In this article we will discuss about the types of abiotic stress.
Extreme environmental conditions such as drought, salinity and freezing temperature cause adverse effect on the growth and productivity of crop plants. The temperature (heat, chilling and freezing), drought and salinity stress together represent abiotic stress. Exposure of plants in general to these abiotic stresses is inevitable in nature (Fig. 15.1).
Several plants, however, respond to abiotic stresses at molecular, cellular and physiological level. Several stress inducible genes have been characterized and are implicated in the protection of plants. Many of these gene products not only enhance stress tolerance but also are involved in the regulation of gene expression and signal transduction.
Abiotic stress triggers secondary effect in plants by producing excess of reactive oxygen species (ROS), which have greater impact on plant’s survival. In stressed plants, the most useful oxygen molecule turns to be lethal and inflicts severe damage to the cell.
Due to the increase in human population, there is more demand for food and hence agricultural practice must feed more people. This increasing demand must combat with new strategies that are to be enforced to enhance crop productivity.
One feasible way to combat stress problem is to develop crops that are more tolerant to abiotic stresses such as drought, flooding, heat, salinity, chilling and freezing, so that many new land can be brought under cultivation.
Although traditional plant breeding method provides marginal relief, genetic engineering offers fastest and effective strategy for dealing stresses problem particularly in enhancing plant tolerance to stress. In nature several organisms have evolved resistant traits that enable them to survive in extreme environment.
One of the most classical ways of improving stress tolerance is to assess and characterize resistant gene(s) that confer these properties and can be introduced into higher plants.
Considering stress factors, drought and salinity are the most significant issues threatening agricultural production on a global scale. It is estimated that the total economic value of loss caused by drought and heat globally is about 1.3 billion, and due to cold is about 18.6 million. But conventional and non-conventional methods have been suggested and information on stress tolerant plant is accumulating.
In Australia, after 25 years of research, commercial release is near completion for a drought tolerant oil seed crop suited to three million hectares of drought proven area [for more details see, www(dot)plantstress(dot)com]. Scientists at the University of Bonn, in Germany have identified the gene which protects the plant against severe drought conditions.
Similarly, Korean team has announced development of oxidative stress resistant Arabidopsis. According to plant molecular biologists at the International Centre for Genetic Engineering and Biotechnology [ICGEB], New Delhi, soil salinity and drought were the two major threats to the crops in India.
The International Crops Research Institute for Semi-Arid Tropics [ICRISAT], currently located in Hyderabad, is actively involved in the development of drought resistant transgenic chick pea and other economically important plants. According to one study, nearly 24 percent of Indian agricultural land has been damaged by salinity. This has fueled scientific manpower to evolve transgenic strategy to enhance plant productivity.