Effects Of Elevated Air Humidity At High Temperature On Organic Acid Metabolism And Intrinsic Quality Of Facility Tomato Fruits

In order to clarify the effect of air humidity on tomato fruit quality formation and organic acid metabolism under high temperature environment,a tomato variety "Pink Roland" was used,and an orthogonal test was performed in a large artificial climate room to design the maximum daily temperature The daily highest air temperature was 32 ?,35 ?,38 ?,41 ?,the air relative humidity was 50% ± 5%,70% ± 5%,90% ± 5%,and set 26 ?,50% as a control(CK).Treatment was performed at the flowering stage and the young fruit stage.The fruit quality,organic acid content and related metabolic enzyme activities were measured during the three development periods of the fruit.The fuzzy mathematical method was used to construct a comprehensive fruit quality model,with a view to providing a theoretical reference for the refined management of summer greenhouses.The results showed:The high temperature significantly increased the content of malic acid(Mal),tartaric acid(TA),succinic acid(SA),acetate(HAc)and ketoglutarate(AKG)in mature fruits.The content of citric acid(CA)decreased first and then increased;HAc was the lowest in air humidity of 70%,and Mal and CA are not sensitive to humidity.High temperature was the main factor affecting the activity of metabolic enzymes.At high temperatures,the activities of phosphoenolpyruvate carboxylase(PEPC)and citrate synthase(CS)increased,and CA synthesis was promoted,but the activities of isocitrate dehydrogenase(IDH)and cytoplasmic aconitase(cyt-ACO)increased first and then decreased with increasing stress temperature,CA accumulation started at 38? and 41?;the activity of malate dehydrogenase(MDH)increased,and it decreased in the fruit treatment of 38 ? and 41 ?,and the activity of malate synthase(ME)was not sensitive to temperature.In this study,Mal was significantly positively correlated with MDH and negatively correlated with ME;CA was significantly positively correlated with CS and PEPC,and negatively correlated with IDH and cyt-ACO.After the high temperature disaster,the soluble solids(SSC),lycopene(Lyc),vitamin C(Vc),soluble total sugar(TSC),and sugar-acid ratio(S/A)decreased,and the titratable acid(TOA)increased.SSC,TSC and S/A were all highest at 70% humidity,Vc and Lyc decreased with increasing humidity while TOA remains stable.Based on the principle of fuzzy mathematics,the weight order of a single quality index determined by objective entropy weight method was: S / A> Lyc> SSC> TOA> TSC> Vc.The comprehensive quality of the fruit after the flowering disaster was higher than the fruiting disaster.With the increase of air humidity at high temperature,the comprehensive quality of tomato fruits first increased and then decreased,and the comprehensive quality gradually decreased with the increase of air temperature.The interaction of temperature and humidity had a positive effect on the comprehensive quality.In the high temperature treatment of 32?-41? during flowering and fruiting period,the air humidity of 56.76%-73.38% and 60.57%-71.62% is the most conducive to the formation of tomato fruit quality.