| Tomato is the main kind of facility vegetables in our country, and the water content of facility tomato is80%-90%, which is a type of large water consumption crops. Water stress directly affect the yield and the quality of tomato. Therefore, it is significantly important to study the water stress of tomato to improve its drought resistance and water use efficiency. In order to study the effects of various water supply on the tomato in the greenhouse, a research has been conducted under four models of water supply such as normal water supply(CK), light water treatment(T1), moderate water treatment(T2) and severe water treatment(T3) to tomato cv.’Jingfen2’which was chosen as a trail material in the greenhouse of Nanjing University of information Science&Technology during September-December in2013&April-July in2013. The simultaneous meteorological data were observed by the meteorological data collection system in the greenhouse and a nearby automatic weather station outside the greenhouse, Discussed the effects of different water treatment on the sap flow and the photosynthesis of tomato in the greenhouse, and established the transpiration simulation model. The results could provide support to environmental regulation and development facilities of the tomato in greenhouse. The main findings are as follows:(1)Build the microclimate simulation model of the Venlo greenhouse. According to the meteorological data inside and outside the greenhouse during the tomato growth period, discussed the seasonal and diurnal variation of air temperature and relative humidity in the greenhouse. The relationship between outside and inside daily maximum temperature, daily minimum temperature were analyzed systematically. The results showed that the temperature in the greenhouse were higher than that out of the greenhouse. The air temperature inside the greenhouse was found to negatively correlate to the relative humidity. Based on these analyses, a maximum, minimum temperature prediction model and a humidity prediction model for greenhouse was using Bp neural network and stepwise regression method, and validate the model with the air temperature and humidity inside the greenhouse. The accuracy of the BP neural network is much higher than stepwise regression, and the accuracy of both method were reliable.(2)The effects of soil water stress on stomatal characteristics. Digital microscopic imaging system and digital measuring system was applied to measure the stomatal length, width, aperture, density, the stomata index and the opening ratio of tomato. The results showed that the stomatal length, width and the aperture were expressed as:CK>T1>T2>T3,and the reducing amplitude increased with the extension of stress time. The stomatal density of tomato in different season increased gradually with the increased of the water stress, and the stomata density of lower epidermis was greater than the upper epidermis stomatal density. The analysis of variance indicated that the stomatal length, width, aperture and density of tomato under different water treatment showed the significant difference under the5%level.(3) The effects of soil water stress on sap flow of tomato. The sap flow rate were large in the day and small at night. The diurnal variation of sap flow rate of tomato were significantly different under different water treatments. In sunny day, the diurnal variation of sap flow rate of tomato under normal water supply CK and Low water treatment T1showed a double-peak curve. The daily sap flow rate reach the maximum at about13:00. The sap flow under high water treatment T3was restrained obviously, the overall trend is gentle. In cloudy days, the diurnal variation of sap flow under normal water supply T1and Low water treatment T2is more gentle. The daily sap flow rate reach the maximum at about9:00-10:00. The sap flow under high water treatment T3was also restrained obviously. The variation trend of sap flow rate was:CK> T1> T2> T3under different water treatment no matter in sunny days or cloudy days. The daily transpiration content showed a significantly difference, and the daily transpiration content was: CK> T1> T2> T3. The correlation analysis show that the important factors effecting sap flow of the tomato were soil moisture, photosynthetically active radiation (PAR), air temperature and relative air humidity (RH). The study also shows that soil moisture, photosynthetically active radiation and air temperature has a positive effect on sap flow, and the relative air humidity has a negative effect. The order of relevant factors were:PAR>soil moisture>air temperature> RH.(4) The simulation and estimate on the amount of transpiration. According to Venlo greenhouse microclimate factors, the study estimated the canopy net interception and leaf area index under different water treatments based on the Penma-Monteith equation as the basic principle. On this basis, simulation model of tomato transpiration under different soil water were established, diurnal transpiration capacity of tomato from seeding to fruit setting were calculated with transpiration measured by sap flow meter to test the simulation results. Root mean squared error (RMSE) of transpiration rate under different water treatments between simulation and measured values were2.813mm· d-1,2.592mm· d-1,2.077mm· d-1,2.678mmd-1respectively, the determination coefficients based on the1:1line were0.872,0.912,0.801,0.779respectively for test one. Root mean squared error (RMSE) of transpiration rate under different water treatments between simulation and measured values were1.650mm· d-1,1.253mm· d-1,1.126mm· d-1,1.912mmd-1respectively, the determination coefficients based on the1:1line were0.935,0.957,0.927,0.897respectively for test two, which indicated that the established model could be better used to calculate diurnal transpiration capacity. |
