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Carbon and Water Economies of Well-Watered and Water-Deficient Cotton Plants Treated with Mepiquat Chloride

Dep. of Soil and Crop Sciences, Texas A&M Univ., College Station, TX 77843-2474

^* Corresponding author.

The growth regulator mepiquat chloride (MC) (1,1-dimethylpiperidinium chloride) inhibits leaf expansion, reduces leaf diffusive resistance, and reduces leaf photosynthetic rates when applied to cotton (Gossypium hirsutum L.). Whole-plant studies in a controlled environment were conducted to evaluate the effect of MC on the C and water economies of ‘Stoneville 825’ cotton plants growing under well-watered and water-deficient conditions. Single, well-irrigated plants were transferred from a nursery room into test chambers when they reached a leaf area of 0.05 m² and were exposed to the following combinations of treatments: treated or not treated with MC and maintained well irrigated or not irrigated. MC treatment consisted of spraying 12 ± 1 mL plant^–1 of a solution with a concentration of 27.3 mg a.i. L^–1. Environmental conditions were typical of sunny humid days in central Texas. Carbon exchange rates and water loss rates were monitored hourly; leaf area, leaf water potential, and leaf osmotic potential were measured daily. Mepiquat chloride inhibited plant leaf area expansion, daily transpiration, daily gross C uptake, daily C loss, and daily net C gains in both water regimes; however, transpiration, gross C uptake, and net C gains of water-stressed plants were less inhibited in MC-treated plants than in nontreated plants toward the end of the water stress cycle. Mepiqnat chloride did not affect C-use efficiency of cotton plants under either water regime nor the water use efficiency (WUE) of well-watered plants, but reduced WUE of water-stressed plants, which indicates a possible inhibition of the leaf internal photosynthetic capacity. Mepiquat chloride did not affect leaf water and osmotic potentials of well-watered plants, but helped to maintain leaf turgor potential in water-stressed plants. It was concluded that MC induces a water-conservative behavior in cotton through its effect on plant leaf area and delays the onset of water stress in plants growing under water-deficient conditions.

Received for publication October 15, 1990.

This article has been cited by other articles:

				S. P. Biles and J. T. Cothren Flowering and Yield Response of Cotton to Application of Mepiquat Chloride and PGR-IV Crop Sci., November 1, 2001; 41(6): 1834 - 1837. [Abstract] [Full Text] [PDF]