Environmental Effects on Dynamics of Fruit Growth and Photoassimilate Translocation in Tomato Plants. (3). Effect of Salt Stress.

Summary

This study examined how salt stress alters the relative contributions of phloem and xylem sap fluxes to tomato fruit development in hydroponically grown plants. Under saline conditions, xylem sap flux declined by 34% whilst phloem flux remained stable, leading to a 25% reduction in fruit growth. The altered water balance and increased reliance on phloem-sourced photoassimilates resulted in smaller fruits with higher sugar content but increased susceptibility to blossom-end rot, providing quantitative evidence for the physiological mechanisms underlying salt-stress effects on fruit quality.

Regional applicability

Whilst the study was conducted in Japan using hydroponic cultivation, the findings on salt stress effects on fruit physiology are applicable to United Kingdom protected horticulture and to regions where soil or water salinity is a concern. The mechanistic understanding of phloem versus xylem contributions to fruit growth could inform management strategies in UK glasshouse tomato production, though direct transferability to field conditions or soil-based systems requires consideration of differing water and nutrient availability regimes.

Key measures

Phloem sap flux; xylem sap flux; fruit expansive growth rate; fruit water balance components; sugar concentration; blossom-end rot incidence; pedicel sap flux dynamics

Outcomes reported

The study measured phloem and xylem sap fluxes through the pedicel and their effects on fruit expansive growth, water balance, and fruit quality under salt stress. Salt stress reduced xylem sap flux by 34% and fruit expansive growth by 25%, whilst phloem sap flux remained largely unaffected, resulting in smaller fruits with higher sugar concentrations and increased blossom-end rot incidence.

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