修枝促接干对泡桐光合特性影响的研究

Study on Effects of Pruning to Promote Trunk Extension on Photosynthetic Characteristics of Paulownia

采用Li-6400光合分析系统,对修枝接干和对照泡桐不同冠层、不同方位叶片在不同光量子密度条件下的净光合速率(Pn)进行测定,并采用经验方程对其光反应曲线进行拟合,结果表明:(1)修枝接干可明显提高泡桐植株总体的光合潜力和适应强光环境的能力,其最大光合速率(Pm ax)、光饱和点(LSP)、光补偿点(LCP)和光合幅度(PR)在修枝后分别达23.93μmol.m-2.s-1、1 966.58μmol.m-2.s-1,53.88μmol.m-2.s-1、1 911.71μmol.m-2.s-1,较对照分别高11.85%、15.61%、29.06%、15.21%。(2)修枝接干对泡桐诸光合指标的影响在树冠下层明显大于上层,并且使其上下冠层之间的差异性显著减小。修枝后泡桐下层树冠的Pm ax、LSP、LCP、PR较对照分别高27.70%、36.74%、34.22%、36.80%,而上层差异不显著。(3)修枝接干对处于不同方位泡桐叶片的光合特性的影响在不同冠层具有不同程度的体现。在树冠上层的阳位与阴位间,修枝接干后的Pm ax、LSP、LCP和PR分别较对照有所提高,但均不显著;而在树冠下层,修枝接干后其阳位叶的Pm ax、LSP、LCP和PR分别较对照高21.80%、39.02%、28.72%和39.26%,阴位叶分别较对照高42.18%、39.35%、48.70%和39.13%,除了LCP在二处理间阳位的差异不显著外,其余的差异性均显著。

Using Li-6400 portable photosynthesis system,the photosynthetic rate of various crowns and directions of paulownia of two treatments, responding to different photosynthetic photon flux density, were measured. Fitting and regression analysis with the equation Pn = Pmax （ 1 - Co e^-αPPFD/Pmax ）, the parameters were calculated and studied. The result showed ： （ 1 ） Technique of pruning to promote trunk extension could improve photosynthetic capacity and adaptive abilities of paulownia to deal with light surroundings. The max photosynthetic rate （ Pmax ）, light saturation point （LSP）, light compensate point （LCP） and photosynthetic range （PR） of pruned paulownia were 23.93μmol·m^-2·s^-1、1966.58μmol·m^-2·s^-1,53.88μmol·m^-2·s^-1、1911.71μmol·m^-2·s^-1.Comparisions with the control, the value of the above parameters was 11.85%, 15.61%, 29.06%, 15.21% higher. （2） Technique of pruning to promote trunk extension had greater effect on lower crown than upper and made the difference between the two crowns shortened. Pmax, LSP, LCP and PR of lower crown of pruned paulownia were 27.70%, 36.74%, 34.22% and 36.80% higher than that of the control. But there was no significant difference between two treatments in the upper crown. （3） Effects of pruning to promote trunk extension on photosynthetic characteristics of various directions among the crowns were different. The parameters of Pmax, LSP, LCP and PR of pruned shade leaves and sun leaves of upper crown were higher than that of the control. But all of them were not significant different. In the lower crown of paulownia, Pmax , LSP, LCP and PR of the treated sun leaves were 21.80%, 39.02%, 28.72% and 39.26% higher than that of the control, and that of the treated shade leaves were 42. 18%, 39.35%, 48.70% and 39.13% higher than that of the control. Except LCP, the differences of all the parameters between the two treatments were significant.