Responses Of Plants To Stress

The internal chemical signals and environmental factors - the external signals which are perceived by special molecules present in the cell. In this last unit of the course, you will study the responses of plants to environmental stress.

You know that certain plant species can grow in severe environmental extremes. For example, plants grow below 0°C in the Himalayas and above 45°C in deserts of Rajasthan. The optimal requirements of water, temperature, light intensity, nutrients and soil vary from species to species. Have you ever wondered why grasses flourish in highlight intensities while growth of many plants comes to a halt or is even inhibited? How do rice plants grow under waterlogged condition while maize and wheat cannot? How do thermophiles remain functional above 70°C, though their cells are also composed of molechles that are broadly similar structurally and functionally to those present in cells of other organisms? Again, why are metabolic reactions of theromophiles not disrupted even at 70°C or is there anything special about the enzymes that-allow certain species to function optimally at very high I temperature and certain others at extremely low temperature. In this unit we will try to find answers to such questions. We will see what are the molecular responses of  certain plant tissues that help them to cope environmental extremes - high  temperature and light intensity.

Extreme pH of soil, salinity and mineral deficiency drastically limit the total arable land available for the growth of crops, fruits, vegetables and other useful plants in our country and elsewhere in the world. It is estimated that over 50% of the potential crop is lost because of stress of various kinds. Scientists are now studying the responses of plants to various stresses in the laboratory and field conditions. The aim is to get maximal yields despite all deviation from necessary optimal conditions for plant growth in the natural environment. In this unit you will find that results of preliminary studies on plant responses to various kinds of stresses look quite promising and we can hope. that it should be possible to manipulate plants by genetic engineering so their performance is improved even under stress conditions.

Objectives After studying this unit you should be able to:

- define stress, photoinhibition, cold hardiness, cold acclimation, an elicitor and osmoregulation, Sunflecks - small zones of light lasting for much shorter duration on a fixed spot.

- describe the various kinds of environmental stresses that plants may have to face,

-discuss the ways adopted by plants to cope with stress conditions,

-explain with examples the different types of responses of plants to cope with various stress wnditions,

-discuss the prospects of manipulating and breeding plants in areas that are under
environmental extremities in our country.