Hu Bo, Henry Amelia, Brown Kathleen M, Lynch Jonathan P
Department of Plant Science, The Pennsylvania State University, University Park, PA 16802, USA.
Ann Bot. 2014 Jan;113(1):181-9. doi: 10.1093/aob/mct259. Epub 2013 Nov 17.
Formation of root cortical aerenchyma (RCA) can be induced by nutrient deficiency. In species adapted to aerobic soil conditions, this response is adaptive by reducing root maintenance requirements, thereby permitting greater soil exploration. One trade-off of RCA formation may be reduced radial transport of nutrients due to reduction in living cortical tissue. To test this hypothesis, radial nutrient transport in intact roots of maize (Zea mays) was investigated in two radiolabelling experiments employing genotypes with contrasting RCA.
In the first experiment, time-course dynamics of phosphate loading into the xylem were measured from excised nodal roots that varied in RCA formation. In the second experiment, uptake of phosphate, calcium and sulphate was measured in seminal roots of intact young plants in which variation in RCA was induced by treatments altering ethylene action or genetic differences.
In each of three paired genotype comparisons, the rate of phosphate exudation of high-RCA genotypes was significantly less than that of low-RCA genotypes. In the second experiment, radial nutrient transport of phosphate and calcium was negatively correlated with the extent of RCA for some genotypes.
The results support the hypothesis that RCA can reduce radial transport of some nutrients in some genotypes, which could be an important trade-off of this trait.
营养缺乏可诱导根皮层通气组织（RCA）的形成。在适应好氧土壤条件的物种中，这种反应具有适应性，可降低根系维持需求，从而允许根系进行更大范围的土壤探索。RCA形成的一个权衡可能是由于活皮层组织减少导致养分径向运输减少。为验证这一假设，在两项放射性标记实验中，对具有不同RCA的玉米（Zea mays）完整根系中的养分径向运输进行了研究。
在第一个实验中，测量了不同RCA形成程度的离体节根中磷酸盐向木质部装载的时间进程动态。在第二个实验中，测量了完整幼苗胚根对磷酸盐、钙和硫酸盐的吸收，其中通过改变乙烯作用或遗传差异的处理诱导RCA产生变化。
在三组配对基因型比较中，高RCA基因型的磷酸盐渗出率均显著低于低RCA基因型。在第二个实验中，某些基因型的磷酸盐和钙的径向养分运输与RCA的程度呈负相关。
结果支持了RCA可降低某些基因型中某些养分径向运输的假设，这可能是该性状的一个重要权衡。
