THAKUR, ANJUSUDARSHNA, KUMARI2017-08-172017-08-172017http://krishikosh.egranth.ac.in/handle/1/5810028842ABSTRACT The present study entitled “Effect of water stress and brassinosteroid on growth and physio-biochemical characteristics of apple plants” was conducted in the field of the Department of Fruit Science and Plant Physiology laboratory of Basic Sciences, Dr. Y.S. Parmar University of Horticulture and Forestry, Nauni, Solan, Himachal Pradesh during January - June 2016. The objective of the experiment was to study the effects of imposed water stress and brassinosteroid on growth and physio-biochemical responses of apple plants. One year old plants of both varieties i.e. Super chief and Red chief were pre-treated by foliar application of brassinosteroid 0.05 and 0.10 ppm, three days before subjecting to stress. Water stress conditions were imposed by withholding watering for 15 and 30 days. Growth characteristics viz. plant height, branch number, leaf area, root length, fresh and dry weight of root and shoot and root-shoot ratio showed significant reduction under water stress. The maximum reduction in growth parameters was registered by plants subjected to 30 of water stress as compared to 15 days of water stress. Physiological indices viz. photosynthesis, chlorophyll fluorescence, canopy temperature depression, transpiration rate, stomatal conductance and water use efficiency showed inhibitions under both water stress durations with maximum reduction under 30 days of water stress than the control for both cultivars. Osmoregulating substances i.e. total free amino acid, total free proline and total soluble sugars showed increased accumulation and enhanced activities of antioxidant enzymes i.e. catalase and peroxidase with increasing duration of water stress which helped in enhancing drought tolerance. However brassinosteroid at both concentrations could help in maintaining vital growth, physiological and biochemical processes under water stress conditions. Foliar spray of brassinosteroid (0.05 ppm) prior to imposition of stress can pave the way to minimize the deleterious effects of water stress on apple plants.ennullThesis