Studies On The Response Of Tomato In Solar-greenhoush To Water Deficit

Moisture plays an important role in tomato growing process，and now the waterresources shortage and unevenly distributed in time and space phenomenon is very seriousin China，water often become one of the main factors of restricting tomato production．Withthe market demand is gradually increasing and improvement of people’s life，consumers arestarting to pay more attention to the quality of the fruit．The production of tomato isnecessary required the intensive cultivation pattern of“high quality and high yield，lowconsumption and high efficiency”，the goals of tomato production has gradually payattention from yield the past to quality and yield．In order to promoting the healthydevelopment of tomato industry，discuss the response mechanism of tomato under waterdeficit，make full use of water deficit compensation effect to tomato，these tests arestudied．This study intend to clarify the influences of tomato biology character under waterstress，and provide theoretical basis for the management for high quality and efficiency ofthe production of the tomato moisture optimization．This experiment was carried in the keylaboratory for Agricultural Soil and Water Engineer in Arid Area of Ministry of Education，Northwest A&F University during March2012to July．By potted tomato experiment，3soilmoisture gradients at flowering period and fruit-setting period were set up, T1、T2and T3respectively were the severe water deficit (50~60%θf)，moderate water deficit (60~70%θf)and light water deficit (70~80%θf) at flowering period，T4、T5and T6respectively were thesevere water deficit (50~60%θf)，moderate water deficit (60~70%θf) and light water deficit(70~80%θf) at fruit-setting period,The soil moisture content which was maintained in80~90%θfduring growing period was control,the effects of water deficit on growth anddevelopment and physiological characteristics of tomato were studied and the responsemechanism of the growth and various physiological processes on tomato under water deficitwere discussed，the main conclusions are as follows：1.Moderate water deficit was conducive to growth and development of tomato plants and the accumulation of dry matter．T3showed rapid growth trend on plant height，and T1hadsuppressed the growth of plants．Water deficit at flowering period was not in favour of theincrease of stem diameter．The growth rate of stem diameter under sufficient water supplytreatment was faster，and the stem diameter of water deficit treatment was relatively lower，and with the degree of water deficit aggravating，stem diameter is reduced gradually．Totalfresh weight，total dry weight，stem dry weight and leaf dry weight of tomato at floweringperiod and fruit-setting period showed downward trend with the degree of water deficitaggravating，while the root dry weight showed an increasing trend，and root dry weight of allwater deficit treatments accounted for the proportion of total dry weight were greater thanCK．Moderate water deficit did not influence tomato normal growth and physiological waterrequirement，could inhibit plant excessive growth of tomato and had an advantage oftransporting photosynthate to fruit and providing a good base for yield formation．2.Diurnal variation of photosynthetic rate，transpiration rate，stomatal conductance andintercellular CO2concentration of T1、T2and T3showed an unimodal curve，and werecharacterized by CK>T3>T2>T1．Diurnal variation of photosynthetic rate，transpiration rateand stomatal conductance of T4、T5and T6showed an unimodal curve while intercellularCO2concentration presented the quadratic curve model of opening upwardly．In case ofwithout significantly decreased the photosynthetic rate and transpiration rate，a highermaterial production capacity can be achieved under using less water by appropriate controlof soil moisture content．Water deficit could increase the chlorophyll content，and the moreserious degree of water deficit，the higher content of chlorophyll．Water deficit would causea large accumulation of proline and MDA content，and the accumulations related to theperiod and intensity of deficit．Each treatments at fruit-setting period were sensitive to waterdeficit more than flowering period．Comparing different degree of water deficit，the prolinecontent of mild water deficit treatment was slightly lower than the severe water deficit．Afterreturning to normal water supply，the MDA content of each treatments decreased to flat oreven lower than that of the contract level from the significantly higher than the contract levelunder water deficit．The root activity of each treatments all decreased under water deficit，and both the two growth period with severe water deficit treatment had the lowest rootactivity．3.The quality of tomato under water deficit had also been improved inordinately．Thesoluble solids，Vc，soluble sugar and organic acid content of tomato fruit could be increasedunder water deficit， and they were increased with the degree of water deficitaggravating．The sugar acid ratio of T1、T2and T3was respectively higher than T4、T5andT6，especially the severe water deficit，the sugar acid ratio of T4treatment was12.9% higher than T1，thus it could be seen that severe water deficit at fruit-setting period couldimprove the quality of tomato fruit．The quality of picking at different time under the samewater treatment also had great difference．The fruit soluble solids，Vc，soluble sugar，sugaracid ratio and nitrate content increased first and then decreased along with the picking time，while the organic acid content was decreased and then increased． Comprehensiveconsiderations of various quality indicators，the fruit quality of2nd truss was relatively best，1st truss was the middle and the fruit quality of3rd truss was the worst．4.Water deficit treatments had reduced the yield of tomato，but improved the water useefficiency．The total irrigation water was gradually reduced with the degree of water deficitaggravating of each treatments，the irrigation of T1was the least，CK was the most，andeach treatments were extremely significant difference with CK．Under the condition ofwater deficit，the yield of each treatments all had declined to various degrees，though T2treatment failed to reach the level of CK，but the water use efficiency improved5.1%thanthat of CK，and had the better water saving effect．Therefore，moderate water deficit atflowering period was recommend，the water use efficiency was improved，while at the sametime，yield was not significantly reduced．5.The gray relative analysis method was used for comprehensively evaluating the qualityof tomato fruits in the sunlight greenhouse under different water deficit．T4achieved thehighest weighted relativity degrees，it was the optimal treatment and had the highestcomprehensive evaluation．T1took the second place，CK had the lowest correlation weightedrelativity degrees and the worst comprehensive evaluation．This showed that severe waterdeficit was favour of improving the quality of tomato fruits．6.Considering the yield and water use efficiency comprehensively，moderate waterdeficit（60~70%θf）at flowering period was recommended．It had the good results ofwater-saving and stable yield．Under the premise of considering improving the fruit qualityonly，severe water deficit（50~60%θf）at fruit-setting period could be carried out，had theoptimal quality．...