Differences in photosynthetic apparatus of leaves from different sides of the chestnut canopy

Abstract

In crowns of chestnut trees the absorption of radiant energy is not homogeneous; leaves from the south (S) side are the most irradiated, but leaves from the east (E) and west (W) sides receive around 70 % and those from north (N) face less than 20 % of the S irradiation. Compared to the S leaves, those from the N side were 10 % smaller, their stomata density was 14 % smaller, and their laminae were 21 % thinner. N leaves had 0.63 g(Chl) m-2, corresponding to 93 % of total chlorophyll (Chl) amount in leaves of S side. The ratios of Chl a/b were 2.9 and 3.1 and of Chl/carotenoids (Car) 5.2 and 4.8, respectively, in N and S leaves. Net photosynthetic rate (P N) was 3.9 μmol(CO2) m-2 s-1 in S leaves, in the E, W, and N leaves 81, 77, and 38 % of that value, respectively. Morning time (10:00 h) was the period of highest P N in the whole crown, followed by 13:00 h (85 % of S) and 16:00 h with 59 %. Below 500 μmol m-2 s-1 of photosynthetic photon flux density (PPFD), N leaves produced the highest P N, while at higher PPFD, the S leaves were most active. In addition, the fruits from S side were 10 % larger than those from the N side. © 2008 Institute of Experimental Botany, ASCR.