Biostimulants alleviate temperature stress in tomato seedlings

Abiotic stresses result in tremendous loss of plant yield during global climate change. Biostimulants, as an environmental-friendly innovation in agricultural practice, can improve plant growth and development, and minimize adverse effects caused by abiotic stresses. In this study, three biostimulants, Boosten, Megafol and Isabion (1:500 dilution) were applied to leaf surfaces of tomato seedlings at four-leaf stage and their effects on seedlings growth after 7 and 15 days of treatment were cross-checked at 10 °C, 25 °C and 35 °C. We observed that the foliar application of biostimulants could promote the accumulation of plant biomass to various degrees under either low or high temperature stress compared to the water control. Specifically, Boosten and Megafol treatments boosted the synthesis of chlorophylls and photosynthetic rates, thereby enhanced the vitality of plants. Under high temperature, biostimulants especially Boosten and Megafol significantly promoted the growth of both aboveground and underground tissues leading to the increased tomato sound seedling index, whereas Isabion mainly improved the growth of aboveground tissues. Clustering analysis and principal component analysis further confirmed that under temperature stress, various biostimulants had different promotion effects on tomato seedlings. This may be explained by the plant species specificity in respond to biostimulants with different chemical compositions and more importantly, by the different responding mechanisms of biostimulants to cold or heat stress. Overall, Boosten was more effective under temperature stress.