Use of Transpiration Decline Curves to Identify Drought-Tolerant Cotton Germplasm1
- J. E. Quisenberry,
- Bruce Roark and
- B. L. McMichael2
Traditional plant breeding approaches have not been very effective in the development of higher yielding cotton (Gossypium hirsutum L.) cultivars for growth under water-deficient field conditions. The purpose of this research was to evaluate the ability of a laboratory technique to identify cotton genotypes with higher growth rates under water stress conditions in the field. The technique consisted of detaching cotton leaves from the plant at sunset and hydrating those leaves overnight. The following day, the leaves were placed under a light-bank in the laboratory and weighed every 2 min as they dried. From that data, transpiration decline curves were plotted. The curves exhibited stomatal and cuticular transpiration phases. The point where those two linear phases intersected was termed “mean stomatal closure” (MSC), and both time and relative water content (RWC) at that point were estimated. Sixteen entries were evaluated for transpiration decline curve components and growth rates in irrigated and dryland field plots in 1978 at Big Spring, Tex. In 1980, 12 different entries were evaluated for the same traits under dryland conditions at the same location.
In 1978, entry differences occurred for all transpiration decline curve components in the irrigated test and for all components, except stomatal transpiration rates, in the dryland test. The interaction between entries and water levels was significant for all components. In 1980, only RWC at MSC and cuticular transpiration rates were different among entries. Growth rates among entries could not be separated statistically within any experiment. However, large negative correlation coefficients were measured between mean RWC at MSC and mean growth rates in the dryland tests in both 1978 and 1980. This relationship indicated that growth rates tended to be higher when the stomates remained open to a lower RWC before closure. The relationship was not significant in the 1978 irrigated test. Transpiration decline curves appear to be useful in screening cotton genotypes for differences in growth rates under conditions of water stress.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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