Abstract:In this study,we examined the influence of low temperature and low light intensity stress on the soluble sugar,soluble protein,and free amino acid content in different organs and on dry matter distribution in greenhouse tomato seedlings.We used Photosynthetically Active Radiation (PAR) at 800 μmol·m-2·s-1 and temperature of 25℃ as control(CK),and set up an experiment involving six treatments[L1T1 (PAR 200 μmol·m-2·s-1,4℃),L1T2 (PAR 200 μmol·m-2·s-1,6℃),L1T3 (PAR 200 μmol·m-2·s-1,8℃),L2T1 (PAR 400 μmol·m-2·s-1,4℃),L2T2 (PAR 400 μmol·m-2·s-1,6℃),and L2T3 (PAR 400 μmol·m-2·s-1,8℃)] that were monitored for 6,12,24,48,and 72 h,respectively.The results showed that the dry matter distribution ratio in the underground part of the plant was lower than that in the ground-level parts and opposite to that in the aboveground part.Low temperature and low light intensity stress significantly reduced the soluble sugar,soluble protein,and free amino acid content of the stems and leaves.The soluble sugar content in the roots was not consistent with the aboveground parts but was highest in the roots,stems,and leaves (94.88 mg·g-1,77.09 mg·g-1 and 41.62 mg·g-1,respectively) after 72 h in the L2T3 treatment.The soluble protein content in the roots was not consistent with the aboveground part but was highest in both the stems and leaves after 12 h in the L2T3 treatment and lowest after 72 h in the L1T1 treatment.The free amino acid content in different organs showed an effect opposite to that of the soluble protein content when the stress exposure time was prolonged.Low light had less of an effect on dry matter and nutrient content than low temperatures did.The results showed that dry matter and nutrients were distributed to the ground-level part of the plant during the early stages of exposure to stress,and then to the root system after 24 h of stress exposure.The results provide a theoretical basis for improved loss prevention due to low temperature or low light stress in crops grown in facilities such as greenhouses.