Calcium‐enhanced phosphorus toxicity in calcifuge and soil‐indifferent Proteaceae along the Jurien Bay chronosequence

Abstract

Summary Many Proteaceae are highly phosphorus (P)‐sensitive and occur exclusively on old nutrient‐impoverished acidic soils (calcifuge), whilst a few also occur on young calcareous soils (soil‐indifferent) that are higher in available calcium (Ca) and P. Calcium increases the severity of P‐toxicity symptoms, but its underlying mechanisms are unknown. We propose that Ca‐enhanced P toxicity explains the calcifuge habit of most Proteaceae. Four calcifuge and four soil‐indifferent Proteaceae from South‐Western Australia were grown in hydroponics, at a range of P and Ca concentrations. Calcium increased the severity of P‐toxicity symptoms in all species. Calcifuge Proteaceae were more sensitive to Ca‐enhanced P toxicity than soil‐indifferent ones. Calcifuges shared these traits: low leaf zinc concentration ([Zn]), low Zn allocation to leaves, low leaf [Zn]:[P], low root : shoot ratio, and high seed P content, compared with soil‐indifferent species. This is the first demonstration of Ca‐enhanced P toxicity across multiple species. Calcium‐enhanced P toxicity provides an explanation for the calcifuge habit of most Proteaceae and is critical for the management of this iconic Australian family. This study represents a major advance towards an understanding of the physiological mechanisms of P toxicity and its role in the distribution of Proteaceae.

Combined Effects of CaCO3 and the Proportion of N-NH4+ Among the Total Applied Inorganic N on the Growth and Mineral Uptake of Rabbiteye Blueberry

“…6) requires further investigation. In a recent publication, Hayes et al (2019) suggested that Ca enhances P toxicity in calcifuges (specifically, a genus of Proteaceae). However, in the current study, no consistent relationship between Ca and P concentrations was observed (Table 4) to support this mechanism.…”

Phosphorus toxicity disrupts Rubisco activation and reactive oxygen species defence systems by phytic acid accumulation in leaves

“…In contrast, several studies have shown that P toxicity is observed in plant leaves despite normal Zn accumulation in the leaves (Cakmak & Marschner, 1987;Hayes et al, 2019;Lambers, Juniper, Cawthray, Veneklaas, & Martínez-Ferri, 2002;Loneragan et al, 1979;Ova et al, 2015;Shane, McCully, & Lambers, 2004).…”

Edaphic niche characterization of four Proteaceae reveals unique calcicole physiology linked to hyper‐endemism of Grevillea thelemanniana

“…Most Proteaceae in south‐western Australia inhabit old nutrient‐impoverished soils with low available soil Ca, and are calcifuge, while only a few occur on young calcareous soils (Zemunik et al ., 2016; Hayes et al ., 2019a,b). In the soil profile of east and west sites at Alison Baird Reserve, there was a considerably large amount of exchangeable Ca below 2 m from the soil surface (Table 1), where G. thelemanniana acquired water (Fig.…”

“…The most surprising and very exciting finding of this study was the accumulation of huge amounts of Ca in the leaves of G. thelemanniana , which is unusual in Proteaceae (Hayes et al ., 2019b). Greater amounts of cellular free Ca may be toxic to plants and may also precipitate PO 4 3− , reducing availability of both elements (Hayes et al ., 2019b).…”

“…The most surprising and very exciting finding of this study was the accumulation of huge amounts of Ca in the leaves of G. thelemanniana , which is unusual in Proteaceae (Hayes et al ., 2019b). Greater amounts of cellular free Ca may be toxic to plants and may also precipitate PO 4 3− , reducing availability of both elements (Hayes et al ., 2019b). To avoid Ca toxicity, plants often biomineralise Ca by making crystals comprising calcium oxalate, calcium sulfate and calcium carbonate (He et al ., 2014; He et al ., 2015).…”