小金海棠和山定子幼苗根自由空间铁累积量和活化量

不同基因型苹果幼苗根系自由空间铁累积量和活化利用能力不同。在缺铁胁迫条件下，抗缺铁的苹果基因型小金海棠幼苗与对缺铁敏感的山定于幼苗相比，根系自由空间铁累积量大，且它对此铁库的活化利用能力强。此外，供给铁源不同，在植物根中形成的自由空间铁库大小就不同；不同植物基因型对此铁库的活化利用能力也不同，因此，根自由空间铁库的大小及植物对该铁库中铁的活化能力大小可作为不同基因型苹果铁营养效率的筛选指标。

Genotype Differences in Fe Accumulation and Mobilization in Root Apoplast of Fe-deficient Apple Seedling

The genotypic differences in Feaccumulation and mobilization in rootapoplast of Fe-deficient apple seedlingsgrown in nutrient solution was studiedin nutrient solution under controlled environmental conditions. Two applegenotypes selected from 5 years fieldexperiments were used to compare theability to accumulat Fe in root apoplastto mobilize it. To obtain different levelsof Fe in the root apoplast, plants weresupplied in the dark for 8 h with microbial siderophore (FeDFOB) and plantborne chelate (FePS ). The mobilization and uptake of Fe from apoplasmicFe pool was studied for 10 d in freshnutrient solution which was free fromFe supply and renewed every 2 days.The results demonstrated that comparedwith Fe-inefficient genotype Malus baccata, Fe-efficient genotype Malus xiaojinensis seedlings had large Fe-pools inroot apoplast, the mobilization of Fefrom this Fe-pools was enhanced considerably under iron deficiency. In addition, the ability to form Fe-pools inplant root apoplast varieda ccording tothe Fe-form supplied: less stable Fechelate (FePS) resulted in a larger rootapoplasmic Fe pool than stable Fechelate (FeDFOB). The implication ofloading of Fe in root apoplasm and Femobilization from this pool was also discussed as a possible screening methodfor genotype selection.