Contrasting leaf development within the genus Syzygium

Abstract

Leaf developmental patterns were characterized in four rainforest tree species of Syzygium. Leaf optical properties, pigment changes, expansion characteristics, stomatal development, and photosynthetic rates were studied. In both S. luehmannii and S. wilsonii photosynthetic development was delayed until after full leaf expansion. Rates of O2 evolution were negative during expansion of S. luehmannii and S. wilsonii leaves and stomatal conductance was 10-20 mmol m-2 s-1 lower than for corresponding leaves of S. moorei. Stomatal conductance data and scanning electron microscopy showed that the development of functional stomata was delayed until after full leaf expansion in S. luehmannii and S. wilsonii, however, low stomatal conductance was not responsible for the lack of photosynthetic potential during leaf expansion in these species. Leaves of S. luehmannii and S. wilsonii required less than 10 d for full leaf expansion and contained anthocyanin during expansion. In contrast, leaves of S. moorei and S. corynanthum expanded slowly (20-40 d required for full leaf expansion), exhibited positive rates of O2 evolution and did not accumulate anthocyanin. In S. luehmannii and S. wilsonii anthocyanin was located in the vacuole of distinct cell layers just below the upper epidermis and the possible functions of anthocyanin accumulation are discussed. This is the first report where such variation in leaf development has been characterized in the one genus.