Application of potassium, zinc and boron as potential plant growth modulators in Gossypium hirsutum L. under heat stress

Abstract

High temperature stress at reproductive stages of cotton crop severely affects the yield and quality of cotton crop under changing climatic conditions. To alleviate the adverse effects of high temperature stress on cotton crop, the regulatory effects of potassium (K), zinc (Zn), and boron (B) were assessed by applying different temperature regimes at three reproductive stages of cotton crop under field and glass house conditions. Cotton plants were subjected to low (32/20 °C ± 2), medium (38/24 °C ± 2), and high (45/30 °C ± 2) temperatures under glasshouse, but sown at specific dates in field to provide different temperatures at three reproductive stages. High-temperature stress at squaring, flowering and boll formation stages in both field studies increased relative cell injury (RCI), total soluble proteins (TSP), reactive oxygen species and reduced fiber yield attributes i.e. total number of bolls per plant (TNBPP), number of sympodial branches per plant (NSBPP) and quality traits. For example, RCI, TNBPP and fiber fineness were reduced by 73%, 42% and 29%, respectively under supra thermal regime (SupTR) of glass house study over the optimal thermal regime (OpTR). Foliar application of K and Zn followed by B increased TSP, RWC, TNBPP, NSBPP, fiber fineness, fiber length and fiber strength. Further, foliar spray of K and Zn followed by B also reduced H2 O2 under SupTR and SubTR over the OpTR. The findings of the present study clearly demonstrate that foliar spray of Zn, K and B alleviated adverse effects of high temperature stress at squaring, flowering and boll formation stages and increased seed cotton yield and quality of cotton crop.