Photosynthesis evaluation and Response of stomata in deficit irrigation and partial root zone drying in potato (Solanum tuberosum L.)

Today, due to limited of water resources, more attention is paid to the use of water storage methods. Thus, a factorial experiment was conducted in a completely randomized design with five replications in a controlled greenhouse in Ferdowsi University of Mashhad in 20017. The studied factors included three irrigation treatments (Full irrigation, deficit irrigation, partial root zone drying) and two levels of phosphate fertilizer (required amount based on soil analysis (25ppm) and adding 25% more than recommended (31ppm)). In partial root treatments, a part of the pots was under drought stress two weeks after planting, and the second part of the zone drying pots was irrigated until the beginning of flowering and 50% of flowering was applied to dry conditions. Results showed that drought stress in both flowering and 21 days after flowering caused a decrease in the physiological traits including chlorophyll content index, photosynthesis rate, stomatal conductance and transpiration rate. As the duration of drought increased, the density of stomata in the lower leaf area increased. In spite of decreasing photosynthesis and dry matter content in drought stressed plants, biomass content in partial root zone drying was higher than deficit irrigated treatment. Increased phosphorus had no significant effect on stomatal density, but at 21 days after flowering the substomatal CO2, photosynthesis rate, transpiration rate, reduced stomatal conductance, and biomass directly were related to increasing phosphorus.