Effect Of Plant Growth Regulator On Tomato Seedlings Under Sub-Optima Temperature

Sub-optimal temperature is one of the limiting factors in winter vegetable production of China. In order to figure out the effect of plant growth regulators on tomatos growth under sub-optimal stress, the present experiments were conducted. 3 different kinds of plant growth regulators were chosen with 3 differen concentrantions of each kind: ABA1(0.2mmol/L), ABA2(0.6mmol/L), ABA3(1.0mmol/L); put1(0.1mmol/L), put2(0.5mmol/L), put3(1.0mmol/L); BR1(0.005mg/L), BR2(0.01mg/L), BR3(0.05mg/L). Chilling-tolerant variety Santiam and chilling sensitive variety Zhongshu 6 are used as test materials. The effect of ABA,Put and BR on tomato seedlings grown under sub-optimal temperature were investigated. The main results obtained were as follow:1. 2 varieties of tomatos seedlings treated with ABA, Put or BR could increase chlorophyll content and net photosynthetic rate under sub-optimal temperature condition. The appropriate concentration were ABA3, put1 and BR2, as compared with the control the content of chlorophyll of ZHONGSHU 6 increased by 37.88%, 27.27% and 15.63% respectively and the net photosynthetic rate increased by 164%, 96% and 58% respectively, while chlorophyll of SANTIAM increased by 16.92%, 12.71% and 2.8% respectively and the net photosynthetic rate of ZHONGSHU 6 increased by 123%, 72% and 66% respectively.2. Exogenous ABA, Put or BR could alleviate the increase of MDA of 2 varieties of tomato seedlings under sub-optimal temperature. The lowest MDA content occurred in ABA2, Put2 and BR2 treatment. After sub-optimal temperature, the MDA content of ZHONGSHU 6 and SANTIAM were decreased by 21.07%, 14.29%, 21.24% and 16.02%, 21.14%, 24.57% respectively as compared with the control.3. Exogenous ABA, PUt or BR enhanced the activity of SOD, POD of 2 varieties of tomato seedlings under sub-optimal temperature. The appropriate concentration for increase POD activity was ABA3, PUt1 and BR3, and the best treatments for SOD activity wasABA3 and BR2; as compared with the control the POD activity of ZHONGSHU 6 increased by 61.29%, 206.77% and 94.14% respectively and SOD activity increased by 29.2%, and 28.6% respectively. Meanwhile, ABA3 and BR2 increased SOD activity of by 19.37% and 18.45% respectively, and ABA3 and BR2 enhanced POD activity by 16.66% and 13.98% in SANTIAM. The CAT activity in ZHONGSHU 6 increased by 45.8%, 81.36% and 38.9% respectively with ABA3, Put1 and BR2 after 8 days sub-optimal temperature.4. ABA3, Put1 and BR2 induced the inceasing content of PRO, soluble sugar and soluble protein in ZHONGSHU 6. The soluble sugar increased as compared with the control in 47.7%, 49.53%, 67.9% respectively and the PRO increased by 14.74%, 11.15%和14.21% respectively.5. ABA3,Put1 and BR2 inceased the root activity of 2 varieties of tomato seedlings. At the end of 8 days sub-optimal temperature treatment, the root activity of ZHONGSHU 6 increased by 59.53%, 48.67% and 41.43% respectively and SANTIAM increased by 31.50%, 23.87% and 30.38% respectively.6. Under sub-optimal temperature the content of ABAraised firstly and then decreased, while the content of GA changed in the opposite way. Tomato seedlings treated with ABA,Put and BR increased the content of ABA, and induced the content of ABA and IAA raised in a high speed. The increased content of ABA and decreased content of GA could inhance the low-temperature tolerance of 2 varieties of tomatos seedlings.7. With the Principal Component Analysis, we can draw conclusion that the optimal concentration for tomatos under sub-optimal temperature were ABA3, Put1 and BR2 for ZHONGSHU 6, and ABA3 and BR2 for SANTIAM.