Plant Growth Regulators

Light and cold act together to break dormancy of imbibed seeds to promote seed germination by increasing GAs levels. A rapid decrease of ABA endogenous content during Phase II is one of many factors that influence the successful completion of germination.

Several reports indicated that application of growth regulator improved the plant growth and yield. The 2, 3, 5-triiodobenzoic acid (TIBA) is well-known plant growth regulators. The application of TIBA in soybean resulted in higher grain yield. The Mrophophysiological 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. foliar application of GA₃ led to an increase in plant height, first node height and stem diameter. Leaf area and dry matter production also increased as a result of GA₃ foliar application. There was no effect of exogenous gibberellin and cytokinin on the number of soybean leaves, number of stem branches and root dry matter. Joint application of gibberellin and cytokinin tended to inhibit gibberellin effects. Cytokinin applied to leaves during soybean vegetative growth was not effective in modifying any of the evaluated plant growth variables. results suggest that an increase in the amount of cytokinin in individual florets might enhance the pod setting of the florets positioned at the middle or distal part within the raceme.