Aluminium (Al) hyper-accumulation is a common trait expressed by tropical woody plants growing on acidic soils. Studies on Al accumulators have suggested that Al addition may enhance plant growth rates, but the functional significance of this trait and the mechanistic basis of the growth response are uncertain. This study aimed to test the hypothesis that differential growth responses to Al among populations of an Al accumulator species are associated with variation in biomass allocation and nutrient uptake. We conducted two experiments to test differential responses to the presence of Al in the growth medium for seedlings of the Al accumulator shrub Melastoma malabathricum collected from 18 populations across Peninsular Malaysia. Total dry mass and relative growth rate of dry mass were significantly greater for seedlings that had received Al in the growth medium than for control plants that did not receive Al, but growth declined in response to 5.0 mM Al addition. The increase in growth rate in response to Al addition was greater for a fast-growing than a slow-growing population. The increase in growth rate in response to Al addition occurred despite a reduction in dry mass allocation to leaves, at the expense of higher allocation to roots and stems, for plants grown with Al. Foliar concentrations of P, K, Mg and Ca increased in response to Al addition and the first axis of a PCA summarizing foliar nutrient concentrations among populations was correlated positively with seedling relative growth rates. Some populations of the Al hyper-accumulator M. malabathricum express a physiological response to Al addition which leads to a stimulation of growth up to an optimum value of Al in the growth medium, beyond which growth declines. This was associated with enhanced nutrient concentrations in leaves, which suggests that Al accumulation functions to optimize elemental stoichiometry and growth rate.

中文翻译：

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铝蓄积植物野牡丹种群对铝添加的生长反应对比

铝 (Al) 超积累是酸性土壤上生长的热带木本植物的一个常见特征。对铝累积体的研究表明，添加铝可能会提高植物生长速度，但这一性状的功能意义和生长反应的机制基础尚不确定。本研究旨在检验以下假设：铝累积物种种群中对铝的差异生长反应与生物量分配和养分吸收的变化相关。我们进行了两项实验，测试从马来西亚半岛 18 个种群收集的铝累积灌木Melastoma malabathricum幼苗对生长介质中铝存在的差异反应。在生长培养基中接受Al的幼苗的总干质量和干质量的相对生长速率显着高于未接受Al的对照植物，但响应于添加5.0 mM Al，生长下降。快速增长的种群对铝添加的响应增长率的增加大于缓慢增长的种群。对于用铝生长的植物来说，尽管分配给叶子的干物质减少了，但增加了铝的生长速率，但代价是分配给根和茎的比例更高。叶面的磷、钾、镁和钙浓度随着铝的添加而增加，总结群体叶面养分浓度的 PCA 的第一轴与幼苗相对生长率呈正相关。Al超累积菌M. malabathricum的一些种群对Al添加表现出生理反应，这导致生长刺激生长至生长培养基中Al的最佳值，超过该值生长下降。这与叶子中养分浓度的增加有关，这表明铝的积累具有优化元素化学计量和生长速率的作用。