Low Temperature and Weak Light Affect Greenhouse Tomato Growth and Fruit Quality

To investigate the effects of low temperature (LT) and weak light (WL) on tomato (Solanum lycopersicum L., cv.) during flowering and fruit-setting periods, a controlled experiment was conducted. Two levels of day/night temperature and PAR were set: S1 (18/8°C, 200 μmol m-2 s-1), S2 (12/2°C, 200 μmol m-2 s-1), S3 (18/8°C, 80 μmol m-2 s-1), and S4 (12/2°C, 80 μmol m-2 s-1 ), taking 28/18°C and 600 μmol m-2 s-1 as control (CK). The results showed that during stress stage, the Chlorophyll (Chl) a, photosynthetic rate at irradiation saturation (Pmax), light saturation point, stomatal conductance, stomatal limitation value, maximal photochemical efficiency of PSII (Fv/Fm), electron transport rate of PSII, and catalase activity of S1, S2, S3, and S4 were lower than that of CK, while the Chl b, carotenoid, light compensation point, superoxide dismutase (SOD), and malondialdehyde (MDA) were opposite. Vitamin C, soluble solid, soluble protein, and lycopene were lower than that of CK, while organic acid was opposite. Plant height and stem diameter significantly correlated with Chl and Pmax. After 25 d of recovery, the Fv/Fm, SOD, and MDA for S1 and S2 almost could recover to CK level, but the values for S3 and S4 could not recover to CK level.