2017 ASHS Annual Conference

Long term drought coupled with tighter regulations on limited water resources have caused growers to seek alternative drought tolerant tree crops in California. For tree crops, proper cultivar selection is crucial when planning a commercial orchard. Knowing how a cultivar is functioning physiologically helps determine which genotypes perform optimally for a given climate. For example, water-use efficiency is a trait that aides in selection of plants that use less water. Although grown throughout the world in various climates, information regarding pomegranate physiology is lacking. The purpose of this research was to determine the effect of time day and cultivar on pomegranate photosynthesis and water relations. The study utilized cultivars in their fourth year of growth, they included ‘Eversweet,’ ‘Haku Botan,’ ‘Parfianka,’ and ‘Wonderful.’ Photosynthetic data were gathered using a LI-COR 6400 photosynthesis system and water potential data was collected using a plant moisture stress instrument. The research took place at a field site in Riverside, California and variables analyzed included photosynthesis, stomatal conductance, transpiration, water-use efficiency, transpiration efficiency, and pre-dawn and midday water potential. Differences were detected for time of day, with higher rates of assimilation, transpiration, and stomatal conductance in morning hours. Water use efficiency was higher in afternoon compared to morning. There were also differences among cultivars for stomatal conductance and transpiration during the morning hours but not during the afternoon hours, with ‘Eversweet’ having significantly lower rates of stomatal conductance and transpiration than ‘Parfianka.’ Cultivars had significant differences in photosynthetic gas exchange variables when comparing morning to afternoon values. These results furthered our understanding of how pomegranate trees function on a physiological level among unique cultivars and during different times of the day.