[Response of Dolichomitriopsis diversiformis photosynthesis rate to light, air temperature and plant water content].

ABSTRACT

The net photosynthetic rate (Pn) of Dolichomitriopsis diversiformis(Mitt.) was measured under controlled air temperature (Ta), plant water content (PWC) and irradiance (Photosynthetically Active Radiation, PAR) in laboratory. The results showed that Pn was closely related to PAR, Ta and PWC. The response curve of Pn to PAR was a right angle hyperbola, and the parameters were affected by Ta and PWC. The Pn reduction was great when PWC was low and Ta was high, or when PWC was high and Ta was low. The peak Pn (Pmax) was observed underweak light (PAR < 200 mumol.s-1.m-2) and relatively low (50%-80%) PWC. Under higher Ta, Pmax was higher, but decreased when Ta was higher than 25 degrees C. The PWC range within which Pmax occurred increased in accordance with the increase of PAR. When PAR was lower than 200 mumol.s-1.m-2, the Ta range within which Pmax occurred was relatively high (20-25 degrees C), and Pmax increased with the increase of PWC. When PWC was higher than 80%, Pmax decreased with the increase of PWC. The Ta range within which Pmax occurred decreased in accordance with the increase of PAR. Under moderate light (230 < PAR < 270 mumol.s-1.m-2), the sensitivity of Pn response to Ta and PWC was higher than that under higher or lower light. The Pn response to Ta and PWC was saddle-like, and its parameters were altered according to the variation in PAR.