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Some anatomical characteristics in leaves relating to hydraulic conductance and stomatal conductance were examined in six temperate deciduous tree species. The fourth power of the radius of the conducting elements in xylem ( r 4) and the area of mesophyll and epidermal cells per unit length of leaf cross-section ( u ) were high in leaves with high hydraulic conductance (L). Stomatal conductance ( g s) and stomatal sensitivity to an increase in leaf water potential ( s i) correlated positively with the length of stomatal pore ( l ), but negatively with the guard cell width ( z ) and the length of the dorsal side of the guard cells ( l d). Stomatal sensitivity to a decrease in leaf water potential ( s d) correlated negatively with l and positively with z and l d. The anatomical characteristics associated with hydraulic conductance ( r 4 and u ) and those associated with stomatal conductance and sensitivity to changes of leaf water potential ( l , z and l d) were correlated. We conclude that hydraulic conductance may depend on anatomical characteristics of xylem, mesophyll and epidermis, and stomatal conductance and its sensitivity to changing water potential may depend on anatomical characteristics of stomata. The correlation of shoot hydraulic conductance with stomatal conductance and its sensitivity may be based largely on the correlation between the anatomical characteristics of the water conducting system and stomata in these trees.
Aasamaa et al. (Mon,) studied this question.