Photosynthetic abilities, light response, and stomatal function in six agroforestry species, Dipterocarpus tuberculatus, D. alatus, Eucalyptus camaldulensis, Hevea brasiliensis, Colocasia gigantea, and C. esculenta in responses to water deficit

We investigated the physiological and morphological responses in six agroforestry tree species Dipterocarpus tuberculatus, D. alatus, Eucalyptus camaldulensis, Hevea brasiliensis, Colocasia gigantea, C. esculenta under limited water availability. Withholding water resulted in reduced field capacity by 71%, 86%, and 48% in D. alatus, D. tuberculatus, and E. camaldulensis, respectively, resulting in wilting, leaf chlorosis, and leaf burn, respectively. Stomatal density varied among the plant species (1.4-6.2 stomata per 0.0625 mm(2)) and was unaffected by water regimes, whereas stomatal conductance (g(s)), transpiration rate (E), and water use efficiency were reduced when plants were subjected to water deficit conditions. Generally, intracellular CO2 of well-watered plants was not always maintained across increasing light intensity flux ( PAR(i)), although for E. camaldulensis this was not the case, as both well-watered and water deficit groups showed a reduction with increasing PAR(i). Net photosynthetic rate was significantly increased in well-watered plants as compared to water stressed plants, depending on the degree of PAR(i). In addition, a positive relation between g(s) and E in each plant was demonstrated.