Effect of low root-zone temperature on photosynthesis, root structure and mineral element absorption of tomato seedlings

Protected tomato cultivation is often subjected to low temperature stress in early spring season in north China. While low soil temperature returns slowly then low air temperature and causes damage to development of tomatoes, thereby reducing the growth of tomatoes, which seriously reduces the yield and quality of tomatoes. This study aimed to explore the effect of low root-zone temperature (LRT, i.e., 7 and 13℃) on the photosynthesis, root architecture, mineral use efficiency and aquaporins genes of tomato. Our findings indicated that LRT decreased the photosynthetic capacity accompanying with the reduction of CO2 assimilation. Meanwhile, a decrease in stomatal density and size occurred under low root-zone temperature. Stomatal conductance tended to reduce, which was unbeneficial to the diffusion of carbon dioxide and thus decreased photosynthesis. And there have the highest enzyme activity, and sucrose content compared to control. Root traits were remarkably affected by environment temperature. LRT delay root development processes and reduce the number and diameters of ducts in root and stem, thereby limiting mineral absorption and transport. Moreover, Under low root-zone temperature, the genes related to the aquaporin and element transport all showed varying degrees of response. Collectively, these results indicate that LRT may reduces the normal physiological activity of shoots by inhibiting the water transport, which inhibits the growth of tomato seedlings. Our research can provide detailed data to clarify the response characteristics of tomato to low root-zone temperature, and provide reference for low root-zone temperature response of tomato in practice.