Effect of Plant Growth Regulators on Thermal Use Efficiency Indices and Yield of Wheat (Triticum aestivum L.) Varieties under Terminal Heat Stress and Changing Climate

Abstract

Terminal heat stress, characterised by a rapid rise in ambient temperature, is one of the major limiting factors for wheat productivity during the reproductive and grain-filling stages. A field experiment was conducted to evaluate the influence of plant growth regulators on heat use efficiency, helio-thermal use efficiency and photo-thermal use efficiency of wheat at the Zonal Agricultural Research Station, Powarkheda, Narmadapuram, during two consecutive rabi seasons in 2020-21 and 2021-22. The experiment was laid out in a split-plot design with four wheat varieties (GW 322, Sujata, C 306 and MP 1202) assigned to the main plots and plant growth regulator treatments comprising the control, CCC @ 1000 ppm, CCC @ 1500 ppm, ethephon @ 10 ppm and ethephon @ 30 ppm assigned to the subplots, with three replications. Among the varieties, MP 1202 recorded the significantly highest heat use efficiency (2.94 kg ha-1 0c-1 day-1 for grain yield and 8.11 kg ha-1 0c-1 day-1 for biological yield), helio-thermal use efficiency (0.47 and 1.30, respectively) and photo-thermal use efficiency (0.26 and 0.67, respectively), followed by GW 322, while Sujata recorded the lowest values for all thermal use efficiency indices. Among the plant growth regulators, application of CCC @ 1500 ppm significantly enhanced heat use efficiency (2.70 and 6.78 kg ha-1 0c-1 day-1), helio-thermal use efficiency (0.43 and 1.08) and photo-thermal use efficiency (0.28 and 0.62) for grain and biological yield, respectively, compared with the control, and was statistically at par with ethephon @ 30 ppm. The results of the present study indicate that the variety MP 1202 with the application of CCC @ 1500 ppm can improve thermal use efficiency indices (heat use efficiency, helio-thermal use efficiency and photo-thermal use efficiency) for grain and biological yield under heat stress and changing climatic conditions in the Central Zone of Madhya Pradesh.