The Photosynthetic Physiological Responses of Leaves from Different Shoots of Taxus Cuspidata to Elevated CO_2

摘要

Net photosynthetic rate (PN), transpiration rate (E), stomatal conductance (Cond), intercellular CO_2 concentration (Ci), and vapor pressure deficit on the surface (VPD) of Taxus cuspidata leaves set at a series of CO_2 concentration were investigated with the LI-COR 6400 portable photosynthesis system. For the annual shoot and the biennial shoots and blades, both PN and E increased with the increase in CO_2 concentration, but the increase in PN was larger than that in E. The maximal PN of the annual shoot (6.95 μmol·m~(-2)·s~(-1)) was larger than that of the biennial shoot (6.87 μmol·m~(-2)·s~(-1)) at a CO_2 concentration as high as 1400*10~(-6). E of the annual shoot was slightly larger than the biennial shoot but with no big disparity. Water use efficiency (WUE=PN/E) of the annual and biennial shoots went up with CO_2 concentration. WUE of the annual shoot was slightly higher than the biennial shoot, yet without significant disparity. The significant ascent of PN played a major role in the WUE of Taxus cuspidata going up with the elevated CO_2 concentration.