Plant life and photosynthesis

 PLANT LIFE 

All living organisms perform some basic functions to keep themselves alive. These basic functions which allow living organisms to live on earth are known as life processes. The basic life processes common to all living organisms are nutrition, respiration, excretion, growth, reproduction, movement to stimuli (singular-stimulus)and response

Living organisms require food, which provides energy to perform life processes. We know that only green

plants have the ability to prepare food by a process called photosynthesis. That is why they are known as

autotrophs or producers. This type of nutrition is called autotrophic nutrition.

PHOTOSYNTHESIS

Photosynthesis is a process by which green plants manufacture food in the presence of sunlight and chlorophyll by using raw materials like carbon dioxide from air and water from soil. The process is accompanied by release of oxygen. Oxygen escapes from the plant body through stomata. Only green plants are capable of making food in the form of glucose. This is because they have chloroplast containing a green pigment called chlorophyll which is essential for the process. sunlight > Glucose + Oxygem

All green parts of the plant carry out the process of photosynthesis, but leaves are the main organs involved in this process for the following reason.

💫Leaves provide broad, wide and flat surface for absorption of light and carbon dioxi

💫Leaves contain the green pigment called chlorophyll which helps to capture the sun's energy (ligh

💫Leaves have minute pores called stomata (singular stoma) on one or both surfaces which help in exchange of carbon dioxide and oxygen between the leaf and the atmospher.

FACTORS AFFECTING PHOTOSYNTHESIS

 There are several factors which affect the rate of phosynthesis like light, temperature, carbon dioxide, water and chlorophyll. All these factors are interdependent and the rate of photosynthesis gets affected if there is a change in any of these factor

In order to perform photosynthesis, a leaf requires the following things.

💫 Carbon dioxide: As the amount of carbon dioxide in the air increases, the rate of photosynthesis also increases. In terrestrial plants, carbon dioxide is obtained from the atmosphere through stomata. Aquatic plants make use of the carbon dioxide dissolved in water

💫Water: If there is less water in the soil, the rate of photosynthesis reduces as there is less water in the cytoplasm and chloroplast. As a result, the stomata close and carbon dioxide does not enter the plants. Plants absorb water from the soil through their roots. This water is then transported up to the leaves through the stem. Xylem tissue present in the stem is responsible for conduction of water. Along with water, minerals present in the soil are also absorbed and transported

💫Sunlight: It is absorbed by the chlorophyll present in the leaves, More the rate of photosynthesis.

💫Chlorophyll: It is the green pigment present in the cells of the leaves.Photosynthesis does not take place in plants or plant parts lacking chlorophyll

Know Your Scientist

Jan Ingenhousz 17301799 a Dutch scientist made a notable contribution to the discovery of photosynthesis in 1779. He found that when a plant was kept under water, its green parts produced bubbles in the presence of sunlight. When the plant was kept in darkness, the bubbles stopped forming, Through a series of experiments, he showed that the bubbles formed were of oxygen gas. Thus, Ingenhousz concluded that plants produce oxygen in the presence of sunlight.

Structure and Working of Stomata

Stomata (singular-stoma) are present on the surface of leaves. They consist of a pore surrounded by two bean shaped or kidney-shaped guard cells. The guard cells are living and have cytoplasm, nucleus and chloroplasts, The Outer wall of these cells is thin and the inner wall is thick.

When water enters the guard cells, they become swollen and the outer thin walls are pushed outwards. The inner thick walls also bulge outwards and the stomatal pore opens On the other hand, when water moves out of the guard cells, they become loose and the outer thin walls move towards the pore. The inner thick walls also return their original position and the stomatal pore closes. Normally, stomata open during the day and close night.

What happens in plants with reduced leaves like the desert plants?

In desert plants like cacti, leaves are reduced to spines. This prevents or reduces the loss of water transpiration. The stem in these plants is green to carry out photosynthesis.

What happens to photosynthesis in plants with red, brown or violet leaves? 

In all such leaves, green colour pigment is also present in addition to red, brown, yellow and other pigments. However, the amount of red, brown, yellow or other pigments is very high in comparison to the green pigment and therefore, these pigments mask the green colour. Photosynthesis takes place in green parts of all these leaves.

You might have seen some plants which have white and green parts in the same leaf. They are called variegated leaves. Remember that photosynthesis will not take place in the white portions of such leaves. Common examples are those of money plant, cronton and coleus.