Photosynthetic Response of Four Species Seedlings to Low Temperature Stress

In order to understand the photosynthetic physiology of seedlings of Ormosia pinnata and Kadsura longipedunculata, Syzygium jambos and Magnoliaceae glance at low temperature, gas exchange parameters of the four species seedlings were studied. Results showed that net photosynthetic rate (Pn), stomatal conductance (Gs) and transpiration rate (Tr) continuously decreased with increasing low temperature time for the four species seedlings. Intercellular mole fraction of CO₂(x_CO2) continuously increased and stomata limitation (Ls) continuously decreased with increasing low temperature time for O. pinnata, K. longipedunculata and M. glance seedlings, whereas x_CO2 decreased followed by an increase, and Ls increased and then decreased for S. jambos seedlings. When treated six days under low temperature, Pn of O. pinnata, K. longipedunculata, S. jambos and M. glance was -0.17, -0.21, 0.27 and 0.15 μmol·m^-2·s^-1, respectively; and their Gs was 0.005, 0.017, 0.003 and 0.006 mol·m^-2·s^-1, respectively; x_CO2 was 440.8, 439.6, 309.8 and 404.8 μmol·mol^-1, respectively; Tr was 0.11, 0.39, 0.09 and 0.11 mmol·m^-2·s^-1, respectively; and Ls was 0.046, 0.047, 0.268 and 0.103, respectively. The photosynthetic ability of the four species seedlings under low temperature was evaluated by using principal component analysis, and its order was S. jambos>M. glauca>K. longipedunculata>O. pinnata.