The Relationship Between the Thickness of Deciduous Leaves and Their Maximum Photosynthetic Rate

M c C lendon , J ohn H. (U. Delaware, Newark.) The relationship between the thickness of deciduous leaves and their maximum photosynthetie rate. Amer. Jour. Bot. 49(4): 320–322. Illus. 1962.—Data of Willstätter and Stoll (25°, saturating light and CO 2 ) are used to show that it is useful to plot photosynthetie rate per unit area as a function of the density thickness (g/cm 2 ; fresh wt) of the leaves. Data for 23 species were plotted together. If P is photosynthetie rate, T the total density thickness, E the density thickness of the epidermis, a linear relation is found using the maximum values of P, such that P = R (T ‐ E), where R is about 30 (mg CO 2 ) (hr) ‐1 (g F.W.) ‐1 . Using this expression, 15 species were represented by values of R over 23, while very young leaves, aurea 2 leaves and a few others fell in the range 8–16. A mean value of E was taken, from other data, to be about 3 × 10 ‐3 g/cm 2 , while T ranged from 10 to 40 × 10 ‐3 g/cm 2 , and P ranged from 0.2 to 0.8 (mg CO 2 ) hr ‐1 cm ‐2 for “normal” leaves.