Effects of low temperature stress on growth and development and physiological characteristics of Pueraria lobata seedlings

【Objective】To investigate the effects of low temperature on the growth and development of Pueraria lobata seedlings,physiological and biochemical indicators,and to provide a reference basis for the identification of low temperature tolerance of P. lobat germplasm and the rational selection of germplasm with strong resistance to cold damage.【Method】The germplasm of P. lobata was used as the experimental material in a potted soil culture test. After a week of pre-cultivation in a light incubator,day/night 25 ℃/20 ℃ was set as control(CK),two temperature gradients were set for low temperature treatment,which were mild low temperature stress(LD,day/night 15 ℃/10 ℃) and severe low temperature stress(SD,day/night 10 ℃/5 ℃).【Result】With the decrease of temperature,the growth rate of P. lobata seedlings slowed down,the leaves became smaller,the water content decreased and the relative conductivity increased. The content of soluble sugars,proline(Pro) and other osmoregulatory substances increased;malonaldehyde(MDA) content increased but the difference was not significant(P>0.05) ;the activities of protective enzymes such as peroxidase(POD),superoxide dismutase(SOD) and ascorbate peroxidase(APX) increased and catalase(CAT) activity showed a decreasing trend but always remained at a high level;the content of endogenous hormones such as abscisic acid(ABA),gibberellin(GA₃) and zeaxanthin(ZT) showed an increasing trend and then decreased;the content of auxin(IAA) showed a decreasing trend.The correlation analysis indicated that growth rate was significantly(P<0.05,the same below) negatively correlated with MDA content;ABA content was significantly negatively correlated with relative conductivity,and soluble sugar content was highly significantly(P<0.01) negatively correlated with relative conductivity;POD content was significantly positively correlated with IAA content. According to the characteristic values,the indexes was divided into 6 principal components. Combined with the membership function analysis,it was found that low temperature would bring negative effects on the growth of P. lobat.【Conclusion】Low temperature has adverse effects on the growth of P. lobata,but P. lobata seedlings resist the adverse effects of low temperature stress by enhancing osmoregulation,increasing protective enzyme activity,increasing the content of growth-inhibiting endogenous hormones,and decreasing the content of growth-promoting hormones in vivo.