Getting to Know Plants

"Plants are the major producers in an ecosystem, and they include trees, herbs, bushes, grasses, vines, ferns, mosses, and green algae"

1.0Introduction

Plants are alive, just like people and animals. How do we know this? Living things all do certain things:

They grow and die, need energy, nutrients, air and water, produce young ones. They are made up of cells. They react to what's around them. Life is not possible without plants. We find plants everywhere around us. Some are small while others are big. Some are found in water and other are present on land in roadside, house, school and farmhouse.

Plants on the basis of size and the nature of their stem can be classified into three categories :- (i) Small plants/herbs (ii) Medium plants/shrubs (iii) Big plants/trees

There is another type of plants that can differ from herbs, shrubs and trees. These are plants with weak stems and cannot stand upright. Some of these spread out on the ground and are called creepers. For example pumpkins, watermelon.

Other climb up with the help of the support, for example grapevine, money plant, beanstalk and gourd. They are called climbers.

2.0Design of Plant Body

Parts of plant that remain under the ground and which is fixed into the soil.

Comparison of plants on the basis of size and nature of their stem

PARAMETER	HERBS	SHRUBS	TREES
Size	Very small, usually less than 1 m high	Medium-sized, usually 1-3 m high	Tall, generally more than 3 m high
Nature of stem	Green, tender stem, few branches	Hard stem but not very thick, branches arise near the base of the stem	Hard, brown thick stem, branches on the upper part of the stem
Example	Grass, tomato, wheat, mint, coriander	Lemon, rose, pomegranate, bougainvillea, China rose, henna	Gulmohar, neem, Peepal, mango

3.0Root system

The structure emerging from the base of stem which act like straws absorbing water and minerals from the soil are roots. Tiny root hairs emerge out of the root helping in the absorption. Roots help to anchor the plant in the soil so it does not fall over. Roots also store extra food for future use like in carrot, sweet potato.

Structure of Root System

(i) Tap root system: In this system, a single root (primary root) comes out from the seed after germination. Many branches and sub-branches come out from this main root called "Lateral roots" and spread out into the soil. It is found in most of the dicot plants. e.g. Mango, neem, pine, sheesham, pea, carrot, radish, turnip and beetroot. Primary Root + Lateral Roots = Tap root system (main root)
(ii) Fibrous Root System: Many plants do not have a main root. Instead they have a cluster of fine roots which come out from the base of stem. These roots does not go down as deep into the soil as tap roots. It is found in most of the monocot plants. e.g. Grasses, cereals (like maize, rice and wheat) bamboo, sugarcane and onion.

Functions of Root

(i) Anchoring the plant: Roots help to anchor (fix) the plant firmly into the ground. (ii) Absorption of water and nutrients from the soil. (iii) Preventing soil erosion: Roots help to bind the soil particles together, thereby preventing them from being carried away by water and wind.

4.0Shoot System

The part of a plant above the ground consisting of stem, branches, leaves, flowers and fruits is called the shoot system.

Stem

Main supporting part of plant. Stem bears leaves, branches, buds, flowers and fruits.

Functions of Stem

(i) Stems keep the plant upright or they support the plant. (ii) They act like the plant's plumbing system, conducting water and nutrients from the roots and food from the leaves to other plant parts. A set of thin tubes from the root are connected to thin tubes in the stem, water and minerals pass through these tubes to leaves, flowers, buds and fruits.

Leaves

The leaf is flat green outgrowth of the stem. The wide flat green portion of the leaf is called lamina or leaf blade. The thin portion of leaf by which it is joined to stem is called stalk or petiole. The petiole extends into the leaf as the midribs and joins the stems at the leaf base. The thin lines arise from the petiole and midribs and spreading across the leaf are called veins. The veins branch into veinlets. The veins provide support to leaf and carry water, minerals and food. The arrangement of veins on a leaf is called venation. Venation is of two types - (a) Parallel venation (b) Reticulate venation

	Parallel venation	Reticulate venation
1.	If veins run parallel to one another from the base to the tip of leaf.	Veins arranged in the net like pattern on both sides of midrib.
2.	Plants whose leaves have parallel venation have fibrous root.	Plants whose leaves have reticulated venation have tap root.
3.	They are mainly found in monocot plants.	They are mainly found in dicot plants.
4.	Example maize, grass and wheat.	Example Tulsi, coriander and China rose.

Functions of the Leaf

(i) The leaves on their surfaces have tiny pores called stomata. Through these pores, plants take in gases for respiration and photosynthesis. The gases produced during these processes are also given out through stomata.

(ii) The process by which plants throw out excess water is called transpiration.

Stomata

(iii) Leaves manufacture food for the plant body. The process of manufacturing food by the leaves is called photosynthesis. Leaves require water, carbon dioxide, sunlight and chlorophyll for making food.

$Carbon dioxide +$ Water $Llucose Chlorophyll +$ Oxygen

(iv) In some plants, leaves bear buds in the marginal notches from which new plants grow and develop. e.g., Bryophyllum.

5.0Flowers, Fruits and Seeds

A flower is the reproductive organ of a plant. A typical flower has a stalk called a pedicel which joins it to stem. The upper most part of pedicel is wider and is known as thalamus. On the base of the thalamus, the different parts of the flower are arranged in concentric rings and whorls.

Flower and its Different Parts

(i) Sepals: The outermost whorl of the flower consists of sepals. These are the green, leaf like structures at the base of flower. Sepals protect flower during its development and support the flower when flower blooms.

(ii) Petals: The second whorl consists of petals. These are colourful structures that surround the inner parts of flower. Its function is to attract the pollinators.

(iii) Stamen : The third whorl of flower consists of stamen. These are male reproductive parts of flower. Each stamen has two parts, a thin stalk called filament and a knob like structure called anther. Anther produces a powdery substance called pollen.

(iv) Carpel : It is a single elongated structure in the centre of the flower. It is broader below and tapers at the top and is also known as pistil. It is the female reproductive part of a flower. It has three parts, a sticky top portion called stigma, an enlarged base called ovary and a stalk called style that connects these two. The ovary contains tiny bulb like structures called ovules (can be one or more) which later become seeds.

A flower having all the whorls i.e. sepals, petals, stamens and pistils is known as a complete flower e.g. hibiscus, rose, tulips.
A flower lacking one or more of such structures, is known as an incomplete flower e.g. sweet corn, grass.
Sunflower, rose, hibiscus have both stamen and carpel. They are bisexual flowers, but some have only stamen or carpel, such flowers are unisexual flowers like papaya, cucumber, maize etc.
Post pollination, seed formation occurs. Ovary of carpel gets converted into fruits. Fruit is the ripened ovary

Functions of flower

(i) It is an organ of sexual reproduction and result in the formation of fruits and seeds. Seeds on germination give rise to new plants. (ii) It is source of food for many insects e.g. Bees (iii) They beautify the surrounding and provide aesthetic value.

6.0Biology Diagrams made Easy

Tap root:

Body Movements

Walk, run, fly, jump, creep, crawl, slither and swim - these are only a few of the ways in which animals move from one place to another. Why are there so many differences in the way that animals move from place to place?

Reproduction in Plants

All living organisms reproduce. What it means in simple terms is that living organisms produce young ones of their own kind. For example, a cat produces kittens which grow into adult cats. In plants too, seeds grow into young seedlings.

Tranportation in Plants and Animals

Transportation whether in plants or animals is the key to the efficient assimilation of the nutrients that the organisms synthesise, get from their environment or digest.

Respiration in Organisms

All organisms are made of small, microscopic units called cells. A cell is the smallest structural and functional unit of an organism. Each cell of an organism performs certain functions such as nutrition, transportation, excretion and reproduction.

The Living Organisms Characteristics and Habitats

There is a large variety of things around us. Some of these are living things whereas others are non-living things. Those things which need food, water and air for their survival are called living things.

Nutrition

All living organisms require energy and other raw materials for performing all the vital activities and for body building, repair, growth, development and regulation. Both energy and raw materials are obtained from the food.

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