Physiological response of growth chamber-grown cotton plants to the plant growth regulator PGR-IV under water-deficit stress

Zhao D. and Oosterhuis D.M. Physiological response of growth chamber-grown cotton plants to the plant growth regulator PGR-IV under water-deficit stress. Environmental and Experimental Botany 38, 7-14, 1997. - The plant growth regulator PGR-IV has been shown to improve the development and yield of cotton (Gossypium hirsutum L.) plants. However, cotton responses to PGR-IV under water-deficit stress have not been investigated. The objective of this study was to determine if PGR-TV could partially alleviate the detrimental effects of water stress on leaf photosynthesis and dry matter accumulation of cotton plants. Results indicated that leaf net photosynthetic rate (P-n) of growth chamber-grown cotton linearly decreased as leaf water potential (Psi(w)) declined when Psi(w) < -1.4 MPa. PGR-IV application prior to water stress treatment did not significantly affect components of Psi(w) of drought-stressed cotton plants. However, the leaves of water-stressed plants treated with PGR-IV had significantly higher stomatal conductance (g(s)) on the 3rd and 4th day of the water stress, and greater P-n between the 4th and 6th day compared to the untreated plants. The average leaf P-n of the plants treated with PGR-IV increased by 13.5% compared with untreated plants during the water deficit stress. The contents of P, Zn, Cu, Mn and Fe in PGR-IV treated plants were 29% to 170% higher than untreated plants under the conditions of water stress (P < 0.05 similar to 0.001). Water-stressed plants with PGR-IV also had significantly higher dry weights of roots and floral buds than the untreated water-stressed plants. PGR-TV has the potential to alleviate partially the detrimental effects of water stress on photosynthesis and dry matter accumulation, and to improve the growth and nutrient absorption of growth chamber-grown cotton plants. (C) 1997 Elsevier Science B.V.