The Effects of Water Stress on Physiology and Growth of Potted Primocane-fruiting Blackberries in a Controlled Environment

A greenhouse experiment was conducted at the University of Arkansas Agricultural Research and Extension Center in Fayetteville to evaluate physiological and growth effects of water stress on potted Prime-Ark® 45 primocane-fruiting blackberries. After plants were actively growing, treatments of 40%, 70%, and 100% (CK) daily transpired water replenishment were imposed and plant response was studied. To estimate soil evaporation, water loss from pots without plants was measured. Physiological and growth responses were recorded for a 70 day experimental period. Reduced water replenishment led to reductions in net assimilation, evapotranspiration, and stomatal conductance for the 40% treatment. Net assimilation peaked at day 45 for the 70% and CK treatments (17.4 and 16.4 µmolCO₂/m² per s, respectively), with the 40% treatment being significantly lower for all dates. Vapor pressure deficit (VPD), however, was significantly greater in the 40% treatment throughout the experiment with highest measurement of 4.5 kPa at day 62. Photosynthetic water use efficiency (WUE_p) peaked at day 52 in the 70% treatment and was significantly greater than the 40% treatment. Although there were few differences in physiological measurements between the 70% and CK treatments, there were multiple differences between all treatments in growth response. The 40% treatment resulted in 89% less total cane length compared to the CK treatment. Cane diameter of the 70% treatment was 18% less than the CK treatment and the 40% treatment resulted in a 29% decrease. Total leaf area differed significantly with the CK treatment having 18,782 cm², the 70% treatment having 9598 cm² and the 40% treatment having 847 cm² leaf area. The CK treatment used the most water (58.6 L) and resulted in the greatest biomass (266 g), whereas the 70% treatment used significantly less water (33.6 L) and had less biomass (188 g). The 40% treatment biomass (46.8 g) was reduced by 83% compared to the CK treatment. The 70% treatment had no significant difference in WUE than the CK treatment. The 40% treatment water use was so minimal that it did not differ from the plant-less treatment (0.58 and 0.54 L,respectively). The 70% treatment began flowering and fruiting earlier than other treatments. These data provide a foundation for additional research on blackberry water use and irrigation management.