Impact of Plant Growth Regulators on the Physiological and Leaf Nutritional Quality of Mulberry (Morus spp.) S-1635

The study evaluated the effects of indole-3-butyric acid (IBA) and kinetin on physiological characteristics and leaf nutritional quality in mulberry (Morus spp.) cultivar S-1635. The present investigation was conducted during 2025–26 at the Department of Sericulture, Assam Agricultural University, Jorhat, to evaluate the effects of plant growth regulators on the physiological and leaf nutritional quality of mulberry (Morus spp.) cultivar S-1635. The experiment consisted of nine treatments, comprising four concentrations of IBA (1000, 2000, 3000 and 4000 ppm), four concentrations of kinetin (50, 100, 150 and 200 ppm), and an untreated control, with each treatment replicated three times. Significant variation was observed among the treatments in both physiological and nutritional attributes of mulberry leaves. For the physiological attributes, kinetin 200 ppm recorded the highest chlorophyll content (3.19 mg g⁻¹ fresh weight), chlorophyll stability index (73.22%), membrane stability index (72.26%) and relative leaf water content (75.27%), followed by IBA 3000 ppm in chlorophyll content (3.04 mg g⁻¹ fresh weight), chlorophyll stability index (69.50%) and membrane stability index (62.13%). Regarding leaf nutritional quality, kinetin 200 ppm recorded the highest protein (14.00%), nitrogen (2.24%), carbohydrate (52.80%) and total soluble sugar (7.16 °Brix) contents. The carbohydrate content under kinetin 200 ppm was statistically comparable to that under kinetin 150 ppm (50.80%). Among the IBA treatments, IBA 1000 ppm recorded comparatively higher protein (12.68%) and nitrogen (2.03%), whereas IBA 3000 ppm recorded higher total soluble sugar content (6.00 °Brix). The untreated control consistently exhibited the lowest values for both physiological and nutritional attributes. Overall, kinetin 200 ppm demonstrated a positive effect on the physiological stability and nutritional quality of mulberry leaves, highlighting its potential for improving leaf quality for sustainable sericulture.