木薯华南8号组培苗对盐胁迫的生理响应

以NaCl胁迫生长的木薯(Manihot esculenta)华南8号(SC8)组培苗为材料,研究不同浓度(0、5、20、35、50 mmol·L-1及R50 mmol·L-1)NaCl处理对SC8组培苗的生长状况及叶绿素、过氧化氢(H2 O2)、丙二醛(MDA)含量,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)、抗坏血酸过氧化物酶(APX)活性的影响.结果表明:≤20 mmol·L-1的NaCl胁迫60 d对SC8组培苗的生长基本无影响;≥35 mmol·L-1的NaCl胁迫60 d抑制了SC8组培苗的生长,但高浓度(50 mmol·L-1)胁迫30 d后正常培养30 d,可以使SC8组培苗的长势得到恢复.叶绿素和MDA含量在≤35 mmol·L-1 NaCl处理下较对照出现积累现象,随NaCl浓度升高(≥50 mmol·L-1)含量开始下降;与对照相比,H2 O2含量在NaCl胁迫下未出现积累现象.NaCl胁迫下,POD、CAT和APX活性较对照均有所提高;较高浓度的NaCl处理下,SOD、CAT和APX活性开始降低.实时荧光定量PCR结果表明,≥50 mmol·L-1NaCl胁迫下,SOD、CAT、POD和APX的表达水平较对照出现上升现象.这说明短时间的盐胁迫不会对木薯造成致死伤害,可以通过调节生理指标的活性来提高木薯的耐盐性.

Physiological mechanism of cassava South China 8 tissue culture seedling under salt stress

The cassava ( Manihot esculenta) South China 8 ( SC8) tissue culture seedlings were conducted to investigate the physiological mechanism in response to salt stress. Effects of MS medium treatment contained NaCl ( 0, 5, 20, 35, 50 mmol·L-1 and R50 mmol·L-1 ) on the growth and physiological indexes activities of Cassava SC8 tissue culture seed-lings were evaluated. The physiological indexes include chlorophyll, hydrogen peroxide ( H2 O2 ) , malonaldehyde (MDA) content, and the activities of superoxide dismutases (SOD), catalases (CAT), peroxidase (POD), ascorbate peroxidase (APX). The results of physiological showed that the growth of SC8 tissue culture seedlings did not change significantly after NaCl content (≤20 mmol·L-1 ) stress for 60 d, but high content (≥35 mmol·L-1 ) of the stress had inhibited SC8 tissue culture seedlings growth. The growth of SC8 tissue culture seedlings could be recovered at NaCl con-cent (50 mmol·L-1) stress for 30 d after they were transferred to the normal MS medium of 30 d. Chlorophyll and MDA contents were accumulated at NaCl content(≤35 mmol·L-1 ) stress, but which were not accumulated at NaCl content (≥50 mmol·L-1 ) stress. H2 O2 content had no obvious change at NaCl content stress which it was compared with con-trol. Activities of antioxidant enzymes including POD, CAT and APX were increased at NaCl stress, whereas the activi-ties of SOD, CAT and APX were decreased at higher NaCl stress. The results of real-time quantitative PCR showed that the expression level of SOD, CAT, POD and APX were higher than control at NaCl content(≥50 mmol·L-1)stress. The results indicated that salt stress for a short period of time would not cause devastating damage to cassava, which could improve the salt tolerance of cassava by regulating the activity of physiological indexes.