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Physiological Responses of Cotton (Gossypium
hirsutumL.) to Salt Stress
Mohammad Pessarakli
The University of Arizona, Tucson, Arizona
681I. INTRODUCTION
No plant species or animals are immune from stress. Any species at least once during its life cycle is sub-
jected to stress. Nutrient uptake and utilization as well as water absorption by plants are adversely affected
under stressful conditions. Plant growth and metabolism are usually impaired under such conditions, re-
sulting in decreased crop yields.
Among the essential nutrient elements, nitrogen is one of the most widely limiting elements for crop
production, and when plants are subjected to stress, N uptake and utilization are likely to be more severely
affected than any other mineral nutrient. Regarding nutrient uptake and metabolism, plant species behave
differently under stressful conditions. The adverse effects of stress are usually less severe on salt-tolerant
plants such as cotton than on the salt-sensitive species such as beans.
Since the first publication of this chapter in 1994, numerous studies have been conducted on cotton
and the findings have already been published [1–31]. Most of these studies were concerned with the cel-
lular and molecular aspects of this plant [3,6,7,9,10,15–18,21,25–27,29,30]. Li et al. [3] studied the effect
of salt stress on the activity of protective enzymes in cotton seedlings and concluded that the adaptation
of cotton seedlings to salt stress was expressed by roots, but the difference in salt tolerance between cul-
tivars was expressed by cotyledons. Studying stomatal density and size under salinity stress conditions,
Jafri and Ahmad [4] reported that a decrease in stomatal density under salt stress was compensated by an
increase in stomatal size and mesophyll surface area. Adaptation to a saline environment was adjusted by
increasing mesophyll surface area to ensure normal exchange of gases and photosynthetic activities un-
der the stress condition.
Evaluating several stages of cotton growth and development, including seedling, preflowering, flow-
ering, and boll formation stages, Khan et al. [5] found that the seedling stage was the most sensitive one
as compared with other growth development stages. In their study [5], the lowest seed cotton yield was
found at this stage of growth. At all growth stages, the yield of the salt-tolerant cultivar was less affected
than that of the salt-sensitive one by salinity stress. Renu and Goswami [6] studied the activities of sev-
eral enzymes at various stages of growth in cotton treated with GA-3 (gibberellic acid) and NaCl. These
investigators [6] observed that nitrate reductase activity in cotyledonary leaves decreased with salt stress
and maximum activity was observed at the first stage. While salinity invariably resulted in an increase in
the cellulase and protease activity at all stages, GA-3 alone as well as its interaction with NaCl increased