Plants - Form And Function

 

Plants have six different parts that work as a team to help the plant function. These six parts are: roots, stems, leaves, fruit, flowers and seeds. We need to understand each part to understand the life of plants.

Roots

Roots help anchor a plant into the ground, rock or wherever it is growing. They have small hairs that extend from the main roots and help with absorption of water and  minerals that help the plant grow. A plant's roots also store nutrients like carbohydrates and sugars. Plants, such as potatoes , radish, carrots, have taproot systems. Others, like grasses and flowers, have fibrous root systems.

Stems

Plant stems are attached to roots , they carry water & nutrients to the rest of the plant. Cells in the stem that carry water are called xylem cells, while those that carry food are called the phloem cells. Stems also provide physical strength and support for a plant to stand upright. Some stems, such as those of flowers, can be soft while some like  tree trunks are woody and strong.

Leaves

Leaves are important to a plant because they make the food in a process called photosynthesis. The leaves capture sunlight and use light, water, chlorophyll and carbon dioxide to make glucose or sugar.

Flowers

Flowers are the reproductive units of plants and create seeds for further cycle of reproduction where the seed can become a plant again. The female part of a flower is called the pistil, which is made up of the stigma, style and ovary. The male part is called the stamen and is made up of the anther and filament.

In most flowers, the stamen surrounds the pistil.

Fruit

Flowers fruits are ripened ovules, containing seeds. Some plant fruits are edible, such as tomatoes, brinjal, lady finger, etc. The fruits develop a fleshy or hard exterior, to protect the developing seeds inside.

Seed

Seeds are plant embryos. Seeds are found within the plant's fruit while they germinate. Animals, wind or water can move the seeds to another place and, under the right conditions, the seed will form another plant.

Root, Stem and Leaf

A plant is  made up of roots that help in anchoring the plant into soil and also facilitates absorption of water and other nutrients. The shoot system is made up of  stem that supports the plant body, conducts minerals and water from roots to leaves and other aerial parts.

Structure of a typical plant

A typical plant contains two main parts, viz. roots and stem. The stem bears leaves, flowers and fruits.

Root

The underground part of a plant is called the root.T he root system consists of two types of root.

  1. Fibrous root: In this type, a cluster of thin fibre-like roots arise from the base of the stem. These roots spread out in the soil.

    Examples: wheat, millet, grass, etc.

  2. Tap root: This is the main root which grows from the base of the stem. Many branches and sub-branches come out of the main root.

    Examples: carrot, mango, marigold, etc.

Functions of Root

  1. Roots hold the plant firmly in the soil and thus provide anchorage to the plant.
  2. Roots absorb water and minerals from the soil.

Stem

Stem usually grows above the ground. The stem is the main structural framework. The stem bears leaves, branches, buds, flowers and fruits. The point from where branches or leaves grow is called node. The portion of a stem between two consecutive nodes are called the internodes.

Functions of stem

  1. The stem gives structural support to the plant.
  2. It bears branches, leaves, flowers and fruits.
  3. The stem carries water and minerals from the roots to different parts of the plant.
  4. Stem gets modified for food storage in some plants, e.g. potato, ginger, turmeric, etc.

Leaf

The leaf is a thin, flat and green structure which arises from the node of the stem. The green colour of leaves is due to the presence of chlorophyll. Chlorophyll is a green-colored pigment..

 

Venation

Arrangement of veins in a leaf is called venation. When the veins make a network like structure, it is called reticulate venation, e.g. leaves of banyan, mango, jackfruit, etc. When the veins run parallel to each other, it is called parallel venation, e.g. leaves of wheat, grass, etc.

Stomata

There are many small openings on the lower surface of a leaf. These are called stomata. Stomata allow gases to enter or exit the leaf. Unwanted water is also removed through stomata; in the form of water vapour.

Transpiration

Loss of water vapour from plants through stomata and lenticels is called transpiration. A major portion of transpiration happens through stomata.

Functions of leaf

  1. Photosynthesis: This is the main function of a leaf. Plants prepare food from carbon dioxide and water; in the presence of chlorophyll and sunlight. This process is called photosynthesis.
  2. Breathing: Stomata in leaves also facilitate breathing by leaves.

Structure of flower

Fig: Structure of flower

 

Following are the main parts of a flower:

Sepal

The outer green leafy structure in a flower is called sepal. It protects the flower at bud stage.

Petals

The coloured leaf-like structures; next to the sepals; are called petals. The bright colours of the petals, attracts insects.

Stamens

Around the centre of the flower there are many little stalks with swollen tops. These are called stamen. It is the male part of the flower. Each stamen consists of a green stalk called filament. A capsule-like structure; called anther is at the top of the stamen. The anther produces pollen grains. Pollen grains are powder like particles and take part in reproduction.

Pistil

It is the female part of the flower. It is a flask- shaped structure in the middle of the flower. It is divided into three parts:

  • Ovary: The lower broader portion of the pistil is called ovary. It contains the ovules which take part in reproduction.
  • Style: The narrow middle portion of the pistil is called style.
  • Stigma: The sticky end at the top of the style is called stigma.