| Cinnamomum camphor a var.linaloolifera Fujta had important economic,cultural,and ecological significance in various provinces and regions in southern China.The demand for the excellent clones of forestry production was increasing day by day.The large-scale nursery work was particularly important.In the case of rapid cutting and breeding of excellent seedlings,water management problems were often caused,resulting in excessive or too little water,which created water stress on the seedlings.In addition,under conditions of high temperature and high humidity,favorable conditions were created for the growth and reproduction of pathogenic bacteria in seedlings.Ultimately,it would affect the normal growth of seedlings and the regularity of emergence.Matrix as the carrier of seedlings to absorb water,the ratio and selection was critical,and carbendazim also played an important role in the prevention and elimination of seedling diseases and insect pests under water stress.The test material was Cinnamomum camphora var.linaloolifera Fujita.One-year-old cutting seedlings,through three variables quadratic regression rotation design method,a combination of five levels of water stress,seedling substrate and carbendazim.For seedlings,height,base diameter,number of leaves,maximum leaf area,biomass,water content,relative chlorophyll content(SPAD),chlorophyll fluorescence parameters,root activity,malondialdehyde(MDA)content,protective enzyme system(SOD,POD,CAT activity),soluble protein content,soluble sugar content,mineral element content(K,Ca,Na,Mg,Fe,Zn,Cu)and mortality of seedlings were studied,combined with the method of variance analysis and the establishment of mathematical models.Each index was analyzed to investigate its growth and physiological and biochemical response,in order to provided a theoretical basis for future nursery work.The main conclusions were as follows:(1)Through the study on the growth of the seedlings base diameter and height,the results showed that the growth of the seedlings base diameter and height in each treatment group was higher than the control,and the increase range of the two was up to 73.89%and 78.66%.All had reached a very significant difference.The short-term mild flooding stress promoted base diameter and height;however,when the drought stress and heavy flooding exceeded 30 days,growth stagnation or inhibition began to appear.Through the single factor analysis of the growth of the ground stem and seedling height,the results showed that both the substrate and the carbendazim played a role of promotion and protection during the test period.The growth of the seedlings base diameter and height was the most sensitive to the peat content in the substrate.The higher the content of peat in the substrate,the better the growth of base diameter and height.Through the interaction analysis of seedling height growth,the results showed that there was a significant interaction between substrate and water stress,and different components of the substrate had different effects on seedling height growth.The yellow soil was conducive to seedlings to resist drought stress,and peat soil was conducive to the growth of seedlings under waterlogging.(2)Through the research on the growth of leaf number and maximum leaf area,the results showed that the number of leaves and the maximum leaf area in each treatment group reached a very significant difference.Long-term drought stress severely reduced the number of leaves and the maximum leaf area,with a decrease of 20.70%and 48.56%,respectively.The use of 16 g·m'3 carbendazim in the substrate ratio B scheme had a good performance for the growth of leaf number and maximum leaf area,with an increase of 168.04%and 72.59%,respectively.(3)Through the study on the distribution of biomass,the results showed that the underground wet weight,the above-ground wet weight,the underground dry weight,and the above-ground dry weight all reached extremely significant differences among the treatment groups.Drought stress had a strong inhibitory effect on wet weight under ground,wet weight on ground,dry weight under ground,and dry weight on ground,with a decrease of 11.42%,50.08%,31.02%,and 60.90%,respectively.The root to shoot ratio of seedlings also reached a significant difference.The composition of the substrate had a greater influence on the rootshoot ratio of each treatment.The matrix of pure yellow soil showed the worst performance with a drop of 39.39%.(4)By studying the water content in different parts of the plant,the results showed that:the underground water content,the aboveground water content,and the overall water content of each treatment group reached extremely significant differences,and the general rule was that the underground water content>aboveground water content rate.Seedlings would increase their own water content to cope with the unfavorable environment of external drought,the overall increase rate was 38.88%,77.55%above the ground,and 28.26%below the ground;and different substrate ratios and application of carbendazim to seedlings in flooding stress maintaining water content in the body played a role.(5)Through the study of mortality,the results showed that:During the experimental period,severe waterlogging stress and drought stress alone would lead to seedling death,the mortality rates were 16.67%,51.11%.The results showed that the drought stress had a greater impact on the seedling mortality.The seedlings were relatively more resistant to waterlogging stress,and only a long period of severe flooding stress would cause seedling death.(6)The relative contents of chlorophyll and the fluorescence parameters of leaves were studied.The results showed that the relative content of chlorophyll was most susceptible to water stress.When the water stress exceeded 15 days,the relative content of chlorophyll showed extremely significant differences among treatments.The effect of severe waterlogging stress was the largest,with a drop of 30.27%.Under drought stress,the initial increase of fluorescence Fo was 9.14%,and the activity of PSII reaction center in leaves was low.However,the long-term severe water-flooding stress was the maximum fluorescence Fm,variable fluorescence Fv value,and maximum photochemical efficiency Fv/Fm value of seedlings.The negative effects of PSII potential activity Fv/Fo and PSII electron transport Fm/Fo had the greatest negative effects,which were 28.43%,47.58%,32.87%,38.48%,and 14.90%,respectively,which made the activity and photochemical efficiency of the PSII reaction center of the leaves.The electron transfer rate was greatly suppressed.(7)Through the study of physiological and biochemical results,the results showed that the MDA content,SOD activity,POD activity,CAT activity,soluble protein content and soluble sugar content all reached extremely significant differences among the treatments.Under drought stress,the MDA content increased the most,reaching 84.98%,which was the greatest damage to seedlings.In the face of external water stress,SOD activity first responded,but the maximum increase was only 4.87%;POD activity,CAT activity increased with the increase of SOD activity,and the highest increase rate reached 99.14%and 75.50%,respectively.They eliminate the active oxygen free radicals in seedlings and reduce the damage caused by water stress on seedlings together.The content of soluble protein and soluble sugar in the seedling osmoregulators increased during the water stress period,and the maximum increase rate reached 52.88%and 94.99%,respectively.(8)Through the study of root activity,the results showed that the root activity values of all treatments showed extremely significant differences.The use of substrate and carbendazim helped to increase the root activity of seedlings under mild waterlogging stress,with the maximum increase rate of 37.7%;however,long-term severe waterlogging stress significantly reduced the root activity,with a decrease of 52.84%,and drought stress.There was also a greater inhibition of root activity.Through single-factor analysis,the results showed that the use of a substrate rich in peat soil and carbendazim had a promoting effect on root activity,but when the content of the substrate peat soil was less than 50%,the promoting effect on the root activity of seedlings began to weaken.Through the analysis of interaction effects on root activity,the results showed that there was a significant interaction between carbendazim and the substrate.When the content of peat in the substrate was more than 80%,increasing the application amount of carbendazim would reduce the root activity of the seedlings.When the peat content was about 50%,increasing the application amount of carbendazim had no significant effect on the root activity of the seedlings.When the content of peat soil was less than 20%,increasing the application amount of carbendazim would promote the root activity.(9)Through the study of mineral elements content in various organs,the results showed that the contents of K,Ca,Na,Mg,Fe,Zn,and Cu in the roots,stems,and leaves of all treatments reached extremely significant differences.The contents of K,Ca,Na,Mg,Fe,Zn,and Cu in roots,stems,and leaves were susceptible to water stress,and the average maximum reductions of different mineral elements in different parts were K(34.59%)and Ca(31.17).%),Na(37.58%),Mg(13.08%),Fe(24.62%),Zn(43.04%),Cu(28.09%).The application of substrate and carbendazim was favorable to F.lindenii to resist water stress.The average maximum increase of different mineral elements in different parts ranged from 28.46%to 198.05%,and the highest was Fe(198.05%),followed by Zn(180.64%).The lowest was Mg(28.46%). |
PDF Full Text Request