Interactive effect of branch source-sink ratio and leaf aging on photosynthesis in pistachio

Frontiers in Plant Science

Plant Science

Emily Santos¹  Bárbara Blanco-Ulate¹  Louise Ferguson¹  Paula Guzmán-Delgado¹  Jaclyn A. Adaskaveg¹  Giulia Marino¹  Maciej A. Zwieniecki¹  Eduardo Fernández-Suela² 

[1] Department of Plant Sciences, University of California, Davis, Davis, CA, United States;Instituto Madrileño de Investigación y Desarrollo Rural, Agrario y Alimentario, Madrid, Spain;

关键词: light response curve;    senescence;    non-structural carbohydrates;    alternate bearing;    thinning;    defoliation formatted: default paragraph font;    font: formatted: font: not italic;   

DOI  :  10.3389/fpls.2023.1194177

 received in 2023-03-26, accepted in 2023-06-27,  发布年份 2023

来源: Frontiers

【 摘 要 】

Tree source-sink ratio has a predominant and complex impact on tree performance and can affect multiple physiological processes including vegetative and reproductive growth, water and nutrient use, photosynthesis, and productivity. In this study, we manipulated the branch level source-sink ratio by reduction of photosynthetic activity (partial branch defoliation) or thinning branch fruit load early in the growing season (after fruit set) in pistachio (Pistacia vera) trees. We then characterized the leaf photosynthetic light response curves through leaf aging. In addition, we determined changes in leaf non-structural carbohydrates (NSC) and nitrogen (N) concentrations. In leaves with high source-sink ratios, there was a gradual decrease in maximum net photosynthetic rate (ANmax) over the growing season, while in branches with low source-sink ratios, there was a sharp decline in ANmax in the first two weeks of August. Branches with high-sink showed an up-regulation (increase) in photosynthesis toward the end of July (at 1,500 growing degree days) during the period of rapid kernel growth rate and increased sink strength, with ANmax being about 7 μmol m-1 s-1 higher than in branches with low-sink. In August, low source-sink ratios precipitated leaf senescence, resulting in a drastic ANmax decline, from 25 to 8 μmol m-1 s-1 (70% drop in two weeks). This reduction was associated with the accumulation of NSC in the leaves from 20 to 30 mg g-1. The mechanisms of ANmax reduction differ between the two treatments. Lower photosynthetic rates of 8-10 μmol m-1 s-1 late in the season were associated with lower N levels in high-sink branches, suggesting N remobilization to the kernels. Lower photosynthesis late in the season was associated with lower respiration rates in low-source branches, indicating prioritization of assimilates to storage. These results can facilitate the adaptation of management practices to tree crop load changes in alternate bearing species.

【 授权许可】

Unknown   
Copyright © 2023 Marino, Guzmán-Delgado, Santos, Adaskaveg, Blanco-Ulate, Ferguson, Zwieniecki and Fernández-Suela