Impact of aqueous extracts of Cinnamomum septentrionale leaf litter on the growth and photosynthetic characteristics of Eucalyptus grandis seedlings

The effects of C. septentrionale leaf litter aqueous extracts (CLAE; controls: 0 g pot(-1), A(1): 40 g pot(-1), A(2): 80 g pot(-1), A(3): 120 g pot(-1)) on seedling growth, chlorophyll content and photosynthesis of Eucalyptus grandis Hill ex Maid were examined. The CLAE at 80 or 120 g pot(-1) significantly decreased net photosynthetic rate (P-n), transpiration rate (T-r) and intercellular CO2 concentration (C-i), followed by a reduction of relative height growth and basal diameter growth. Under light saturation, apparent quantum yield, light-saturated photosynthetic rate (P-n (max)) in all treated groups and light respiration (R-d) in A(1) and A(2) showed a decreasing trend, whereas light compensation point and light saturation point had an increased tendency. Under CO2 concentration saturation, carboxylation rate, P-n max and light respiration (R-p) first increased (A(1)) and dramatically decreased (A(2) and A(3)) thereafter, whereas CO2 compensation point and CO2 saturation point increased. However, all parameters of the chlorophyll content of E. grandis seedlings were found to decrease with increased concentrations of CLAE. The results demonstrate that the aqueous extracts from C. septentrionale leaf litter have allelopathic potential and that a higher concentration of CLAE presents a risk or disadvantage to the growth of E. grandis seedling which suggests that the growth of E. grandis seedlings could be inhibited when planted under or near mature C. septentrionale plantation, and it is better not to develop mixed-plantation of C. septentrionale and E. grandis.