Effect Of Sub-low Temperature At Seedling Stage On Reproductive Growth In Tomato And The Method Of Chilling Tolerance Identification

10 tomato varieties (lines) with different genotype were used as experiment materials in this study. Effects of 10/5°C at seedling stage (2-8 leaf stage) on net photosynthesis rate, chlorophyll fluorescence parameters and reproductive growth of tomato, as well as the most suitable index to estimate tomato chilling tolerance ability were studied, with the purpose to supply theory support for tomato breeding and cultivation. The main result was as the following.1. Net photosynthesis rate (Pn) and chlorophyll fluorescence parameters (F_v/F_m,Φ_{PSII and qP} of tomato leaves were influenced after the tomato plant suffered from low temperature stress at 7-8 leaf stage. There was significant difference during stress for Pn, F_v/F_m andΦ_PSII, while qP not. In nature condition the recovery levels ofΦ_PSII, qP were relevant to recovery time, while F_v/F_m and Pn's were relevant to genotype.2. After suffered from low temperature at 7-8 leaf stage, changes of photosynthesis of tomato leaves was relevant to stomata and water stress, but irrelevant to chlorophyll content.3.After treated with sub-low temperature at 2-8 leaf stage, especially at 7-8 leaf stage, the flowering date was postponed and the fruit setting rate of the first florescence was significantly influenced, and the irregular fruit rate was increased especially at 2-3 and 7-8 leaf stages.4. Sub-low temperature at seedling stage influenced tomato reproductive growth and consequently the decrease of fruit-set rate and increase of irregular fruit rate were represented. But it differed with genotype. Among different varieties (lines), the sensitive stages to sub-low temperature were different. .5. Anthocyanin coloration of hypocotyls,Φ_PSII, qP after stress for 3 days and the increase of tomato fresh weight after low temperature stress can be used as effective and feasible methods to estimate chilling tolerance ability. Among them, the correlation of anthocyanin coloration of hypocotyis and increase of fresh weight with relative fruit-set rate is negative and positive respectively, while the correlation of qP after stress for 3 days and Φ_SPII with irregular fruit rate increased by low temperature stress is positive and negative respectively.