Functioning and role of stomata in mango leaves.
Urban L., Jannoyer M.
Author Affiliation: INRA/CIRAD-Flhor, Station de Bassin-Martin, BP 180, 97455-000 Saint-Pierre, France.
: 441-446
Abstract : Understanding stomatal functioning and its role is important since stomata control both photosynthesis, i.e. the production potential, and transpiration, which in turn influences irrigation management. Moreover, it is well known that stressing conditions, which induce stomatal closure are needed for flowering in mango. A study was carried out in La Réunion, France, with 3 cultivars of 11-year-old mango trees, at 3 developmental stages: (1) young newly emerged leaves characterized by the presence of anthocyanins, (2) expanding leaves which has lost all traces of red colour, and (3) hardened mature leaves. Mango seemed to be well protected against excessive loss of water through transpiration. Stomatal frequency was high but stomata were small, which allows for quick responses to relevant stimuli. Transpiration curves showed that a loss of less than 2% of water could lead to complete stomatal closure. Stomatal conductance (gs) was also very sensitive to the ambient concentration of CO2 of the air. This is consistent with the linear relationship observed between gs and net photosynthesis all year round. High water availability and humidity of the air plus the presence of an intense sink acitivity were needed to achieve the highest gs values. Measurements of chlorophyll flourescence did not reveal any photoinhibition in high photosynthetically photon flux density and low gs conditions. The practical consequences of these observations are discussed.