地表臭氧浓度增加对冬小麦光合作用的影响

采用开顶式气室(OTC),在大田试验条件下系统研究了地表臭氧浓度增加对冬小麦光合作用的胁迫效应。结果表明,在(100±8)nmo.lmol-1的O3处理下,与对照相比,从抽穗期到成熟期冬小麦叶绿素a、叶绿素b和总叶绿素含量均呈先上升后降低的变化趋势,而类胡萝卜素的含量和Chla/b的比值则分别持续升高和下降,净光合速率和气孔导度在抽穗初期无明显下降,但是随着熏蒸时间的增加下降幅逐步变大。在整个试验期间冬小麦表观量子产额、单位面积叶片活性以及PSII最大光量子效率均无明显降低,而蒸腾速率、暗呼吸速率、光补偿点以及最大光合速率却受到较大程度的抑制。当采用(150±8)nmol.mol-1O3处理时,各生育期中小麦叶片类胡萝卜素含量、暗呼吸速率和光补偿点均显著高于对照组,其余参数均较对照组明显降低。以上结果表明,地表臭氧浓度增加对冬小麦光合作用的影响阈值在100 150 nmol.mol-1之间,且随着熏蒸时间的增加,叶片光合作用受抑制的程度逐步增强。

Experiment with effects of increased surface ozone concentration upon winter wheat photosynthesis

Studied are stress effects of surface increased ozone concentration on winter wheat photosynthesis in an open field in open top chambers (OTCs). Results show that results under the treatment of (100±8) nmol?mol-1 of ozone are compared to those from the control run (CK), indicating that from the heading to mature stage contents of chlorophylls a and b as well as the total increase first and then drop, but the carotenoid content and the value of value of chl a/b keep steadily rising and declinling, respectively, there is no significant decrease in the net photosynthetic rate and stomatic conductance during the early stage of heading but their drops increase gradually with prolonged smoking time. In the whole experiment the apparent quantum yield and activation per unit area and PSII maximum light quantum efficiency of winter wheat display no perceptible reduction while the transpiration rate, dark respiratory rate, light compensation point and maximal photosynthetic rate are suppressed more greatly. For the treatment of (150±8) nmol?mol-1 of O3 the leaf carotenoid content, dark respiratory rate and light compensation point are all well above those of the CK in all growth/development stages, the other parameters being significantly below. These results indicate that the increase in surface ozone concentration has its photosynthesis threshold range over 100-150 nmol?mol-1 and as the smoking time increases, and the degree at which the leaf photosynthesis is suppressed becomes intensified step by step.