| Leymus chinensis?Trin.?is usually used as a forage crop for grazing animals since it is high-yielding and protein-rich.As one of high-quality plants,L.chinensis makes sense for environmental protection and resource utilization.So it is widely cultivated in Chi-na.L.chinensis,a typical clonal plant,is sensitive to the changes of habitat factors.In order to explore the growth characteristics of L.chinensis,we simulated three different environment conditions by controlling temperature,moisture and illumination.The main results are as follows:1.Effects of different temperatures on growth and physiological characteristics of L. chinensis.The experiment was carried out in artificial climate incubators by controlling temperatures and setting up three treatments:CK?20?day/15?night?,low tempera-ture?5?day/1?night?and high temperature?38?day/25?night?.Each treatment set10 hours light each day.The results showed that:?1?Plant height,leaf area,biomass,photosynthetic pigment contents and root activity of L.chinensis were significantly decreased after high or low temperature treatment,and the influence of high tempera-ture was more.?2?Temperatures heightened MDA,soluble sugar,soluble protein and proline.The high content of MDA indicated that heat injury could be far worse.?3?The activities of antioxidant enzymes increased after high or low temperature treatment.At38?day/25?night,the superoxide dismutase?SOD?was highest,so were peroxidase?POD?and catalase?CAT?.At 5?day/1?night,ascorbate peroxidase?APX?and glu-tathione reductase?GR?were highest.In general,there was a better vision for cold ad-aptation in L.chinensis.2.Effect of a water gradient on growth and physiological characteristics of L. chinensis.There were pot experiments and set up three treatments:CK?80%-85%field ca-pacity?,moderate drought?50%-55%field capacity?and severe drought?30%-35%field capacity?.The results showed that:?1?With the drought degree increasing,the bi-omass and photosynthetic pigment contents were decreased significantly,but the plant height was not sensitive to soil moisture and the ratio of chlorophyll a and b increased slightly.?2?Chlorophyll fluorescence analysis indicated that the maximum fluorescence?Fm?,the variable fluorescence?Fv?,the PSII maximal photochemical quantum yield?Fv/Fm?and potential activity of PSII?Fv/Fo?decreased gradually with the decrease of soil moisture,except for the initial fluorescence?Fo?.?3?Gas exchange indicators man-ifested that water deficit significantly lowered the net photosynthetic rate?Pn?,sto-matal conductance?Gs?,transpiration rate?Tr?,transient energy utilization rate?SUE?,instantaneous carboxylation efficiency?CUE?and stomatal limitation value?Ls?level,while evidently added the intercellular CO2 concentration?Ci?and instantaneous water use efficiency?WUE?level.?4?Water shortage leaded to a significant increase in MDA,osmolytes contents and elative electrical conductivity of the plant.And the proline highly accumulated under severe drought.?5?As the drought intensified,activities of POD,SOD and CAT first increased and then declined,being the highest in moderate drought treatment.?6?With the reducing of soil moisture content,the abscisic acid?ABA?content increased and zeatin riboside?ZR?relative content decreased gradually.The indole acetic acid?IAA?and gibberellin?GA?contents firstly increased under moderate drought and then decreased under severe drought.Overall,different soil moistures had different impacts on L.chinensis and the plant could have fared worse under severe drought.3.Effects of different light intensities on growth and physiological characteristics of L.chinensis.The experiment was carried out by artificial shading and set up three treatments:CK?100%natural light?,light shading?70%natural light?and moderate shading?50%natural light?.The results were as follows:?1?It was found that over time,light shading better reinforced its plant height,fresh weight and dry weight in the L.chinensis that also received moderate shading.?2?When shading increased to 50%,the photosynthetic pigment contents became maximum and stable,while the chlorophyll a/b decreased significantly.?3?In this experiment condition,the diurnal changes of photosynthesis of L.chinensis possessed typicality.Shading significantly enhanced the photosynthetic capacity of L.chinensis,best results for light shading.?4?The contents of soluble sugar,soluble protein and proline were increased gradually during the whole growth stage.Shading significantly decreased the leaf relative conductivity and MDA content.The effect of 70%nature light was the best,then 50%nature light.?5?There had been so little difference between POD,SOD and CAT in early growth period.Latterly,POD activity decreased rapidly,and SOD,CAT activity increased rapidly.?6?Early,the IAA/ABA,ZR/ABA and?IAA+ZR+GA?/ABA greatly increased as the weakness of light strength.Lately,the trend was opposite.In general,70%nature light was propi-tious to the development of L.chinensis in this experiment condition.4.Comprehensive analysis about effects of different environment factors on L. chinensis growth adaptabilityFrom the growth properties,we can know that adaptabilities of L.chinensis to temperature,water and shading were distinctive.The adaptability of L.chinensis to low temperature was better than high temperature in the temperature test.Although grow rate of L.chinensis was remarkably reduced in the drought,the plant still showed strong drought resistance in adversity.Even under severe drought,L.chinensis could maintain its basic life activities.70%nature light made L.chinensis grow better,be-cause the shading provided a suitable light.Furthermore,there might be different re-sponse mechanisms to the different habitats.In times of low or high temperature,L.chinensis might mainly modulate its related enzymes to adapt the present environment.In dry times,the osmolytes contents might have to be raised to meet the basic moisture.Under different light treatments,L.chinensis kept appropriate growth by changing the photosynthetic pigment contents,regulating photosynthesis and balancing the leaf dy-namics.On the whole,L.chinensis might have distinct physiological mechanisms in the different environment conditions,such as temperature,moisture and light.The growth adaptabilities in low temperature,moderate drought and light shading were better than in high temperature,severe drought and moderate shading.The experiment results may be enlightening to reproduction,introduction and cultivation of L.chinen-sis,but further research is needed for understanding the mechanism. |
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