Photosynthetic Characteristics of Wet Tropical Forest Plants

Abstract

The leaves of forest trees of the wet tropics are generally large and live an average of about one year. They, however, vary greatly, dependent on site, in their average leaf specific weights and nitrogen contents, encompassing values found for leaves of plants inhabiting arid climates. Those factors which affect photosynthesis, either directly or indirectly, light, humidity, and CO2 concentration, vary greatly from the top of the forest canopy to the forest floor. Those species which inhabit the understory, where the radiation level is only a few percent of that received in the open, utilize brief sunflecks to fix a large fraction of their daily carbon gain. They are able to respond quickly to an abrupt increase in radiation since stomata remain open even at very low light intensities. There is little information available on the photosynthetic responses of tropical trees to CO2, humdity, temperature, and water potential.