Interactive regulation of light quality and temperature on cherry tomato growth and photosynthesis

•The suppression of stem elongation by lower temperature is spectral-independent.•Lower temperature has a most significant effect on tomato seedling morphology under red light.•Lower temperature suppresses tomato growth under red-blue light.•Lower temperature promotes root growth under monochromatic red and blue lights.•Different responses to lower temperature under red and red-blue lights involve in photoinhibition. We investigated the interactive effects of three lights (red light, R; blue light, B; red-blue light, RB) and two day temperatures (26 °C and 21 °C) on growth and photosynthesis of tomato seedling. Lowered temperature inhibited plant height but increased the angle of petiole and main stem under all lights. While the regulation on stem diameter, root and shoot growth by temperature was spectral-dependent. Compared with 26 °C, 21 °C was more beneficial to tomato healthy growth under R, but the reverse effect was exhibited under RB. A similar thermal-sensitivity of root growth was observed under B and R, while a similarity in shoot growth induced by temperature was observed under B and RB. Temperature alteration hardly changed the net photosynthetic rate (PN) in the daytime under R compared to 26 °C, but the PN was significantly reduced by 21 °C under B and RB. The most pigments were found under R, and less chlorophyll contents were observed at 21 °C than at 26 °C under all lights. The correlation analysis suggested that plant height was highly positively correlated with chlorophyll contents, while shoot and plant growth were highly negatively the βp which reflects photoinhibition. The higher positive Pearson’s coefficients were observed between plant growth and the PN, respiration in the nighttime and dark respiration, whereas a negative coefficient were observed between plant growth and photorespiration. The results suggested that higher temperature combined with RB is indisputable optimal regimes for tomato growth, but a combination of lower temperature and R regime are required further attention in plant production.