盐胁迫对台湾海桐幼苗光合生理及离子吸收的影响

为了解台湾海桐在盐胁迫下生长减弱的光合机理，通过温室盆栽的方法，设置0、6、9、12、15 g/kg 5个盐浓度，处理1年生台湾海桐实生苗，胁迫2个月后，对其主要光合参数、含水率变化及离子吸收与运输等指标进行测定。结果表明：随着盐浓度的升高，台湾海桐叶净光合速率(Pn)、蒸腾速率(Tr)和气孔导度(Gs)均显著下降，胞间CO₂浓度则缓慢升高，气孔限制值(Ls)和水分利用效率(WUE)均缓慢降低；随着盐浓度的升高，台湾海桐根部含水率降低，地上部分含水率升高；盐胁迫下，台湾海桐受Na⁺和Cl^-毒害严重，对K⁺和Ca²⁺的吸收受到抑制，其根部选择性吸收限制有害离子进入体内的能力有限。综合以上分析，盐胁迫下导致台湾海桐Pn下降的主要因素是非气孔限制因素，即叶肉细胞光合能力下降，这也许与其受到严重的离子毒害有关。

Effects of Salt Stress on the Photosynthetic Physiology and Ions Absorption of Pittosporum pentandrum Seedlings

In order to study photosynthetic mechanism of growth reduction of P. pentandrum under salt stress, the author used the method of pot experiment, took 1 year P. pentandrum as material and set salt solutions with the concentration of 0, 6, 9, 12, 15 g/kg. After two months stress, the main photosynthetic parameters, water content, and ions content were determined. Results indicated that Ls, Tr and Gs of P. pentandrum decreased with the increasing concentration of salt, intercellular CO₂ increased slowly, while Pn and WUE decreased slowly. The water content of P. pentandrum root decreased while that of the overground part increased with the concentration increasing. P. pentandrum poisoned by Na and Cl^- seriously under salt stress, K and Ca² absorption were restricted, the selective absorption ability was limited. In conclusion, the results suggested that the reason of Pn decrease in P. pentandrum under salt stress was non-stomata limitation, namely the photosynthetic activity descent of mesophyll cell. This might be related to seriously ion toxicity.