Contrasting leaf development within the genus Syzygium

Abstract

full leaf expansion ( Turgeon, 1989). During leaf expan- sion the formation of chloroplast ultrastructure, chloro- Leaf developmental patterns were characterized in phyll accumulation, and synthesis of other components four rainforest tree species of Syzygium. Leaf optical of the photosynthetic apparatus proceed almost in parallel properties, pigment changes, expansion character- and are often reflected in a proportional increase of net istics, stomatal development, and photosynthetic rates photosynthetic rate (Sestak, 1985). These characteristics were studied. In both S. luehmannii and S. wilsonii of photosynthetic development are found commonly in photosynthetic development was delayed until after herbaceous and deciduous plants with short leaf lifetimes. full leaf expansion. Rates of O 2 evolution were negative Leaves of many rainforest plants exhibit an unusual during expansion of S. luehmannii and S. wilsonii form of development in which the expanding leaves leaves and stomatal conductance was 10-20 mmol m'2 contain little chlorophyll, are often brightly coloured and s'1 lower than for corresponding leaves of S. moorei. where leaf greening and photosynthetic capacity develop Stomatal conductance data and scanning electron after full leaf expansion (Richards, 1952; Baker and microscopy showed that the development of functional Hardwick, 1973; Kursar and Coley, 1992a, c). Leaf colour stomata was delayed until after full leaf expansion in varies from red through blue and sometimes white. Red S. luehmannii and S. wilsonii, however, low stomatal to blue coloration is due to anthocyanin pigmentation conductance was not responsible for the lack of photo- and in developing mango (Mangifera indica) leaves antho- synthetic potential during leaf expansion in these cyanin is located in the vacuole of cells just above the species. Leaves of S. luehmannii and S. wilsonii lower epidermis (Jacquemin, 1970; Lee et al., 1987). required less than 10 d for full leaf expansion and Anthocyanins may act as visual attractants in flowers and contained anthocyanin during expansion. In contrast, fruit (Harborne, 1993). The ecophysiological role of these leaves of S. moorei and S. corynanthum expanded pigments in juvenile leaves is, however, poorly under- slowly (20-40 d required for full leaf expansion), exhib- stood, although, photoprotective (Gould et al., 1995), ited positive rates of O 2 evolution and did not accumu- UV screening (Lee and Lowry, 1980) and anti-herbivore late anthocyanin. In S. luehmannii and S. wilsonii (Coley and Kursar, 1996) functions have been proposed. anthocyanin was located in the vacuole of distinct cell Stomata play a pivotal role in controlling the balance layers just below the upper epidermis and the possible between water loss and carbon gain (Beadle et al., 1993). functions of anthocyanin accumulation are discussed. The development of stomatal conductance ( g s ), its max- This is the first report where such variation in leaf imal values and the time when this is reached, depend on development has been characterized in the one genus. the plant species and environmental conditions (Catsky ´ et al., 1985). In some species changes in g s are associated