Mechanisms Of Flooding Tolerance And Penoxsulam Resistance In Aeschnomene Indica L.

Aeschynomene indica L.is a commonly found one-year leguminous weed in rice fields.It has the ability to survive for an extended period under flooded environmental conditions,which enhances its waterlogging tolerance and allows it to successfully evade the harm caused by flooded management in rice fields.Furthermore,A.indica has been observed to respond well to the herbicidal effect of stem and leaf herbicides,which increases its competitive strength in rice fields.As a result,there has been a widespread outbreak of A.indica in the middle and lower reaches of the Yangtze River in recent years.However,the germination mechanism and waterlogging tolerance regulation mechanism of A.indica have yet to be reported,and the weed’s resistance mechanism to herbicides requires further study.In this study,the culture dish and pot experiments were carried out,A.indica was treated with different level of flooding conditions（0.0 cm,1.0 cm,2.0 cm,4.0 cm,and6.0 cm,respectively）.The phenotype,physiological response,and the alteration of rhizosphere bacterium microbial community during the treatments were investigated.Moreover,after 14 days nature cultivation,the 3 pair-leaf uniform seeding was treated with nature（CK,wetness）and continues flooding（CF）,and combine with spraying 0 g a.i.ha^-1,30 g a.i.ha^-1 and 60 g a.i.ha^-1penoxsulam OD,one most widely used herbicide in rice domain.After 14 days treatment,the phenotype,antioxidant capacity,fungal community,and penoxsulam OD metabolism were investigated.Consequently,the regulatory functions of A.indica under CF and its physiology mechanisms resistance to penoxsulam OD were clarified.In addition,the main results from this study are as follows:（1）A.indica is a low O₂ quiescence syndrome（LOQS）plant,it germinated under either of the above flooded conditions,the 6 different levels of flooding conditions have no significantly difference in seedling rates.Flooding time up to 72h,the seed water absorption,gibberellin（GA）and abscisic acid（ABA）content were gradually increased over every 12 h periods.Theα-amylase activity was activated,and soluble sugar content were also gradually increased,when compared with 0 h.Although these indexes also increased under CK condition,the CF promoted these processes more quickly significantly by increasing sugar metabolism,which supply the seed energy to secure seed germination.（2）After 14 day’s CF treatment,A.indica still alive even under 6 cm treatment,the plant height,fresh weight and dry weight were severely suppressed under such deficient oxygen（O₂）condition,and the inhibition degree significantly related to the flooding depths.In this case,the anaerobic respiration was up regulated by enhanced alcohol dehydrogenase（ADH）and pyruvate decarboxylase（PCD）activities,to ensure the survival of A.indica Additionally,beneficial bacterium microbial such as Defluviicoccus,Budomonas,Bacillus,Clostridium and Acidirobacter appeared in the rhizosphere under CF,which may enhance the plant viability by related increased hormones biosynthesis.（3）A.indica can avoid the killing effect of penoxsulam OD under CF condition.Under CK condition,30 g a.i.ha^-1 penoxsulam OD can effectively control A.indica before3 pair leaves,while under CF condition,360 g a.i.ha^-1 had the same control effects,and the herbicide dosage was used over 12 times.Actually,The penoxsulam content was certainly diluted when spraying under CF condition,which fail to inhibited the acetolactate synthetase（ALS）active in the root and shoot of the plant seedlings.The results suggested that CF condition hinder its translocation to the growth point,and help to escape the killing effect of penoxsulam OD.（4）Under CF condition,the root and shoot MDA content were not changed after spray 60 g a.i.ha^-1 penoxsulam OD when compared to CK.Moreover,the antioxidant enzyme activity,such as SOD and APX,were also not significantly changed.However,root CAT activity was significantly increased,and root and shoot POD activity were significantly reduced.These results indicated the mitigation under CF combine with herbicide treatment.In addition,the increased abundance of beneficial fungi of Chaetomium,which previously reported to increase stress resistance,still requires to be further study.The study concludes that A.indica is a new type of rice field invasive weed that can germinate and grow under flooded conditions.This is due to the fact that the weed enhances its metabolic capacity by up-regulating its sugar metabolism and increasing the energy supply to its seeds.In addition,A.indica can also increase its anaerobic respiration capacity by up-regulating the activity of ADH and PDC,which helps it survive in flooded environments.A microbial community was found in the rhizosphere of A.indica,which adds beneficial factors for plant hormone and physiological metabolism,enhancing its ability to resist stress.Furthermore,A.indica is also tolerant to the penoxsulam OD,which increases its ability to respond to environmental risks.In conclusion,A.indica tolerance to flooding helps it successfully evade the physical control of flooding and the killing effect of herbicides.In recent years,the outbreak of A.indica is not due to its own development of herbicide resistance,but rather to ineffective control resulting from excessive use of herbicides.Therefore,it is necessary to consider combining water management and herbicide usage to control A.indica.The results of this study have important theoretical implications for efficient weed management and practical significance for guiding rice production.