| Due to the rapid development of economic globalization and transportation,species invasion has become one of the biggest threats to the sustainable development of biodiversity.According to the new millennium ecosystem assessment,the harm caused by the invasion of alien species will continue to increase.The invasion success of most invasive species mainly inhibits another plant in the living range through the release of allelochemicals,and nearly dominate the natural plant community.Allelochemicals affect the morphological behavior of plants,seed germination and growth,and affect the morphology and physiology of plants,as well as the inhibition of ethylene biosynthesis,transpiration and stress tolerance of plants by destroying the metabolic activities including cell respiration,protein content and enzyme activity,stomatal closure,photosynthesis and ion absorption.Parthenium hysterophorus.L,because of its strong allelopathy,it has become one of the most harmful weeds in most ecosystems in the world.In this study,we chose Parthenium hysterophorus.L as the research object,in order to evaluate the sensitivity of selected Kenyan cultivated Zea mays L.,Phaseolus vulgaris L.,Vigna unguiculata(L.)Walp and Vigna radiata(L.)R.Wilczek varieties,on seedling development and physiological response,through the influence of aqueous extract of Parthenium hysterophorus.L on seed germination.To achieve this,we carried out different bioassay analysis using different concentrations of aqueous extracts of P.hysterophorus leaf,root and stem to determine the effect on the germination,seedling development of the different selected Kenyan cultivated Zea mays L.,Phaseolus vulgaris L.,Vigna unguiculata(L.)Walp and Vigna radiata(L.)R.Wilczek varieties.In order to study the effects of synthetic phenols,1 mm of m-anisic acid(MA),P-Anisic acid(PA),coumaric acid(PA)and hydrobenzoic acid(HB)were used in this study.The seeds were added to agar plates with different synthetic phenolic contents,and then randomly put into the germination incubator at temperature of 25 / 20 ° C(day / night)and the temperature of12 / 12 h(light intensity of 100 ? mol / night)M-2s-1),80% humidity.In order to study the physiological effects,pot experiments were carried out and different physiological characteristics were measured.Our results showed that the aqueous extract of Parthenium hysterophorus.L had an effect on germination,seedling development and physiological response,and its effect changed with the increase of concentration.We also found that the effect varied depending on the plant part in which the aqueous extracts were obtained,with the leaf having the greatest inhibition effect due to high quantities of phenols as most varieties showed zero germination from 50 g L-1 and this can be attributed to the high levels of allelochemicals that are present in the leaf compared to the root and stem..The effects found in the synthesis of phenols vary depending on whether the phenolic compounds have-Oh(Hb and PA)or-OCH3(PA and MA)ring substituents.It was found that the growth of seed batches in the aqueous extracts of Parthenium hysterophorus.L and phenolic compounds containing-OCH3 ring substituents resulted in the decrease of morphological and physiological responses,while the treatment of seeds with phenolic compounds containing-Oh ring substituents increased the morphological and physiological responses.Our results can provide a scientific basis for further research on the effects of allelochemicals on cultivated crop varieties,help to develop high varieties with stronger resistance to allelochemicals inhibition,and provide suggestions for the best cultivated varieties,so as to ensure high yield in the invasion of invasive alien species(such as Parthenium hysterophorus.L). |
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