Studies On Adaption Of Medicago Sativa Under Fe～(2+) And Acid Stress

Alfalfa (Medicago sativa) is a kind of perennial forage grass of leguminosae, growth rapidly, yield is high and rich in protein content, the ability of tolerance are strongly, adaption broad, palatableness is good, usually be named "king of the foragegrass". Is widely cultivated in world. But if we want to promote it acidic and iron-rich soil which are 40% of whole area in world, we should face the stress factor that reduce yield of alfalfa in acid and iron-rich soil. Traditional research primarily use sour soil cultivation.Be in the very good simulation of real environment.But it's unable to concretely inquired the effective of single stress factor on alfalfa respectively, therefore it's unable to determine dominate factor causes the damage, and difficult to proposes the corresponding countermeasure and find the special details in the different regions.In this experiment, separation acid and iron-rich soil to research the iron stress and acid stress respectively simulates solely forces of factor, carries on the single factor to the alfalfa seedling the different acidity to experimental two level of acidity environment combine different Fe²⁺ density. To discussion alfalfa regarding various limit for acidity tolerance, forces the performance, as well as and suffers injury the performance under the different acidity to the Fe²⁺ tolerance difference.Following is the conclusion:1.Alfalfas has the difference for the different acid treatment germination responded, between pH5-6 for the growth receives the promotion, under the pH=5 environment, germination be speed up, the new born rate of leaves are speed up, the nodule number and biomass remarkable increased, the physiological target basically is in surpasses the comparison (pH=7); Explained the pH=5 environment most is suitable for the alfalfa germination and growth, have a difference with others results.2.pH=4 is the lowest acidity of alfalfa, in this environment, the alfalfa show the symptom causes by acid, but the difference of vigorous of roots , photosynthesis efficiency,the biomass accumulation comparison are not obviously,and may maintain the normal growth. After the removal forces of acid, the symptom in acid will be possible gradually to vanish, restores to the better growth condition. When the pH value is lower than this level, the plant couldn't tolerant.3.The environment of pH4.5 not achieved the limit of alfalfa; this pH value also is the majority sour soil area average acidity. Fe²⁺ experiment in this pH value, then by better simulation objective sour soil environment, also may guarantee alfalfa living, without excessively disturbance the effect of Fe²⁺.Dual forces the experimental means that alfalfa more sensitive in pH4.5 to the Fe²⁺ than in pH6, executes in10mg/kg inputs displays the remarkable nutrition function; the durable limit is 100mg/kg treatment density.50mg/kg Fe²⁺ treatment displays the good nutrition function under pH6, and the limited is the 150mg/kg density4.The acid and the iron forces have own sensitive physiology or the shape target. such as the rate of germination, newborn leaves and leaf blade number and chlorophyll content main factor is the acidity; The nodule number, the chlorophyll fluorescence characteristic (Fv/Fm) (Fv/Fo),and the root vigor is more sensitive to the Fe²⁺; some part of targets sensitive with two kind factors together, as under-ground biomass, plant survival rate and protoplasmic membrane penetrability under the low Fe²⁺ density, the function which the acidity forces quite is obvious, with the increases of Fe²⁺ concentration the relationship of acidity wreaked gradually.