© 1993 Heron Publishing—Victoria, Canada
Growth and photosynthesis of tropical forest tree seedlings (Bischofia javanica Blume) as influenced by a change in light availability
M. Kamaluddin and J. Grace
Institute of Ecology and Resource Management, University of Edinburgh, Darwin Building, Edinburgh EH9 3JU, U.K. / Received January 16, 1992
Summary
Acclimation in seedlings of Bischofia javanica Blume, which are commonly found in canopy gaps in the moist forests of tropical Asia, to a change in light availability was
examined in a controlled environment simulating forest shade and daylight. Seedlings were grown in a high (1000 µmol m–2 s–1; red/far-red, 1.45) or low (40 µmol m–2 s–1; red/far-red, 0.10) light regime and then transferred to the contrasting light environment for nine weeks. Control seedlings
were maintained in the same light regime throughout the study. The availability of light influenced relative growth rate through
morphological and physiological
adjustments. Transferred seedlings retained the leaves that had been developed before transfer, and no leaf-shedding was observed
till the end of the experiment. Leaves formed in the new light regime were physiologically and morphologically identical to
those of the corresponding controls. High-light seedlings transferred to low light displayed significantly lower relative
growth rate than the low-light controls because of a lower leaf area ratio carried over from the previous high-light environment.
A reverse pattern of response with respect to relative growth rate was observed for the low-light seedlings transferred to
high light compared to the high-light controls. The higher relative growth rate in the low-light seedlings transferred to
high light was the result of higher net assimilation rate and higher leaf area ratio. The higher leaf area ratio in the low-light
seedlings transferred to high light was the consequence of the effects of
previous environment, and the relatively lower net assimilation rate in the high-light control seedlings was, at least partly,
due to the effects of self-shading rather than to the photosynthetic capacity of the leaves. The results suggest that the
species has a wide acclimation potential to a change in light availability that might occur in nature following gap creation
or canopy closure.
Keywords:
leaf area ratio, leaf morphology, leaf physiology, leaf weight ratio, light acclimation, net assimilation rate, relative growth
rate, shade, specific leaf area.
