Banksia species (Proteaceae) from severely phosphorus‐impoverished soils exhibit extreme efficiency in the use and re‐mobilization of phosphorus

Abstract

Banksia species (Proteaceae) occur on some of the most phosphorus (P)-impoverished soils in the world. We hypothesized that Banksia spp. maximize P-use efficiency through high photosynthetic P-use efficiency, long leaf lifespan (P residence time), effective P re-mobilization from senescing leaves, and maximizing seed P concentration. Field and glasshouse experiments were conducted to quantify P-use efficiency in nine Banksia species. Leaf P concentrations for all species were extremely low (0.14-0.32 mg P g -1 DM) compared with leaf P in other species reported and low relative to other plant nutrients in Banksia spp.; however, moderately high rates of photosynthesis (13.8-21.7 mmol CO2 m -2 s -1 ), were measured. Some of the Banksia spp. had greater P proficiency (i.e. final P concentration in senesced leaves after re-mobilization; range: 27-196 mg P g -1 DM) than values reported for any other species in the literature. Seeds exhibited significantly higher P concentrations (6.6-12.2 mg P g -1 DM) than leaves, and species that sprout after fire ('re-sprouters') had significantly greater seed mass and P content than species that are killed by fire and regenerate from seed ('seeders'). Seeds contained only small amounts of polyphosphate (between 1.3 and 6 mg g -1 DM), and this was not correlated with P concentration or fire response. Based on the evidence in the present study, we conclude that Banksia species are highly efficient in their use of P, explaining, in part, their success on P-impoverished soils, with little variation between species.

Lipid Biosynthesis and Protein Concentration Respond Uniquely to Phosphate Supply during Leaf Development in Highly Phosphorus-Efficient Hakea prostrata

“…This assessment is consistent with the observations by Sulpice et al (2014) and suggests a very high efficiency of the photosynthetic machinery, given that overall leaf area-based rates of photosynthesis in Proteaceae spp. leaves are similar to those of other plants (Denton et al, 2007;Lambers et al, 2012b).…”

“…prostrata Leaves Senesce Slowly with Early Remobilization of P from RNA Southwestern Australian Proteaceae spp. remobilize scarce nutrients, such as P, very efficiently (Denton et al, 2007), perhaps through a process that extends cell viability (Hörtensteiner and Feller, 2002). Plants grown at the lowest Pi supply in this study showed similar leaf P concentrations compared with plants sampled in the field (Lambers et al, 2012b).…”

“…Reduced PLDa activity in mature leaves, on the other hand, could delay leaf senescence (Fan et al, 1997;Lee et al, 2012), promoting leaf longevity, which is characteristic of Proteaceae spp. like H. prostrata (Wright et al, 2002;Denton et al, 2007). The facts that NPC4 is only involved in lipid remodeling in the roots of P-limited Arabidopsis (Nakamura et al, 2005) and that HpNPC4 transcripts are more abundant in young H. prostrata leaves without functional chloroplasts suggest that this phospholipase is important for lipid turnover in sink tissues.…”

“…Leaf senescence progresses slowly, beginning with the degradation of rRNA pools, while plasma and chloroplast membranes are maintained. Ultimately, P remobilization from fully senescent leaves can be as high as 80% (Denton et al, 2007). To reduce the complexity of the figure, protein and RNA pools are shown only in the cytosol, representing their overall concentration across compartments.…”

“…are adapted to severely phosphorus (P)-impoverished soils and operate at very low leaf P status without compromising rates of photosynthesis (Denton et al, 2007;Lambers et al, 2012b;Sulpice et al, 2014). A large number of these species are endemic to the South West Australian Floristic Region, which features highly weathered, P-impoverished soils (Hopper, 2009;Laliberté et al, 2012;Hayes et al, 2014).…”