| With the aggravation of climate change,the stability and sustainability of irrigation water in arid areas are threatened.Irrigation is an important aspect of agricultural production,especially with regards to seedling growth,and different irrigation methods and quantities can directly affect seedling growth and development.Therefore,studying irrigation is of great significance for dealing with climate change in arid areas and can provide theoretical guidance for selecting reasonable irrigation modes,improving seedling quality,and enhancing water resource utilization efficiency.In this study,1-year-old Amorpha fruticosa L.seedlings were used as materials,and three irrigation methods(sprinkler irrigation,drip irrigation,and flood irrigation)were applied with three irrigation levels(7.22 kg·plant-1,8.61 kg·plant-1,and 10.00 kg·plant-1),resulting in ten different treatments:high,medium,and low levels of sprinkler irrigation(P1,P2,P3),drip irrigation(D1,D2,D3),and flood irrigation(M1,M2,M3),as well as a control group with no irrigation(CK).Based on the differences in growth indicators,physiological indicators,and leaf chemical metric characteristics under different irrigation conditions,the most suitable irrigation mode for Amorpha fruticosa L.seedlings in the northwestern arid regions was evaluated by principal component analysis,with the aim of providing practical technical guidance to farmers and planting enterprises and promoting sustainable development of agriculture in the northwestern arid regions.The main research results are as follows:(1)Under different irrigation modes,plant height and ground diameter increased significantly,with the fastest growth observed for P2.P2 treatment showed the most significant effect on the phenotypes of compound leaves;leaflet area,petiole length,and ratio of petiole length to blade length were easily affected by irrigation modes,whereas the length and width of leaflets had a stronger adaptability to irrigation treatments.Different irrigation modes had no significant effect on root surface area or root length;P2 had the largest root surface area(315.11 cm2),while M3 had the longest root length(42.22 cm),indicating that water deficiency could stimulate seedling roots to grow downwards to seek water.Overall,P2 treatment can promote root growth.Sprinkler irrigation significantly increased biomass,with P2 treatment having the highest total dry weight(91.56 g),root dry weight(48.69 g),and stem dry weight(42.87 g).Amorpha fruticosa L.seedlings invest more biomass in roots than in aboveground parts,and sprinkler irrigation is conducive to the growth of aboveground parts.Increasing irrigation amount can promote the allocation of biomass to stems.(2)Sprinkler irrigation was more conducive to increasing chlorophyll content(SPAD)and net photosynthetic rate(Pn)than flood irrigation,while drip irrigation was beneficial to improving leaf water use efficiency(WUE).Different irrigation modes had a significant effect(p<0.05)on lignin content,but no significant effect(p>0.05)on soluble sugar content,with D3 having the highest soluble sugar content(12.52%)and M3 having the lowest(9.22%);M3 had the highest lignin content(17.13%),while D1 had the lowest(14.19%).Moderate-level drip irrigation was conducive to the accumulation of lignin in seedlings.Under drought conditions,applying a small amount of flood irrigation was beneficial to improving seedling quality.(3)The correlation analysis between various indicators showed that specific leaf area(SLA)and relative chlorophyll content(SPAD)had no significant correlation with other indicators.All photosynthetic indicators had significant positive correlations with each other.Root length showed significant correlation with water use efficiency(WUE),lignin content,and root surface area(RSA).WUE had a significant negative correlation with photosynthetic indicators and root length,while having no correlation with other indicators.Soluble sugar content had no significant correlation with any indicator.Comprehensive analysis showed that leaf area,compound leaf dimensions,plant height,biomass,and photosynthetic indicators contributed more to evaluating seedling quality,which could be used for preliminary judgment of seedling quality.According to principal component analysis,the comprehensive score was ranked as P2>P1>P3>D1>M2>M1>D2>CK>M3>D3.Sprinkler irrigation was more conducive to the growth Amorpha fruticosa L.seedlings than other methods.Insufficient water supply seriously inhibited the growth and development of seedlings.In summary,different irrigation modes have significant influences on the growth and physiological indicators of Amorpha fruticosa L.seedlings,and sprinkler irrigation is more conducive to the growth of seedlings than other methods.Moderate-level irrigation(8.61 kg·plant-1)is the most suitable amount for seedling growth.It is recommended to promote the use of sprinkler irrigation with moderate-level water supply for the irrigation of Amorpha fruticosa L.seedlings,in order to ensure healthy growth of seedlings. |
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