Fruit Load Effects on Water Status and Growth of Date Palms.

The cultivation of date palms in Israel’s Arava Region is largely depending on irrigation. For the purpose of obtaining bigger, high quality fruits, date palm trees are usually thinned at the beginning of growing season. Given the irrigation water quota restrictions in this region, the investigation of fruit load effects on date palms’ water status and growth will facilitate the adjustment of fruit load and water demand of date palms.

Twelve date palms, six with fruits removed (“without fruits”) and six non-thinned (“with fruits”), were irrigated with equal amounts of water at levels sufficient for maintaining optimal soil water conditions. The sap flow in the trunk was continuously estimated by Granier heat dissipation sensors, while the frond elongation was also continuously measured by a newly developed device. Additionally, physiological functions (i.e., photosynthetic rate and stomatal conductance) and fruit growth (i.e., fruit size, mass and sugar concentration) were monitored periodically. The results showed that assimilates demand at early fruit development stages led to the increase of photosynthetic rate and stomatal conductance in trees with fruits compared to those without fruits. Frond elongation of trees with fruits was lower than those without fruits, as fruits continued to grow till maturation. The water consumption increase of trees with fruits was detected, toward the end of sugar accumulation period and throughout harvest, suggesting a certain physiological delay. Better understanding of crop load effects on date palms’ water consumption and physiological behaviors will be helpful in proper water management for sustainable cultivation of date palms in Israel’s Arava Region.