Physiological Responses To Exogenous SA And ABA In Alfalfa Varieties Under Chilling Stress

Alfalfa (Medicago sativa L.) is an important leguminous forage. It is widely culticated all over the world. Nowadays lower temperature in winter becomes a key point of restricting the alfalfa’s growth in Northern High Latitudes China.Salicylic acid (SA) and abscisic acid (ABA) is of vital importance in the response to abiotic stress of plants. The Salicylic acid is a kind of hydroxybenzene ramification of rash oxalic acid metabolize track, which has a function of signal molecule, and it can regulate the growth abloom, heat, absorb hydronium, respond to biology stress and non-biology stress. Abscisic acid(ABA) is important hormones and playimportant roles in growth and development in responses to stress. In this study, Alfalfa were three cultivars with different winter hardiness (The differences of hardiness with the three alfalfa varieties under chilling stress was significant, from high to low, which in turn for:Gongnong No.1> Golden Empress> Sandeli.) This study through spraying the appropriate concentration of the exogenous salicylic acid and abscisic acid, selecting dry weight and plant height of alfalfa seedlings、the election conductivity value、 the content of soluble sugar、free praline、soluble protein、POD、SOD and CAT as indices, studing the change condition of every physiology index and the relationship of every physiology index and cold resistance of different Alfalfa varietie to research the physiological responses to exogenous SA and ABA in alfalfa varieties under chilling stress, the results show that:1、By measuring the dry weight and plant height of the three alfalfa varieties(Gongnong No.1, Golden Empress, Sandeli.) under chilling after sraying SA(50ml/L), ABA(5ml/L),SA+ABA, it showed that the SA, ABA, treatment can improve the dry weight and plant height of alfalfa seedlings significantly than those of warter-treated plants. Spraying ABA and SA at the same time, the some of the dry weight and plant height of alfalfa seedlings was the largest and the most obvious effect..The plant height ofgongnong NO.1is the highest, the dry weight was the largest,and the hardiness was the strongest in three alfalfa varieties.2、By measuring the contents of soluble sugar of the three alfalfa varieties(Gongnong No.1, Golden Empress, Sandeli.) under chilling after sraying SA(50ml/L), ABA(5ml/L),SA+ABA, it showed that there were no significant differences of the contents of soluble sugar between the ABA-treated plants and the water-treated ones. the SA, SA+ABA treatment can improve the contents of soluble sugar of the alfalfa seedlings significantly than those of warter-treated plants. Spraying ABA and SA at the same time, the contents of soluble sugar of the alfalfa seedlings was the most and the effect was the most obvious. The contents of soluble sugar of gongnong NO.1was the most, and the hardiness is the strongest in three alfalfa varieties.3、By measuring the contents of soluble protein of the three alfalfa varieties(Gongnong No.1, Golden Empress, Sandeli.) under chilling after sraying SA(50ml/L), ABA(5ml/L), SA+ABA, it showed that there were no significant differences of the contents of soluble protein between the ABA-treated plants and the water-treated ones.the SA, SA+ABA treatment can improve the contents of soluble protein of the alfalfa seedlings significantly than those of warter-treated plants. Spraying ABA and SA at the same time, the contents of soluble protein of the alfalfa seedlings was the most and the effect was the most obvious. The contents of soluble protein of gongnong NO.1was the most, and the hardiness is the strongest in three alfalfa varieties.4、The contents of free proline of different Alfalfa varieties had different change after the low temperature.By measuring the free proline contents of the three alfalfa varieties(Gongnong No.1, Golden Empress, Sandeli.) under chilling after sraying SA(50ml/L), ABA(5ml/L), SA+ABA, it showed that there were no significant differences of the contents of free proline between the SA-treated plants and the water-treated ones. the ABA, SA+ABA treatmented can improve the contents of free proline of the alfalfa seedlings significantly than those of warter-treated plants. Spraying ABA and SA at the same time the contents of free proline of the alfalfa seedlings was the most and the effect was the most obvious. The contents of free proline of gongnong NO.1was the most, and the hardiness is the strongest in three alfalfa varieties.5、The contents of MDA of different Alfalfa varieties had different change after the low temperature.By measuring the MDA contents of the three alfalfa varieties(Gongnong No.1,Golden Empress, Sandeli.) under chilling after sraying SA(50ml/L), ABA(5ml/L), SA+ABA,it showed that the SA, ABA, SA+ABA treatmented can decrease the contents of MDA of the alfalfa seedlings significantly than those of warter-treated plants. Spraying ABA and SA at the same time, the contents of MDA of the alfalfa seedlings was the least and the effect was the most obvious. The contents of MDA of gongnong NO.1was the least, and the hardiness is the strongest in three alfalfa varieties.6、with SA+ABA treatment the most significant of all. Spraying SA and ABA signal material together can reduce the relative electrical conductivity in the alfalfa seedlings. Spraying SA or ABA separately can reduce the relative electrical conductivity in the alfalfa seedlings, but with no significant difference to contrast.7、with SA+ABA treatment the most significant of all. Spraying SA and ABA signal material together can greatly improve the enzyme activity of SOD and POD in the alfalfa seedlings, but CAT enzyme activity with no significant difference to contrast. Spraying SA or ABA separately can greatly improve the enzyme activity of POD and CAT in the alfalfa seedlings, but SOD enzyme activity with no significant difference to contrast.