以典型的不同磷效率小麦品种为材料，对磷低效（L）、吸收高效（Ha）和利用高效（Hu）品种的光合特性及其生理机制进行了研究。随着叶片生长进程，供试品种旗叶CO2传导参数气孔导度（Gs）、叶肉导度（Gm）和碳酸酐酶（CA）活性，春4叶和旗叶叶绿素含量（Chl）、可溶蛋白含量（SP）、叶绿体无机磷（Pi）浓度和Mg2+-ATPase活性以及光合速率（Pn）均不断降低。光合暗反应关键酶RuBPCase活性则以叶片全展后15 d较高，叶片全展时次之，全展后30 d最低。在缺磷条件下，春4叶和旗叶各测定时期上述参数均以L较低，Ha和Hu较高。表明磷高效小麦品种（Ha和Hu）叶片光合碳同化作用的相对提高，是其光合器官捕光能力较强、光合作用的气孔限制和非气孔限制程度较低和暗反应速率较高综合作用的结果。叶片全展后15 d的RuBPCase活性及单位RuBPCase蛋白的比活性较叶片全展时有所增加，暗示着在叶片老化过程中或在磷营养逆境胁迫条件下，植物体内部分代谢酶类，如RuBPCase，存在着一定的自我调节和保护机制以维持自身功能。
The experiment was conducted using the typical wheat cultivars with different phosphorus (P) efficiencies with normal P (P+) and P deficiency (P－) two treatments to study the photosynthetic characteristics and their physiological mechanism. With the leaf growth the CO2 conductance parameters, such as stomatal conductance (Gs), mesophyll conductance (Gm) and carbonic anhydrase (CA) activity in flag leaves (Table 2), the chlorophyll content (Chl) and soluble protein content (SP) in the fourth spring leaves and flag leaves (Fig.1, Fig.5), as well as the inorganic phosphorus (Pi) content in the chloroplast (Fig.3), Mg2+-ATPase activity in the chloroplast and the photosynthetic rate (Pn) (Fig.2, Fig.4) were all decreased. Meanwhile, the key enzyme in the dark reaction of photosynthesis, RuBPCase, showed the highest activities at 15 d after leaf expansion, the middle at the early growth stage (0 d after leaf expansion), and the lowest at 30 d after leaf expansion (Fig.6). Under P-deficient condition, all the physiological parameters measured in the whole experiment in the fourth spring leaves and flag leaves of cultivars with high absorption efficiency (Ha) and high utilization efficiency (Hu) were higher than those with low P efficiency (L), implicating that the relative improvement in photosynthesis of Ha and Hu under P-deficient condition were coordinately caused by the increase of light energy capture, the decrease of the stomatal limitation and non-stomatal limitation of CO2 conductance, and the enhancement of dark reaction of photosynthesis. The higher Mg2+-ATPase activities of chloroplast in leaves of cultivars with high P efficiency were possibly related to the more Pi content of the chloroplast, RuBPCase activities and RuBPCase specific activities at 15 d after leaf expansion were higher than those at the early growth stage (0 d after leaf expansion), implying that some metabolic enzymes in plants, such as RuBPCase, had some self-regulation and protection mechanisms to maintain plant function under the conditions of leaf aging and P-deficiency.
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