盐胁迫对蒙桑种子萌发及幼苗生长的影响

为研究盐胁迫对蒙桑种子萌发及幼苗生长的影响，共设置0、20、30、50、70、100 mmol·L-1六个NaCl浓度梯度，对蒙桑种子及幼苗进行胁迫处理，测定蒙桑种子的萌发指标和蒙桑幼苗的生理指标，阐述其应对盐胁迫的响应变化特征。结果表明:①随着NaCl浓度的升高，蒙桑种子的萌发率、发芽指数均显著下降；胚根长度、胚芽长度在20 mmol·L-1时受到抑制，胚根生长速度在30 mmol·L-1时受到抑制；在盐胁迫条件下，活力指数与耐盐指数均呈下降趋势，且在NaCl浓度为20 mmol·L-1时，二者均下降至对照的50%左右。②对种子萌发指标、活力指数指标及幼苗生长指标与盐浓度进行相关性和回归分析，发现蒙桑种子发芽率、活力指数、胚根长度、胚根生长速度的耐盐临界值分别为2.55、59.71、2.42、0.67 mmol·L-1。③随着NaCl溶液浓度的增加，蒙桑幼苗丙二醛（malondialdehyde，MDA）含量、可溶性蛋白质（soluble protein，SP）含量、游离脯氨酸（free proline，Pro）含量、相对电导率均显著上升；超氧化物歧化酶（superoxide dismutase，SOD）活性在50 mmol·L-1 NaCl浓度时显著下降；可溶性糖（soluble sugar，SS）含量呈现震荡上升的趋势。因此，盐胁迫下蒙桑种子萌发和幼苗生长均受到一定程度的抑制，但幼苗可通过调节自身有机渗透物质及提高保护酶活性主动适应逆境，表现出较强抗盐能力。研究结果为蒙桑在盐碱地区的育苗推广提供理论基础，并对培育和保护抗盐植物资源以及盐碱地带植物种群的重建和植被恢复提供科学依据。

Effects of Salt Stress on Seed Germination and Seedling Physiological Characteristics of Morus mongolica

In order to study the effects of salt stress on seed germination and seedling growth of Morus mongolica, the salt stress experiments on M. mongolica seeds and seedlings were carried out with 0, 20, 30, 50, 70, 100 mmol·L-1 NaCl solutions. The germination indexes of seeds and the physiological indexes of M. mongolica seedlings were detected to reflect the response characteristics of salt stress. The results showed that: ① the germination rate and germination index of M. mongolica decreased significantly with the increase of NaCl concentration; the radicle length and germ length were inhibited over 20 mmol·L-1, and the radicle growth rate was inhibited from 30 mmol·L-1. At the same time, the activity index and salt tolerance index showed a downward trend under salt stress conditions, and when the NaCl concentration was 20 mmol·L-1, both decreased to about 50% of the control. ② Correlation and regression analysis results of seed germination index, vigor index, seedling growth index and salt concentration showed that the salt tolerance thresholds of germination rate, vigor index, radicle length and radicle growth rate of M. mongolica seed were 2.55, 59.71, 2.42, 0.67 mmol·L-1, respectively. ③ With the increase of NaCl concentration, malondialdehyde (MDA) content, soluble protein (SP) content, free proline (Pro) content and relative conductivity were all observed significantly increased. Superoxide dismutase (SOD) activity decreased significantly at 50 mmol·L-1 NaCl concentration. Soluble sugar (SS) content showed a tendency of volatility. Therefore, under salt stress, seed germination and seedling growth of M. mongolica were inhibited to some extent, but the seedlings could adapt to the adversity by regulating their own organic penetrating substances and improving the protective enzyme activity, showing strong salt tolerance. The present research provided a basic theory for the promotion of seedlings of M. mongolica in saline-alkali areas, and provided a scientific basis for the cultivation and protection of salt-tolerant plant resources and the reconstruction of plant populations in saline-alkali areas.