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Background and Aims: Soils in south-western Australia are severely phosphorus (P) impoverished, and plants in this region have evolved a variety of P-acquisition strategies. Phosphorus acquisition by Adenanthos cygnorum (Proteaceae) is facilitated by P-mobilizing neighbours which allows it to extend its range of habitats. However, we do not know if other Adenanthos species also exhibit a strategy based on facilitation for P acquisition in P-impoverished environments., Methods: We collected leaf and soil samples of Adenanthosbarbiger, A. cuneatus, A.meisneri,A. obovatus, A. sericeus and Adenanthos sp. Whicher Range (G.J. Keighery 9736) growing in their natural habitats at different locations within the severely P-limited megadiverse environment of south-western Australia. Hydroponic experiments were conducted to collect the carboxylates exuded by cluster roots. Pot experiments in soil were carried out to measure rhizosheath phosphatase activity., Key Results: We found no evidence for facilitation of P uptake in any of the studied Adenanthos species. Like most Proteaceae, A. cuneatus, A. meisneri, A. obovatus, A. sericeus and Adenanthos sp. Whicher Range (G.J. Keighery 9736) expressed P-mining strategies, including the formation of cluster roots. Cluster roots of A. obovatus were less effective than those of the other four Adenanthos species. In contrast to what is known for most Proteaceae, we found no cluster roots for A. barbiger. This species probably expressed a post-fire P-acquisition strategy. All Adenanthos species used P highly efficiently for photosynthesis, like other Proteaceae in similar natural habitats., Conclusions: Adenanthos is the first genus of Proteaceae found to express multiple P-acquisition strategies. The diversity of P-acquisition strategies in these Proteaceae, coupled with similarly diverse strategies in Fabaceae and Myrtaceae, demonstrates that caution is needed in making family- or genus-wide extrapolations about the strategies exhibited in severely P-impoverished megadiverse ecosystems., (© The Author(s) 2024. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Background and Aims: Phosphorus (P) and nitrogen (N) are essential nutrients that frequently limit primary productivity in terrestrial ecosystems. Efficient use of these nutrients is important for plants growing in nutrient-poor environments. Plants generally reduce foliar P concentration in response to low soil P availability. We aimed to assess ecophysiological mechanisms and adaptive strategies for efficient use of P in Banksia attenuata (Proteaceae), naturally occurring on deep sand, and B. sessilis, occurring on shallow sand over laterite or limestone, by comparing the allocation of P among foliar P fractions., Methods: We carried out pot experiments with slow-growing B. attenuata, which resprouts after fire, and faster growing opportunistic B. sessilis, which is killed by fire, on substrates with different P availability using a randomized complete block design. We measured leaf P and N concentrations, photosynthesis, leaf mass per area, relative growth rate and P allocated to major biochemical fractions in B. attenuata and B. sessilis., Key Results: The two species had similarly low foliar total P concentrations, but distinct patterns of P allocation to P-containing fractions. The foliar total N concentration of B. sessilis was greater than that of B. attenuata on all substrates. The foliar total P and N concentrations in both species decreased with decreasing P availability. The relative growth rate of both species was positively correlated with concentrations of both foliar nucleic acid P and total N, but there was no correlation with other P fractions. Faster growing B. sessilis allocated more P to nucleic acids than B. attenuata did, but other fractions were similar., Conclusions: The nutrient allocation patterns in faster growing opportunistic B. sessilis and slower growing B. attenuata revealed different strategies in response to soil P availability which matched their contrasting growth strategy., (© The Author(s) 2021. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Hakea prostrata R.Br. (Proteaceae) shows a 'delayed greening' strategy of leaf development characterised by reddish young leaves that become green as they mature. This trait may contribute to efficient use of phosphorus (P) during leaf development by first investing P in the development of leaf structure followed by maturation of the photosynthetic machinery. In this study, we investigated the properties of delayed greening in a highly P-efficient species to enhance our understanding of the ecological significance of this trait as a nutrient-saving and photoprotective strategy. In glasshouse-grown plants, we assessed foliar pigments, fatty acids and nutrient composition across five leaf developmental stages. Young leaves had higher concentrations of anthocyanin, P, nitrogen (N), copper (Cu), xanthophyll-cycle pigments and saturated fatty acids than mature leaves. As leaves developed, the concentration of anthocyanins decreased, whereas that of chlorophyll and the double bond index of fatty acids increased. In mature leaves, ~60% of the fatty acids was α-linolenic acid (C18:3 n-3). Mature leaves also had higher concentrations of aluminium (Al), calcium (Ca) and manganese (Mn) than young leaves. We conclude that delayed greening in H. prostrata is a strategy that saves P as well as N and Cu through sequential allocation of these resources, first to cell production and structural development, and then to supplement chloroplast development. This strategy also protects young leaves against photodamage and oxidative stress during leaf expansion under high-light conditions.

Phosphorus (P) fertilisers, made from rock phosphate, are used to attain high crop yields. However, rock phosphate is a finite resource and excessive P fertilisers pollute our environment, stressing the need for more P-efficient crops. Some Proteaceae have evolved in extremely P-impoverished environments. One of their adaptations is to curtail the abundance of ribosomal RNA, and thus protein, and tightly control the acquisition and assimilation of nitrogen (N) and sulfur. This differs fundamentally from plants that evolved in environments where N limits plant productivity, but is likely common in many species that evolved in P-impoverished landscapes. Here, we scrutinise the relevance of these responses towards developing P-efficient crops, focusing on plant species where 'P is in the driver's seat'., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Hakea prostrata (Proteaceae) has evolved in extremely phosphorus (P)-impoverished habitats. Unlike species that evolved in P-richer environments, it tightly controls its nitrogen (N) acquisition, matching its low protein concentration, and thus limiting its P requirement for ribosomal RNA (rRNA). Protein is a major sink for sulfur (S), but the link between low protein concentrations and S metabolism in H. prostrata is unknown, although this is pivotal for understanding this species' supreme adaptation to P-impoverished soils. Plants were grown at different sulfate supplies for 5 wk and used for nutrient and metabolite analyses. Total S content in H. prostrata was unchanged with increasing S supply, in sharp contrast with species that typically evolved in environments where P is not a major limiting nutrient. Unlike H. prostrata, other plants typically store excess available sulfate in vacuoles. Like other species, S-starved H. prostrata accumulated arginine, lysine and O-acetylserine, indicating S deficiency. Hakea prostrata tightly controls its S acquisition to match its low protein concentration and low demand for rRNA, and thus P, the largest organic P pool in leaves. We conclude that the tight control of S acquisition, like that of N, helps H. prostrata to survive in P-impoverished environments., (© 2017 The Authors. New Phytologist © 2017 New Phytologist Trust.)

Hakea prostrata (Proteaceae) has evolved in an extremely phosphorus (P)-limited environment. This species exhibits an exceptionally low ribosomal RNA (rRNA) and low protein and nitrogen (N) concentration in its leaves. Little is known about the N requirement of this species and its link to P metabolism, despite this being the key to understanding how it functions with a minimal P budget. H. prostrata plants were grown with various N supplies. Metabolite and elemental analyses were performed to determine its N requirement. H. prostrata maintained its organ N content and concentration at a set point, independent of a 25-fold difference nitrate supplies. This is in sharp contrast to plants that are typically studied, which take up and store excess nitrate. Plants grown without nitrate had lower leaf chlorophyll and carotenoid concentrations, indicating N deficiency. However, H. prostrata plants at low or high nitrate availability had the same photosynthetic pigment levels and hence were not physiologically compromised by the treatments. The tight control of nitrate acquisition in H. prostrata retains protein at a very low level, which results in a low demand for rRNA and P. We surmise that the constrained nitrate acquisition is an adaptation to severely P-impoverished soils., (© 2016 John Wiley & Sons Ltd.)

Hakea prostrata (Proteaceae) is adapted to severely phosphorus-impoverished soils and extensively replaces phospholipids during leaf development. We investigated how polar lipid profiles change during leaf development and in response to external phosphate supply. Leaf size was unaffected by a moderate increase in phosphate supply. However, leaf protein concentration increased by more than 2-fold in young and mature leaves, indicating that phosphate stimulates protein synthesis. Orthologs of known lipid-remodeling genes in Arabidopsis (Arabidopsis thaliana) were identified in the H. prostrata transcriptome. Their transcript profiles in young and mature leaves were analyzed in response to phosphate supply alongside changes in polar lipid fractions. In young leaves of phosphate-limited plants, phosphatidylcholine/phosphatidylethanolamine and associated transcript levels were higher, while phosphatidylglycerol and sulfolipid levels were lower than in mature leaves, consistent with low photosynthetic rates and delayed chloroplast development. Phosphate reduced galactolipid and increased phospholipid concentrations in mature leaves, with concomitant changes in the expression of only four H. prostrata genes, GLYCEROPHOSPHODIESTER PHOSPHODIESTERASE1, N-METHYLTRANSFERASE2, NONSPECIFIC PHOSPHOLIPASE C4, and MONOGALACTOSYLDIACYLGLYCEROL3. Remarkably, phosphatidylglycerol levels decreased with increasing phosphate supply and were associated with lower photosynthetic rates. Levels of polar lipids with highly unsaturated 32:x (x = number of double bonds in hydrocarbon chain) and 34:x acyl chains increased. We conclude that a regulatory network with a small number of central hubs underpins extensive phospholipid replacement during leaf development in H. prostrata. This hard-wired regulatory framework allows increased photosynthetic phosphorus use efficiency and growth in a low-phosphate environment. This may have rendered H. prostrata lipid metabolism unable to adjust to higher internal phosphate concentrations., (© 2014 American Society of Plant Biologists. All Rights Reserved.)

Background and Aims: There are more than 80 species of Leucadendron and most are used as cut flowers. Currently, more than 100 cultivars are used by industry and many of them are interspecific hybrids. The origin of most cultivars is unclear and their genetic diversity and relationships have not been studied. This investigation was carried out to evaluate the genetic variation and relationships among 30 Leucadendron cultivars., Methods: ISSR markers were applied to determine the genetic variation and to discriminate Leucadendron cultivars. Sixty-four ISSR primers were screened and 25 primers were selected for their ability to produce clear and reproducible patterns of multiple bands., Key Results: A total of 584 bands of 305-2400 bp were amplified, of which 97 % were polymorphic. A dendrogram generated using the Unweighted Pair Group Method with Arithmetic Average based on a distance measure of total character difference showed that the Leucadendron cultivars clustered into two main groups. Twenty-four of the 30 cultivars can be unequivocally differentiated, but identical profiles were observed for three cultivar pairs, 'Katie's Blush' and 'Silvan Red', 'Highlights' and 'Maui Sunset', and 'Yellow Crest' and 'Yellow Devil'., Conclusions: ISSR profiling is a powerful method for the identification and molecular classification of Leucadendron cultivars. A fingerprinting key was generated based on the banding patterns produced using two ISSR primers (UBC856 and UBC857). In addition cultivar-specific ISSR bands were obtained for 17 of the 30 Leucadendron cultivars tested.

Background and aims: Hakea prostrata (Proteaceae) is a highly phosphorus-use-efficient plant native to southwest Australia. It maintains a high photosynthetic rate at low leaf phosphorus (P) and exhibits delayed leaf greening, a convergent adaptation that increases nutrient-use efficiency. This study aimed to provide broad physiological and gene expression profiles across leaf development, uncovering pathways leading from young leaves as nutrient sinks to mature leaves as low-nutrient, energy-transducing sources. Methods: To explore gene expression underlying delayed greening, we analysed a de novo transcriptome for H. prostrata across five stages of leaf development. Photosynthesis and respiration rates, and foliar pigment, P and nitrogen (N) concentrations were determined, including the division of P into five biochemical fractions. Key results: Transcripts encoding functions associated with leaf structure generally decreased in abundance across leaf development, concomitant with decreases in foliar concentrations of 85% for anthocyanins, 90% for P and 70% for N. The expression of genes associated with photosynthetic function increased during or after leaf expansion, in parallel with increases in photosynthetic pigments and activity, much later in leaf development than in species that do not have delayed greening. As leaves developed, transcript abundance for cytosolic and mitochondrial ribosomal proteins generally declined, whilst transcripts for chloroplast ribosomal proteins increased. Conclusions: There was a much longer temporal separation of leaf cell growth from chloroplast development in H. prostrata than is found in species that lack delayed greening. Transcriptome-guided analysis of leaf development in H. prostrata provided insight into delayed greening as a nutrient-saving strategy in severely phosphorus-impoverished landscapes. [ABSTRACT FROM AUTHOR]

Numerous phosphorus (P)‐acquisition and ‐utilisation strategies have evolved in plants growing in severely P‐impoverished environments. Although these strategies have been well characterised for certain taxa, like Proteaceae, P‐poor habitats are characterised by a high biodiversity, and we know little about how species in other families cope with P scarcity. We compared the P‐acquisition and leaf P‐allocation strategies of Fabaceae and Myrtaceae with those of Proteaceae growing in the same severely P‐impoverished habitat. Myrtaceae and Fabaceae exhibited multiple P‐acquisition strategies: P‐mining by carboxylates or phosphatases, P uptake facilitated by carboxylate‐releasing neighbours, and dependence on the elevated soil P availability after fire. Surprisingly, not all species showed high photosynthetic P‐use efficiency (PPUE). Highly P‐efficient species showed positive correlations between PPUE and the proportion of metabolite P (enzyme substrates), and negative correlations between PPUE and phospholipids (cellular membranes) and nucleic acid P (mostly ribosomal RNA), while we found no correlations in less P‐efficient species. Overall, we found that Myrtaceae and Fabaceae used a wider range of strategies than Proteaceae to cope with P scarcity, at both the rhizosphere and leaf level. This knowledge is pivotal to better understand the mechanisms underlying plant survival in severely nutrient‐impoverished biodiverse ecosystems. [ABSTRACT FROM AUTHOR]

Summary In severely phosphorus (P)‐impoverished environments, plants have evolved to use P very efficiently. Yet, it is unclear how P allocation in leaves contributes to their photosynthetic P‐use efficiency (PPUE) and position along the leaf economics spectrum (LES). We address this question in 10 species of Banksia and Hakea, two highly P‐efficient Proteaceae genera. We characterised traits in leaves of Banksia and Hakea associated with the LES: leaf mass per area, light‐saturated photosynthetic rates, P and nitrogen concentrations, and PPUE. We also determined leaf P partitioning to five biochemical fractions (lipid, nucleic acid, metabolite, inorganic and residual P) and their possible association with the LES. For both genera, PPUE was negatively correlated with fractional allocation of P to lipids, but positively correlated with that to metabolites. For Banksia only, PPUE was negatively correlated with residual P, highlighting a strategy contrasting to that of Hakea. Phosphorus‐allocation patterns significantly explained PPUE but were not linked to the resource acquisition vs resource conservation gradient defined by the LES. We conclude that distinct P‐allocation patterns enable species from different genera to achieve high PPUE and discuss the implications of different P investments. We surmise that different LES axes representing different ecological strategies coexist in extremely P‐impoverished environments. [ABSTRACT FROM AUTHOR]