Objective   Growth and root physiology of tomato seedlings and water-dissipation of substrate under ebb-and-flow irrigation in tray cultivation were studied.

  Methods  Growth and root physiology of Ouxiu 201 Tomato seedlings as well as dissipation of moisture in the substrate irrigated by either ebb-and-flow or sprinkling method were monitored in a greenhouse experimentation.

  Results   Under the ebb-and-flow irrigation, the seedling tray weight correlated linearly with the greenhouse temperature at a correlation coefficient of −0.846 and with the RH at 0.920. The weight loss due to evaporation increased with rising temperature at a coefficient of 0.966 and RH at −0.853. In comparison to sprinkling, the ebb-and-flow irrigation resulted in higher fresh weight, dry weight, volume, and length of roots at 4-leaves-and-one-bud stage of the seedlings by 44.81%, 45.91%, 93.81%, and 9.41%, respectively, and significantly elevated antioxidant enzyme activity of the roots as well as the Pn, and Gs of the plant, but significantly lower MDA content.

  Conclusion  In the tray cultivation of tomato seedlings, the gain and loss of water in the substrate significantly correlated with the ambient temperature and RH under the ebb-and-flow irrigation which enhanced the seedling growth and fostered a vital root system with robust photosynthesis.