Published online by Cambridge University Press: 12 June 2017
The capacity for photosynthetic acclimation to light intensity in Sakhalin knotweed (Polygonum sachalinense F. Schmidt) was studied by growing plants in four light environments [out-of-doors in full sun and under 50% shade, and in a growth chamber at 800 μE m2 sec-1 photosynthetically active radiation, 400 to 700 nm (PAR) and 150 μE m-2 sec-1 PAR], and then determining, with an infrared gas analyzer (IRGA), the photosynthetic rates of single leaves exposed to a range of light intensities from 100 to 2000 μE m2 sec-1 PAR. The plants grown in high light had higher photosynthetic rates throughout the range of 100 to 2000 μE M-2 sec-1 PAR. Maximum photosynthetic rates were 37 mg CO2 dm-2 h-1 for plants grown in full sun out-of-doors and 16.5 mg CO2 dm-2 h-1 for plants grown in low light in the growth chamber. There was no indication of positive adaptation to low light intensity in Sakhalin knotweed. Differences in light-saturated photosynthetic rates were closely related to differences in mesophyll conductance and chlorophyll content per unit leaf area.