| Drought,as one of the biggest natural disasters,was often causes forage to encounter physiological droughts and to emergence difficulties or dead seedlings,which seriously affects the survival rate of seedlings.It was a key factor for the success of artificial grassland establishment and grassland ecological restoration.Dactylis glomerata was a fine perennial forage of the Gramineae Dactylis,and was an important grass species for artificial grassland establishment and ecological reseeding.In this study,5 wild Dactylis glomerata from Xinjiang(from Altay,Urumqi,Tacheng,Qitai and Nileke counties)and 2drought-resistant cultivated orchardgrass(Baoxing Dactylis,Oregon Dactylis)as the research object.The experiment was used to control the water content by the weighing method.The appropriate water content(85 % of saturated water holding capacity)and moderate stress(60 % of saturated water holding capacity)and severe stress(35 % of saturated water holding capacity)were set,research on water consumption law,growth characteristics,root morphological characteristics,anatomical characteristics and physiological and biochemical characteristics of the seedling stage,and explore the adaptive change of Dactylis glomerata under different water conditions;and through principal component analysis and other methods to screen drought-resistant sensitivity indicators,the difference in drought tolerance of Dactylis glomerata was evaluated,in order to provide a theoretical basis for the selection of grass species in artificial grassland establishment and grassland ecological restoration.The main findings are as follows:(1)The results of water consumption characteristics show that the total water consumption and weekly water consumption of all materials are basically the same,and they are all inhibited by water stress,showing as suitable water>moderate stress>severe stress,and water use efficiency shows the opposite law.The total water consumption showed a gradual decrease trend with the increase of water stress,the total water consumption of each material under suitable water conditions increased by 33 %-136 % compared with moderate stress,and increased by 77 %-231 % when compared with severe stress;the peak of water consumption in the next week appeared in the third and fourth weeks,and both reached the peak in the second week under stress conditions,and then tended to be flat;The efficiency gradually increases with the severity of stress,the difference between the materials is small.Among them,the water use efficiency of Oregon Dactylis is less affected by the stress,and the water use efficiency of the other materials is more suitable for an increase of 39 %-151 % under severe stress.Dactylis glomerata in Baoxing of Sichuan and Nileke County in Xinjiang are materials with high water consumption and high water use efficiency,while Dactylis glomerata in Urumqi,Xinjiang is a material with low water consumption and high water use efficiency.(2)The results of growth characteristics showed that all materials maintained a high growth rate in the first week of the stress treatment,and the growth rate gradually decreased with the extension of the stress time;the plant height showed suitable water>moderate stress>severe stress,the plant height of each material under suitable water conditions increased by 5 %-43 % compared with moderate stress,and increased by 13 %-91 % when compared with severe stress;the number of tillers was suppressed with the degree of stress,but did not show a continuous decreasing trend;both the above-ground and under-ground biomass showed a gradually decreasing trend as the stress intensified,the above-ground biomass of each material under different treatments was significantly different(P<0.05).The comparison between the materials showed that cultivated materials generally had higher plant height,growth rate and above-ground biomass,while wild materials generally had higher tiller number,under-ground biomass and root-to-shoot ratio.(3)The results of root morphological characteristics showed that water stress inhibited the growth of total root length,total root surface area,total volume and average root diameter,resulting in an increase in specific root length,root specific surface area and specific root area as the stress intensified.The results of leaf anatomical structure showed that the upper epidermis of the Dactylis glomerata plant leaf midribs all had larger vesicle cells,and the vesicle cell volume of wild materials was larger than that of cultivated materials;with increasing stress,the thickness of the Dactylis glomerata leaf gradually decreased,and the thickness of upper epidermal cells was also the same trend.The anatomical structure of the root system shows that as the stress increases,the proportion of the cortex of cultivated materials increases,and water absorption is blocked,but the water transport efficiency is enhanced by more ducts,while the proportion of the cortex of wild materials decreases with the increase of stress,which is conducive to water absorption and improves water absorption efficiency.(4)The results of physiological and biochemical characteristics showed that with the increase of water stress and the prolongation of time,except for the relative water content of leaves,SOD enzyme activity and CAT enzyme activity,the other indexes showed significant differences under different water conditions(P<0.05).The overall index materials showed significant differences(P<0.05),among them,the difference between soluble protein and soluble protein is the largest among materials,and the coefficient of variation under different treatments is 14 %-23 % and 8 %-15 %,respectively.All 7 materials showed a gradual decrease in relative water content and chlorophyll content of leaves,the osmotic adjustment substances all show an upward trend,the cell membrane permeability changes,mainly reflected in the increase in relative conductivity and malondialdehyde content,and the overall increase in antioxidant enzyme activity,the activity of SOD enzyme showed a trend of first decreasing and then increasing.(5)Drought index screening results show that under moderate and severe stress,anatomical parame-ters of leaves and roots are the most sensitive indicators,followed by under-ground biomass,Root total length,root surface area and average root diameter in root morphology index and chlorophyll content,malondialdehyde content and soluble protein content in physiological and biochemical indexes can also be used as drought sensitive indicators;the comprehensive ranking of drought resistance of 7 Dactylis glomerata materials showed that the ranking is: YM-1>YM-2>YM-6>YM-7>YM-4>YM-3>YM-5.Taken together,water stress leads to a decrease in water consumption of Dactylis glomerata and an increase in water use efficiency,inhibits the growth of Dactylis glomerata,reduces above-ground and under-ground biomass,changes the morphology and anatomical structure of leaves and roots,and increases or decreases itself.The various physiological and biochemical indexes adapt to drought stress.The drought adaptability of 7 materials presents their own characteristics,and there are certain differences in drought resistance.Among them,the wild materials of 7 materials have the characteristics of low water consumption and high drought resistance,which can be used as excellent germplasm potential resources and provide basic materials for drought resistance breeding. |
