| Hemerocallis fulva is a perennial perennial herb in the Asphodelaceae family.It has rich varieties,long flowering period and strong garden landscape benefits.It is an excellent material in landscaping.At present,the variety of Hemerocallis used in Changsha is relatively simple,and Hemerocallis is prone to high heat and drought in the midsummer in Changsha.In this study,the Hemerocallis Hemerocallis varieties introduced in Hunan Forest Botanical Garden in recent years were used as research materials to carry out systematic observation and analysis of biological characteristics,comprehensive evaluation of Hemerocallis introduction,and evaluation of the physiological response mechanism and drought resistance of Hemerocallis under drought stress.In order to provide materials and reference for the introduction and selection of Hemerocallis in Changsha area and the application of garden open field cultivation.The results of the study are as follows:(1)Observation and analysis of biological characteristics of introduced Hemerocallis.The phenological period,biological characters and adaptability of 77 introduced Hemerocallis cultivars were observed,and the data of 8 phenotypic characters related to flowering were statistically analyzed.The results showed that under normal planting and maintenance conditions,75 cultivars could complete the entire life cycle,and 33 Hemerocallis cultivars,including ’Salomon Pagoda’,’Xue Budiao’,and’Janice Brown’,were evergreen in Changsha.The phenological periods of different Hemerocallis varieties are relatively different.Each variety begins to germinate in the middle and early March,and completes the leaf-expansion period in the middle and late March.From November to December,some Hemerocallis begin to enter the dormant period.The flowering period of introduced Hemerocallis is concentrated in May-June.The first flowering period is ’Butter Roll’ and ’Salomon Pagoda’ is the latest.The coefficients of variation of flowering amount,scape diameter,scape height,inner tepal length and width,outer tepal length and width and flower diameter of flowering Hemerocallis cultivars were 62.05%,35.96%,27.37%,12.26%and 24.14%,12.79%,24.53%,17.56%.(2)AHP Evaluation of Introduced Hemerocallis Varieties.On the basis of th e investigation data of the biological characteristics of the introduced Hemeroca llis cultivars,a comprehensive evaluation of the introduction adaptability and or namental characters of the Hemerocallis cultivars was constructed by using the Analytic Hierarchy Process.In the construction of the evaluation system,the w eight values of each index in the constraint layer(B)of the evaluation system are ranked B1(growth traits)>B3(flowering traits)>B2(quantitative traits),T he weight values of each indicator of the standard layer(C)are sorted as C5>C14>C10>C4>C8>C3>C11>C2>C12>C1>C7>C13>C6>C9,The ability to resist pests and diseases(C5)has the largest weight and is the primary reference index for ev aluating the comprehensive evaluation of the introduction of Hemerocallis cultiv ars;In addition,the indicators such as flower color(C14),flowering period(C10),heat tolerance(C4)and single-spread flower amount(C8)have a great influenc e on the comprehensive evaluation of its introduction.According to the compre hensive score,the introduced Hemerocallis cultivars can be divided into 4 grad es:grade Ⅰ(excellent),grade Ⅱ(good),grade Ⅲ(moderate)and grade Ⅳ(poo r).Class Ⅰ has 10 varieties,such as ’Salomon Pagodar’,’Xue budiao’,’Butter R oll’,etc.;Class Ⅱ has 27 varieties,including ’Little Beauty’,’Xiangtan Evergree n No.l’,’Music Genius’,etc.Class Ⅲ includes 31 varieties including ’Latin D ance’,’Rainbow Eye’,and ’Chongqing Honghua’;Grade Ⅳ includes 9 varieties i ncluding ’Purple Light’,’Pretty Girl’ and ’Charcoal’.The cultivars with the comp rehensive ranking of grades Ⅰand Ⅱ are the Hemerocallis varieties suitable for open field cultivation in Changsha,and can be popularized and applied.(3)Physiological Response of Hemerocallis Varieties to Drought Stress.Physiological responses of Hemerocallis cultivars to drought stress.Three varieties of’Salomon Pagoda’,’Xue Bu diao’ and ’Wan Xiong’ with relatively high comprehensive evaluation were used as materials,and potted water control was used to explore the physiological response mechanism of drought and evaluate the drought resistance.First,with the intensification of drought stress level and the prolongation of stress duration,the degree of withering of Hemerocallis leaves will gradually deepen.Physiologically,in the early stage of stress,the content of Rec and MDA in Hemerocallis leaves gradually increased,but relatively slowly,the cell membrane system was damaged,and the content of osmotic regulators such as Pro and SP in Hemerocallis began to increase.At the same time,the content of chlorophyll and Superoxide dismutase(SOD)activity increased.has seen an increase.However,with the increase of drought stress intensity and the prolongation of drought time,the damage to the structure and function of the cell membrane of Hemerocallis gradually increased.At this time,the activity of superoxide dismutase(SOD)in the leaves of Hemerocallis decreased,and the increase of Rec and MDA contents changed.At the same time,the ability of leaves to maintain the dynamic balance of osmotic pressure by increasing the content of Pro and SP was also weakened.The photosynthetic characteristics of drought stress showed that the light response curve,maximum net photosynthetic rate(Pnmax),light saturation point(LSP)and dark breathing rate(Rd)decreased significantly,while light compensation point(LCP)showed an upward trend.Combined with membership function and principal component analysis,it can be seen that the comprehensive evaluation values of ’Salomon Pagodar’,’Xue Budiao’,and’Wan Xiong’ are 0.159,0.692,and 0.801,respectively.According to the larger the value,the more drought-resistant the plant is.The drought-resistant ability of the three Hemerocallis cultivars from strong to weak is in the order of " Wan Xiong’>‘Xue Budiao’>’Salomon Pagoda’. |
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