| Abstrakt: |
Reductions of leaf development and transpiration are closely related to soil water deficits. Few studies have analyzed the effects of water deficits on both processes during different growth stages. A study was conducted to analyze and quantify the effects of water deficits during different growth stages on leaf development (number, extension, and senescence) and transpiration rates of sorghum [Sorghum bicolor(L.) Moench] and cotton (Gossypium hirsutumL.). The study was conducted at the Blackland Research Center at Temple, TX, in a glasshouse using covered pots and in the field using covered lysimeters. In the glasshouse, the sorghum and cotton pre‐flowering treatments were irrigated at 60, 35, 15, and 0% of water used in the control pots. In the lysimeters, water deficit treatments of 50, 30, and 0% plant available water (PAW) were imposed on sorghum during the vegetative period (before panicle initiation and between panicle initiation and anthesis) and after anthesis. Leaf length and transpiration rates were measured two to three times per week. Leaf extension was reduced to 0% of well‐watered sorghum and cotton when the PAW decreased from 50 to 0%. Transpiration per unit leaf area decreased from 100 to 0% of well‐watered sorghum and cotton when PAW decreased from 28 to 0% for each stressed period. Sorghum leaf senescence was enhanced and leaf number increased in the 0% PAW treatments compared to the well‐watered and 30% treatments. These relationships of leaf development, transpiration, and PAW compare favorably with other published results. The PAW threshold values when each process is affected would be useful in developing criteria for scheduling irrigation and in improving the accuracy of crop growth models in estimating leaf development and transpiration. |
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