Abstract:

Photosynthesis parameters, contents of carbohydrate such as glucose, fructose, and starch, activities of invertase and amylase, along with their relationships were studied in the functional leaves of one-year-old twigs of two grape cultivars “Beta” and “Cabernet Sauvignon” after the flower stage. Results showed that the apparent photosynthesis rate and the Rubisco carboxylation efficiency decreased after the flower period. Meanwhile, the fructose content kept constant but the contents of glucose and sucrose increased with fluctuation patterns in the two cultivars’ functional leaves. In the same stage, the neutral invertase had a small variation but the α-amylase and the β-amylase had higher activities in the former stage and the latter stage, respectively, in both “Beta” and “Cabernet Sauvignon” functional leaves. After the flower period, the Rubisco carboxylation efficiency had a highly significant positive correlation with the apparent photosynthesis rate, and a significant negative correlation with the ratio of glucose/(fructose+sucrose) in “Beta” and “Cabernet Sauvignon” functional leaves. There were highly significant positive correlation and significant positive correlation between the glucose contents and the activities of β-amylase in “Beta” and “Cabernet Sauvignon” functional leaves, respectively. It can be deduced that: after the flower stage, the accumulation of glucose in “Beta” and “Cabernet Sauvignon” functional leaves is mainly generated from the metabolism pathway of β-amylase, which bring about the feedback inhibition to the photosynthesis of the two cultivars’ functional leaves.