Plants have to exploit their immediate environment to maximum effect. Their inability to move swiftly means that the best way of dealing with many stresses is through physiological or morphological changes. Abiotic stresses, and ways to adapt to them are numerous and interlinked, Salt, Drought and Cold Stress. There are habitats throughout the world that present challenges to crop plants through a lack of water and excessive, or toxic, salts in the soil.  Although sodium and chloride are the major ions in many soils, and in seawater, other salts such as sulphate and calcium are important in some areas. Problems can be combined, so that drought can be accompanied by a build-up of salinity in soils from irrigation water. Cold stress, although seasonal, has some similarities to a drought, since as water freezes it creates concentrated solutions of solutes. It also subjects the plant to a shortage of liquid water. The native flora of any region has morphological and physiological adaptations to the stresses they will encounter. Crop plants have been selected by humans for particular characteristics, such as rapid growth and high yields, which can make them perform poorly if subjected to any stress. An interest in the response of plants to other abiotic stresses therefore developed, with research extending from whole plant studies through aspects of physiology to molecular biological studies.

Salt Stress

Salinity is one of the major obstacles to increasing production in crop growing areas throughout the world. Salinity in soil or water is one of the major stresses and especially in arid and semi-arid regions. Salinity impairs seed germination, reduces nodule formation, retards plant development and reduces crop yield. The plants that grow in saline soils have diverse ionic compositions and a range in concentrations of dissolved salts. Salinity can affect any process in the plant’s life cycle, so that tolerance will involve a complex interplay of characters. Current estimates indicate that 10 – 35% of the world’s agricultural land is now affected, with very significant areas becoming unusable each year. It is a world-wide problem, careful water management practices can avoid, or even reclaim damaged land, crop varieties that can maintain yields in saline soils also have an important role. In contrast to crop plants, there are wild plants that thrive in the saline environments along the sea shore, in estuaries and saline deserts, these plants are called halophytes, have distinct physiological adaptations to counter the dual hazards. Investigated details of the physiology and biochemistry of salt tolerance and also looked at overall plant performance, two species of sorghum (Sorghum bicolor and S. sudanense) represented by 21 accessions. Although increasing sodium chloride concentrations significantly reduced all aspects of growth, there was considerable variation between the accessions. Root and shoot length measurements of the accessions, and the progeny of a cross between four of them, indicated that a great proportion of the differences was genetically determined.

     * Mean relative total fresh weight of 21 accessions of two sorghum species after growing in 200mM NaCl for 15 days.

Measurements of internal solutes indicated that there was a physiological basis to these differences. The more tolerant accessions tended to select against uptake of sodium ions, and to synthesize increased amounts of organic solutes (such as proline) for osmotic adjustment. Synthesis of organic solutes appears to be a common strategy for osmotic adjustment by plants despite the fact that it channels photosynthetic resources away from other aspects of growth.

Proline accumulation in one accession of sorghum grown for 14 days in saline solutions (from LHS: control, (one-tenth Long Ashton culture medium) supplemented with 100, 150 and 200 mM NaCl)

The results of this project indicate that there is scope within the sorghum gene-pool to increase the salt tolerance of commercial varieties, as well as indicating the physiological traits that are advantageous.

Drought stress

Drought is the most important abiotic stress factor that limiting the crop growth and production in favorable condition. Drought is prevalent all over the world, especially in semi-arid and arid regions. It is one of the major constraints for productivity of a number of crops. In many developing countries the water stress is the major constraint to agricultural production and also reduced the quality, growth and production of crops. Investigated the potential within oilseed brassicas for drought tolerance. Plants are relating to species of the Brassicaceae (cabbage family). They are the main edible plant oil crop and a major crop in other parts of the world. The effects of drought from germination to seed set on 5 species of oilseed brassica, covering a total of 120 varieties.

The dry weight of seedlings rises as they are subjected to increasing water stress, as they accumulate increased amounts of solutes.

This study showed that drought tolerance is a complex trait where several characters, influence plant success during the life-cycle.

Cold Stress

An adverse force or a condition, which inhibits the normal functioning and well being of a biological system such as plants. Various types are Cold, heat, drought, salinity, etc. Low temperature stress Chilling stress. when plants are exposed to a low temperature above 0 ºC.Plants living in temperate climates require tolerance to the seasonal advent of cold. However, tropical or sub-tropical species may also experience sudden cold spells, in unseasonal weather or at higher altitudes. Rice is a tropical crop where growth is checked by chilling. rice seedlings to cold under controlled conditions. The objective was to screen rice varieties for cold tolerance. It was important to know that brief exposure to cold in the laboratory was a true guide to the plant’s potential to recover from a real frosty night. Analyses of   biochemical changes in the seedlings revealed characteristics typical of plants exposed to cold weather, measuring a real parameter of cold tolerance.

This article is collectively authored by Muhammad Nazim*1, Salman Haider Abbasi 1, Muqarrab Ali1 and Afnan Sehar2. 1 Department of Agronomy, Muhammad Nawaz Sharif, University of Agriculture Multan, Pakistan. 2Department of Plant Pathology, University of Poonch Rawalakot, Azad Kashmir, Pakistan.

Technology TimesArticlesabiotic,effects,plants,stressPlants have to exploit their immediate environment to maximum effect. Their inability to move swiftly means that the best way of dealing with many stresses is through physiological or morphological changes. Abiotic stresses, and ways to adapt to them are numerous and interlinked, Salt, Drought and Cold Stress. There...Pakistan's Only Newspaper on Science and Technology