Root Phosphatase Activity Research Articles

Evolutionary history and root trait coordination predict nutrient strategy in tropical legume trees.

Plants express diverse nutrient use and acquisition traits, but it is unclear how trait combinations at the species level are constrained by phylogeny, trait coordination, or trade-offs in resource investment. One trait - nitrogen (N) fixation - is assumed to correlate with other traits and used to define plant functional groups, despite potential confounding effects of phylogeny. We quantified growth, carbon metabolism, fixation rate, root phosphatase activity (RPA), mycorrhizal colonization, and leaf and root morphology/chemistry across 22 species of fixing and nonfixing tropical Fabaceae trees under common conditions. Belowground trait variation was high even among closely related species, and most traits displayed a phylogenetic signal, including N-fixation rate and nodule biomass. Across species, we observed strong positive correlations between physiological traits such as RPA and root respiration. RPA increased ~ fourfold per unit increase in fixation, supporting the debated hypothesis that N-fixers 'trade' N for phosphatases to enhance phosphorus acquisition. Specific root length and root N differed between functional groups, though for other traits, apparent differences became nonsignificant after accounting for phylogenetic nonindependence. We conclude that evolutionary history, trait coordination, and fixation ability contribute to nutrient trait expression at the species level, and recommend explicitly considering phylogeny in analyses of functional groupings.

Exploring plant adaptation strategies to phosphorus limitation induced by nitrogen addition: foliar phosphorus allocation and root functional traits analysis in two dominant subalpine tree species

Abstract Plants adapt to the limitation of soil phosphorus (P) induced by nitrogen (N) deposition through a complex interaction of various root and leaf functional traits. In this study, a pot experiment was conducted to explore the effects of different levels of N addition (control, low N [LN]: 25 kg N ha−1 yr−1, high N [HN]: 50 kg N ha−1 yr−1) on tree growth, leaf nutrient content, foliar P fractions and root characteristics of two dominant tree species, the pioneer species Salix rehderiana Schneid and the climax species Abies fabri (Mast.) Craib, in a subalpine forest in southwestern China. The results demonstrated that LN addition had a minimal impact on leaf N and P contents. Conversely, HN addition significantly decreased the leaf P content in both species. Salix rehderiana exhibited more pronounced increases in specific root length and specific root area under P deficiency triggered by HN addition when compared with A. fabri. In contrast, A. fabri showed weaker morphological responses to N addition but had a higher proportion of foliar P to metabolic P, as well as higher root exudates rate and root phosphatase activity in response to HN addition. Abies fabri employs a synergistic approach by allocating a greater amount of leaf P to metabolite P and extracting P from the soil through P-mobilizing exudates and root phosphatase activity, while S. rehderiana exhibits higher flexibility in modifying its root morphology in response to P limitation induced by HN addition. This study provides insights into subalpine tree species adaptation to N-induced P limitation, emphasizing its significance for guiding forest management and conservation in the context of global climate change.

Nitrogen and phosphorus availability alters tree‐grass competition intensity in savannas

Abstract Plant essential macronutrients like nitrogen (N) and phosphorus (P) can limit savanna tree growth and are important determinants of savanna vegetation dynamics, along with rainfall, fire and herbivory. How nitrogen and phosphorus shape tree‐grass competition and their coexistence remain unclear, hindering our ability to predict how savannas may respond to altered nutrient cycling. Here, we evaluate (1) if trees and grasses respond differently to N versus P availability, or (2) if grasses are more competitive in low nutrient environments while trees are more competitive in high nutrient environments. To do this, we grew saplings of 6 tree and 1 grass species from the Kruger National Park, South Africa, for 16 weeks under fully factorial nutrient and competition treatments (with/without competitors, low/high rate of N supply and low/high rate of P supply) under a watering regime designed to mimic wet season rainfall in a mesic savanna. Trees and grasses foraged most aggressively for nitrogen and allocated biomass differently depending on nitrogen availability. Overall, tree growth decreased in competition with grass, even in high nutrient environments where they grew faster. Grasses were always better below‐ground competitors, utilising aggressive nutrient foraging strategies, including high root phosphatase activity in response to nitrogen and large root biomass allocation. Synthesis. In low nutrient environments (e.g. on nutrient‐poor sandy soils), nutrients may limit tree growth. Nutrient rich environments enable tree growth, but grasses continue to compete effectively with trees. Understanding what this means for ecosystem responses to nutrient availability is not trivial, especially in the context of fire and herbivory. However, it is clear that soil nutrients likely affect tree and grass growth and competition in savannas, which suggests that future changes in nutrient cycling, such as N deposition, may have important effects on savanna vegetation.

Biodegradable Dextrin-Based Microgels for Slow Release of Dual Fertilizers for Sustainable Agriculture.

In this research, we report dextrin-based biodegradable microgels (PDXE MGs) having phosphate-based cross-linking units for slow release of urea and a potential P source to improve fertilization. PDXE MGs (∼200 nm) are synthesized by cross-linking the lauroyl-functionalized dextrin chains with sodium tripolyphosphate. The developed PDXE MGs exhibit high loading (∼10%) and encapsulation efficiency (∼88%) for urea. It is observed that functionalization of PDXE MGs with lauroyl chains slows down the release of urea (90% in ∼24 days) as compared to nonfunctionalized microgels (PDX MGs) (99% in ∼17 days) in water. Further studies of the developed formulation display that Urea@PDXE MGs significantly boost maize seed germination and overall plant growth as compared to pure urea fertilizer. Moreover, analysis of maize leaves obtained from plants treated with Urea@PDXE MGs reveals 3.5 ± 0.3% nitrogen content and 90 ± 0.7 mg/g chlorophyll content. These values are significantly higher than 1.4 ± 0.6% nitrogen content and 48 ± 0.05 mg/g chlorophyll content obtained by using bare urea. Further, acid phosphatase activity in roots is reduced upon treatment with PDXE MGs and Urea@PDXE MGs, suggesting the availability of P upon degradation of PDXE MGs by the amylase enzyme in soil. These experimental results present the developed microgel-based biodegradable formulation with a slow release feature as a potential candidate to move toward sustainable agriculture practices.

Plant Adaptation and Phosphorus Limitation in Tropical Forests: A Theoretical and Empirical Assessment

Ecosystem dynamics are shaped by plant adaptation to environmental stress, yet the conditions under which this occurs remain poorly understood. We developed a theoretical framework to predict how strategies used by tropical trees to cope with low-phosphorus (P) availability (that is, traits related to P uptake, and use) influence growth under P limitation. We then tested this framework against data on tree species in Borneo and a meta-analysis of results from pantropical nutrient addition experiments. Our theoretical framework predicts that plant traits associated with low-P environments, including enhanced P allocation to leaves, efficient P resorption, and root phosphatase activity, alleviate the negative effects of P scarcity more strongly for “inefficiently” growing plants, represented by large trees and old-growth forests, compared with saplings or secondary forests. In agreement with this prediction, changes in traits related to low-P environments increased the potential relative growth rate of large trees more than small trees in Borneo. Finally, theoretical expectation was supported by a meta-analysis which revealed stronger P limitation in saplings and secondary forests than in old-growth forests. Together, these findings provide a novel framework to interpret the relationship between resource constraints and plant performance and reinforce the importance of accounting for plant adaption to predict ecosystem responses to P limitation in tropical forests.

Root phosphatase activity is coordinated with the root conservation gradient across a phosphorus gradient in a lowland tropical forest.

Soil phosphorus (P) is a growth-limiting nutrient in tropical ecosystems, driving diverse P-acquisition strategies among plants. Particularly, mining for inorganic P through phosphomonoesterase (PME) activity is essential, given the substantial proportion of organic P in soils. Yet, the relationship between PME activity and other nutrient-acquisition root traits remains unclear. We measured root PME activity and commonly measured root traits, including root diameter, specific root length (SRL), root tissue density (RTD), and nitrogen concentration ([N]) in 18 co-occurring species across soils with varying P availability to better understand trees response to P supply. Root [N] and RTD were inversely related, and that axis was not clearly related to soil P supply. Both traits, however, correlated positively and negatively with PME activity, which responded strongly to P supply. Conversely, root diameter was inversely related to SRL, but this axis was not related to P supply. This pattern suggests that limiting similarity influenced variation along the diameter-SRL axis, explaining local trait diversity. Meanwhile, variation along the root [N]-RTD axis might best reflect environmental filtering. Overall, P availability indicator traits such as PME activity and root hairs only tended to be associated with these axes, highlighting limitations of these axes in describing convergent adaptations at local sites.

Dissimilarity in root traits and spatial distribution promotes the productivity of Piper nigrum L. and tree species in mixture systems

Background and aimsClarifying why species mixtures produce greater biomass compared to monocultures is important for understanding the effect of biodiversity in natural and agricultural systems. At present, it remains unclear whether differential root traits and spatial distribution between the liana and tree species can promote productivity of mixtures. MethodsA 4-month glasshouse experiment and a 3-year field trial were conducted to examine the influence of root traits and the vertical and horizontal root distribution on productivity of independently supported liana Piper nigrum (Pn) and five other species. In the glasshouse experiment, Pn was grown in monoculture or mixed with one of five species: Coffea arabica, Areca catechu, Artocarpus heterophyllus, Camellia oleifera, and Coffea canephora. In the field trial, the Pn/Ac system and each monoculture were tested. ResultsCompared with monoculture, all Pn and mixture systems showed a positive net effect and a high complementarity effect on shoot biomass. The variation in complementarity effect was mainly associated with dissimilarity in the multidimensional root space trait and a few specific individual traits (root phosphatase activity and mycorrhizal colonization) between Pn and the neighbors. In the field, Pn in the mixture increased proportion of root length in the 20–40 cm soil layer and allocated less root length in the space shared between Pn and Ac, thus achieving spatial separation of roots and promoting the final yield. ConclusionThese findings suggest that the dissimilarity in root traits and spatial distribution may be an important mechanism for promoting the productivity of mixtures of liana and tree species.

Fine-root traits are devoted to the allocation of foliar phosphorus fractions of desert species under water and phosphorus-poor environments.

Traits of leaves and fine roots are expected to predict the responses and adaptation of plants to their environments. Whether and how fine-root traits (FRTs) are associated with the allocation of foliar phosphorus (P) fractions of desert species in water- and P-poor environments, however, remains unclear. We exposed seedlings of Alhagi sparsifolia Shap. (hereafter Alhagi) treated with two water and four P-supply levels for three years in open-air pot experiments and measured the concentrations of foliar P fractions, foliar traits, and FRTs. The allocation proportion of foliar nucleic acid-P and acid phosphatase (APase) activity of fine roots were significantly higher by 45.94 and 53.3% in drought and no-P treatments relative to well-watered and high-P treatments, whereas foliar metabolic-P and structural-P were significantly lower by 3.70 and 5.26%. Allocation proportions of foliar structural-P and residual-P were positively correlated with fine-root P (FRP) concentration, but nucleic acid-P concentration was negatively correlated with FRP concentration. A tradeoff was found between the allocation proportion to all foliar P fractions relative to the FRP concentration, fine-root APase activity, and amounts of carboxylates, followed by fine-root morphological traits. The requirement for a link between the aboveground and underground tissues of Alhagi was generally higher in the drought than the well-watered treatment. Altering FRTs and the allocation of P to foliar nucleic acid-P were two coupled strategies of Alhagi under conditions of drought and/or low-P. These results advance our understanding of the strategies for allocating foliar P by mediating FRTs in drought and P-poor environments.

Integrated use of polyphosphate and P-solubilizing bacteria enhanced P use efficiency and growth performance of durum wheat.

Coupling phosphate-solubilizing bacteria (PSB) with P fertilizers, including polyphosphates (PolyP), was reported as eco-efficient approach to enhance P use efficiency. Although PSB have been recently reported to hydrolyze PolyP, the plant growth promoting mechanisms of PolyP-PSB co-application were not yet uncovered. This study aims to evaluate the effect of a PSB consortium (PSBCs) on growth, P use efficiency (PUE), and wheat yield parameters under PolyP (PolyB) application. Co-application of PolyB-PSBCs significantly enhanced wheat growth at 75 days after sowing (DAS) compared to 30 DAS. A significant increase in shoot dry biomass (47%), shoot inorganic P content (222%), PUE (91%), and root P absorption efficiency (RPAE, 99%) was noted compared to unfertilized plants. Similarly, the PolyB-PSBCs co-application enhanced morphological root traits at 30 DAS, while acid phosphatase activities (root and rhizosphere), RPAE, and PUE were significantly increased at 75 DAS. The improved wheat P acquisition could be attributed to a lower investment in root biomass production, and significant induction of acid phosphatase activity in roots and rhizosphere soil under PolyB-PSBCs co-application. Consequently, the PolyB-PSBCs co-application significantly improved aboveground performance, which is reflected by increased shoot nutrient contents (P 300%, K 65%), dry weight (54%), and number (50%) of spikes. Altogether, this study provides relevant evidence that co-application of PolyP-PSBCs can be an integrated and environmentally preferred P fertilization approach owing to the dual effects of PolyP and PSBCs on wheat PUE.

Root phosphatase activity is a competitive trait affiliated with the conservation gradient in root economic space

BackgroundThe diversity of resource acquisition strategies of plant roots determines the species coexistence patterns to a certain extent. However, few root physiological traits have been investigated, such as root phosphatase activity (PA) that affects plant phosphorus (P) uptake. MethodsRoot PA and classical root functional traits were investigated for 21 coexisting species in a deciduous broad-leaved forest in warm temperate-subtropical transition zone, China. We analyzed the root order variation of absorptive fine root PA, clarified the attribution of root PA in root economic space (RES) and the different P acquisition strategies of co-occurring species based on the multidimensional RES theory, and determined the dominant factors affecting interspecific variation in root PA. ResultsThere was no distinct pattern of PA variation with root order in the first three root orders of absorptive fine roots, and root PA was constrained by phylogeny. Root PA is a competitive trait affiliated with the conservation gradient in RES. The tight linkages among root PA, mycorrhizal colonization, diameter, specific root length, and nitrogen concentration suggested trade-offs among P acquisition strategies of co-occurring species, i.e. species with long and fine roots acquire inorganic P by actively exploring the soil and secreting phosphatase to mineralize and hydrolyze organic P, while species with short and thick roots obtain P mainly by investing C in mycorrhizal partners. ConclusionsCollectively, our study provides an insight into the forest species coexistence in climatic transition zones, i.e. species coexistence mechanisms based on diverse phosphorus acquisition strategies.

Phosphorus limitation of early growth differs between nitrogen-fixing and nonfixing dry tropical forest tree species.

Tropical forests are often characterized by low soil phosphorus (P) availability, suggesting that P limits plant performance. However, how seedlings from different functional types respond to soil P availability is poorly known but important for understanding and modeling forest dynamics under changing environmental conditions. We grew four nitrogen (N)-fixing Fabaceae and seven diverse non-N-fixing tropical dry forest tree species in a shade house under three P fertilization treatments and evaluated carbon (C) allocation responses, P demand, P-use, investment in P acquisition traits, and correlations among P acquisition traits. Nitrogen fixers grew larger with increasing P addition in contrast to non-N fixers, which showed fewer responses in C allocation and P use. Foliar P increased with P addition for both functional types, while P acquisition strategies did not vary among treatments but differed between functional types, with N fixers showing higher root phosphatase activity (RPA) than nonfixers. Growth responses suggest that N fixers are limited by P, but nonfixers may be limited by other resources. However, regardless of limitation, P acquisition traits such as mycorrhizal colonization and RPA were nonplastic across a steep P gradient. Differential limitation among plant functional types has implications for forest succession and earth system models.

Watermelon responds to organic fertilizer by enhancing root-associated acid phosphatase activity to improve organic phosphorus utilization

Organic fertilizer is commonly used to increase crop yields and improve soil quality. However, it is unclear whether crops adapt to organic fertilizer by regulating metabolic pathways that are involved in nutrient utilization. In this study, we focused on the organic phosphorus (Po) in organic fertilizer and, using watermelon, investigated changes in gene expression and metabolic pathways in response to organic fertilizer and the combination of chemical fertilizer and organic fertilizer (chemical fertilizer 70% and organic fertilizer 30%, based on phosphorus supply). Purple acid phosphatase (PAP) gene expression was upregulated in leaves and roots of watermelon grown in organic fertilizer alone and in the combination of chemical/organic fertilizer, resulting in enhanced phosphatase activity in roots. When the ratio of chemical to organic fertilizer was 85/15, root-associated acid phosphatase (APase) activity increased over chemical fertilizer alone. This formulation also resulted in increased inorganic phosphate (Pi) concentration in roots and leaves, and the upregulation of the secretory APase genes ClaPAP10/12/15/26, and ClaPAP18 in roots. In conclusion, watermelon responds to organic fertilizer by upregulating expression of secretory ClaPAP genes, subsequently enhancing root-associated APase activity further improving the hydrolysis of phosphomonoesters, and ultimately facilitating Po utilization by roots. The mechanisms of P utilization by roots comprise the enhancement of APase and phytase activity, absorption of small Po molecules, uptake of Pi, and the increase of lateral root number when organic fertilizer is applied to the plants. These findings help to establish the mechanisms by which plants respond to organic fertilizer by regulating metabolic pathways at the transcriptional level.

The purple acid phosphatase GmPAP17 predominantly enhances phosphorus use efficiency in soybean

Purple acid phosphatase (PAP) is an important plant acid phosphatase, which can secrete to the rhizosphere to decompose organophosphorus, promote phosphorus use efficiency, plant growth and development. However, little is known about the functions of intracellular PAP in plants, especially for soybean. Our previous study integrating QTL mapping and transcriptome analysis identified an promising low phosphorus (LP)-induced gene GmPAP17. Here, we determined that GmPAP17 was mainly expressed in roots and had a strong response to LP stress. Furthermore, and the relative expression in the root of LP tolerant genotypes NN94–156 was significantly greater than that of LP sensitive genotype Bogao after LP stress treatment. The overexpression of GmPAP17 significantly enhanced both acid phosphatase activity and growth performance of hairy roots under LP stress condition, it was vice versa for RNAi interference of GmPAP17, indicating that GmPAP17 plays an important role in P use efficiency. Moreover, yeast two-hybrid and bimolecular fluorescence complementation analysis showed that GmRAP2.2 was involved in the regulation network of GmPAP17. Taken together, our results suggest that GmPAP17 is a novel plant PAP that functions in the adaptation of soybean to LP stress, possibly through its involvement in P recycling in plants.

Interspecific differences in the responses of root phosphatase activities and morphology to nitrogen and phosphorus fertilization in Bornean tropical rain forests.

Soil organic phosphorus (P) compounds can be the main P source for plants in P‐limited tropical rainforests. Phosphorus occurs in diverse chemical forms, including monoester P, diester P, and phytate, which require enzymatic hydrolysis by phosphatase into inorganic P before assimilation by plants. The interactions between plant interspecific differences in organic P acquisition strategies via phosphatase activities with root morphological traits would lead to P resource partitioning, but they have not been rigorously evaluated. We measured the activities of three classes of phosphatases (phosphomonoesterase, PME; phosphodiesterase, PDE; and phytase, PhT), specific root length (SRL), root diameter, and root tissue density in mature tree species with different mycorrhizal associations (ectomycorrhizal [ECM] or arbuscular mycorrhizal [AM]) and different successional status (climax or pioneer species) in Sabah, Malaysia. We studied nitrogen (N)‐ and P‐fertilized plots to evaluate the acquisition strategies for organic P under P‐limited conditions 7 years after fertilization was initiated. P fertilization reduced the PME activity in all studied species and reduced PhT and PDE activities more in climax species than in the two pioneer species, irrespective of the mycorrhizal type. PDE activity increased in some climax species after N fertilization, suggesting that these species allocate excess N to the synthesis of PDE. Moreover, PME and PhT activities, but not PDE activity, correlated positively with SRL. We suggest that climax species tend to be more strongly dependent on recalcitrant organic P (i.e., phytate and/or diester P) than pioneer species, regardless of the mycorrhizal type. We also suggest that trees in which root PME or PhT activity is enhanced can increase their SRL to acquire P efficiently. Resource partitioning of soil organic P would occur among species through differences in their phosphatase activities, which plays potentially ecologically important role in reducing the competition among coexisting tree species in lowland tropical rainforests.

Root response of soybean genotypes to low phosphorus availability from juvenile to adult vegetative stages

ABSTRACT Due to the rapid exhaustion of global phosphorus (P) resources, P-efficient crops are required. In this study, we used various soybean genotypes collected from around the world and investigated the morphophysiological responses of their roots to low-P conditions at the cotyledon emergence (VE), unifoliate leaves emergence (VC), and fourth trifoliate leaflet emergence (V4) growth stages. First, we compared the growth of 81 soybean genotypes under different P conditions at the VC stage. The root morphology of most genotypes did not differ according to P conditions. However, GmWMC138 showed increased root weight under low-P conditions at the VC stage, and was therefore selected for further comparative analysis with genotypes with similar seed weights. Four selected genotypes were compared in terms of their seed storage P content and responses of plant growth and phytase and acid phosphatase activities to low-P conditions at the VE and VC stages. The inorganic-P (Pi) levels and shoot growth at the VE and VC stages of GmWMC138 were less affected by low-P conditions compared to the other genotypes. In this genotype, root fresh weight at the VC stage, phytase activity in roots at the VE stage, and acid phosphatase activity in roots at the VC stage increased under low-P conditions. The differences in these enzyme activities may have led to the maintenance of root Pi content and subsequent increase in the root fresh weight at the VC stage under low-P conditions. In addition, the low-P responses of growth and P content at the V4 stage were compared among the selected genotypes. In GmWMC138, fine-root length increased and total P content was maintained under low-P conditions compared to normal-P conditions. These results imply that in soybeans morphological changes in roots in response to low-P conditions at juvenile growth stages, such as the VE and VC stages, may contribute to P-deficiency tolerance in subsequent growth stages, such as the V4 stage.

Root phosphatase activity aligns with the collaboration gradient of the root economics space.

The adoption of diverse resource acquisition strategies is critical for plant growth and species coexistence. Root phosphatase is of particular importance in the acquisition of soil phosphorus (P), yet it is often overlooked in studies of root trait syndromes. Here, we evaluated the role of root phosphatase activity (RPA) within the root economics space and the order-based variation of RPA, as well as the correlations between RPA and a suite of leaf traits and soil properties over a range of evergreen tree species in a subtropical forest. Root phosphatase activity exhibited a high degree of inter-specific variation. We found that there were two leading dimensions of the multidimensional root economics space, the root diameter-specific root length axis (collaboration trait gradient) and the root tissue density-root nitrogen concentration axis (classical trait gradient), and RPA aligned with the former. Root phosphatase activity is used as a 'do it yourself' strategy of soil P acquisition, and was found to be inversely correlated with mycorrhizal colonization, which suggests a trade-off in plant P acquisition strategies. Compared with soil and foliar nutrient status, root traits mattered most for the large inter-specific changes in RPA. Furthermore, RPA generally decreased from first- to third-order roots. Taken together, such diverse P-acquisition strategies are conducive to plant coexistence within local forest communities. The use of easily measurable root traits and their tight correlations with RPA could be a feasible and promising approach to estimating species-specific RPA values, which would be helpful for better understanding plant P acquisition and soil P cycling.

Fertilization integrated with microbial inoculants improves bell pepper production

ABSTRACT Increased use of fertilizers under intensive agriculture has the possibility of environmental contamination. The use of microbial inoculants may be effective in sustaining crop productivity, soil health, and supplementing chemical fertilizers. The investigation evaluated responses of arbuscular mycorrhizal (AM) fungi, Glomus mosseae (G) and Acaulospora laevis (A) and the bacterium Pseudomonas fluorescens (Pf) on bell pepper (Capsicum annuum L.) when provided superphosphate at F1 = 60 kg ha−1 (0.45 g/pot), F2 = 120 kg ha−1 (0.90 g/pot), or F3 = 240 kg ha−1 (1.80 g/pot). Plant growth, nutrient content, and yield 120 days after transplanting (DAT) were determined. Plants responded best to F1 followed by F2, while F3 produced inhibitory effects. The highest AM colonization and spore numbers were with G + A+ Pf, resulting in an increase in chlorophyll content, root phosphatase activity, shoot fresh weight, early fruit formation, number of fruit/plant, fruit size, weight, and early ripening. Inoculation with G. mosseae alone increased leaf area, photosynthesis, plant height, root freshness and dry weight. The G+ Pf commonly produced highest shoot fresh weight and fruit nutrient content. The effectiveness of these inoculants on bell pepper growth and yield was highest; 60 and 120 kg ha−1 P-fertilizer level when amended with G + A+ Pf. Use of AM or micro-inoculants may reduce fertilizer input and enhance nutrient utilization efficiency, which positively affected qualitative characteristics, nutrient uptake, and resistance to suboptimal conditions, but has few or little effect on quantitative characteristics. More work is needed to determine optimum rates of the materials tested to produce marketable size fruit.

Trade-Offs in Phosphorus Acquisition Strategies of Five Common Tree Species in a Tropical Forest of Puerto Rico

Tree species that are successful in tropical lowlands have different acquisition strategies to overcome soil phosphorus (P) limitations. Some of these strategies belowground include adjustments in fine-root traits, such as morphology, architecture, association with arbuscular mycorrhizal fungi, and phosphatase activity. Trade-offs among P-acquisition strategies are expected because of their respective carbon cost. However, empirical evidence remains scarce which hinders our understanding of soil P-acquisition processes in tropical forests. Here, we measured seven fine-root functional traits related to P acquisition of five common tree species in three sites of the Luquillo Experimental Forest in Puerto Rico. We then described species-specific P-acquisition strategies and explored the changes in fine-root trait expression from 6 months before to 6 months after two consecutive hurricanes, Irma and María, passed over the island. We found that variations in root trait expression were driven mainly by the large interspecific differences across the three selected sites. In addition, we revealed a trade-off between highly colonized fine roots with high phosphatase activity and fine roots that have a high degree of branching. Furthermore, the former strategy was adopted by pioneer species (Spathodea campanulata and Cecropia schreberiana), whereas the latter was adopted by non-pioneer species (mostly Dacryodes excelsa and Prestoea montana). Additionally, we found that root trait expression did not change comparing 6 months before and after the hurricanes, with the exception of root phosphatase activity. Altogether, our results suggest a combination of structural and physiological root traits for soil P acquisition in P-poor tropical soils by common tropical tree species, and show stability on most of the root trait expression after hurricane disturbances.

Nitrogen enrichment intensifies legume reliance on root phosphatase activity but weakens inter-specific correlations between N2 fixation and mycorrhizal colonization

Nitrogen enrichment intensifies legume reliance on root phosphatase activity but weakens inter-specific correlations between N2 fixation and mycorrhizal colonization

Effects of Funneliformis mosseae on the utilization of organic phosphorus in Camellia oleifera Abel.

Arbuscular mycorrhizal (AM) fungi play an important role in the acquisition of phosphorus(P) by plants. The external hyphae of AM fungi function as an extension of plant roots and may downregulate related functions in the roots. It is not clear whether the ability of AM fungi to mineralize organicP affects root phosphatase activities. A pot experiment was conducted to investigate the effect of Funneliformis mosseae on soil organicP mineralization under phytate application and to explore root phosphatase activities, Puptake, and growth in Camellia oleifera Abel. The plants and their growth substrates were harvested 4 and 8months after planting. The results showed that organicP application had no effect on the total dry mass of nonmycorrhizal plants, but differences in dry mass under P application were observed in mycorrhizal plants in both harvests. Inoculation with F.mosseae increased soil acid phosphatase, phytase, and alkaline phosphatase activities and reduced the soil organicP content. Mycorrhizal plants had higher root activity, shoot and root P contents and root acid phosphatase and phytase activities than nonmycorrhizal plants irrespective of organicP application. In conclusion, AM fungi enhanced the mineralization of soil organicP and positively affect root phosphatase activities.