THE UTILIZATION OF LIGHTFLECKS FOR GROWTH IN 4 AUSTRALIAN RAIN-FORESTSPECIES

1. The ability of rain-forest plants to utilize sunflecks for growth w as investigated using the following species: Alocasia macrorrhiza, Dip loglottis diphyllostegia, Micromelum minutum and Omalanthus novo-guine nsis. 2. Growth analysis and gas-exchange measurements were used to as sess performance of the four species when exposed to either constant o r fluctuating light. 3. Final biomass (g dry wt) in D. diphyllostegia and M. minutum grown under the lightfleck regime (total daily PFD = 7. 02 mol m(-2) day(-1)) was significantly greater than in the same speci es grown under constant low PFD (total daily PFD = 4.86 mol m(-2) day( -1)). In contrast, final biomass in lightfleck O. novo-guinensis and A . macrorrhiza was significantly reduced in comparison with the same sp ecies grown under constant low PFD. 4. When grown under either constan t or fluctuating light but with the same total daily PFD, A. macrorrhi za and O. novo-guinensis had significantly lower final biomass in fluc tuating light as compared to constant light. Final biomass in D. diphy llostegia was not significantly different in either regime, while M. m inutum had significantly higher final biomass in the fluctuating light regime. 5. Responses of the four species to fluctuating or constant l ight appeared to be the result of physiological rather than morphologi cal acclimation as net assimilation rate was more closely correlated w ith relative growth rate than was leaf area ratio.