盐胁迫对油菜幼苗生长和光合特征的影响

采用盆栽砂培试验,研究了不同浓度(0、50、100、200、300mmol·L-1)NaCl胁迫10和30d对油菜(Brassica napus)幼苗干质量、叶绿素(Chl)含量、净光合速率(Pn)、气孔导度(Gs)、细胞间CO2浓度(xi)、蒸腾速率(Rt)、水分利用效率(Ew,u)和气孔限制值(Ls)等的影响.结果表明,在NaCl胁迫下,油菜幼苗植株干质量显著降低,长期高盐胁迫下油菜干质量降低更显著；随NaCl浓度的增加,Chl含量、Chl a/Chl b比值均呈先升高后降低的变化趋势,处理10d,Chl含量、Chl a/Chl b比值在NaCl浓度为200mmol·L-1条件下达最大值,处理30d,在NaCl浓度为100mmol·L-1条件下达最大值.在50～100mmol·L-1NaCl胁迫下,油菜叶片的Pn、xi和Ls所受影响均很小；高盐胁迫下,其Pn、Gs、xi和Rt均显著下降,而Ew,u和Ls则显著上升.相关分析显示,植株干质量与Chl含量、Chl a/Chl b比值间无相关性,与Na+、Cl-含量,Ew,u和Ls间呈显著负相关(P＜0.01),与根冠比,K+、Ca2+含量,K+/Na+、Ca2+/Na+比值,K+与Na+的选择性比率S(K+,Na+)],Ca2+与Na+的选择性比率S(Ca2+,Na+)],Pn,Gs,xi和Rt间呈显著正相关(P＜0.01).上述结果表明,200mmol·L-1 NaCl胁迫10和30d、300mmol·L-1 NaCl胁迫10d,油菜幼苗光合抑制主要来自气孔限制,而300mmol·L-1 NaCl胁迫30d,气孔限制和非气孔限制在油菜幼苗光合抑制中均具有重要作用.Na+、Cl-、K+、Ca2+含量,Ew,u,Ls,根冠比,K+/Na+、Ca2+/Na+比值,S(K+,Na+),S(Ca2+,Na+),Pn,Gs,xi和Rt均可作为油菜生长盐适应性的评价指标.

Effects of Salt Stress on Growth and Photosynthetic Traits of Canola Seedlings

A pot experiment was carried out using canola in sand culture to explore effects of 10 and 30 days of NaCl stress(0,50,100,200,300 mmol·L-1) on biomass,chlorophyll(Chl),net photosynthetic rate(Pn),stomatal conductivity(Gs),intercellular CO2 concentration(xi),transpiration rate(Rt),moisture utilization rate(Ew,u) and stomatal limitation(Ls) of canola seedlings.Results show that NaCl stress decreased significantly plant dry weight,especially when the salt was high in concentration and existed for a long time;with increasing NaCl concentration,chlorophyll(Chl) content and Chl a/Chl b ratio both displayed a variation pattern of ascending first and descending later,and peaked under the stress of 200 mmol·L-1 NaCl,for 10 days and under the stress of 100 mmol·L-1 NaCl for 30 days.Pn,xi and Ls in canola leaves growing under the stress of 50 and 100 mmol·L-1 NaCl stress were not much affected,but,Pn,Gs,xi and Rt were markedly decreased when the stress was higher,however,in this case,Ew,u and Ls increased significantly.Correlation analysis indicated that biomass(dry weight) of canola was insignificantly related to Chl content and Chl a/Chl b ratio,but significantly and negatively related to Na+,Cl-content,Ew,u and Ls,and significantly and positively related to root/shoot ratio(R/S),K+,Ca2+ content,K+/Na+,Ca2+/Na+ ratio,K+ and Na+ selectivity ratio S(K+,Na+)],Ca2+ and Na+ selectivity ratio S(Ca2+,Na+)],Pn,Gs,xi and Rt.The findings indicate that in seedlings under the stress of 200 mmol·L-1 NaCl for 10 or 30 days,or 300 mmol·L-1 NaCl for 10 days,stomatal limitation was the major restraint of photosynthesis.But when the stress was increased to 300 mmol·L-1 NaCl for 30 days,both stomatal and non-stomatal limitations played important roles in restraining photosynthesis.Na+,Cl-,K+ and Ca2+ contents,Ew,u,Ls,R/S, K+/Na+,Ca2+/Na+,S(K+,Na+),S(Ca2+,Na+),Pn,Gs,xi and Rt can all be regarded as indexes for evaluation of canola in salt adaptability.