| Leymus chinensis,a perennial grass of the gramineous family,is a kind of high-quality rhizomatic herbage,which is of great significance for the restoration of degraded grassland,the construction of artificial grassland,the prevention of soil and water loss and the production of high-quality forage grass.With the change of environment,especially the change of water condition,the morphological,photosynthetic and anatomical structure of Leymus chinensis had different degree of variation and differentiation,and the drought resistance of different Leymus chinensis populations was very different.At present,there are few studies on different varieties of Leymus chinensis on drought resistance,breeding and production of stress resistant varieties of Leymus chinensis.This study took 54 different germplasm resources of Leymus chinensis,to research the morphological,photosynthetic,ultrastructural and molecular changes of different Leymus chinensis germplasm resources under different drought stress intensities,and graded drought resistance and selected the drought resistance extreme materials.The effects of drought stress on photosynthetic characteristics and leaf ultrastructure of Leymus chinensis were further studied,and response of different germplasm resources of Leymus chinensis to drought stress and expression of related drought-resistant genes were preliminarily discussed.The main research results were as follows:1.Drought stress had different effects on various traits of 54 wild Leymus chinensis germplasm resources,among which tiller number,malondialdehyde?MDA?and proline?Pro?had higher correlation degree and higher sensitivity to comprehensive drought resistance of Leymus chinensis.Through membership function and clustering analysis,could be divided into high drought-resistant?,drought-resistant?,moderate drought?,sensitive?and high sensitive?class five classes,screening strong drought resistance germplasm resources was LC24 and LC34,and weak drought-resistant germplasm resources was LC40 and LC43.2.Drought stress had different effects on photosynthetic characteristics and leaf ultrastructure of different germplasm resources of Leymus chinensis.The net photosynthetic rate?Pn?,stomatal conductance?Gs?,transpiration rate?Tr?,water use efficiency?WUE?and SPAD of the three Leymus chinensis germplasm resources showed similar trends,and generally showed a downward trend with the aggravation of drought,contrary to the trend of intercellular CO2 concentration?Ci?.The results showed that under drought stress,the order of photosynthetic ability of the three Leymus chinensis germplasm resources was LC24>LC2>LC40.Through observing the ultrastructure of mesophyll cells from different germplasm resources of Leymus chinensis,it was found that under drought stress,and the mesophyll cells with high drought resistance LC24 had the most complete structure and low condensation degree of nuclear chromatin.Chloroplast dilation was less,and the granule and stromal thylakoid structure inside chloroplast was more clear than other parts.The structure of the mitochondrial membrane was complete and less deformed,and starch grains in chloroplast was low.Moderate drought resistant LC2 followed,and the mesophyll cells with high drought sensitivity LC40 were most seriously damaged by drought stress,and starch grains in chloroplast was rich and full.3.In this study,gene expression levels of drought-resistant genes NAC1,LcWRKY5 and LcDREB3a were different in different germplasm resources of Leymus chinensis.Under drought stress,most of the germplasm genes of Leymus chinensis were up-regulated.Combined with the classification of drought resistance grade of the tested Leymus chinensis germplasm resources,NAC1?LcWRKY5?LcDREB3a in high drought-resistant?LC24?LC34?LC46 the relative expression was higher,and lower in drought and high sensitive?LC16?LC40?LC43. |
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