Photosynthetic characteristics of Salix matsudana×alba seedlings

The LI-6400 portable photosynthesis measuring system was used to determine photosynthetic characteristics of leaves in one-year-old seedlings of Salix matsudana × alba and then fitted to the Farquhar model. Results showed that (1) During the growing season,diurnal changes in leaf net photosynthetic rate (Pn) had a single-peak curve that appeared at 11 :00 o'clock with a maximum net photosynthetic rate (Pmax) of 20.8 μmol.m-2.s-1. (2) When CO2 concentration (350 μmol.mol-1) and temperature(25 ℃) were controlled,the photosynthetic light saturation point (PLS) was 1 847.6 μmol.m-2.s-1,and the photosynthetic light compensation point (PLC) was 58.1 μmol.m-2.s-1 indicating a sun-tolerant plant. (3) The Farquhar model fitting the response of leaf Pn to intercellular CO2 concentration(Ci),with light intensity(1 500 μmol. m-2.s-1) and temperature (25 ℃) being controlled,showed that when Ci400 μmol.mol-1,the maximum carboxylation rate (Vcmax) was 91.6 μmol.m-2.s-1,the CO2 compensation point (Г *) was 46.5 μmol.mol-1,and the respiration rate (Rd) was 4.9 μmol.m-2.s-1. From 400 to 1 000 μmol.mol-1 of Ci,increasing the CO2 concentration increased leaf Pn and light utilization efficiency with a leaf CO2 saturation point (PCS) of about 1 000 μmol.mol-1 and a maximum electron transport rate (Jmax) of 256.0 μmol.m-2.s-1. When Ci was supersaturated (1 000 μmol.mol-1),the rate of leaf triose phosphate utilization (UTP) was 19.7 μmol.m-2. s-1.