Study On The Effects Of Simulated Salt Stress On The Growth And Invasiveness Of Wedelia Trilobata,An Alien Plant

With the frequent changes of global climate,the changes of abiotic environmental factors in time and space significantly affect the growth and metabolism of plants.These abiotic environmental factors alter the competitive situation between native and alien species,not only increase the intrusiveness of local ecosystems,but also aggravate the harm caused by the invasion of alien plants.The purpose of this study was to compare the physiological and ecological responses of Wedelia trilobata and Wedelia chinensis to simulated salt stress,and to preliminarily explore their adaptability to salt environment.On this basis,the internal mechanism of the response of exotic plant Wedelia trilobata to simulated salt stress and its invasiveness was revealed by studying the effects of simulated salt stress on the growth of two plants under different nutrition,light intensity and species competition conditions,combined with the effects of simulated salt stress on the activities of antioxidant enzymes and the ratio of endogenous hormones of the two plants under different environmental conditions.The main results of this paper are as follows:(1)The results of the response of Wedelia trilobata to simulated salt stress showed that: Wedelia trilobata showed a law of inhibiting growth under salt stress,and Wedelia chinensis showed a law of promoting growth under low salt stress(100 mM)and inhibiting growth under medium and high salt stress(200 mM and 300 mM).The effects of salt stress on the growth of the two plants were mainly manifested in total biomass,plant height,node number and root length.Wedelia trilobata will transfer more biomass to the ground and Wedelia chinensis will transfer more biomass to the ground under salt stress.At the same time,the contents of proline,MDA,POD and CAT in the leaves of the two plants increased and then decreased with the increase of salt concentration.The IAA/ABA and GA/ABA values of Wedelia trilobata decreased with the increase of salt stress concentration,and the IAA/ABA values of Wedelia chinensis increased first and then decreased with the increase of salt stress concentration.(2)The effects of simulated salt stress on the growth of Wedelia trilobata under different nutrient conditions showed that: the growth of the two plants under low nutrient conditions was mainly manifested in the decrease of plant height,leaf number and total biomass under low salt stress.The changes of nutrient conditions had a great effect on the two plants,but the specific manifestations were different under high salt stress: both high and low nutrient levels inhibited the plant height and total biomass of Wedelia trilobata,while only the plant height,leaf number and root length decreased significantly at low nutrient levels for Wedelia chinensis.The content of proline,MDA,POD and CAT in the leaves of two plants were lower in the high nutrient environment,and the content of proline and MDA in the low nutrient environment was higher under low salt stress.The increased or decreased nutrition under high salt stress will promote the POD and CAT content of Wedelia trilobata.The GA/ABA,IAA/ABA and GA/ABA values of Wedelia trilobata were significantly different in the treatment group and the control group under low salt stress.The GA and IAA content decreased and ABA content increased in the leaves of Wedelia chinensis under high salt stress.(3)The effects of simulated salt stress on the growth of Wedelia trilobata under different light intensities showed that: the two plants showed obvious but different growth patterns under low light and low salt stress environment: medium light and low light increased the plant height of Wedelia trilobata significantly,and decreased the leaf number,root length and total biomass of Wedelia chinensis significantly.The low light environment inhibited the plant height,leaf number,node number and root length of the two plants under the high salt stress.The content of proline,MDA,POD and CAT of Wedelia trilobata increased with the decrease of light intensity under low salt stress.High salt stress increased the POD content and decreased the CAT content of Wedelia trilobata in low light environment.Both high and low salt stress increased the content of MDA and decreased the content of CAT of Wedelia trilobata in medium light environment.The GA/ABA and IAA/ABA values of the leaves of two plants decreased with the decrease of light intensity under no salt,low salt and high salt stress,and the GA/IAA values of two plants under low salt and high salt stress were higher than those in normal light environment.(4)The effects of simulated salt stress on the growth of Wedelia trilobata under different competition patterns showed that: The effects of salt stress on the growth of Wedelia trilobata under different competitive modes are mainly manifested in leaf number,node number,root length and total biomass.The low salt stress decreased the accumulation of the total biomass of Wedelia trilobata in monoculture,and the high salt stress was just the opposite.The salt stress increased the plant height and total biomass and decreased the node number and root length of Wedelia chinensis in monoculture.Wedelia trilobata gained its competitive advantage mainly by increasing the plant height,root length and root mass fraction.The low salt stresses of two plants had a positive RII values,so both them could benefit from mixed planting.Low salt stress reduced the negative effects of the two plants due to competition.The RII value of Wedelia chinensis was positive under high salt stress,so Wedelia chinensis dominated in the competition,and Wedelia trilobata was inferior in the competition.