Effects Of Copper Stress On The Growth Of Alfalfa At The Germination Period

Alfalfa has the reputation of"king of the forage grass",which has the characteristics of high yield,good quality,fast growth and multiple cutting,and the planting area of alfalfa in the South has been expanding in recent years.But the soil is slightly acidic in the south of China.With the improvement of chicken manure and organic fertilizer,the copper content in the soil is out of limit and copper stress is easy to occur in the soil of the planting-breeding combination zone in the southern area.According to this phenomenon,copper stress on alfalfa germination growth period were analyzed to obtain sentsitive alfalfa copper concentration,semi lethal and lethal concentration;using the critical concentration to evaluate the resistance ability to copper of 19 alfalfa varieties;and then selected the 3 alfalfa varieties randomly as materials of the study of procyanidins used in alfalfa seed germination on alleviatingcopper stress.To provide scientific basis for the new application of proanthocyanidins,the main results of this experiment are as follows:1,With the increase of Cu²⁺concentration,the germination index and root index of"Gong Nong 5"showed a decreasing trend in different degrees,in which the germination rate,relative germination rate,germination potential and germination index were decreased significantly?P<0.01?.According to the regression of relative germination rate,the semi lethal concentration of alfalfa germination was 107.15 mg/L Cu²⁺,and the concentration of lethal concentration was 307.83 mg/L Cu²⁺.When copperion concentration was 6.25 mg/L,the root index of seedling showed a sharp decrease,the root tolerance index dropped down remarkably,so Cu²⁺6.25 mg/L?pH=5?is the sensitive concentration to radicle growth of alfalfa.2,Analysis on the resistance of 19 alfalfa cultivars,showed that the stress of 6.25,110.00 and 200.00 mg/L Cu²⁺inhibited the germination and root growth of alfalfa varieties.By using correlation analysis and principal component analysis on the relative values of 10germination period indexes,the evaluation indexes of copper resistance in germination period of 3 Cu²⁺concentrations were obtained.The evaluation indexes of 6.25 mg/L Cu²⁺were relative germination rate,relative root length and relative average diameter;110 mg/L Cu²⁺evaluation indexes were relative germination potential,relative vigor index and relative average diameter;200.00 mg/L Cu²⁺evaluation indexes were relative germination percentage,relative vigor index and relative average diameter.Under the stress of 3 different concentrations of copper,the evaluation indexes were analyzed by membership function and clustering,selecting copper stress,moderate resistance and copper sensitive by 19 alfalfa varieties.Under the stress of 3 different concentrations of copper.the evaluation indexes were analyzed by grade correlation respectively,founding significant hierarchical correlation between 6.25 and 110.00 and 200.00 mg/L Cu²⁺in acid copper stress sequencing.However,there was no significant hierarchical correlation between 110.00 and 200.00 mg/L Cu²⁺.3,Study on the effect of procyanidins on the growth of alfalfa at the germination period under copper stress showed that copper stress inhibited the germination and root growth of alfalfa seeds.The physiological and biochemical analysis of the 3 varieties found that the copper stress not only promoted the activity of SOD and POD in the germination period of the 3 alfalfa varieties,inhibited the activity of CAT and the growth of the seedlings,but also increased the accumulation of MDA content and the permeability of the cell membrane.after the adding proanthocyanidins of different concentrations,the synthesis of SOD and POD in3 species were all higher than those of the control,and the activity of CAT was reduced and then decreased,MDA content and cell membrane permeability were all lower than those of copper.All above proved that procyanidins could alleviate copper toxicity.