The bundle sheath extension of a dicot leaf is parenchymatous whereas the bundle sheath extension of a monocot leaf is sclerenchymatous.16.The bulliform (Motor) cells are absent in the epidermis of a dicot plant leaf. In contrast, the bulliform (motor) cells are very much present in the epidermis of a monocot plant leaf.

Difference Between Dicot And Monocot Leaf In Tabular Form

THE BASIS OF COMPARISON DICOT LEAF MONOCOT LEAF

StomataThe guard cells of stomata are kidney-

shaped in dicot leaf

The guard cells of stomata are dumb-bell

shaped in monocot leaf.

ShapeThe shape of a dicot plant leaf is broader

and relatively smaller.

A monocot plant leaf is slender and long in

shape.

Leaf OrientationThe orientation of a dicot leaf is

dorsiventral.

The orientation of a monocot leaf is

isobilateral.

Upper and Lower Surface Color

The upper surface of a dicot leaf is dark

green while the lower surface is light green

in color.

The upper and lower surfaces of a

monocot leaf are equally green.

Size of the Vascular Bundles The vascular bundle is large in dicot leaf.Both small and large vascular bundles are

present.

Stomata Arrangement

In a dicot leaf stomata are usually present

on the lower surface of the leaf, a

condition referred to as hypostomatic.

The leaves of monocot plant have stomata

on both surface of the leaf, a condition

referred to as amphistomatic.

Intercellular Spaces

The intercellular spaces of a dicot plant leaf are

relatively large due to presence of loosely packed

mesophyll cells.

In monocot plant leaf, the intercellular spaces are

relatively small due to compact arrangement of

mesophyll cells.

Silica DepositionThe walls of epidermal cells of a dicot leaf do not have

silica deposition.

The walls of epidermal cells of a monocot plant leaf

have heavy deposition of silica.

Stomata ArrangementThe stomata are arranged randomly on the epidermis

of a dicot plant leaf.

The stomata are arranged in parallel rows and are

uniformly present on both the leaf surfaces.

Bundle SheathThe bundle sheath of a dicot plant leaf generally has a

single layer and formed of colorless cells.

The bundle sheath of a monocot plant leaf may have a

single or double layer and formed of colored cells due

to presence of chloroplasts.

Mesophyll DifferentiationThe mesophyll of a dicot leaf is differentiated into two

parts, the lower spongy mesophyll and upper palisade.

The mesophyll of a monocot plant leaf has no such

differentiation.

Venation Pattern

The venation pattern in a dicot plant leaf is reticulate

(veins are interconnected and form a web like

network).

The venation pattern of a monocot plant leaf is

parallel (whereby the secondary veins run parallel to

each other off a central, perpendicular primary vein).

The Hypodermis of the MidribThe hypodermis of the midrib region of a dicot plant

leaf is collenchymatous.

In a monocot plant leaf, the hypodermis of the midrib

region is sclerenchymatous.

Vascular Bundle DifferentiationIn dicot leaf large vascular bundles do not show

differentiation into protoxylem elements.

In monocot leaf, large vascular bundles may show

differentiation into protoxylem and meta-xylem

elements.

Nature of the Bundle Sheath ExtensionThe bundle sheath extension of a dicot leaf is

parenchymatous

The bundle sheath extension of a monocot leaf is

sclerenchymatous.

The Bulliform (Motor) CellsThe bulliform (Motor) cells are absent in the

epidermis of a dicot plant leaf.

The bulliform (motor) cells are very much present in

the epidermis of a monocot plant leaf.

What are the Similarities Between Monocot and Dicot Leaves

•Both have vascular bundles with a bundle sheath extension.•Both monocot and dicot leaves are differentiated internally into mesophyll , epidermis and vascular tissues.•They both possess chloroplasts.•In monocot and dicot leaves, xylem and phloem consist of protoxylem and protophloem; and metaxylem and metaphloem.•Both monocot and dicot leaves contain stomata and guard cells.•Vascular bundles are conjoint and collateral in both monocot and dicot leaves.•In both monocot and dicot leaves the major portions of the ground tissue is parenchymatous.•Hypodermis is present in both dicot and monocot leaves.

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Life can only be understood backwards; but it must be

lived forwards....

Neha Singh Parihar

TOPIC – IVth ( POLLINATION )

Pollination is the act of transferring pollen grains from the male another of a flower to the female stigma. The goal of every

living organism, including plants, is to create offspring for the next generation. One of the ways that plants can produce

offspring is by making seeds. Seeds contain the genetic information to produce a new plant.

Flowers are the tools that plants use to make their seeds. The basic parts of the flower are shown in the diagram below.

Seeds can only be produced when pollen is transferred between flowers of the same species. A species is defined a

population of individuals capable of interbreeding freely with one another but because of geographic, reproductive, or other

barriers, they do not interbreed with members of other species.

How does pollen get from one flower get from one flower to another? Flowers must rely on vectors to move

pollen. These vectors can include wind, water, birds, insects, butterflies, bats, and other animals that visit

flowers. We call animals or insects that transfer pollen from plant to plant “pollinators”.

Pollination is usually the unintended consequence of an animal’s activity on a flower. The pollinator is often

eating or collecting pollen for its protein and other nutritional characteristics or it is sipping nectar from the flower

when pollen grains attach themselves to the animal’s body. When the animal visits another flower for the same

reason, pollen can fall off onto the flower’s stigma and may result in successful reproduction of the flower.

Referring to the animated image, pollen from the anthers of Flower 1 is deposited on the stigma of Flower 2.

0nce on the stigma, pollen may “germinate,” which means that a “pollen tube” forms on the sticky surface of the

stigma and grows down into the ovule of the plant.

This growth can result in:

•Successful fertilization of the flower and the growth of seeds and fruit; or,

•A plant can be only partially fertilized, in which the fruit and/or seeds do not fully develop; or,

•The plant can completely fail to be pollinated, and may not reproduce at all.

Plants can be:

•Self-pollinating - the plant can fertilize itself; or,

•Cross-pollinating - the plant needs a vector (a pollinator or the wind) to get the pollen to another flower of the

same species.

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It’s better to be a lion for a day than a sheep all your

life.

Neha Singh Parihar

TOPIC –Vth ( DOUBLEFORTELLIZATION )

DOUBLE FERTILIZATION - Double fertilization is a complex fertilization mechanism of flowering plants

(angiosperms). This process involves the joining of a female gametophyte (megagametophyte, also called the embryo sac)

with two male gametes (sperm). It begins when a pollen grain adheres to the stigma of the carpel, the female reproductive

structure of a flower. The pollen grain then takes in moisture and begins to germinate, forming a pollen tube that extends

down toward the ovary through the style. The tip of the pollen tube then enters the ovary and penetrates through

the micropyle opening in the ovule. The pollen tube proceeds to release the two sperm in the megagametophyte.

The cells of an unfertilized ovule are 8 in number and arranged in the form of 3+2+3 (from top to bottom) i.e. 3

antipodal cells, 2 polar central cells, 2 synergids & 1 egg cell. One sperm fertilizes the egg cell and the other sperm

combines with the two polar nuclei of the large central cell of the megagametophyte. The haploid sperm and haploid egg

combine to form a diploid zygote, the process being called syngamy, while the other sperm and the two haploid polar

nuclei of the large central cell of the megagametophyte form a triploid nucleus (triple fusion). Some plants may

form polyploid nuclei. The large cell of the gametophyte will then develop into the endosperm, a nutrient-rich tissue

which provides nourishment to the developing embryo. The ovary, surrounding the ovules, develops into the fruit, which

protects the seeds and may function to disperse them.

Double Fertilization in Plants :- Angiosperms undergo two fertilization events where a zygote and endosperm are

both formed.

Key Points•Double fertilization involves two sperm cells; one fertilizes the egg cell to form the zygote, while the other fuses with the two polar nuclei that form the endosperm.•After fertilization, the fertilized ovule forms the seed while the tissues of the ovary become the fruit.•In the first stage of embryonic development, the zygote divides to form two cells; one will develop into a suspensor, while the other gives rise to a proembryo.•In the second stage of embryonic development (in eudicots), the developing embryo has a heart shape due to the presence of cotyledons.•As the embryo grows, it begins to bend as it fills the seed; at this point, the seed is ready for dispersal.Key Terms•double fertilization: a complex fertilization mechanism that has evolved in flowering plants; involves the joining of a female gametophyte with two male gametes (sperm)•suspensor: found in plant zygotes in angiosperms; connects the endosperm to the embryo and provides a route for nutrition from the mother plant to the growing embryo•proembryo: a cluster of cells in the ovule of a fertilized flowering plant that has not yet formed into an embryo

Double FertilizationAfter pollen is deposited on the stigma, it must germinate and grow through the style to reach the ovule. The microspores, or the pollen,contain two cells: the pollen tube cell and the generative cell. The pollen tube cell grows into a pollen tube through which the generativecell travels. The germination of the pollen tube requires water, oxygen, and certain chemical signals. As it travels through the style to reachthe embryo sac, the pollen tube’s growth is supported by the tissues of the style. During this process, if the generative cell has not alreadysplit into two cells, it now divides to form two sperm cells. The pollen tube is guided by the chemicals secreted by the synergids present inthe embryo sac; it enters the ovule sac through the micropyle. Of the two sperm cells, one sperm fertilizes the egg cell, forming a diploidzygote; the other sperm fuses with the two polar nuclei, forming a triploid cell that develops into the endosperm. Together, these twofertilization events in angiosperms are known as double fertilization. After fertilization is complete, no other sperm can enter. The fertilizedovule forms the seed, whereas the tissues of the ovary become the fruit, usually enveloping the seed.

After fertilization, embryonic development begins. The zygote divides to form two cells: the upper cell (terminal cell) and the lower cell (basal cell). The division of the basal cell gives rise to the suspensor, which eventually makes connection with the maternal tissue. The suspensor provides a route for nutrition to be transported from the mother plant to the growing embryo. The terminal cell also divides, giving rise to a globular-shaped proembryo. In dicots (eudicots), the developing embryo has a heart shape due to the presence of the two rudimentary cotyledons. In non-endospermic dicots, such as Capsella bursa, the endosperm develops initially, but is then digested. In this case, the food reserves are moved into the two cotyledons. As the embryo and cotyledons enlarge, they become crowded inside the developing seed and are forced to bend. Ultimately, the embryo and cotyledons fill the seed, at which point, the seed is ready for dispersal. Embryonic development is suspended after some time; growth resumes only when the seed germinates. The developing seedling will rely on the food reserves stored in the cotyledons until the first set of leaves begin photosynthesis.

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Neha Singh Parihar

TOPIC –VIth ( FOOD CHAIN )

Food chain:- Food chain, in ecology, the sequence of transfers of matter and energy in the form of food from

organism to organism. Food chains intertwine locally into a food web because most organisms consume more than one

type of animal or plant. Plants, which convert solar energy to food by photosynthesis, are the primary food source. In

a predator chain, a plant-eating animal is eaten by a flesh-eating animal. In a parasite chain, a smaller organism consumes

part of a larger host and may itself be parasitized by even smaller organisms. In a saprophytic chain, microorganisms live

on dead organic matter.

Because energy, in the form of heat, is lost at each step, or trophic level, chains do not normally encompass more than four or five trophic levels. People can increase the total food supply by cutting out one step in the food chain: instead of consuming animals that eat cereal grains, the people themselves consume the grains. Because the food chain is made shorter, the total amount of energy available to the final consumers is increased.

TOPIC –VIIth ( PLANT SUCCESSION )

Introduction

Succession is a directional non-seasonal cumulative change in the types of plant species that occupy a given area through

time. It involves the processes of colonization, establishment, and extinction which act on the participating plant species.

Most successions contain a number of stages that can be recognized by the collection of species that dominate at that

point in the succession. Succession begin when an area is made partially or completely devoid of vegetation because of

a disturbance. Some common mechanisms of disturbance are fires, wind storms, volcanic eruptions, logging, climate

change, severe flooding, disease, and pest infestation. Succession stops when species composition changes no longer

occur with time, and this community is said to be a climax community.

The concept of a climax community assumes that the plants colonizing and establishing themselves in a given region can

achieve stable equilibrium. The idea that succession ends in the development of a climax community has had a long

history in the fields of biogeography and ecology. One of the earliest proponents of this idea was Frederic Clements who

studied succession at the beginning of the 20th century. However, beginning in the 1920s scientists began refuting the

notion of a climax state. By 1950, many scientists began viewing succession as a phenomenon that rarely attains

equilibrium. The reason why equilibrium is not reached is related to the nature of disturbance. Disturbance acts on

communities at a variety of spatial and temporal scales. Further, the effect of disturbance is not always 100 percent. Many

disturbances remove only a part of the previous plant community. As a result of these new ideas, plant communities are

now generally seen as being composed of numerous patches of various size at different stages of successional

development.

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Neha Singh Parihar

TOPIC –VIII-th

( IN SITU & EX SITU CONSERVATION )

Difference between In-Situ and Ex-Situ conservation Conservation of biodiversity and genetic resources helps protect, maintain and

recover endangered animal and plant species. There are mainly two strategies for the conservation of wildlife: In-situ conservation and

Ex-situ conservation. Although, both the strategies aim to maintain and recover endangered species, they are different from each other.

Let us see how they differ from each other!

In-situ Conservation:

In-situ conservation, which is also known as "on-site conservation", refers to the conservation of wild species in their natural habitats and environment. It aims to conserve the natural habitats of the living creatures and maintain and recover wild species, especially the endangered species. The national parks, wildlife sanctuaries and biosphere reserve are some of the examples of in-situ conservation. This method of conservation allows animals flourish in their natural habitat and food chain and offers more mobility to the animals. It is suitable for the conservation of animals that are found in abundance.Ex-situ Conservation:

Ex-situ conservation, which is also known as off-site conservation, refers to the conservation of endangered species in the artificial or man-made habitats that imitate their natural habitats, e.g. zoo, aquarium, botanical garden etc. It offers less mobility to the animals as it is smaller in area than the area of in-situ conservation. This method of conservation is suitable for the animals which are not found in abundance

It provides protection to animals against predators, unfavourable climatic conditions and other hostile factors. Furthermore, proper food and care is provided under good supervision.Based on the above information some of the key differences between in-situ and ex-situ conservation are as follows:

Based on the above information some of the key differences between in-situ and ex-situ conservation are as follows:

In-situ Conservation Ex-situ ConservationIt means onsite conservation. It means offsite conservation.

It is the conservation of wild species in their natural habitats in order to maintain and recover endangered species.

It is conservation of species in the man-made habitats that imitate the natural habitats of species.

It is more dynamic as it involves natural habitats of organisms.

It its less dynamic as it involves man-made habitats.

It provides protection to endangered species against predators.

It provides protection against all hostile factors.

It is suitable for animals that are found in abundance. It is suitable for animals that are not found in abundance.

It is not suitable in the event of a rapid decline in the number of a species due to environmental, genetic or any other factor.

It is an ideal option in case of rapid decline in the number of a species due to environmental or any other reason.

Wildlife and livestock conservation involve in-situ conservation.

It can be used to conserve crops and their wild relatives.

Examples include national parks, wildlife sanctuaries, biospheres reserve etc.

Examples include zoo, aquarium and botanical garden.

It involves designation, management and monitoring of the target species in their natural habitat.

It involves sampling, storage and transfer of target species from their natural habitats to man-made habitats.

It helps maintain the ongoing process of evolution and adaptation within the natural environment of the species.

It separates the animals form the ongoing process of evolution and adaptations within their natural environment.

TOPIC –VIXth( PHYSICAL & CHEMICAL PROPERTIES OFSOIL )

A soil's physical and chemical properties affect plant growth and soil management. Some

important physical and chemical properties of soil are mineral content, texture, cation exchange capacity, bulk

density, structure, porosity, organic matter content, carbon-to-ni- trogen ratio, color, depth, fertility, and pH.

TOPIC – X ( CONSERVATION & MANAGMENT OF NTURAL RESOURCE )

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