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ARS Home » Pacific West Area » Davis, California » Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes » Research » Publications at this Location » Publication #343060

Research Project: Management of Genetic Resources & Associated Information for Grape, Tree Fruit, Tree Nut, & Other Specialty Crops to Mediterranean Climates

Location: Nat'l Clonal Germplasm Rep - Tree Fruit & Nut Crops & Grapes

Title: Diurnal patterns of photosynthesis and water relations for four orchard-grown pomegranate (Punica granatum L.) cultivars

Author
item CHATER, JOHN - University Of California
item SANTIAGO, LOUIS - University Of California
item MERHAUT, DONALD - University Of California
item Preece, John
item ZHENYU, JIA - University Of California

Submitted to: Journal of American Pomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/17/2018
Publication Date: 7/1/2018
Citation: Chater, J.M., Santiago, L.S., Merhaut, D.J., Preece, J.E., Zhenyu, J. 2018. Diurnal patterns of photosynthesis and water relations for four orchard-grown pomegranate (Punica granatum L.) cultivars. Journal of American Pomological Society. 72(3):157-165.

Interpretive Summary: Long-term drought, coupled with tighter regulations on limited water resources have caused growers to seek drought tolerant cultivars of common tree crops in California. Yet information on pomegranate physiology is lacking, even though it is grown throughout the world in various climates. The purpose of this research was to determine the effect of time of day and cultivar on pomegranate photosynthesis and water relations, and calculate values for water-use efficiency, defined as photosynthetic carbon gain divided by water lost during transpiration. The study utilized four field-grown cultivars in their fourth year of growth (‘Eversweet,’ ‘Haku Botan,’ ‘Parfianka,’ and ‘Wonderful’), in Riverside, California. Variables analyzed included photosynthesis, stomatal conductance, transpiration, instantaneous water-use efficiency, intrinsic water-use 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. Intrinsic water-use efficiency was higher in afternoon compared to morning. There were also differences among cultivars for stomatal conductance and transpiration during the morning but not during the afternoon, with ‘Eversweet’ having significantly lower rates of stomatal conductance and transpiration than ‘Parfianka’: other cultivars were intermediate. These results further our understanding of how pomegranate cultivars function on a physiological level during different times of the day, and suggest that efficiency of production can be improved through cultivar selection. Increasing global temperatures coupled with unpredictable changes in climate threatens food security globally (Altieri and Nicholls, 2017). California has experienced extreme drought conditions for several years, causing fruit growers to face water limitations affecting production and leading to hundreds of millions of dollars in crop revenue losses in 2016 alone (Medellín-Azuara et al., 2016). To lessen the impacts of climate change and increasing temperatures on food security, it is important to utilize diversified cropping systems to reduce vulnerability to extreme climatic events as experienced in California and other regions of the United States (Altieri and Nicholls, 2017). Long term drought in California and other regions of commercial tree fruit production in the United States has caused growers to abandon fruit crops and seek alternatives with less water demand in the short term. Options for mitigating long term drought in California have included crop abandonment, stress irrigation, switching to alternative crops with new plantings (Medellín-Azuara et al., 2016) and utilization of lower quality secondary water sources. It has been proposed that physiologists and breeders focus on increasing the efficiency of water use in agriculture (Wallace, 2000). Improving production efficiency and drought tolerance through cultivar or variety selection has been proposed in tree crops, such as citrus (Savé et al., 1995) Prunus species (Rieger and Duemmel, 1992), dates (Djibril et al., 2005), and coffee (DaMatta, 2004). Because tree crops can have a considerable amount of variability in terms of physiological traits, it is useful to study diversity in crop species to determine if there are cultivars that use water more efficiently or are able to be productive in stressful conditions. Because pomegranate (Punica granatum L.) is a drought tolerant crop, especially once established (Stover and Mercure, 2007), it is a candidate crop for growers wishing to switch from more water-intensive species, such as avocado, citrus or almond. Pomegranate is a drought tolerant crop that has been grown in California since the Spanish missionaries arrived from Spain and planted mongrel seeds at missions up and down the coast (Day and Wilkins, 2009; Stover and Mer

Technical Abstract: Long-term drought, coupled with tighter regulations on limited water resources have caused growers to seek drought tolerant cultivars of common tree crops in California. Yet information on pomegranate physiology is lacking, even though it is grown throughout the world in various climates. The purpose of this research was to determine the effect of time of day and cultivar on pomegranate photosynthesis and water relations, and calculate values for water-use efficiency, defined as photosynthetic carbon gain divided by water lost during transpiration. The study utilized four field-grown cultivars in their fourth year of growth (‘Eversweet,’ ‘Haku Botan,’ ‘Parfianka,’ and ‘Wonderful’), in Riverside, California. Variables analyzed included photosynthesis, stomatal conductance, transpiration, instantaneous water-use efficiency, intrinsic water-use 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. Intrinsic water-use efficiency was higher in afternoon compared to morning. There were also differences among cultivars for stomatal conductance and transpiration during the morning but not during the afternoon, with ‘Eversweet’ having significantly lower rates of stomatal conductance and transpiration than ‘Parfianka’: other cultivars were intermediate. These results further our understanding of how pomegranate cultivars function on a physiological level during different times of the day, and suggest that efficiency of production can be improved through cultivar selection. Increasing global temperatures coupled with unpredictable changes in climate threatens food security globally (Altieri and Nicholls, 2017). California has experienced extreme drought conditions for several years, causing fruit growers to face water limitations affecting production and leading to hundreds of millions of dollars in crop revenue losses in 2016 alone (Medellín-Azuara et al., 2016). To lessen the impacts of climate change and increasing temperatures on food security, it is important to utilize diversified cropping systems to reduce vulnerability to extreme climatic events as experienced in California and other regions of the United States (Altieri and Nicholls, 2017). Long term drought in California and other regions of commercial tree fruit production in the United States has caused growers to abandon fruit crops and seek alternatives with less water demand in the short term. Options for mitigating long term drought in California have included crop abandonment, stress irrigation, switching to alternative crops with new plantings (Medellín-Azuara et al., 2016) and utilization of lower quality secondary water sources. It has been proposed that physiologists and breeders focus on increasing the efficiency of water use in agriculture (Wallace, 2000). Improving production efficiency and drought tolerance through cultivar or variety selection has been proposed in tree crops, such as citrus (Savé et al., 1995) Prunus species (Rieger and Duemmel, 1992), dates (Djibril et al., 2005), and coffee (DaMatta, 2004). Because tree crops can have a considerable amount of variability in terms of physiological traits, it is useful to study diversity in crop species to determine if there are cultivars that use water more efficiently or are able to be productive in stressful conditions. Because pomegranate (Punica granatum L.) is a drought tolerant crop, especially once established (Stover and Mercure, 2007), it is a candidate crop for growers wishing to switch from more water-intensive species, such as avocado, citrus or almond. Pomegranate is a drought tolerant crop that has been grown in California since the Spanish missionaries arrived from Spain and planted mongrel seeds at missions up and down the coast (Day and Wilkins, 2009; Stover and Mer