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

Abstract

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-IV 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 ( Ψ w ) declined when Ψ w < −1.4 MPa. PGR-IV application prior to water stress treatment did not significantly affect components of Ψ 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 ∼ 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-IV 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.