Department of Chemistry and Biochemistry, Haryana Agricultural University, 125 004, Hissar, India.
Photosynth Res. 1986 Jan;8(2):113-22. doi: 10.1007/BF00035242.
Activities of key enzymes of Calvin cycle and C4 metabolism, rate of (14)CO2 fixation in light and dark and the initial products of photosynthetic (14)CO2 fixation were determined in flag leaf and different ear parts of wheat viz. pericarp, awn and glumes. Compared to the activities of RuBP carboxylase and other Calvin cycle enzymes viz. NADP-glyceraldehyde-3-phosphate dehydrogenase, NAD-glyceraldehyde-3-phosphate dehydrogenase and ribulose-5-phosphate kinase, the levels of PEP carboxylase and other enzymes of C4 metabolism viz. NADP-malate dehydrogenase, NAD-malate dehydrogenase, NADP-malic enzyme, NAD-malic enzyme, glutamate oxaloacetate transaminase genase, NADP-malic enzyme, NAD-malic enzyme, glutamate oxaloacetate transaminase and glutamate pyruvate transaminase, were generally greater in ear parts than in the flag leaf. In contrast to CO2 fixation in light, the various ear parts incorporated CO2 in darkness at much higher rates than flag leaf. In short term assimilation of (14)CO2 by illuminated ear parts, most of the (14)C was in malate with less in 3-phosphoglyceric acid, whereas flag leaves incorporated most into 3-phosphoglyceric acid. It seems likely that ear parts have the capability of assimilating CO2 by the C4 pathway of photosynthesis and utilise PEP carboxylase for recapturing the respired CO2.
卡尔文循环和 C4 代谢关键酶的活性、光暗条件下（14）CO2 的固定速率以及光合作用（14）CO2 固定的初始产物，在小麦的旗叶和不同的穗部部位（如颖壳、芒和内稃）中进行了测定。与 RuBP 羧化酶和其他卡尔文循环酶（如 NADP-甘油醛-3-磷酸脱氢酶、NAD-甘油醛-3-磷酸脱氢酶和核酮糖-5-磷酸激酶）的活性相比，PEP 羧化酶和 C4 代谢的其他酶（如 NADP-苹果酸脱氢酶、NAD-苹果酸脱氢酶、NADP-苹果酸酶、NAD-苹果酸酶、谷氨酸草酰乙酸转氨酶、NADP-苹果酸酶、NAD-苹果酸酶、谷氨酸草酰乙酸转氨酶和谷氨酸丙酮酸转氨酶）的水平在穗部通常比在旗叶中更高。与光下的 CO2 固定相比，各种穗部在黑暗中固定 CO2 的速率比旗叶高得多。在光照下对（14）CO2 的短期同化中，大部分（14）C 存在于苹果酸中，而 3-磷酸甘油酸中的含量较少，而旗叶则将大部分（14）C 同化到 3-磷酸甘油酸中。似乎穗部有通过光合作用的 C4 途径同化 CO2 的能力，并利用 PEP 羧化酶重新捕获呼吸作用释放的 CO2。
