Evaluation of leaf yield, physiological and biochemical characteristics of Green Tea (Camellia sinensis L.) in response to different irrigation regimes and foliar application of Cu and Zn nano-Chelate

Tea (Camellia sinensis L.) with high production potential in acidic soils and adapted to soil and climatic conditions of Guilan province, is a calcareous, thermophilic and moisture-loving plant whose leaves are the main part of this plant in terms of economy and utilization (Taiefeh et al., 2013). Various studies have shown that the yield of green tea leaves and its physiological and biochemical properties depend on factors such as soil type, altitude, season, climatic conditions, and the amount of water available to the plant and the consumption of macro and micro elements (Owuor and Bowa, 2012). One of the prominent issues in the production of crops and orchards, including tea orchards, is strengthening their resistance to dry conditions, and among them, water deficite stress is the most common type of environmental stress that affects plant growth and production (Kirigwi et al., 2004). The element copper is very important in the growth and production of quality tea, so that by interfering with the oxidation of green tea leaves, it directly affects the taste and color of tea (Singh and Singh, 2004). Zinc as a major factor in the activity of many enzymes involved and play a major role in the structure of proteins that regulate transcription in leaves of tea plays, hence, reduce the concentration of zinc in the tea plant reduced stomatal conductance and transpiration rate and adjust the performance of antioxidant enzymes (Upadhyaya et al., 2013). This study was conducted to investigate the effect of application of copper and zinc nano-fertilizers and irrigation water deficiency on different morphophysiological and biochemical characteristics of tea plant in garden conditions. This research was carried out as a factorial experiment in a randomized complete block design with three replications in selected tea research gardens of Rudsar city under the supervision of Tarbiat Modares University Department of Agronomy in 2018. Factorial combinations of three treatments of water deficit stress (15% (un-stressed control, IR1), 30% (moderate stress, IR2) and 45% (severe stress, IR3) of FC depletion) and four foliar application (FA1: use distril water, control, FA2: Copper nano-chelate (0.5 mg per one liter of distilled water), FA3: Zinc nano-chelate (2.5 mg per one liter of distilled water) and FA4: Copper nano-chelate + Zinc nano-chelate) were considered. The applied drought stress levels were determined between the field capacity and the permanent wilting point of the soil in the tested area to determine the plant response to different soil water levels (Mokhtassi-Bidgoli et al., 2013). The amount of chemical fertilizers required was determined based on the results of soil test (Table 1) and the amount of nutrients harvested by tea plants (Table 2) (Sedaghathoor et al., 2003). The results of this study showed that the interaction of irrigation regimes and foliar application on green leaf yield, photosynthesis rate, proline concentration, catalase, peroxidase and superoxide dismutase activity were significant. Under moderate stress conditions, optimal green leaf yield and plant photosynthesis rate were obtained from the combined foliar application of copper and zinc nano-fertilizers. Also, under severe stress conditions, the highest amount of antioxidant activity and proline concentration was observed in the combined spraying of copper and zinc nano-fertilizers. Total chlorophyll decreased fewer than 62.5 and 75 % under moderate and severe stress conditions compared to the control treatment. In general, it can be concluded that the application of combined foliar application of copper, zinc foliar application and foliar application of zinc increased 58.40, 32.54 and 31.28% of green tea leaf yield compared to the control under moderate stress conditions, respectively, that Demonstrates the ability of copper and zinc micronutrients to increase green leaf yield, photosynthetic rate, photosynthetic pigments, soluble carbohydrate and protein concentrations, as well as increase the activity of antioxidants in stress conditions and in resistance to tea plant and reduction of dehydration damage in tea gardens is very effective.