Analysis of photosynthetic ability and related physiological traits in nodal leaves of grape

Abstract

Fruiting shoots are comprised of leaves, fruits, and branches, which determine the grape yield and the quality of produce. Fruiting shoots are also the important structural unit for studying the relationship between the source and sink. The number of leaves, leaf area, photosynthetic activities, and density are directly or indirectly affecting the ability of the fruiting shoot to fix CO2 and provide a carbon source for the fruit growth and development. ‘Summer Black’ is used as the main test material and observed certain differences in appearance, microstructure, photosynthetic pigments, relative water content (RWC), organic acids, carbohydrates, mineral elements, and photosynthetic capacity at different nodal leaves. The net photosynthetic rate (A) was significantly positively correlated with leaf shape parameters (the ratio between branch point to lobe tip and distal sinus to petiolar junction), leaf structure thickness, RWC, carotenoids, soluble sugars, and organic acids, but it was significantly negatively correlated with intercellular CO2 concentration (Ci), Chlorophyll b and phosphorus content. The variations in magnesium, water, glucose, and fructose content in leaves matched the expression patterns of aquaporin, magnesium transporter, and sugar metabolism-related genes in various nodal leaves. In addition, the physiological traits and photosynthetic capacity at different nodal leaves of ‘Shine Muscat’ and ‘Kyoho’ were similar to those of ‘Summer Black’. The results of this study will provide a reference for the differences in leaf sink–source effects at different nodes and provide a basis for reasonably removing leaves.