磷对铝胁迫紫花苜蓿幼苗根系生长和生理特征的影响

为了探究磷对铝胁迫下紫花苜蓿幼苗生长和生理特征的影响，分别用不含和含200 μmol·L^-1磷（P）、100 μmol·L^-1铝（Al）、200 μmol·L^-1 P+100 μmol·L^-1 Al的简易 ［Ca（NO₃）₂］营养液（pH=4.5）处理铝敏感紫花苜蓿品种‘Wl440’幼苗。结果表明，在铝处理中添加磷后，苜蓿幼苗根系和叶片中的铝含量分别比铝处理降低81.53%和61.47%，苜蓿幼苗的根长和根系活力显著提高，叶片电导率和丙二醛（MDA）含量显著下降；光合生理得到明显改善，与铝处理相比，磷添加处理幼苗叶片的叶绿素含量、蒸腾速率、气孔导度和光合速率明显提高，光系统Ⅱ和光系统I的电子传递速率增加；磷添加处理明显提高了铝胁迫苜蓿根系的草酸和苹果酸含量，体内有机酸螯合铝离子的能力增强，光合能力提高。因此，磷能够通过增加根系有机酸含量，改善铝胁迫苜蓿光合系统，从而缓解苜蓿铝毒害。

Effects of phosphorus on root growth and photosynthetic physiology of alfalfa seedlings under aluminum stress

In order to explore the effects of phosphorus （P） on growth and photosynthesis physiology of alfalfa seedlings under aluminum stress. Simple Ca（NO₃）₂ nutrient solution （pH=4.5） containing 200 μmol·L^-1 P or 100 μmol·L^-1 Al or 200 μmol·L^-1 P+100 μmol·L^-1 Al was used to treat ‘Wl440’ seedlings， and Ca（NO₃）₂ nutrient solution （pH=4.5） without P and Al was as control. It was found that application of P significantly decreased the Al content in roots （81.53%） and leaves （61.47%） of alfalfa under Al stress. Application of P significantly increased the root length， root activity， leaf chlorophyll content， transpiration rate， stomatal conductance， photosynthetic rate， and electron transfer rate of photosystem I and Ⅱ， and significantly decreased electrical conductivity and malondialdehyde （MDA） content. The contents of oxalic acid and malic acid in Al-stressed alfalfa roots were significantly increased by phosphorus addition. In summary， these results indicate that phosphorus addition can effectively increase organic acid contents， improve the photosynthetic system， and consequently alleviate alfalfa aluminum toxicity.