UWA School of Agriculture and Environment, The University of Western Australia, Perth, WA, Australia.
UWA School of Biological Sciences, The University of Western Australia, Perth, WA, Australia.
J Exp Bot. 2021 Feb 24;72(4):1490-1505. doi: 10.1093/jxb/eraa515.
Very few of the >650 Proteaceae species in south-western Australia cope with the high calcium (Ca) levels in young, calcareous soils (soil indifferent); most are Ca sensitive and occur on nutrient-impoverished, acidic soils (calcifuge). We assessed possible control points for Ca transport across roots of two soil-indifferent (Hakea prostrata and Banksia prionotes) and two calcifuge (H. incrassata and B. menziesii) Proteaceae. Using quantitative X-ray microanalysis, we investigated cell-specific elemental Ca concentrations at two positions behind the apex in relation to development of apoplastic barriers in roots of plants grown in nutrient solution with low or high Ca supply. In H. prostrata, Ca accumulated in outer cortical cells at 20 mm behind the apex, but [Ca] was low in other cell types. In H. incrassata, [Ca] was low in all cells. Accumulation of Ca in roots of H. prostrata corresponded to development of apoplastic barriers in the endodermis. We found similar [Ca] profiles in roots and similar [Ca] in leaves of two contrasting Banksia species. Soil-indifferent Hakea and Banksia species show different strategies to inhabit calcareous soils: H. prostrata intercepts Ca in roots, reducing transport to shoots, whereas B. prionotes allocates Ca to specific leaf cells.
在澳大利亚西南部，仅有极少数 (>650 种)的山龙眼科植物能够适应年轻的钙质土壤（土壤非石灰性）中的高钙水平（土壤非石灰性）；大多数山龙眼科植物对钙敏感，生长在养分贫瘠、酸性土壤上（钙非专性）。我们评估了两种土壤非石灰性（平卧山龙眼和短丝柏）和两种钙非专性（厚叶山龙眼和班克西亚）山龙眼科植物根系中钙跨根运输的可能控制点。使用定量 X 射线微分析，我们研究了在低钙或高钙养分溶液中生长的植物根尖后两个位置的细胞特异性元素钙浓度与质外体屏障发育的关系。在平卧山龙眼中，钙在根尖后 20 毫米的外皮层细胞中积累，但其他细胞类型中的 [Ca] 较低。在厚叶山龙眼中，所有细胞中的 [Ca] 都较低。平卧山龙眼根系中钙的积累与内皮层质外体屏障的发育相对应。我们发现，两种不同的班克西亚属植物的根和叶中存在相似的 [Ca] 分布。能在石灰性土壤中生存的土壤非石灰性山龙眼科和班克西亚属植物表现出不同的策略：平卧山龙眼在根系中拦截钙，减少向地上部分的运输，而短丝柏则将钙分配到特定的叶细胞中。
