The Effect Of Simulated Acid Rain On Three Osmanthus Fragrans Color Groups Of Growth And Physiology

Osmanthus fragrans color group is a new species we discovered in recent years,featuring a high ornamental value for combining the fragrance of sweet osmanthus and color of color-leafed plants.However,the regions of China where the Osmanthus fragrans color group is perfectly popularized at present,such as Hunan,Chongqing and Zhejiang,are all severely polluted by acid rain.Therefore,it is quite essential to discuss whether the osmanthus fragrans color group is appropriate to be grown in the district with serious pollution of acid rain.In this experiment,the cutting seedling of the annual-growth plants of ’Yuntian Caigui’,’Yinbi Shuanghui’,and ’Qiannan Guifei’ were planted in pots inside the room.Then,these three plants received stress treatment with four simulated acid rain solutions respectively with pH values of 5.6(CK),4.0,3.0 and 2.0,based on which the changes of these three plants in terms of the growth morphology indicator,photo synthetic physiological indicator,physiological and biochemical indicator were studied and analyzed.The experiment results are illustrated as follows:(1)The influences of the acid rain stress on the growth morphology of these three osmanthus fragrans color groups indicate:the damage to these three plants caused by the acid rain is closely correlated to the pH value of the acid rain.Simulated acid rains with different concentrations would lead to damages of different degrees to these three types of osmanthus fragrans color groups.According to the experiment,fresh leaves were too vulnerable to be injured,with injury spots firstly appearing on the rim of the leaves.The pH4.0 acid rain did not cause obvious injury spots on these three osmanthus fragrans color groups.However,obvious injury spots at different degrees were found on the leaves of these three osmanthus fragrans color groups treated by pH3.0 acid rain.And these three osmanthus fragrans color groups under the treatment of pH2.0 acid rain were obviously hazarded by acid.As the concentration of acid rain stress is rising and the stress is continuing,the acid hazard indicator and level of the plants are gradually increased.The suppression rate of the acid rain stress for these three osmanthus fragrans color groups was rising as the increase of the acid rain concentration.From the external appearance,the tolerance degree of these three plants specific to the acid rain is as follows:’Qiannan Guifei’>’Yinbi Shuanghuui’>Yuntian Caigui’.(2)The influences of the acid rain stress on the photo synthetic system of these three osmanthus fragrans color groups indicate:during the period of stress,the chlorophyll contents for these three plants witnessed a declining trend as a whole and the a/b value of chlorophyll remained consistent with the changes of the chlorophyll contents.After treated by the third simulated acid rain with pH value of 2.0,the chlorophyll contents of ’Yuntian Caigui’,’Yinbi Shuanghui ’,’Qiannan Guifei ’respectively dropped to 65.8%,68.8%and 68.8%of the contrasted value,revealing that the long-term acid rain stress would affect the Osmanthus fragrans color group in its chlorophyll content and reduce the photosynthetic capacity of the plant.The declining of the chlorophyll content for these three plants can be ranked in a descending order as follows:’Yuntian Caigui’>’Qiannan Guifei’>’Yinbi Shuanghui’.Affected by the acid rain stress,these three plants presented a decrease in the net photosynthetic rate,stomatal conductance and transpiration rate while the intercellular CO2 concentration was continually growing,indicating that the photosynthetic rate of the osmanthus fragrans color group was reduced by the non-stomatal limitations.(3)The influences of the acid rain stress on the fluorescence parameter of these three osmanthus fragrans color groups indicate:during the period of stress,the Fo values of three plants were on a rise.The increase of Fo values can be ranked in a descending order as follows:’Qiannan Guifei’>’Yinbi Shuanghui’>’Yuntian Caigui’.The Fv/Fm values,qP values and ETR values of these three plants were seeing a reduction as the following descending order ’Yuntian Caigui ’>’Yinbi Shuanghui’>’Qiannan Guifei ’,presenting a proper consistency.And the decrease of Fv’/Fm’ values for these three plants can be arranges in a descending order as:’Yuntian Caigui’>’Qiannan Guifei ’>’ Yinbi Shuanghui’.(4)The influences of the acid rain stress on the physiology and biochemistry of these three osmanthus fragrans color groups indicate:under the simulated acid rain stress,the pH values of leave juice of these three plants were decreased as the pH concentration was rising.In the event of concentration with pH2.0,these three plants were reduced in the following descending order:’Yuntian Caigui ’>’Yinbi Shuanghui ’>’Qiannan Guifei ’ No obvious regularity can be concluded concerning the ratio of the free water and irreducible water for ’Yuntian Caigui ’and ’Yinbi Shuanghui ’.In addition,’Yuntian Caigui’ achieved a high ratio but a weak resistance.The MDA content of these three osmanthus fragrans color groups presented an overall increase as the decrease of the pH value and the growing number of the treatment,showing that the acid rain cause the aggravating peroxidation of the cell membrane lipid.Under the acid rain stress,the activity of the peroxidase POD was greatly rising.With the increase in the number of treatment,the POD activity revealed an increase firstly and decrease at later stage.The increase period of ’Yuntian Caigui’ was shorter than that for ’Yinbi Shuanghui’ and’Qiannan Guifei’ while its decrease is a little longer.The final declining degree of’Yuntian Caigui ’is more than that of ’Yinbi Shuanghui ’,indicating that ’Yuntian Caigui’is more likely to be affected by the acid rain stress.Based on the above indicator changes,three kinds of the osmanthus fragrans color group including ’Yuntian Caigui’,’Yinbi Shuanghui’ and ’Qiannan Guifei’can get used to slight(pH4.0)acid rain stress.However,under a condition of growing acid rain concentration and continuous stress,’Qiannan Guifei’presents a superior performance.As a whole,the acid resistance of these three osmanthus fragrans color groups can be ranged in the following order:’Qiannan Guifei ’>’Yinbi Shuanghui’>’Yuntian Caigui’.