A Structural And Physiological Study Of Winter Hardiness Of Different Variance-typed Hibiscus Syriacus

In this study, by using the printing method, parafin section, determination of dynamic transpiration, resolution method and photomicrography techniques or methods, with five kinds of different variance-typed Hibiscus syriacus for the research object, the different variance-typed developmental characteristics and shoots shriveling rates were recorded, the electrical conductivity and water content of branch barks were measured, the leaves stomata, leaves anatomy and stems anatomy were observed, the characteristics of tracheary elements of shoots and roots were compared, and the dynamics transpiration of leaves and branches was analyzed.The results indicated that the order of winter hardiness of different variance-typed Hibiscus syriacus was M005>M025>M024>M015>M014 by the winter hardiness of investigation and analysis.Five kinds of different variance-typed Hibiscus syriacus had a certain degree of difference in some developmental characteristics. The stronger the winter hardiness of different variance-typed Hibiscus syriacus, the larger the sum of transpiration capacity per unit area of the leaf in 10 hours.The stronger the winter hardiness of different variance-typed Hibiscus syriacus, the larger the width of the periderm in stems, while the weaker their winter hardiness, the smaller the width of the periderm in stems. The stronger their winter hardiness, the larger the proportion of the stem secondary phloem in the stem radius, while the weaker their winter hardiness, the smaller the proportion of the stem secondary phloem in the stem radius.Three structural indices including palisade tissue thickness, stomatal circumference in upper epidermis and main vein xylem and vascular bundle area ratio were selected from seventeen structural indices. By evaluating winter hardiness with the fuzzy membership function, the results showed that the order of the winter hardiness of different variance-typed Hibiscus syriacus was M005>M025>M015> M024>M014. Among them, in addition to M015, the other four kinds of variance-typed Hibiscus syriacus were consistent with the findings of the winter hardiness of investigation.The order of the average length of the VE of five kinds of different variance-typed Hibiscus syriacus in roots was M015>M024>M014>M025>M005. The order of the average length of the VE of M015, M025, M005 and M024 in roots was reverse with winter hardiness, and the stronger the winter hardiness,the smaller the average length of the VE in roots.The order of the average length of the vessel elements(VE) of five kinds of different variance-typed Hibiscus syriacus in shoots was M014<M015<M024 <M025<M005, and the order of the average width of the VE in shoots was M014>M015>M024>M025>M005. The results showed that the stronger the winter hardiness of the five kinds of different variance-typed Hibiscus syriacus, the longer the average length of the VE in shoots, and the smaller the average width of the VE in shoots.Transpiration characteristics of five kinds of different variance-typed Hibiscus syriacus in shoots had a certain degree of difference, and they also had a certain degree of relationship with winter hardiness. The stronger the winter hardiness of different variance-typed Hibiscus syriacus, the larger the sum of transpiration capacity per unit area of the stem in 24 hours in the spring.