Flooding, gas exchange and hydraulic root conductivity of highbush blueberry

Abstract

Highbush blueberry plants ( Vaccinium corymbosum L. cv. Bluecrop) growing in containers were flooded in the laboratory for various durations to determine the effect of flooding on carbon assimilation, photosynthetic response to varying CO 2 and O 2 concentrations and apparent quantum yield as measured in an open flow gas analysis system. Hydraulic conductivity of the root was also measured using a pressure chamber. Root conductivity was lower and the effect of increasing CO 2 levels on carbon assimilation less for flooded than unflooded plants after short‐(i‐2 days), intermediate‐(10–14 days) and long‐term (35–40 days) flooding. A reduction in O 2 levels surrounding the leaves from 21 to 2% for unflooded plants increased carbon assimilation by 33% and carboxylation efficiency from 0.012 to 0.021 mol CO 2 fixed (mol CO 2 ) −1 . Carboxylation efficiency of flooded plants, however, was unaffected by a decrease in percentage O 2 , averaging 0.005 mol CO 2 fixed (mol CO 2 ) −1 . Apparent quantum yield decreased from 2.2 × 10 −1 mol of CO 2 fixed (mol light) −1 for unflooded plants to 2.0 × 10 −3 and 9.0 × 10 −4 for intermediate‐ and long‐term flooding durations, respectively. Shortterm flooding reduced carbon assimilation via a decrease in stomatal conductance, while longer flooding durations also decreased the carboxylation efficiency of the leaf.