Activities of key enzymes involved in photosynthesis and expression patterns of corresponding genes during rapid growth of Phyllostachys edulis

Objective  The aim is to reveal the law of photosynthetic carbon assimilation of Phyllostachys edulis stem during rapid growth period. Method  The activities of ribulose-1,5-diphosphate oxidase (Rubisco), phosphoenolpyruvate carboxylase (PEPC), NADP-malate (NADP-ME), NADP-malate dehydrogenase (NADP-MDH), PEP carboxykinase (PEP-CK) and phosphoene alcohol pyruvate double kinase (PPDK) in the stems of different internodes of Ph. edulis shoots and mature leaves were determined by spectrophotometry, the relative expression of photosynthetic key enzyme genes in the corresponding parts was analyzed by real-time fluorescence quantitative polymerase chain reaction (qPCR). Result  The Rubisco activity of the 7−19 internodes of the stems was significantly lower than that of the leaves (P＜0.01). With the increase of the internodes, the Rubisco activity gradually decreased first. The activities of PEPC, NADP-ME, NADP-MDH and PPDK in the stems were the highest among the 7th internodes, which were 3.01 times, 5.69 times, 4.46 times and 4.05 times of the leaves (P＜0.01), with the increase of internodes, the activity of PEPC, PPDK, NADP-ME and NADP-MDH first significantly reduced (P＜0.01). The gene expression levels of PePEPC, PeNADP-ME, PeNADP-MDH and PePPDK in the stems were the highest among the 7th nodes, which were 3.48 times, 7.89 times, 6.48 times and 3.46 times of the leaves (P＜0.01). Increased, PePEPC, PeNADP-ME, PeNADP-MDH, PePPDK gene expression was significantly reduced (P＜0.01). Conclusion  The fast growing stems of Ph. edulis mainly fix the high concentration of CO2 in the bamboo cavity through the NADP-ME and NAD-ME pathways to reduce their own carbon loss, and the carbohydrates formed are rapidly grown and reused by the stalks. [Ch, 13 fig. 1 tab. 37 ref.]