Heat stress can drastically reduce crop yields by 50% to 70%, posing significant challenges for organically growing hydroponic tomatoes in controlled environments.
This issue is largely due to the inadequate stress tolerance of current tomato cultivars, which limits their fruit set and yield optimization. A recent study evaluated the effects of three biostimulants—Liquid Seaweeds, MycoApply V R, and MycoLife—applied to tomato plant leaves every 7 days, starting 4 weeks after planting. These biostimulants were tested at application intervals of 4, 8, 12, and 16 weeks to determine the optimal frequency for enhancing plant growth, physiology, phenology, fruit yield, and quality. The study used a strip plot design with biostimulants as the main treatments and application frequency as subplots. Results showed that foliar application of biostimulants improved plant vigor under heat stress conditions compared to untreated controls. Notably, MycoApply V R applied over 12 weeks significantly enhanced chlorophyll synthesis and photosynthesis rates, boosting overall plant productivity. Tomato plants of the 'Valdeon RZ' variety treated with MycoApply V R exhibited a 20% increase in net assimilation rate, a 40% increase in stomatal conductance, and reductions in transpiration loss (28%) and electrolyte leakage (31%), while maintaining intercellular CO2 levels. Additionally, flowering occurred 5 days earlier in MycoApply V R-treated plants, which also showed improved fruit set (19%), pollen viability (37%), and fewer flower drops (10%) compared to controls. Among the different application frequencies, MycoApply V R applied for 12 weeks resulted in superior plant growth and tomato productivity. It significantly increased marketable fruit yields by 30% and enhanced postharvest quality, including firmness, soluble solids, acidity, and color dynamics.
Analysis using correlogram, heat map, and cluster analysis confirmed that biostimulants had various positive effects on tomato growth and productivity under heat stress. Consequently, MycoApply V R emerged as a promising biostimulant with strong heat stress tolerance capabilities for organic hydroponic systems.
Dash, Prosanta & Mehanical, Bing & Leskovar, Daniel. (2025). Biostimulants Alleviate Heat Stress in Organic Hydroponic Tomato Cultivation: A Sustainable Approach. 60. 344-352. 10.21273/HORTSCI18039-24.
Source: Research Gate