ORIGINAL RESEARCH article
Front. Plant Sci.
Sec. Plant Abiotic Stress
Coordinated Regulation of Tomato Sugar Accumulation by Relative Humidity and Field Capacity through Source–Sink–Transport Balance
Provisionally accepted
- 1Nanjing University of Information Science and Technology, Nanjing, China
- 2Shandong Academy of Agricultural Sciences, Jinan, China
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To clarify the regulatory mechanism underlying the interaction between air relative humidity (RH) and soil moisture (field capacity, FC) on sugar accumulation in tomato fruits, this study used two tomato cultivars, 'Xiuzhen' and 'Jinhong 208', as materials. Four RH levels (40%, 60%, 80%, and 95%) and two FC levels (40% and 80% FC) were established in artificial climate chambers to systematically analyze the relationships among photosynthesis, transpiration, vascular transport, sugar metabolism enzyme activity, and sugar accumulation. The results showed that low soil moisture (40% FC) reduced the photosynthetic rate but significantly increased sugar metabolism enzyme activity, thereby promoting sugar accumulation. In contrast, high soil moisture (80% FC) was associated with higher photosynthetic rates but lower sugar-metabolizing enzyme activity. High air humidity (95% RH) markedly associated with lower photosynthesis, stomatal conductance, and sugar metabolism enzyme activity, accompanied by a significant decrease (P < 0.01) in glucose, fructose, and sucrose contents; conversely, low humidity promoted sugar accumulation. Both 'Xiuzhen' and 'Jinhong 208' achieved the highest soluble sugar content under 40% RH and 40% FC conditions. Gray relational analysis revealed that FC had a stronger influence on photosynthesis, while RH had a more pronounced effect on sugar metabolism. Under sufficient water supply, air humidity management played a greater role in regulating fruit quality. Path analysis indicated that RH exerted significant negative effects on sugar accumulation via reduced transpiration (path coefficient = –0.590), sugar metabolism enzyme activity (–0.358), and phloem transport (–0.424). In contrast, FC promoted phloem transport (0.680) but somewhat associated with lower enzyme activity (–0.500). Humidity is closely related to sugar accumulation, but weakly related to yield and its components. This study reveals the specific strategies of sugar regulation among different tomato cultivars and provides insights for humidity and irrigation optimization in greenhouse tomato production.
Keywords: Phloem transport, Photosynthesis, Sugar metabolic enzymes, Tomato, transpiration, Xylem flow
Received: 25 Dec 2025; Accepted: 09 Feb 2026.
Copyright: © 2026 Han, Zhang, Hao, Sun and Lin. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Wei Han
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