Effect of Abiotic Stresses on Crop Plants
Authors: Rekha Sodani, Seema, Jyoti Chauhan, Sunita Chaudhary

Abiotic stress is defined as the negative impact of non-living factors on the living organisms in a specific environment. The non-living variable must influence the environment beyond its normal range of variation to adversely affect the population performance or individual physiology of the organism in a significant way. Abiotic stress is essentially unavoidable. Abiotic stress affects animals, but plants are especially dependent on environmental factors, so it is particularly constraining. Abiotic stress is the most harmful factor concerning the growth and productivity of crops worldwide (Gao, Ji-Ping; et al.,2007). Many research have also shown that abiotic stressors are at their most harmful when they occur together, in combinations of abiotic stress factors Mittler, Ron (2006).

Most abiotic stresses includes :

1. Water stress

2. High temperature stress

3. Chilling stress

4. Salinity stress

5. Heavy metal stress

6. Oxidative stress

Effect of water stress on crop plants:

Plants experience water stress either when the water supply to their roots becomes limiting, or when the transpiration rate becomes intense. Water stress is primarily caused by a water deficit, such as a drought or high soil salinity Wilting is the first obvious effect of water stress because turgor pressure, which inflates plant cells and keeps them erect, is lost. The amount of water, sunlight and carbon dioxide available to the plant directly influences the amount of food a plant can produce. When water levels are low due to water stress, photosynthesis can slow or even stop. Low availability of water reduce respiration and transpiration and ultimately reduce crop production.

Effect of High temperature stress on crop plants:

At very high temperatures cause severe cellular injury and cell death may occur within short time, thus leading to a catastrophic collapse of cellular organization (Schoffl et al., 1999). However, under moderately high temperatures, the injury can only occur after longer exposure to such a temperature however the plant efficiency can be severely affected. High temperature directly affect injuries such as protein denaturation and aggregation, and increased fluidity of membrane lipids . Other indirect or slower heat injuries involve inactivation of enzymes in chloroplast and mitochondria , protein degradation, inhibition of protein synthesis , and loss of membrane integrity. Heat stress associated injuries ultimately lead to starvation, inhibition of growth, reduced ion flux, production of toxic compounds and production of reactive oxygen species (ROS). Immediately after exposure to high temperature stress the expression of heat shock proteins (HSPs), protein with 10 to 200 kDa, is supposed to be involved in signal transduction during heat stress.

Effect of chilling stress on crop plants:

Freezing temperatures induce dehydrative stress on plants, as water absorption in the root and water transport in the plant decreases (Smallwood et al., 2002) Water in and between cells in the plant freezes and expands, causing tissue damage. Symptoms of extracellular freezing include structural damage, dehydration, and necrosis. If intracellular freezing occurs, it will lead to death. Freezing injury is a result of lost permeability, plasmolysis, and post-thaw cell bursting.

Effect of salinity stress on crop plants:

Salt water has more salt and as a result, the hardness of the water is more. When the roots absorb the water, the salt, which in itself is a solid, gets in more and as a result, the minerals essential for the growth is not provided. So, for these minerals, the roots try to do more work but, the plant has less food for itself and therefore, it cannot let any part do more or less work.

Effect of heavy metal stress on crop plants:

Excessive heavy metal accumulation in plant tissue impairs either directly or indirectly several biochemical, physiological, and morphological functions in plants and in turns interferes with crop productivity. Heavy metals reduce crop productivity by inducing deleterious effects to various physiological processes in plants including: seed germination, accumulation and remobilization of seed reserves during germination, plant growth, and photosynthesis. At the cellular level, heavy metal toxicity reduces crop productivity by producing reactive oxygen species, disturbing the redox balance and causing oxidative stress.

Effect of oxidative stress in crop plants:

Oxidative stress is a component of many abiotic stress conditions such as drought, high temperature stress, salinity and heavy metal stress and biotic stress conditions such as herbivory and plant pathogen interactions. During these stress conditions, levels of reactive oxygen species (ROS) increase, potentially resulting in oxidations of DNA, proteins and lipids.

References:

Gao, Ji-Ping; et al. (2007). "Understanding Abiotic Stress Tolerance Mechanisms: Recent Studies on Stress Response in Rice". Journal of Integrative Plant Biology. 49 (6): 742â€"750.: 10.1111/j.1744-7909.2007.00495.x .

Mittler, Ron (2006). "Abiotic stress, the field environment and stress combination".Trends in Plant Science. 11 (1): 15â€"19. : 10.1016/j.tplants.2005.11.002 .

Schoffl, F., Prandl, R., Reindl, A., 1999. Molecular responses to heat stress. In: Shinozaki, K., Yamaguchi-Shinozaki, K. (Eds.), Molecular Responses to Cold, Drought, Heat and Salt Stress in Higher Plants . R. G. Landes Co.,Austin, Texas, pp. 81â€"98.

Smallwood, Maggie; Bowles, Dianna J. (2002). "Plants in a cold climate" . Philosophical Transactions of the Royal Society B: Biological Sciences . 357 (1423): 831â€"847.



About Author / Additional Info:
I am persuing ph.D degree from BHU varansi with UGC fellowship