On Morphological And Physiological Adaptations Of Mosses To Environments

Because of their simple morphological and anatomical structures,mosses are easily influenced by environmens,and often be used as indicator of environmental variations.The studies of morphological and physiological adaptations of mosses to environemts could provide new information of the mechanism of mosses adaptation to environments,of the influences of environmental changes on mosses,and could also provide new ways to select sensitive bioassay moss species using new morphological and physiological indices.The moss species which were collected from different water conditions were morphologically and anatomically studied.Hypnum fertile Senden.was empolyed as a mode material to test the influences of stress environments in relation to drought,temperature, acid rain,nitrogen deposition,UV-B radiation on the physiological indices of mosses.The main results and conclusions are as follows:1.The stems of 30 mosses from different water conditions were transected and comparatively observed by means of paraffin wax section.We found that the features including stem shape,cell shape,the layers numbers of epidermis, the epidermis thickness,the differentiation and layers of cortex,the presence or absence and the scale of the axial part of stems vary highly among these 30 moss species.For the mosses in relation to the present paper,the numbers of epidermis layers and external cortex,together with the thickness of cell walls, were obviously influenced by their habitats.2.The leaf structures of 17 mosses collected from different water conditions were transected and compared by means of paraffin wax section.The results showed that moss species vary much among the features such as whether the hydrome cells are present or not,the differentiation state of steroid cells,the cell layer numbers and density of the costa,the laminal cell layer number,and the leaf microscopic characteristics et al.The leaves of mosses exhibited adaptation to water condition,whereas the leaf cell density is not significant correlated with the water conditions of the habitats.3.PEG-6000 was used to simulate drought tress on H.fertile.Afer treatment for 3 day with -5Bar～50Bar PEG solution,the contents of chlorophyll and MDA of H.fertile were no significantly changed.The content of soluber sugar increased significantly when the stress intensity heavier than-25Bar.The content of proline and the activities of SOD,POD and CAT increased significantly when stress intensity heavier than-15Bar.The results shows that H. fertile protect itself from drought injury by increasing the content of osmotic substances and increase the activities of anti-oxygen enzymes.4.Cultured under 5℃,the contents of soluble sugar,free proline,MDA and the activities of SOD,POD in H.fertile all increased gradually,and the activity of SOD decreased gradually;Under high temperature of 40℃,the content of soluble sugar increased first then decreased,proline content increased gradually; the activities of SOD,POD and CAT increased first then decreased under high temperature,MDA content increased gradually and higher than that under 5℃. The enzymes in H.fertile cultivated under 20℃were relatively higher.This study shows that the moss of H.fertile can protect itself from temperature stress by increasing osmotic substances and anti-oxygen enzymes.Compared with that at high temperatures,the moss of H.fertile grows better in the environments with lower temperature.5.The effect of simulated acid rain on the physiological and biochemical characteristics of H.fertile was investigated by spraying the solutions with different pH values.The results showed that the content of chlorophyll and soluble sugar in H.fertile decreased with the decline of pH value of simulated acid rain,but the contents of proline and MDA and relative permeability of membrane were increased.The activities of SOD and CAT firstly increased then decreased slowly,and then decreased fast,the activity of POD increased slowly then increased fast.Statistic analyses show that H.fertile could be damaged when sprayed with the solutions with pH value lower than 4.0.6.In order to investigate the effect of UV-B radiation to H.fertile,we used artificial light to simulate ambient UV-B radiation(6.93 KJ m^-2·d^-1)and enhanced UV-B radiation(9.01 KJ m^-2·d^-1)in laboratory.The results show that enhanced UV-B radiation(higher than normal by 30%)resulted in the decrease of the content of chlorophyll and carotenoid,the increase of MDA content and the decrease of activities of SOD,POD and CAT in H.fertile.It suggested that UV-B radiation caused oxidative stress to H.fertile. 7.We also determined the short-term response of nitrate reductase activity in H.fertile and Pogonatum inflexum(Lindb.)Lac.after treated with nitrate and ammonium at different pH value and concentrations.The results showed that the activity of nitrate reductase enzyme could be enhanced by the addition of nitrate, the change of nitrate reductase enzyme activity in H.fertile was more than that of P.inflexum after sprayed with nitrate.Ammonium solution reduced the activity of the enzyme.The solution at pH 3.0 significantly reduced the activity of nitrate reductase enzyme of H.fertile,whereas had no significant influence on that of P.inflexum.Compared with P.inflexum,H.fertile is more susceptive to N deposition.