Morphologie und Physiologie von Rebblättern mit lokalen Aufwölbungen

Anatomy and photosynthesis of grapevine leaf affected by protuberant growth Grapevine cultivated under controlled environmental conditions developed leaves affected by abaxial protuberant growth in form of raised patches in the intercostal region which were examined by SEM and porometry. Cross‐sections of freeze‐fractured raised patches without prior fixation showed an increase in the number of mesophyll cells responsible for the emergence, without superficial epidermal cracks, necrosis or deformed stomata. Leaves with wide spread symptoms appeared more shiny and curled and, showed a larger reduction in photosynthesis, by up to 76 %, than in transpiration, by up to 20 %, relative to unaffected leaves. It is concluded that this reduction in photosynthesis may be caused by increased mesophyll resistance to CO 2 andless light transmission. The protuberant growth was not correlated with ambient CO 2 concentrations ranging from 340–700 μl CO 2 l −1 .