盐胁迫对地木耳和葛仙米生理生化特性的影响

EFFECTS OF HYPERHALINE STRESS ON THE PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERISTICS OFNOSTOC COMMUNE AND NOSTOC SPHAEROIDES

地木耳为一种耐干旱的陆生念珠藻 ,葛仙米则是水生念珠藻 ,由于对各自生境的适应 ,二者在对盐胁迫的反应上可能会有差异。为了阐明这种差异 ,研究了不同盐度胁迫下它们的光合活性、可溶性糖、脯氨酸含量及质膜透性的变化。结果表明 ,高盐胁迫下地木耳和葛仙米的光合活性均降低 ;在 0 .8mol·L- 1 的盐浓度下胁迫 48和 96h后 ,地木耳仍可检测到微弱的光合活性 ,而在葛仙米中已检测不到。地木耳中脯氨酸升高 ;可溶性糖含量升高 ,增幅为87%— 2 0 0 % ;质膜透性比对照略有增加 ,但不同盐度之间差别不大。葛仙米中脯氨酸含量降低 ;可溶性糖含量在NaCl小于 0 .4mol·L- 1 时随盐度的升高而升高 ,增幅为 1 0 0 %— 1 0 0 0 % ,当高于 0 .4mol·L- 1 时随盐度的升高而降低 ;质膜透性随盐度增加而增加 ,在盐浓度为 0 .6和 0 .8mol·L- 1 时 ,均达 90 %以上。结果表明 ,地木耳比葛仙米更能耐受盐度胁迫 ;可溶性糖在地木耳和葛仙米抵抗盐胁迫中有重要作用 。

Nostoc commune is a terrestrial Nostoc species with high desiccation tolerant ability, while Nostoc sphaeroides is an aquatic ones.Their reactions to salt stress might be different for the adaptation to their habitats. In order to clarify the differences, the effects of hyperhaline stress on their photosynthesis, contents of soluble carbohydrates, proline and plasmalemma permeability were investigated. Photosynthesis was significantly inhibited when the Nostoc species were submerged in salty water. Net photosynthesis could still be detected in N. commune after incubating in salty water for 48,96h at the concentrations of 0.6 and 0.8mol·L -1 .However, it could not be detected in N.sphaeroides at the same conditions. In Nostoc commune, the contents of proline and soluble carbohydrates increased when treated with increased NaCl concentrations to 0.8mol·L -1 ,and the increases of soluble carbohydrate ranged from 87% to 200%, and the plasmalemma permeability increased with increased NaCl levels till 0.4mol·L -1 .In Nostoc sphaeroids, proline decreased, but soluble carbohydrates showed a straight increase with the elevated level of salt when submersed in NaCl solutions of less than 0.4mol·L -1 and the increases ranged from 100% to 1000%, but decreased with higher NaCl concentrations and plasmalemma permeability showed a straight increase with the elevated level of salt concentration. The plasmalemma permeability could reach above 90% in N.sphaeroides when the salt concentrations were 0.6 and 0.8mol·L -1 ,however, it was only 31% and 37% for N.commune. The results indicated that N.commune was more tolerant to salt stress compared with N.sphaeroides. Soluble carbohydrates might act as an important role in resisting salt stress in N.commune and N.sphaeroides, however,it was impossible for proline to be a compatible solute in resisting salt stress in N.sphaeroides.