Poster: Ecophysiology

Abs # 49: Surface wetness induces changes in stomatal and non-stomatal limitation to photosynthesis in bean and pea, having contrast leaf wettability

Presenter:	Hanba, Yuko T., hanba@rib.okayama-u.ac.jp
Authors	Hanba, Yuko T. (A)
Affiliations:	(A): Research Institute for Bioresources, Okayama University

Leaf surface wetness occurs frequently in a natural environment, having a significant impact on leaf photosynthesis. However, the physiological mechanisms for the photosynthetic responses to wetness are not well understood. We compared the response of leaf CO₂ assimilation rate (A_max) to 72 h pre-treatment of mist between a ewettablef and a enon-wettablef species (bean; Phaseolus vulgaris and pea; Pisum sativum), and analyzed the stomatal and non-stomatal limitations to A_max. A 28% inhibition of A_max was observed in the bean leaves as a result of an alternation in non-stomatal limitation; the amount of Rubisco was decreased by 55% due to an enhanced degradation. The mist on the leaves inhibited CO₂ diffusion into the bean leaves, inducing a low CO₂ availability and a photoinhibition that may cause protein degradation in this species. In contrast, a 32% stimulation of A_max was obtained in the mist-treated pea leaves, which was attributed to an alternation in the stomatal limitation; stomatal conductance was significantly increased. The surface water may enhance CO₂ diffusion during the mist pre-treatment, causing a stomatal insensitivity to the vapor pressure deficit in this species.