Responses Law Study Of Physiological Information Of Leaf Vegetables To Particulate Matter In Greenhouse

The pollution of particulate matters of haze has been a hot topic.The particulate matters have adverse effects on human health,human life and plants.Particulate matters not only cause environmental pollution in greenhouse,but also deposit on leaf surface and affect the photosynthesis of crops.Particulate matter（PM）produces adverse effects on quality and yield when absorbed into crops.Based on the active component simulation method,the artificial simulator for the generation of PM was constructed.With oilseed rape（Brassica napus L.）,lettuce（Lactuca sativa L.）and small Chinese cabbage（Brassica chinensis L.）as the research objects,the gas exchange parameters,fluorescence induction kinetic parameters,growth indicators and chemical indicators were detected.The hyperspectral technology,chlorophyll fluorescence analysis,microscopic observation,chemical analysis,image processing and other means were used.The rules of photosynthetic physiological characteristics,chlorophyll fluorescence characteristics,hyperspectral characteristics,key enzymes and other information of the three leaf vegetables were analyzed under the artificial simulated PM environment and the natural haze PM environment.Combined with the growing period of leaf vegetables,the dynamic response monitoring of leaf vegetables to PM pollution was realized.The changes of temperature,air quality and illumination intensity in the solar greenhouse under natural haze were studied.In order to reduce the harm of PM to leaf vegetable production,based on image processing technology,a method of counting PM deposited in leaves was proposed to judge the pollution degree of PM in haze weather in advance.In order to reduce the adverse effects of PM on leaf vegetables,the regulation strategy and cultivation optimization suggestions of greenhouse were put forward.A new method to achieve high quality and yield of greenhouse crops was got.A reference for in-depth research on the mechanism of physiological and biochemical reactions of leaf vegetables affected by PM was provided.The study could provide theoretical and technical support for the realization of precise control of greenhouse facilities.The main research results are as follows:1.The active component simulation method was used to build an artificial PM simulation environment.The quantitative and timed output of PM was realized.The hyperspectral reflectance and first derivative characteristics of lettuce,oilseed rape and small Chinese cabbage in the harvest period were studied under the PM pollution environment and the natural haze environment.After the PM pollution,the reflectance of leaf vegetables was high in visible band.The yellow spectral position changes were consistent with the blue spectral position,but the red edge position blue shifted.The spectral reflectance peak of lettuce was the largest in visible light green range,followed by small Chinese cabbage and oilseed rape.These spectrum response characteristics could be used as a sensitive indicator to PM pollution effect.By comparing the microscopic results of 1-hour and 3-hours effects of PM on leaves,the mechanism of how PM blocked leaf stomata and then affected photosynthesis was obtained.According to the hyperspectral characteristics,plant phenotypic differences and microscopic deposition image of leaf vegetables,the retention capacity of small Chinese cabbage and lettuce was stronger than that of oilseed rape.The phenomenon of red edge and blue shift of oilseed rape was the most obvious,and it was most affected by PM and was the most sensitive to particulate pollution.2.Based on two ways of discontinuous and continuous which PM pollution effected,the physiological indexes were measured during different growing periods,including the gas exchange parameters（net photosynthetic rate,stomatal conductance,intercellular CO₂ concentration,etc.）,the growth index（leaf area,height,pigment content,relative chlorophyll content,fresh and dry weight,etc.）,the fluorescence kinetics parameters(Fv/Fm,Φ_PSⅡ)and three chemical resistant index quantitative（total protein,malondialdehyde content,peroxide enzyme activity）.The SPAD content of three leaf vegetables increased with the development of growth period.The control group had much higher growth rate than the experimental group.The growth rate of small Chinese cabbage was about 14.22%in the control group（CG）,the experimental group 1（EG1）and group 2（EG2）were 3.74%and 3.77%respectively.The damage effect of PM pollution on small Chinese cabbage’s SPAD was remarkable.The growth rate of plant height in the experimental group was lower than that in the control group,and the fresh weight,dry weight,water content and pigment concentration of the leaves were also decreased in different degrees.Vegetables growing in healthy environment grew better than those exposed to PM pollution,and the number and size of leaves in the control group were better than those in the experimental group.The degree of leaf growth was as follows:CG>EG2>EG1.The MDA content of the three kinds of leaf vegetables in the control group was higher than that in the experimental group,which indicated that the long-term effect of PM pollution made the leaf vegetables resistant.By improving the ability of cells to be attacked by free radicals,the effects of PM on cell membrane damage were minimized.The POD activity in the experimental group was higher than that in the control group,so the ability of resisting PM pollution was the strongest.Compared with the control group,the two kinds of particulate pollution caused adverse effects on the physiological indexes of the three kinds of leaf vegetables.Through studying the different dynamic response characteristics of leaf vegetables,the mechanism of particulate pollution on leaf vegetables was analyzed.The differences on the ability of lettuce,oilseed rape and small Chinese cabbage to absorb PM were obtained.Overall,oilseed rape had the lowest ability to resist PM pollution,and the ability to retain,attach and absorb PM was:oilseed rape<lettuce<small Chinese cabbage.The results could provide references for species allocation of crops in greenhouse in autumn and winter.3.Based on hyperspectral technology,the hyperspectral characteristics,first derivative spectral characteristics and vegetation index responses of lettuce,oilseed rape and small Chinese cabbage were dynamically monitored under the two particulate pollution modes.With the advance of leaf vegetable growth stage,the sensitive vegetation index increased because of the PM.The characteristic parameters,vegetation index,the sensitive wave bands and characteristic wavelengths were as the spectrum characteristic variables in the modeling.First derivative（FD）,second derivative（SD）,Savitzky-Golay smooth（SG）,multiple scatter correction（MSC）and standard normal variable change（SNV）these five methods were used to spectral preprocess.Correlation analysis method（CC）,original extraction,FD extraction and MSC extraction these four methods were used to extract spectral feature variables.Classical least squares（CLS）,partial least squares（PLS）,principal component regression（PCR）and stepwise multiple linear regressions（SMLR）these four methods were used to spectral model.Through the combination of different methods,the optimal inversion models of the net photosynthetic rate of the three leaf vegetables in different growth stages were established respectively.The optimal combination of spectral pretreatment and modeling methods for three growth stages of lettuce were PLS+MSC+SG（SD1）,PLS+MSC+SG+FD（SD2 and SD3）,respectively,and the correlation coefficients of the models were all above 0.92.The optimal method combinations of oilseed rape were PLS+MSC+SG+SD（YD1 and YD3）,PLS+MSC+SG（YD2）.The model correlation coefficients of YD1 were above 0.8,and those of YD2 and YD3 were above 0.94.The optimal combination methods for small Chinese cabbage were PLS+SNV+SG+FD（BD1）,PLS+SNV+SG+SD（BD2and BD3）,and the correlation coefficients were above 0.85（BD1）and 0.90（BD2 and BD3）,respectively.The accurate inversion of net photosynthetic rate of leaf vegetables was realized,which provided a basis for the inversion of physiological information of plants considering PM pollution.The predicted and measured results showed that the model was reliable,which provided reference for the model accuracy and correction in the future.4.The adverse effects of haze weather on temperature,illumination and air quality in solar greenhouse were studied.The management suggestions of reducing PM by leaf vegetables in greenhouse were put forward.Small Chinese cabbage chould be chosen as far as possible in the study of reducing haze in greenhouse.It was recommended to choose lettuce when early warned haze weather.When planting in autumn and winter,oilseed rape could reduce the impact of haze weather.Measures to deal with haze weather were put forward from aspects of greenhouse management,haze reduction and dust removal,air purification,etc.,which provided reference for realizing high quality and yield of greenhouse crops.5.The microscopic images of particulate deposition characteristics in the leaves showed that the capacity of small Chinese cabbage to absorb particulate matters was the strongest.The longer the time of particulate pollution was,the more particulate matters were deposited on the leaves,and the coarse particulate matters were aggregated.The PM pollution degree in haze weather was determined in advance by image processing technology and counting deposited particulate matters.This method could reduce the negative effects of PM to leaf vegetables and provide the reference to haze weather warning.