影响菜豆体内铁再利用效率的因素及其机理

FACTORS AFFECTING REUTILIZATION EFFICIENCY OF IRON IN BEAN PLANTS AND THEIR MECHANISM

本文在人工气候室中，用营养液培养方法，并结合同位素示踪技术研究了铁的供应状况、两种形态氮素（NO3--N和NH4+-N）及叶片遮光对菜豆体内铁再利用效率的影响，并对其有关机理进行了深入的研究。结果表明，铁的缺乏有利于累积在根和初生叶中的铁向新生组织中转移，铁的再利用效率明显提高。无论在缺铁还是供铁条件下，NH4+-N的供应使得菜豆新叶中活性铁含量、新叶叶绿素含量及体内铁的再利用效率都明显高于NO3--N处理，叶绿体超微结构完整，井且新叶未出现黄化现象；特别是在处理后期，差异更加明显。初生叶遮光使得新叶中活性铁含量增加，体内铁的再利用效率提高了6个百分点左右，在一定程度上改善了NO3－－N营养缺铁菜豆新叶的铁营养状况。可见，NH4+-N的供应和叶片遮光都可提高菜豆体内铁的再利用效率，明显改善菜豆新叶的铁营养状况。

The effects of iron supply, nitrogen forms (NO_3^-N and NH+ -M) andprimary-leaves-shading on reutilization efficiency of Fe in bean plants and their mechanism were studied in nutrient solutions under controlled conditions. The ^(59)Fe isotopic method was also used to identify the iron reutilization efficiency. The results showed that Fe deficiency could enhance Fe translocation to young leaves from roots and primary-leaves, thus increasing Fe reuitlization efficiency. The plants added with NH.+ -N had a much higher content of active Fe, more chlorophyll in young leaves and high Fe reutilization efficiency, much better ultrastructute chloroplast than those fed with NO-3, -N,and these were true both in Fe-sufficient and deficient treatments.No chlorosis occurred in young leaves of beau plants fed with NH+4 -N under Fe-deficient condition. More active Fe and 6 percent enhancement in Fe reutilization efficiency were found in the primary-leaves-shading treatment which improved Fe nutrition in young leaves of Fe-deficient plants fed with NO-3, -N. All these results demonstrated that both NH4+-N and primary-leaves-shading had a beneficial effect on increasing Fe reutilization efficiency, improving Fe nutrition in young leaves and depressing chlorosis symptom in beau plants.