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Plants

 

Plants are mostly multicellular organisms however, few unicellular organism like algae are also considered as plants. So, we can say term plant is very broad and it includes single celled algae to flower and fruit bearing trees. Plants may be terrestrial or aquatic, plants which are present on the land surface is called terrestrial plant while the plant which floats, submerged or remain suspended in water is called aquatic plants.

 

2.1 Different Parts of Plants

 

Whole structure of plant is divided into different parts. These different parts perform different functions. Different parts of plants are following

 

2.1.1 Root System

 

In the root system, soil have water and nutrients required for plant growth, to meet this requirement the underground part of plant called roots help the plant. Roots, root hairs and all its parts together constitute the root system. The first root comes from a plant is called radicle. There are two types of root system, which are as follow

 

1. Tap Root System

It is characterised by large, central and dominant root from which other roots sprout laterally. Tap roots develop from the radicle of a seed forming the primary root. It branches of secondary roots and then further tertiary rootlets.

Some modification of tap roots for storage of carbohydrates are as follow

·                     Conical root e.g. carrot

·                     Fusiform root e.g. radish

·                     Napiform root e.g. turnip

Tap roots are also important adaptations for searching for water, as those long tap roots found in mesquite and poison ivy.

 

2. Fibrous Root System

 

This root system is characterised by thin, moderately branching roots growing from the stem. In monocots mostly fibrous root system present. Some examples are coconut, grass and onion. Plants with fibrous roots systems are excellent for erosion control, because the mass of roots cling to soil particles.

 

Functions of the Plant Root

 

Important functions of plants root system are as follow

 

1. Anchorage and Support The plant root system anchors the plant body to the soil and provides physical support. In general, however, taproot system provides more effective anchorage such that they are more resistant to toppling during storms.

 

2. Absorption and Conduction The plant root system absorbs water, oxygen and nutrients from the soil in mineral solution, mainly through the root hairs. They are capable of absorbing inorganic nutrients in solution. Plants with a fibrous root system are more efficient in absorption from shallow sources.

 

3. Storage Some root store food as carbohydrates e.g. potato, sweet potato, carrot, turnip etc.

 

4. Vegetative' Reproduction roots also help in vegetative reproduction e.g. fasmine and grass.

 

5. Prevents Soil Erosion Plant root system keep soil integrated and prevents soil erosion during heavy rain.

 

Modification of Root

 

1. Prop Roots For additional support in banyan tree, these pillar roots grow vertically downwards from aerial branches.

 

2. Stilt Roots These are aerial adventitious roots and grow obliquely downwards from basal nodes of the main stem and fire in the soil. e.g. maize and sugarcane.

 

3. Pneumatophores These are vegatively geotrophic (grow away from gravity) respiratory roots found in mainly mangrove plants or plants grow in swampy areas, e.g. Rhizophora and Avicennia.

 

Difference between Tap Root and Fibrous Root

 

S. No.	Tap Root	Fibrous Root
1.	Tap root has only one main and long root. The smaller roots that grow from the main root are called lateral root.	Fibrous roots do not have a main root. All roots seem similar.
2.	Tap root goes deep into the soil.	They do not go deep into the soil.
3.	Tap root are found in plants which have reticulate venation in their leaves.	These are found in plants which have parallel venation in their leaves.

 

2.2 Shoot System

 

The shoot system is above the ground. This system includes stems, flower, seeds, fruits and birds.

2.2.1 Stem

 

The stem is the ascending part of axis bearing branches leaves, flowers and fruits. It develops from plumule of the embryo of a germinating seed. The main function of the stem is spreading out branches bearing leaves, flowers and fruits. It conducts water, minerals and photosynthates some stems perform the function of storage of food, support, protection and of vegetative propogation. In sugarcane food is stored in the stem.

 

Types of Stem

There are two types of stem, which are as follow

 

1. Erect Stem

It grows straight upright without any kind of support above the surface of the soil. e.g. bamboo banyan tree.

 

2. Weak Stem

It is incapable of growing straight, upright and under natural conditions trail on the surface of the soil or climb with the help of some support. Weak stem are classified as

(i) Climbers These are weak stems which climb with the assistance of tendrils, hooks, spines, prickles, roots etc. e.g. pea, passion flower and vine etc.

(ii) Twiner Such weak-stems ascend by coiling around some support e.g. ipomoeo palmata.

(iii) Trailers Trailers are prostrate plants having weak, long and slender stems which trail along the surface and do not try to climb up with any support e.g. portulaca and evolvulus. These are single plant do not root from the nodes and thus do not form daughter plants.

(iv) Creepers These stems creep on the ground by various means and accordingly may be runner, stolen, offset or sucker, e.g. grasses.

 

Functions of the Stem

In growth and development of the plant, stem performs the following functions

 

·         It supports the leaves, flowers and fruits and connects them with the roots. In trees and shrubs, the main stem or trunk provides a strong columnar structure from which branches are attached, raising the leaves upward to exposed more fully to the Sun.

·         Transportation conducts water, nutrients and the products of photosynthesis to and from roots and leaves. It accommodates the transport system which is necessary for the vertical and lateral movement of water and sap within the plant body.

·         It helps store water, as in cacti, and the products of photosynthesis, as in the trunk of sago palm

(Metroxylon sagu) and sweet palm (Arenga pinnat a) which store large stock of starch.

·         Young green stem also performs a minor role in the production of food through the process of photosynthesis, but in some species (e.g. cactus) the stem is the chief photosynthesising organ.

·         The plant stem serves as a means of a sexual reproduction in many plant species.

·         Transfer of food translocate organic food from leaves to the rest of the play.

 

2.2.2 Bud

 

A bud is an undeveloped shoot and normally occurs in the axial of a leaf or at the tip of a stem. Its stem is very short and its leaves are so close that they overlap, each one wrapping round the next above it. The inner leaves are crinkled and folded, since a large surface area is packed into a small space.

The outermost leaves are often thicker and tougher and sometimes black or brown. These are the bud scales and they protect the more delicate, inner, foliage leaves from drying up, from damage by birds, insects, fungi etc and to some extent, from extremes of temperature. At the end of the bud's short stem is either a flower or a growing point where rapid cell division will take place later on when the next bud is forming.

Types of Bud

There are three types of bud, which are as follow

 

1. Terminal When located at the tip of a stem

(apical is equivalent but rather reserved for the one at the top of the plant).

 

2. Axillary When located in the axil of a leaf

(lateral is the equivalent but some adventitious buds may be lateral too).

 

3. Adventitious When occurring elsewhere, for example on trunk or on roots (some adventitious buds may be former axillary ones reduced and hidden under the bark, other adventitious buds are completely new formed ones).

·         Cablage is a codified bud.

·         Cloves are the aromatic flower buds.

 

2.2.3 Leaf

 

Different plant has specific kind of leaves. Leaves are main sites of photosynthesis. They uptake \[C{{O}_{2}}\] from atmosphere water and other nutrient from soil and energy from sunlight. Colour of leaves is green due to presence of pigment chlorophyll, when amount of chlorophyll in leaves decreases colour of leaves also changes and it may turn to yellow.

 

Function of Leaves

Some important function of leaves are

 

Manufacture of Food

 

It is the primary function of green leaves. The process is called photosynthesis by which leaf manufactures food material in the presence of sunlight and green pigment called chlorophyll present in the leaf. The preparation of food material takes place out of water and carbon dioxide obtained from the soil and the air respectively. Because plants make their own food in the presence of light hence called as autotrophs.

 

In Plants Both Respiration and

Photosynthesis Takes Place

 

There are numerous, minute openings present on the leaves, called stomata, through which gaseous exchange takes place between the atmosphere and the plant body.

 

Evaporation of Water

 

Water absorbed by the root hairs of the plant is evaporated from the leaf surface during the day time.

It generally takes place through the stomatal openings. The phenomenon is known as transpiration. This process allows the plant to absorb water and minerals from the soil and conduct the same to the top of the plant.

 

Storage of Food

 

Fleshy leaves of Indian aloe, portulaca and fleshy scale leaves of onion store food materials and water for the future use of the plants. Fleshy and succulent leaves of xerophytic plants growing in desert area always store a huge quantity of water, mucilage and food materials.

 

Vegetative Propagation

 

Leaves of Bryophyllum, Begonia and Kalanchoe produce buds by means of which they give rise to new plants by vegetative propagation. In these cases, when leaf lamina touches the ground, the leaf margin produces roots and form a bud that grows into a new plant. Lid of pitcher plant is a modified leaf.

 

2.2.4 Flower

 

The flower is the reproductive unit in the angiosperm. A typical flower has four different kinds of whorls arranged on swollen end of the stalk or pedicel called 'thalamus' or receptacle. These four whirls are calyx, corolla, androecium and gynoecium.

 

Flower Showing Part of Male and Female Structure

 

Parts of Flower

 

Important parts of flower are given as under

 

1. Calyx It is the outermost whorl of the flower and each part of the calyx is called sepals. Sepals are green, leaf like and protect the flower in the bud stage.

 

2. Corolla It is composed of petals. Petals are brightly butterflies, honeybees- coloured to attract insects butterflies, honeybees for pollination.

 

3. Androecium It is composed of stamens. Each stamen consists of a stalk or a filament and an anther. Meiosis takes place in anther.

 

4. Gynoecium It is the female reproductive part of the flower and made up of one or more carpels. A carpel consists three parts: stigma, style and ovary. Ovary is enlarged basal part, on which a elongated tube called style lies. The style connects ovary to stigma. Stigma is usually at the tip of the style and pollen grain receptive site.

 

2.2.5 Fruit

 

It is amateur or ripened ovary, developed after fertilisation, it is a seed bearing structure in flowering plants.  

 

Fruit protects the enclosed seed.

Fruit helps in dispersal of seeds.

Apple, fig are not true fruit as edible part is thalamus not ovary.

 

2.3 Different Types of Plants

 

Plants can be classifed on various basis. Such as physical basis, on the basis of life span and on the basis of region where they are found. Classification of plants on these basis are given below

 

2.3.1 On the Basis of Physical Structure

 

Classification of plants on the basis of physical characteristics are given below

 

1. Herbs It is delicate seed bearing plant which lacks woody stem and it cannot stand errect.

Herbs are commonly used for flavouring food, as medicines and perfumes, e.g. brinjal, coriander, tomato, tulsi etc.

 

2. Shrubs It is small to medium size woody plant.

Its stem is not as strong as tree. In shrubs, several main stem arises at or near the ground. e.g. rose, bougainvillea and cotton etc.

 

3. Tree They are strong plants, may be very tall or medium height. Stems are strong, woody and are known as trunks. Branches grows out of tree's trunk, e.g. mango tree, banyan tree etc.

 

4. Climbers They are the plant that does not have stem and if stem is present it is very weak.

These plants grow readily on support or over other plants, e.g. money plant, grapevine, pea etc.

 

5. Creepers These plants also have very weak stem and plants creeps along the surface of ground and spread on the ground, e.g. watermelon, pumpkin and bottle gourd.

 

2.3.2 On the Basis of Life Span

 

Classification of plants on the basis of life are given below

 

1. Annual Plants These plants complete its whole life cycle within a year from germination of seeds to production of seeds, e.g. wheat, maize, sunflower etc.

 

2. Biennial Plants These plants take two years to complete its biological life cycle. In first year, plant grows roots, stem, leaves and in second season it bears flowers, e.g. carrot, radish etc,

 

3. Perennial Plants These plants lives for many growing seasons. Roots of these plant develops in large area. Perennial flowering plant grows and bloom in the spring and summer, shed its leaves in autumn and winter e.g. mango, apple etc.

 

2.3.3 On the Basis of Region

 

Plants are categorised into the following

 

1. Hydrophytes These plants grow only in or on water. They have several adaptations like thin cuticle, large flat leaves; air sacs for flotation; reduction in roots; a waxy coating on leaves are present, e.g. lotus; hydrila, water lilly.

 

2. Xerophytes These plants normally grow in those area which have deficient water supply like desert condition. These plants have normally deep root, pointed, waxy and small leaves; thick cuticle; stomata less in number increased water storage.

 

3. Mesophytes These plants normally grow in an environment which is neither very dry nor very wet. e.g. mango, neem. Due to flood, these plants does not able to survive because roots of these plant does not able to respire.

 

4. Halophytes These plants grow in water of high salinity such as in saline semi-deserts, mangrove swamps, marshes and seashores. These plants have special adaptation in roots like they show growth above the surface of land. e.g. rhizophora.

 

2.3.4 Significance and Importance of Plants

 

Earth is called a green planet due to the presence of plants or it plants are considered to be the first living organisms born on the Earth. Plants are beneficial in following ways

 

·         Plants help in maintaining gaseous balance in the air through photosynthesis. They consume \[C{{O}_{2}}\] emitted by animals and produce oxygen.

 

·         Plants help in maintaining temperature, soil erosion, ecological balance, support rainfall, maintain soil fertility etc through various mineral and water cycles.

 

·         Plants are the shelter for birds and few animals like monkeys and squirrels.

 

·         Plants are called as autotrophs because it produces their own food in the presence of sunlight and chlorophyll by the use of \[C{{O}_{2}}\]and water. They provide food comprising of carbohydrates, fats, protems, vitamins and minerals.

 

·         Plants provide oils to consume mustard oil, groundnut oil, coconut oil, sunflower oil etc. Mostly oils are obtained by crushing of the seeds some oils of commercial importance are obtained from leaves and fruit.

 

·         Plants provide material that have medicinal value.

Tulsi, neem, garlic, aloevera, cinchona, poppy etc are some of the plant that have medicinal value.

 

·         There are some flowers which are consumed, e.g. kachnar in Uttar Pradesh, banana flower in Kerala, Sahjan flower in Maharashtra.

 

·         Plants like teak, sal, sesam provide wood for various uses. Different plants including bamboo provides paper, babul, acacia and kikar tree produces the gum and plants like cotton and jute provides fibre for cloth making, bags, ropes etc.

 

 

·         Different kind of beverages are obtained from plant and plant products like tea, coffee and alcoholic drink. Plants provide numerous kind of spices, perfumes, dyes, natural colour etc.

 

Plants provide following material for humans to consume

 

Cereals	Rice, wheat, millet, maize, barley, oats etc.
Pulses	Arhar, moong, horsegram, other kind of grams.
Roots	Radish, turnip, carrot, beetroot etc.
Stems	Ginger, garlic, potato, onion etc.
Leaves	Cabbage, spinach etc.
Nuts	Almonds, walnut, cashewnat, peanut etc.

 

2.3.5 Special Plants and their Features

 

Some special plants and their unique features are given below

 

Desert Oak

 

·         It is an attractive, medium sized, slow growing tree found in the dry desert region of the

Northern territory, South and Western Australia.

 

·         Its roots are around 3 times more than its length due to search of underground water. Instead of leaves trees has long segmented, branchlets.

 

Australian peoples used the trees as a source of water.

Nepenthes/Pitcher Plant

 

·         It is an example of carnivorous and insectivorous plants it traps insects, frogs and mouses in its pitfall trap. It has a modification of leaf over its pitfall trap cavity. To attract insects it produces good smell.

 

·         Generally, it is found in Indonesia, Australia and Meghalaya of India. Plant is able to do photosynthesis due to presence of chlorophyll but to overcome-the deficiency of nitrogen it will eat insects.

 

·         Virus Fly Trap and Sundew Plant/Drosera are also example of insectivorous plants.

 

Khejri Tree (Prosopis Cineraria)

 

·         This is Rajasthan state tree and environmentalists have warned about its slow dying.

 

·         It covers around 2/3rd of total geographical area of the state, and it supports rural economy of the state.

 

·         Its fruits are eaten as a rich protein source, bark of the tree is used as medicine. Insects cannot harm its wood.

 

Banana

 

·         The banana stem is really not a stem, it is a flower stalk of the banana plant.

 

·         It is a 'herb'. Its flower and fruit both are edible.

 

Croton

 

·         It is used as a indicator plant for water deficiency.

·         For this purpose croton is grown with crops, when the leaves of croton become it means water is required in crops.

 

Banyan Tree

 

·         It begins its life as an epiphyte, i.e. it grows on another plant.

 

·         Old banyan trees has aerial prop roots as piller to support the tree.

 

Tomato, Potato, Green Chilli

 

These plants came to India from South America.

Cabbage, orange, pea came from Europe, bhindi

(Okra), coffee, bean from Africa to India.

 

2.3.6 Nutrient in Plants

 

Plants can be classified in two groups on the basis of their nutrient habbits

 

1.  Autotrophs These plants can produce their own food using light, water and \[C{{O}_{2}}\]. Because autotrophs produce their own food, they are sometimes called producers.

 

2. Heterotrophs These plants are not able to prepare their food and dependent on other plants and animals for their food. These are of following types

 

(i) Parasites These cannot synthesize their own food because they are not having chlorophyll. They have sucking root to take prepared food from its host, e.g. cuscuta; broomrape.

 

(ii) Saprophytes They grow on decaying vegetable or animal matter and absorb organic food material, e.g. mushrooms, monotropa, bacteria and fungi.

 

(iii) Symbiontes Two organisms that live in close physical association and are of mutual benefit to each other are called symbionts e.g. lichens and mycorrhizae.

 

(iv) Insectivorous Plants Because these plants grow in swampy soil, which is deficient in nitrogen they are notable to synthesize proteins so they eat small insects. They are able to do photosynthesis e.g. Pitcher Plants (Nepenthes), Sundew (Drosera), Venns fly trap etc.

 

2.3.7 Photosynthesis

 

It is a process by which plants convert light energy into chemical energy, this chemical energy stored in, the form of carbohydrate. In photosynthesis, carbon dioxide and water is used in the presence of Sunlight and chlorophyll green pigment present on the leaves of the plant) and carbohydrate and oxygen is produced as the end product.

 

·         Due to splitting of \[{{H}_{2}}O\] (water) hydrogen molecule freed, this will form two immediate energy storage molecules NADPH and ATP.

 

·         NADPH C nicotinamide adetiine dinucleotide phosphate).

 

·         ATP (Adenosine triphosphate) Both are called as energy currency of the cell.

 

Foodchain

 

·         A foodchain shows the feeding relationship between different living things in a particular environment or habitat. Plants are at the bottom of any foodchain because they make their food by the process photosynthesis.

 

·         Next levels are for consumers, they eat producers and other animals. The animals that eats the producers are called as herbivorous or primary consumers.

 

·         The animals that eats primary consumers called as secondary consumers and so on to third, fourth etc.

 

·         Decomposers don't have the place in foodchain, but these are very important organisms for any foodchain, because they convert dead organic matter into inorganic matter.

 

Importance of Plant on Development of Child

 

·         By knowing the different role played in life of human and animal like providing oxygen to breathe, food to eat etc. Child will be able to understand the importance of plant in human survival.

 

·         By studying about its role in nature child will be more sensitive towards nature and environment.

 

·         By observing plants growth and development child will develop curiosity about them and will try to study more about them.