Effect of Plant Growth Regulators on Phenology and Heat Unit of Wheat (Triticum aestivum L.)
Wheat (Triticum aestivum L.) productivity is strongly influenced by crop phenology and thermal accumulation during different growth stages. Plant growth regulators may modify phenological development and heat-unit accumulation, thereby affecting crop adaptation under varying environmental conditions. An experiment was conducted during the rabi seasons at the Zonal Agricultural Research Station, Powarkheda, JNKVV, Narmadapuram, to evaluate the influence of plant growth regulators on the phenology and heat indices of wheat varieties. The experiment comprised twenty treatment combinations, with four wheat varieties (GW 322, Sujata, C 306, and MP 1202) as the main-plot treatments and five plant growth regulator treatments (CCC @ 1000 and 1500 ppm, ethephon @ 10 and 30 ppm, and a control) as the sub-plot treatments, arranged in a split-plot design with three replications. Observations were recorded at the following phenological stages: emergence, crown root initiation, tillering, jointing, booting, heading, anthesis, milking, dough, and physiological maturity. Accumulated growing degree days, helio-thermal units, and photo-thermal units were also calculated at the specified phenological stages. Among the varieties, C 306 required the longest duration (123 days) to attain physiological maturity and recorded the highest accumulated growing degree days (1659.27 °C day), helio-thermal units (11299.30 °C day hour), and photo-thermal units (19525.89 °C day hour) at physiological maturity. Regarding plant growth regulators, CCC @ 1500 ppm resulted in the longest duration (119 days) to reach physiological maturity. The highest accumulated growing degree days (1513.75 °C day) were recorded with CCC @ 1500 ppm; the corresponding helio-thermal units (10134.42 °C day hour) and photo-thermal units (19112.46 °C day hour) were statistically at par with ethephon @ 30 ppm.