Effects of Different Stresses on the Agronomic Traits,Physiological Indicators and Endogenous Hormones of Lotus corniculatus
[Objective]The aim of the present study was to assess the effects of different stresses on the agronomic traits,physiological indicators and endogenous hormones of Lotus corniculatus.[Method]Using Lotus corniculatus as the experimental material,3 stress treatments,including low nutrition(LN),high bicarbonate(HB)and low phosphorus(LP)were set up by preparing different nutrient solutions.Hoagland′s nutrient solution prepared with distilled water was used as blank control(CK).Lotus corniculatus seedlings at 2-3 leaves stage were transplanted into bottles containing different nutrient solutions,with 5 seedlings in each bottle and 15 bottles for each treatment.The nutrient solutions were changed every 3 d.Plants were harvested after 1 month of cultivation.The agronomic traits,physiological indicators and endogenous hormone levels of Lotus corniculatus under different stress treatments were measured and statistically compared.Membership function analysis method was used to comprehensively evaluate the effects of different stress treatments on the agronomic traits,physiological indicators and endogenous hormone levels of Lotus corniculatus.The growth performance of Lotus corniculatus under different stresses were analyzed.[Result]The plant height of Lotus corniculatus was the highest under LP treatment.Compared with CK,the root length,rhizosphere diameter,stem thickness,root volume,number of branches,above-ground and under-ground fresh weights,and single plant fresh weight of Lotus corniculatus under the 3 stress treatments all decreased,while the above-ground and under-ground dry matter contents increased.The root to shoot ratios of fresh weight and dry weights were the highest under LN treatment.Under LN treatment,the taproot activity of Lotus corniculatus was the highest,and the fibrous root activity was significantly(P<0.05)higher than that under the other treatments.The leaf chlorophyll content under LP treatment was significantly(P<0.05)higher than that under the other treatments,and the stem chlorophyll content was the highest under HB treatment.Under the 3 stress treatments,leaf protein content of Lotus corniculatus was significantly(P<0.05)lower than CK,stem protein content was higher than CK,leaf malondialdehyde content was significantly(P<0.05)higher than CK,stem malondialdehyde content was significantly(P<0.05)lower than CK,and both leaf and stem proline contents were higher than CK.The 3 stress treatments significantly(P<0.05)reduced the stem superoxide dismutase and peroxidase activities of Lotus corniculatus,and significantly(P<0.05)increased the stem catalase activity and the leaf glutamine synthetase activity.HB and LP stress treatments significantly(P<0.05)reduced the leaf superoxide dismutase and peroxidase activities of Lotus corniculatus.LN and LP stress treatments significantly(P<0.05)reduced the leaf catalase activity and significantly(P<0.05)increased the stem glutamine synthase activity.Compared with CK,the contents of acetylene(ACC),jasmonic acid and its derivatives(JA)in Lotus corniculatus significantly(P<0.05)decreased under the 3 stress treatments,while the contents of free cytokinin(CTK),abscisic acid(ABA)and gibberellins(GAs)significantly(P<0.05)increased.Except for the ACC/BHA under LP treatment,the ratios of ACC to the other endogenous hormones in Lotus corniculatus decreased to varying degrees under the 3 stress treatments,with some ratios less than 1.The membership function analysis showed that the comprehensive growth performance of Lotus corniculatus was in the order of LP treatment>CK>HB treatment>LN treatment.[Conclusion]Based on the various indicators,low phosphorus stress had minor impacts on the growth of Lotus corniculatus,while high bicarbonate and low nutrient stresses had a greater impact.Under low phosphorus,high bicarbonate and low nutrient stresses,Lotus corniculatus can regulate its growth and development by adjusting the morphological structure,activating the antioxidant system and balancing endogenous hormones,thereby adapting to the adverse environments.
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