Carbon dioxide exchange in primary bean leaves as affected by water stress

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Abstract
Net photosynthetic rate decreased sharply to zero in the range of water potential- 8.0 to -10.4 x 105 Pa. The observed decrease in photosynthetic rate was due not only to the decrease in epidermal conductance, but also to the decrease in intraoellular conductance. Both conductances decreased in the same range of water potential. With decreasing water potential photorespiration rate decreased whereas dark respiration rate remained rather unchanged. Simultaneously CO2 compensation concentration increased. These facts constitute an indirect evidence that water stress inhibited not only transport of CO2 from atmosphere to carboxylation sites in chloroplasts, but also its conversion into photosynthates.