对0.00(对照)～0.50 mol.L^-1NaCl处理48 h后萝卜(Raphanus sativus L.)幼苗叶片的叶绿素含量、净光合速率、丙二醛(MDA)含量和相对电导率进行了测定,并观察了根尖细胞核形态变化和胁迫后幼苗生长的恢复状况。测定结果表明:经0.05 mol.L^-1 NaCl处理后,叶片的叶绿素含量和净光合速率均高于对照(0.00 mol.L^-1NaCl);而用0.10～0.50 mol.L^-1 NaCl处理后,叶绿素含量和净光合速率均随NaCl浓度的提高逐渐降低且与对照差异显著,其中,经0.35～0.50 mol.L^-1NaCl胁迫处理后叶片净光合速率降至0.00μmol.m^-2.s^-1。随NaCl浓度的提高,MDA含量和相对电导率呈先快速上升而后逐渐下降的趋势,且均与对照差异显著;其中,经0.30 mol.L^-1NaCl处理后MDA含量最高,经0.40 mol.L^-1NaCl处理后相对电导率最高。观察结果显示:经0.05～0.25 mol.L^-1NaCl处理后根尖细胞核由规则的圆形向各种不规则形状转变,染色质出现不同程度的浓缩,表现出不同程度的程序性细胞死亡特征;经0.30～0.50 mol.L^-1NaCl处理后则出现中空细胞与部分正常细胞并存的现象。经0.05和0.10 mol.L^-1 NaCl处理后,萝卜幼苗可恢复正常生长,且株高与对照无明显差异;而经0.25～0.50 mol.L^-1NaCl处理后,幼苗均较难恢复正常生长,且随NaCl浓度的提高,幼苗出现枯萎、糜烂现象。研究结果显示:低浓度NaCl处理不仅对萝卜幼苗的生长、生理代谢及细胞核形态结构没有明显伤害反而有一定的促进作用,而高浓度NaCl胁迫可导致萝卜幼苗不可逆伤害。

The chlorophyll content， net photosynthetic rate， MDA content and relative electric conductivity in leaf of Raphanus sativus L． seedlings treated by 0.00 ( CK) -0. 50 mol·L^-1 NaCl for 48 h were determined， and morphological change of cell nuclear in root-tip and recovery state of seedling growth after NaCl stress were observed． The determination results show that chlorophyll content and net photosynthetic rate in leaf treated by 0． 05 mol·L^-1 NaCl are all higher than those in the control． While，with 0． 10 - 0． 50 mol · L^-1 NaCl stressed， chlorophyll content and net photosynthetic rate decrease gradually with rising of NaCl concentration and have the significant difference with the control， in which net photosynthetic rate decreases to 0． 00 μmol·m^-2·s^-1 after treated by 0.35-0.50 mol·L^-1 NaCl．With rising of NaCl concentration， MDA content and relative electric conductivity appear the trend of rapidly increasing firstly and then gradually decreasing， and all have the significant difference with those of the control． In which， MDA content is the highest after treated by 0. 30 mol·L^-1 NaCl and relative electric conductivity is the highest after treated by 0.40 mol·L^-1 NaCl． The observation result shows that after treated by 0.05 -0. 25 mol·L^-1 NaCl， cell nuclear morphology in root-tip changes from circle to irregular shapes， and chromatin condenses at different degrees， appearing characteristics of programmed cell death ( PCD) at different degrees． But treated by 0. 30 -0. 50 mol·L^-1 NaCl， there is coexistence phenomenon of empty cells and normal cells in root-tip． After treated by 0.05 and 0.10 mol·L^-1 NaCl，the seedlings can resume to normal growth， and seedling height without obvious difference with that of the control． But seedlings after treated by 0. 25-0.50 mol·L^-1 NaCl can not resume to normal growth and appear to wither and rot phenomenon with rising of NaCl concentration． It is suggested that NaCl treatment with lower concentration not only has no obvious injury but also has a certain promotion impact on growth， physiological metabolism and cell nuclear morphological structure of R． sativus seedlings．While， NaCl treatment with higher concentration can cause irreversible damage to R． sativus seedlings．