7. Effect of Plant Growth Regulators on Morphological, Physiological and Biochemical Parameters of Soybean (Glycine max L. Merrill)

Plant growth and developmental processes are very much regulated by certain chemical substances called Growth regulators. Growth regulators are known to improve the physiological efficiency including photosynthetic ability and can enhance the effective partitioning of accumulates from source and sink in the field crops. The present study was conceptualized and executed with the prime objective of study the effect of chlormequat chloride, NAA, Mepiquat chloride and Brassinosteroids on morphological, physiological and biochemical parameters of soybean. The field trial was conducted following randomized block design with nine treatments replicated thrice. The basic material for the present investigation consisted of soybean cv. Js-335 and two growth promoting (NAA and Brassinosteroid) and growth retarding substances (chlormequat chloride and mepiquat chloride). These growth regulators were sprayed at flower initiation stage. The Morphophysiological parameters, namely, Plant height, number of branches, number of trifoliates per plant, dry matter accumulation in leaf, stem and reproductive parts, LAI, CGR and RGR was observed to increase significantly with the application of NAA (20 ppm) and brassinosteroid (25 ppm). However, it decreased with the application of chlormequat chloride and mepiquat chloride. The Biochemical parameters, namely, chlorophyll content was observed to increase significantly with application of NAA (20 ppm), brassinosteroid (25 ppm), mepiquat chloride 5 %, AS (5 %) and chlormequat chloride 50 % SL at different concentrations compared to control and water spray but whereas fluorescence emission and photosynthetic rate were noticed to be non-significant. A significant increase in the seed protein content was also noticed with the application of NAA (20 ppm), brassinosteroid (25 ppm), mepiquat chloride 5 %, AS (5 %) and chlormequat chloride at different concentrations, compared to control and water spray. In conclusion, the study revealed the superiority of NAA (20 ppm) treatment for majority of the morphological, physiological and biochemical parameters at different growth stages, compared to other growth regulator and control treatments studied in the present investigation for Rabi soybean.