Abstract
Tomato flower abscission is a critical agronomic problem directly affecting yield. It often occurs in greenhouses in winter, with the weak light or hazy weather leading to insufficient photosynthates. The importance of carbohydrate availability in flower retention has been illustrated, while relatively little is understood concerning the mechanism of carbohydrate regulation on flower abscission. In the present study, we analyzed the responding pattern of nonstructural carbohydrates (NSC, including total soluble sugars and starch) and the potential sugar signal pathway involved in abscission regulation in tomato flowers under shading condition, and their correlations with flower abscission rate and abscission-related hormones. The results showed that, when plants suffer from short-term photosynthesis deficiency, starch degradation in flower organs acts as a self-protection mechanism, providing a carbon source for flower growth and temporarily alleviating the impact on flower development. Trehalose 6-phosphate (T6P) and sucrose non-fermenting-like kinase (SnRK1) signaling seems to be involved in adapting the metabolism to sugar starvation stress through regulating starch remobilization and crosstalk with IAA, ABA, and ethylene in flowers. However, a continuous limitation of assimilating supply imposed starch depletion in flowers, which caused flower abscission.
Highlights
In flowering crops, florescence is the initiation of reproductive growth which determines fruit set and the future yield formation directly
The source leaves of shaded plants exhibited a significant lower net photosynthetic rate (Pn) when compared to control plants under the normal sunlight condition (Figure 1)
Trehalose 6-phosphate (T6P) and SnRK1 signaling seem to be involved in adapting metabolism to sugar starvation stress through regulating starch remobilization in flowers
Summary
Florescence is the initiation of reproductive growth which determines fruit set and the future yield formation directly. As developing flowers are strong sinks for sugars, there will be a distinct allocation shift to floral organs, and this allocation strategy will affect the flowers’ fate. These crops are sensitive to carbohydrate fluctuation during flowering. Any perturbation of the sugar metabolism and supply from source to sink (floral organ) leads to gametophyte abortion, reducing the success of fertilization and increasing the flower abscission rate [2]. Carbohydrate, as a metabolic resource for intermediary metabolism, is related to flower quality and initial ovary growth and retention [3,4,5]. Trehalose 6-phosphate synthase (TPS) genes showed a different expression pattern in abscising apple fruitlets; this has not yet been further investigated [12]
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