Flooding, gas exchange and hydraulic root conductivity of highbush blueberry
Davies, F.S.; Flore, J.A.
Physiologia Plantarum 67(4): 545-551
Highbush blueberry plants (Vaccinium corymbosum cv. Bluecrop) growing in containers were flooded in the laboratory for 1-2, 10-14 or 35-40 days. The effects on carbon assimilation, photosynthetic response to varying CO2 and O2 concentrations, and apparent quantum yield were measured in an open flow gas analysis system, and the hydraulic conductivity of the root was measured using a pressure chamber. Root conductivity was lower, and the effect of increasing CO2 levels on carbon assimilation was less, for flooded than for unflooded plants. A reduction in O2 levels surrounding the leaves, from 21 to 2%, increased carbon assimilation in unflooded plants by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO2 fixed/mol CO2. Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O2, averaging 0.005 mol CO2 fixed/mol CO2. Apparent quantum yield decreased from 2.2 x 10-1 mol of CO2 fixed/mol light for unflooded plants to 2.0 x 10-3 and 9.0 x 10-4 for intermediate- and long-term flooding durations, respectively. Short-term flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf, indicating that the highbush blueberry is physiologically intolerant to flooding and appears to survive prolonged flooding via stomatal closure rather than through morphological or anatomical adaptations as observed in other plants.