Data from: Strategies in Ericaceae to acquire phosphorus in phosphorus-impoverished habitats in the southwest Australian biodiversity hotspot.

We hypothesised that some Ericaceae exhibit high leaf manganese (Mn)
concentrations [Mn], a proxy for rhizosphere carboxylates, and release
root carboxylates. We compared their leaf [Mn] with that of positive and
negative reference species, known to release carboxylates or not,
respectively. To follow up, we measured the carboxylate-exudation rates of
targeted species with high and low leaf [Mn] using seedlings grown in
low-P nutrient solutions. Using these complementary approaches, we
confirmed that Ericaceae in P-impoverished habitats with high leaf [Mn]
exhibit a carboxylate-releasing P-mobilising strategy, like
non-mycorrhizal Proteaceae. Surprisingly, some species with low leaf [Mn],
which occurred in habitats with high soil pH, also released carboxylates.
Therefore, low leaf [Mn] cannot conclusively indicate the absence of
carboxylate exudation. These species may release carboxylates along with
cations such as potassium or magnesium, which increase the rhizosphere pH,
thereby decreasing Mn availability and accumulation in mature leaves. The
lack of a significant phylogenetic signal detected for leaf [P] and leaf
[Mn] across sampled taxa indicated these nutrient-acquisition traits are
not limited to certain clades but likely evolved independently multiple
times in Ericaceae. Styphelia sensu lato exhibited the widest trait
variation (highest to lowest leaf [P] and [Mn]) of all genera included in
this study.

本研究提出假说：部分杜鹃花科（Ericaceae）植物可表现出较高的叶片锰（manganese, Mn）浓度——该指标可作为根际羧酸盐释放情况的替代指标——且会主动释放根系羧酸盐。我们将这类植物的叶片锰浓度与已知分别会释放、不会释放羧酸盐的阳性、阴性参考物种进行了对比。后续实验中，我们利用低磷营养液培养的实生苗，测定了叶片锰浓度高低各异的目标物种的羧酸盐分泌速率。通过上述互补性研究方法，我们证实：栖息于磷匮乏生境、叶片锰浓度较高的杜鹃花科植物，会采用释放羧酸盐的磷活化策略，这与非菌根型山龙眼科（Proteaceae）植物的养分获取策略一致。令人意外的是，部分叶片锰浓度较低、且生长于高土壤pH值生境的物种，同样会释放羧酸盐。因此，仅通过较低的叶片锰浓度，无法确凿判定某物种不存在羧酸盐分泌现象。这类物种可能会在释放羧酸盐的同时，伴随释放钾、镁等阳离子，进而提升根际pH值，最终降低成熟叶片中锰的生物有效性与积累量。对所采样类群的分析显示，叶片磷浓度与叶片锰浓度均未表现出显著的系统发育信号，表明这类养分获取性状并非局限于特定演化支，而是可能在杜鹃花科中独立演化多次。本研究纳入的所有属中，广义澳石楠属（Styphelia sensu lato）的性状变异幅度最广，其叶片磷浓度与锰浓度的跨度覆盖了从最高至最低的全部范围。