GROWTH AND PHOTOSYNTHETIC RESPONSES TO TEMPERATURE IN SEVERAL MALAYSIAN TREE SPECIES

Abstract

Responses of seed germination, seedling growth, and photosynthesis to temperature regimes were determined in four dipterocarp, two non-dipterocarp and an exotic planting species from Peninsular Malaysia. All the seeds and seedlings showed chilling injuries below 15° C, although their occurrence time differed from species to species. Species such as Shorea assamica and Duabanga grandifolia which are found mainly in the monsoon forests of India and Myanmar could tolerate longer periods at 10 to 15°C than the species like Shorea parvifolia and Dryobalanops aromatica which are confined to the evergreen rain forests. The relative growth rate, net assimilation rate, net photosynthesis rates, and stomatal conductance of the tropical tree species were similar in magnitude to those of the temperate ones, while these rates for shade tolerant species like D. aromatica and Neobalanocarpus heimii tended to be lower than those for light demanding species such as Du. grandifolia and Bombax valetonii. Growth and photosynthetic characteristics of dipterocarp species, especially those in evergreen rain forests such as S. parvifolia, N. heimii and D. aromatica showed narrow plasticity to environmental temperature changes.