| Alfalfa is an important perennial legume forage crop,with high nutritional value,high hay yield,strong grass persistence and other excellent traits,known as the "king of forage grass".In China,alfalfa is mainly distributed in northern areas,mostly in arid and semi-arid habitats,with low greening temperatures in early spring,and salinization caused by high water table is very common in some areas,as the yield,adaptability,stress resistance and disease resistance of different alfalfa varieties vary greatly,the production performance and forage quality performance varies,screening suitable varieties matching the growth environment is crucial to the alfalfa industry.The selection of suitable varieties to match the growing environment is crucial to the alfalfa industry.In northern Shaanxi,the main production area of alfalfa on the Loess Plateau,planting and production under the influence of adverse conditions such as low rainfall,low temperature and salinity often encounter problems such as uneven seedling emergence,slow growth and low yield.In this paper,four alfalfa varieties,including Qin Mu No.1(QM),Zhong Mu No.1(ZM),WL 358(WL)and Ladak(LDK),were selected to explore the physiological adaptation characteristics of the test varieties in terms of drought resistance,low temperature tolerance and salt resistance through indoor adversity sprouting tests and seedling stress tests,and to compare and analyze the growth differences in order to identify alfalfa varieties suitable for the climatic characteristics of northern Shaanxi.The main results obtained were as follows:(1)The germination rate of the test varieties all showed a decreasing trend with increasing PEG concentration,and QM and WL(25%)showed better resistance than ZM(20%)and LDK(15%);drought inhibited the growth of alfalfa seedlings,and the above-ground part was larger than the below-ground,with QM and LDK showing a lower reduction.Drought inhibited alfalfa leaf growth,among which QM and ZM at 14 d and WL and LDK at 7 d significantly decreased;drought conditions favored alfalfa root growth,with significant increases in length,surface area,volume,and root tip number,among which QM was more sensitive to water changes;water limitation had a greater effect on alfalfa aboveground biomass and decreased with prolonged drought,among which WL had a relatively smaller decrease.The antioxidant enzyme activities of alfalfa seedlings under drought stress treatment showed an increasing and then decreasing change pattern with the prolongation of drought time,with peak POD QM appearing at 14 d of drought and other varieties at 7 d,SOD and CAT both at 7 d and 14 d,respectively,and QM and LDK overall higher than the other two varieties.(2)The germination rate of all varieties except QM showed a decreasing trend with the increase of NaCl concentration,and at 400 m M NaCl concentration,all did not germinate;meanwhile,the salt concentration inhibited the growth of alfalfa seedlings,and the underground part was larger than the above ground,among which QM had the lowest reduction.The growth of alfalfa leaves tended to increase and then decrease with the increase of salt concentration,among which the leaf area of QM;the effect of salt stress on alfalfa root growth was the same as that of leaves,among which QM was significantly higher than other species;the increase of salt concentration significantly inhibited the aboveground biomass of alfalfa,but the aboveground biomass of WL and LDK increased at50 and 150 m M NaCl concentrations.Alfalfa seedlings showed a pattern of increasing and then decreasing antioxidant enzyme activities with increasing NaCl concentration,with peak POD QM at 50 m M NaCl and other varieties at 150 m M NaCl,peak SOD QM at 50 m M NaCl,WL at 100 m M NaCl,ZM and LDK at 150 m M NaCl,and the peak CAT was at 100 m M NaCl in all varieties except LDK at 50 m M NaCl,and QM and WL were higher than the other two varieties.(3)High temperature treatment reduced the germination rate of QM,ZM and WL,and LDK did not germinate,and under low temperature treatment,all varieties except QM were significantly reduced;high temperature significantly inhibited the growth of alfalfa seedlings,and the test alfalfa all stopped growing after germination.Under the low temperature treatment,WL and LDK were significantly lower than the control,while QM and ZM both had an increasing trend;temperature changes affected the growth of alfalfa leaves,under the high temperature treatment,while the leaf area of WL and LDK was significantly higher than the control,while QM and ZM were smaller than the control,under the low temperature treatment,the test alfalfa were higher than the control,of which QM was not sensitive to temperature changes;changes in the root system of alfalfa under the temperature treatment were not significant;temperature changes affected the above-ground biomass of alfalfa.The inhibition effect of temperature change on above-ground biomass of alfalfa was higher,with the smallest reduction of LDK under high temperature treatment and the smallest reduction of QM under low temperature treatment.The antioxidant enzyme activities of alfalfa seedlings under temperature stress treatment were significantly higher than those of the control under high temperature treatment,except for LDK,as shown by the activities of POD,SOD and CAT.In this study,the results of the comprehensive analysis using the subordinate function showed that ’Qin Mu No.1’ is a suitable variety for cultivation in the Loess Plateau region of northern Shaanxi.’Qin Mu No.1’ has better resistance to adversity and can enhance the germination rate and seedling growth activity of alfalfa seeds under habitat conditions in the Loess Plateau region of northern Shaanxi. |
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