Sensitivity of Cotton to Water-Deficit Stress
By Derrick Oosterhuis, Ph.D.
Distinguished Professor of Crop Physiology
Department of Crop, Soil
and Environmental Sciences
University of Arkansas
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Water deficit is the major abiotic factor limiting plant growth and crop productivity around the world. In all agricultural regions, yields of rain-fed crops are periodically reduced by drought, and the severity of the problem may increase due to changing world climatic trends. Water is essential for plant growth and development and effects plant morphology as well as critical physiological functions, the results of which are manifested in poor growth and decreased yield and fiber quality. The effects of water stress depend on the severity and duration of the stress, the genotype of the plant, as well the growth stage at which stress is imposed. Adequate water is essential at planting for germination and the establishment of a good plant stand, but shortages seldom occur at this stage. Both the squaring phase and the flowering phase are sensitive to water deficit, and water shortages during these stages will decrease boll and seed number, and yield. Water deficit during boll development is less critical than during squaring and flowering, but can still affect boll size and fiber quality. From peak bloom to open bolls, water stress can result in square and young boll shedding. However, these losses of late fruit have less impact on yield than loss of early season bolls. Fiber quality parameters affected by stress during boll development are fiber length and micronaire, particularly in the young bolls, due to carbohydrate shortages. After bolls start opening, plants should be allowed to become water stressed to allow for better harvest conditions. Stress at this time hastens boll opening, makes defoliation easier, and reduces regrowth.