Study On The Influence Model And Risk Assessment Of Low Temperature Sparse Sunlight In Flowering And Fruiting Period Of Greenhouse Cucumberin Jiangsu Province

Facilities cucumber plant with its short cultivation period,quick effect and economic benefits of higher advantage to become one of the fastest emerging industries in agricultural development,low temperature and sparse sunlight as is autumn and winter season affect facilities cucumber growth and fruit quality of the main meteorological disasters,how to effectively preventing low temperature and sparse sunlight according to the meteorological disasters facilities cucumber is key problem urgently to be solved in industrial development.This study"Jingyou 101"as material,using artificial control experimental study on the low temperature,sparse sunlight and according to under combined intimidation of facilities according to leaf physiological characteristics of cucumber blossom period,the growth and quality index,the influence mechanism,based on low temperature is constructed according to the facilities of cucumber plant dry matter production and the influence of leaf area model,extract the low temperature according to the meteorological disaster index,to carry out the risk zoning of low temperature and sparse sunlight during flowering and fruiting period of cucumber in Jiangsu Province.The main results are as follows:(1)The fluorescence intensity of cucumber leaves under low temperature,sparse sunlight and combined stress showed a typical chlorophyll fluorescence induction kinetic curve(OJIP curve).The photosynthetic active radiation(PAR)was in the range of 0?12?and0?800?mol·m^-2·s^-1,and the photosynthetic fluorescence parameters(total chlorophyll CHL,light saturation photosynthetic rate Pmax,light saturation point LSP,apparent quantum efficiency AQE,maximum fluorescence FM),endogenous hormones(abscisic acid ABA,auxin IAA,trans zeatin ZT)and the activities of carbon and nitrogen metabolism enzymes(sucrose synthase SSC,sucrose phosphate synthase SPS,nitrate reductase NR,glutamine synthase GS)were decreased,while the activities of antioxidant enzymes(catalase CAT,superoxide dismutase SOD,peroxidase POD)were firstly increased and then decreased,while the contents of light compensation point LCP,gibberellin GA3 and malondialdehyde MDA in leaves were increased.Correlation analysis showed that Pmax was positively correlated with ZT and AQE,and negatively correlated with SOD,POD,CAT and LCP.Study found that single stress at low temperature and low temperature according to photosynthetic rate under complex stress drop is mainly caused by non stomatal factors limit,and oligonucleotides according to net photosynthetic rate under the single stress caused by stomatal factors limit,low temperature according to seriously reduce the ability of cucumber leaf tissue synthesis of sucrose,inhibition of blade to nitrogen utilization and protein synthesis,thereby reducing plant and fruit sugar content.(2)The leaf area per plant,leaf dry weight,stem dry weight and fruit dry weight of cucumber decreased significantly under single and combined stress treatments of low temperature and sparse sunlight stress,and the decrease amplitude increased with the increase of stress.The leaf area per plant and dry weight of each organ could not reach the control level in the normal environment 50 days after the daily minimum temperature of 3?for 5d,6?for 8d and 200?mol·m^-2·s^-1 for 8d.Low temperature according to the fruit cucumber plants treated leaf ratio,fruit stalk ratio and the specific leaf area were increased,root-shoot ratio was significantly decline,showed that under low temperature according to stress the cucumber leaves thin,dry matter of unit form more leaf area,leaf photosynthate produced mainly to the fruit of transshipment,and lowering the allocation proportion of root and stem.Under low temperature and sparse sunlight stress,fruit weight,fruit length,maximum fruit diameter,minimum fruit diameter,organic acid content increased,while vitamin C,anthocyanin and soluble sugar were decreased.The comprehensive evaluation model of cucumber fruit quality under low temperature and sparse sunlight stress was established by fuzzy mathematics method,and the relationship model of comprehensive quality index with temperature,radiation and stress time was established.(3)The concept of low temperature and low illumination stress effect was proposed,and the relationship model of stress effect with low temperature,sparse sunlight and duration was established.The logistic equation and LTE index were used to establish a simulation model of dry matter of cucumber overshoot under low temperature and sparse sunlight.The R² and RMSE between the simulated and actual values were 0.935 and 4.2g·plant^-1,respectively.The dry matter allocation model of cucumber leaves,stems and fruits under low temperature,sparse sunlight and compound stress was established.Independent data verification showed that the R² of simulated and measured dry weight of each organ was greater than 0.900 based on a 1:1 line.The specific leaf area(SLA)method was used to establish the simulation model of cucumber leaf area per plant.The decision coefficient of leaf area fitting under different treatments was more than 0.950,and the simulation accuracy was good.(4)Principal component analysis method was used to select Pmax,MDA,ABA,SSc,NR and other indicators as the judging basis for the classification of low temperature and sparse sunlight stress level of cucumber,and the stress index Z model was constructed to determine the low temperature and sparse sunlight meteorological disaster level index of greenhouse cucumber during flowering and fruit setting stage.Based on the daily meteorological data of 65 stations in Jiangsu province from 1995 to 2019,and combined with the existing greenhouse microclimate model in Jiangsu Province,the spatial distribution of low temperature and sparse sunlight disasters of cucumber was studied.The comprehensive risk index model was established by using entropy weight method and natural breakpoint method to carry out the risk regionalization of cucumber gas disaster in Jiangsu facilities.The low temperature is mainly concentrated from December to February,and the risk in Northern Jiangsu is high,among which the low temperature risk in January covers most of Jiangsu;Few photos are mainly concentrated from November to January,mainly distributed in coastal areas in November,and mainly distributed in southern Jiangsu in December and January;Low temperature and low light are mainly concentrated in southern Jiangsu from December to February.The generalized extreme value distribution(GEV)function was used to fit the recurrence periods of low temperature,low illumination and low illumination disasters,and the spatial distribution characteristics of low illumination disasters of greenhouse cucumber in Jiangsu province in different recurrence periods were analyzed.The recurrence period of low temperature in Northern Jiangsu is 1-4 years,and the recurrence periods of low temperature and low temperature in southern Jiangsu are 1-5 years and 1-8 years.