Some relationships between leaf anatomy and photosynthetic characteristics of willows

The photosynthetic light response curves and stomatal conductance of four cultivars of Salix viminalis, S. burjatica and S. × dasyclados were measured using leaves growing on unshaded plants from the field. Light saturated rates of net photosynthesis (P_{n, max} ) ranged from 13.9 to 22.5 μ mol m^-2 s^-1 . Cultivars of S. viminalis had the highest values of P_{n. max} but the lowest stomatal conductances, and as a consequence they also had the highest water use efficiency. Observations on anatomical characteristics of leaves used for photosynthesis measurements indicated a significant positive correlation between P_{n. max} and the ratio of the exposed surface area of mesophyll cells to leaf surface area (A_mes /A) and chlorophyll content, and a significant negative correlation between P_{n, max} and area of fully expanded leaves. These observations show that there are a number of selection criteria based on both physiological and anatomical measurements which may be used to select for potentially high yielding willows.