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Background: Tropical tree species can maintain high growth rates on low-phosphorus (P) soils. However, the physiological basis of the high growth rates of tropical tree species remains unknown. Scope: Here, we examine how traits related to P uptake and use efficiency might account for this phenomenon. Based on a comparison of plant physiological responses to P and nitrogen (N) limitation, we hypothesize that distinct evolutionary processes have occurred on strongly weathered tropical soils characterized by low P availability relative to weakly and moderately weathered temperate soils characterized by low N availability. Efficient P-use arises through the synthesis of galactolipids rather than phospholipids, small genome size, preferential and flexible P allocation to leaves, efficient P resorption from wood and leaves, tissue longevity, and a decrease in P allocation to reproduction. Efficient P uptake mechanisms include synthesis of phosphatase in roots to acquire organic P from phosphodiesters and phytate, association with mycorrhizal fungi efficient at acquiring P, secretion of organic anions from roots to mobilize soil P, increased mass flow, and modifications of root depth distribution and structure. Conclusions: Despite the prevalence of low P soils throughout the tropics, few studies have explored P-use efficiency and acquisition mechanisms in tropical trees. We predict that the wide range of mechanisms by which plants can efficiently acquire and use P maintains productivity and promotes species diversity on low P soils in the tropics and elsewhere. [ABSTRACT FROM AUTHOR]

Background and aims: Soybean plants frequently encounter challenges such as phosphorus (P) deficiency and water stress in many regions. However, the mechanisms governing low P and water stress tolerance in soybeans at different growth stages remain unclear. This study investigates the effect of P availability and water stress on soybean growth, morpho-physiological traits, and seed yield.We conducted experiments using the soybean genotype (PI 561271) grown under two P levels (10 or 60 mg P kg−1 dry soil) with three watering conditions: well-watered (WW), early water stress (EWS) and terminal water stress (TWS). Plant assessments occurred at the vegetative, flowering, seed formation, and maturity stages.Water stress decreased leaf area, shoot and root dry weights, root length, photosynthetic rate, stomatal conductance, total carboxylates, water use, water use efficiency, shoot, root and seed P contents, seed nitrogen contents, and seed yield compared to WW at the corresponding P level and growth stage. P60 significantly increased all parameters except P use efficiency (PUE) under all water treatments. EWS plants supplemented with P60 exhibited the highest root dry weight, root length and total carboxylates. Notably, flowering and seed formation stages had the highest carboxylate proportions (oxalic, malic, malonic and citric acids) under WW and EWS at P60. P10 had significantly higher PUE than P60, irrespective of water treatments during flowering and seed formation, while the opposite trend occurred at the maturity stage. Seed protein content significantly varied between P treatments regardless of the water stress.Our findings underscore the adverse impacts of combined low P and water stress on soybean growth, morpho-physiological traits, seed yield and protein content. Moreover, increased P availability alleviated the adverse effects of water stress, highlighting the importance of adequate P fertilisation for soybean resilience to water stress.Methods: Soybean plants frequently encounter challenges such as phosphorus (P) deficiency and water stress in many regions. However, the mechanisms governing low P and water stress tolerance in soybeans at different growth stages remain unclear. This study investigates the effect of P availability and water stress on soybean growth, morpho-physiological traits, and seed yield.We conducted experiments using the soybean genotype (PI 561271) grown under two P levels (10 or 60 mg P kg−1 dry soil) with three watering conditions: well-watered (WW), early water stress (EWS) and terminal water stress (TWS). Plant assessments occurred at the vegetative, flowering, seed formation, and maturity stages.Water stress decreased leaf area, shoot and root dry weights, root length, photosynthetic rate, stomatal conductance, total carboxylates, water use, water use efficiency, shoot, root and seed P contents, seed nitrogen contents, and seed yield compared to WW at the corresponding P level and growth stage. P60 significantly increased all parameters except P use efficiency (PUE) under all water treatments. EWS plants supplemented with P60 exhibited the highest root dry weight, root length and total carboxylates. Notably, flowering and seed formation stages had the highest carboxylate proportions (oxalic, malic, malonic and citric acids) under WW and EWS at P60. P10 had significantly higher PUE than P60, irrespective of water treatments during flowering and seed formation, while the opposite trend occurred at the maturity stage. Seed protein content significantly varied between P treatments regardless of the water stress.Our findings underscore the adverse impacts of combined low P and water stress on soybean growth, morpho-physiological traits, seed yield and protein content. Moreover, increased P availability alleviated the adverse effects of water stress, highlighting the importance of adequate P fertilisation for soybean resilience to water stress.Results: Soybean plants frequently encounter challenges such as phosphorus (P) deficiency and water stress in many regions. However, the mechanisms governing low P and water stress tolerance in soybeans at different growth stages remain unclear. This study investigates the effect of P availability and water stress on soybean growth, morpho-physiological traits, and seed yield.We conducted experiments using the soybean genotype (PI 561271) grown under two P levels (10 or 60 mg P kg−1 dry soil) with three watering conditions: well-watered (WW), early water stress (EWS) and terminal water stress (TWS). Plant assessments occurred at the vegetative, flowering, seed formation, and maturity stages.Water stress decreased leaf area, shoot and root dry weights, root length, photosynthetic rate, stomatal conductance, total carboxylates, water use, water use efficiency, shoot, root and seed P contents, seed nitrogen contents, and seed yield compared to WW at the corresponding P level and growth stage. P60 significantly increased all parameters except P use efficiency (PUE) under all water treatments. EWS plants supplemented with P60 exhibited the highest root dry weight, root length and total carboxylates. Notably, flowering and seed formation stages had the highest carboxylate proportions (oxalic, malic, malonic and citric acids) under WW and EWS at P60. P10 had significantly higher PUE than P60, irrespective of water treatments during flowering and seed formation, while the opposite trend occurred at the maturity stage. Seed protein content significantly varied between P treatments regardless of the water stress.Our findings underscore the adverse impacts of combined low P and water stress on soybean growth, morpho-physiological traits, seed yield and protein content. Moreover, increased P availability alleviated the adverse effects of water stress, highlighting the importance of adequate P fertilisation for soybean resilience to water stress.Conclusions: Soybean plants frequently encounter challenges such as phosphorus (P) deficiency and water stress in many regions. However, the mechanisms governing low P and water stress tolerance in soybeans at different growth stages remain unclear. This study investigates the effect of P availability and water stress on soybean growth, morpho-physiological traits, and seed yield.We conducted experiments using the soybean genotype (PI 561271) grown under two P levels (10 or 60 mg P kg−1 dry soil) with three watering conditions: well-watered (WW), early water stress (EWS) and terminal water stress (TWS). Plant assessments occurred at the vegetative, flowering, seed formation, and maturity stages.Water stress decreased leaf area, shoot and root dry weights, root length, photosynthetic rate, stomatal conductance, total carboxylates, water use, water use efficiency, shoot, root and seed P contents, seed nitrogen contents, and seed yield compared to WW at the corresponding P level and growth stage. P60 significantly increased all parameters except P use efficiency (PUE) under all water treatments. EWS plants supplemented with P60 exhibited the highest root dry weight, root length and total carboxylates. Notably, flowering and seed formation stages had the highest carboxylate proportions (oxalic, malic, malonic and citric acids) under WW and EWS at P60. P10 had significantly higher PUE than P60, irrespective of water treatments during flowering and seed formation, while the opposite trend occurred at the maturity stage. Seed protein content significantly varied between P treatments regardless of the water stress.Our findings underscore the adverse impacts of combined low P and water stress on soybean growth, morpho-physiological traits, seed yield and protein content. Moreover, increased P availability alleviated the adverse effects of water stress, highlighting the importance of adequate P fertilisation for soybean resilience to water stress. [ABSTRACT FROM AUTHOR]

Background and aims: Twenty-four species of eucalypts were studied regarding their ability to grow under low P and their responsiveness to P inputs. Methods: Growth and photosynthesis-related parameters were evaluated. Results: Growth of all species was influenced by low P availability. No significant correlation was found between leaf P concentration and biomass, indicating that P concentrations in leaves cannot be solely considered an indication of the responsiveness to P in eucalypts. Species responsive to P-input (high agronomic P efficiency values, APE) were those with low P use efficiency - PUE (here assessed as relative efficiency of P-use, REP) and low P uptake efficiency (PUpE). But, non-responsive species were related to higher P-efficiency under low soil P-availability. Eucalyptus tereticornis, E. cladocalyx, E. globulus and E. camaldulensis were efficient under low-P availability. Whereas, E. crebra and E acmenoides were the most responsive species, with high APE, suggesting that for these species P-inputs are needed to guarantee plant growth. The root:shoot ratio remained constant at different P availabilities, suggesting that biomass allocation towards the root in response to P and greater investment in roots were not correlated with greater PUE. Under limited P, E. robusta and E. botryoides exhibited low foliar P contents and higher root:shoot ratios than those of other species with higher P contents, indicating that greater root investment does not necessarily result in greater PUE. Conclusion: The results suggest that the divergence among species is probably related to different mechanisms, which may improve P-use efficiency. [ABSTRACT FROM AUTHOR]

Aims: Progress in improving the internal phosphorus utilisation efficiency of crops has been limited, which may be due to poor screening methods that allow differences in P uptake among genotypes grown in soil to mask genotypic differences in shoot biomass produced per unit of shoot P (PUE). We investigated alternative soil and hydroponic screening methods for their capacity to produce a consensus ranking of genotypes with regard to PUE. Methods: Six rice genotypes previously identified in hydroponic screening studies as being high, intermediate or low in PUE were screened using multi P rate hydroponic and soil-based experiments. Results: Comparisons made at each rate of soil-P supply produced estimates of PUE strongly biased by P uptake differences among genotypes. Using multiple-rate data to derive response functions per genotype showed that similar P content was achieved at different rates of P supply but that high-PUE genotypes clearly separated from intermediate- and low-PUE genotypes if equal P content was used. Ranking analysis suggested that results obtained from soil agreed well with those from the hydroponic study. Conclusions: PUE was significantly influenced by genotype and P supply, but there was no significant genotype x P supply interaction. Hence, we conclude that screening genotypes using hydroponics at one or two P supply levels is the most cost- and time effective means to screen large numbers of rice genotypes for PUE. [ABSTRACT FROM AUTHOR]

Plants recycle substantial amounts of phosphorus (P) from senescing tissues, reducing the need to take up P from soils. This paper reviews P recycling in plants, factors that determine its quantitative importance, and evidence that species from low-P ecosystems possess traits that enhance P recycling. It focuses on roots and leaves where most P turnover occurs. Knowledge of root traits and dynamics lags far behind that of leaves, but P concentrations, lifespans, resorption percentages and biomass allocation of roots are all comparable to those of leaves. Relationships among traits that influence P recycling appear more complex in roots than in leaves. Long root lifespans may not be adaptive in soils with very low P availability. At the plant level, the quantitative importance of P resorption to support P requirements decreases with net growth rate and with tissue longevity. Leaf lifespans are negatively correlated with growth rates and resource availability, but root lifespans may not be, indicating that further research into root dynamics and P resorption is essential to understand the role of roots in both P conservation and P acquisition. [ABSTRACT FROM AUTHOR]

Background: Crop production in China has been greatly improved by increasing phosphorus (P) fertilizer input, but overuse of P by farmers has caused low use efficiency, increasing environmental risk and accumulation of P in soil. From 1980 to 2007, average 242 kg P ha−1 accumulated in soil, resulting in average soil Olsen P increasing from 7.4 to 24.7 mg kg−1. China is facing huge challenges to improve P use efficiency through optimizing corresponding technology and policies. The problem is exacerbated because people have been shifting their diet from plant-based to animal-enriched foods. This results in higher P load in the food chain and lower P use efficiency. Scope: A multidisciplinary approach has been used to improve P management at the field and national level in China. Management strategies based on the soil and on the plant rhizosphere have been developed to increase efficient use of P. A national soil testing and fertilizer recommendation program has been used since 2005 to control build-up and maintenance of P levels. Interactions between root growth and the rhizosphere have been manipulated in intercropping systems and plant genetic traits have been exploited. Phosphorus surplus is highly associated with animal concentrated feed. Conclusions: The P-saving potential by the integrated P management strategies of P flow reaches 1.46 Mt P in 2050 compared to 2005. [ABSTRACT FROM AUTHOR]

This study assessed the suitability of two deciduous woody perennials ( Salix spp. and Populus spp.) and two summer green herbaceous perennials ( Phragmites australis and Urtica dioica) for purification of nutrient enriched wastewater. The main hypothesis tested was that species with a particular trait combination of high relative growth rate (RGR), low nutrient productivity ( A) and high mean residence time (MRT) of nutrients would be most effective in accumulating nutrients. The nitrogen and phosphorus use efficiency at the whole plant level was analysed. Four treatments comprising two possible phytoremediation substrates (municipal wastewater and landfill leachate) and two control plant nutrition situations (balanced nutrient solution and pure water) were applied in four replications to the four plant species. Generally, all four species studied showed a high RGR and a low P productivity in the balanced nutrient solution treatment, while the opposite (low RGR and high P productivity) was seen in the phytoremediation substrate and pure water treatments. The general conclusion is that if P is present in marginal proportions in the wastewater, a vegetation filter with Phragmites would have an advantage since biomass and nutrient accumulation in Phragmites does not decrease as much during phytoremediation as that in deciduous woody perennials. [ABSTRACT FROM AUTHOR]

Improved methods for selecting cultivars for their ability to grow well on low P soils will improve productivity and minimise pollution. Estimates are required of the relative values for different genotypes of physiologically meaningful parameters that define yield response to increasing levels of plant available soil P. The object of this study was to devise ways of obtaining these estimates from conventional trials that include numerous genotypes but only two P treatments. The parameters were estimated as coefficients of a modified Michaelis–Menten equation, namely A, the maximum yield that can be obtained with ample P, Km, the concentration of plant available P in the rooting medium at which yield is half the maximum, and B, the gradient of yield against available P as it approaches the origin. Two novel methods of estimation were devised. They both require inputs of yield and its variance at each of two concentrations of available P, but these must be within certain limits. Estimates of parameter values for 12 Brassica oleracea genotypes made by these methods from two P-levels in each of two experiments with six P levels were compared with the values obtained by conventional fitting to the data from all six P levels. According to regression and ranking analyses, the relative values of A obtained for the different genotypes by both two P-level methods were similar to those from the six P-level method and both were reproducible. None of the methods however detected any reproducible differences in Km. Application of one of the two P-level methods to published data for genotypes of other species indicated that there was little intra-species variation in Km within some data sets on maize, beans and leguminous cover crops but much within other data sets. Sensitivity and algebraic analyses are presented to define the experimental conditions required for successful use of two P-level methods. It is concluded that, provided these experimental conditions are met, measurements at two P levels can give almost as much information about intra-species differences in P response parameters as measurements at six P levels. The procedure may also be useful for interpreting other responses of a “diminishing returns” type such as those to other nutrients or plant spacing. [ABSTRACT FROM AUTHOR]

Differences in growth, nodulation and arbuscular mycorrhizal fungi (AMF) root infection among recent cowpea breeding lines from IITA wereexamined at low and high P levels in pot (94 lines) and field experiments (43 lines) at Fashola in the derived savanna zone of Nigeria. Based on their growth performance, these lines were subdivided into 5 groups: (i) poor performance under low and high P conditions; (ii) good performance under low P and poor performance under high P; (iii) intermediate performance under high and low P; (iv) good performance under high and low P conditions; and (v) good performance under high Pand poor performance under low P. About 42% of the breeding lines (18 out of 43 lines tested) had the same grouping for the field and potexperiments. Eight cowpea lines (4 P-responders and 4 non-P-responders) were selected from the first experiment for subsequent studies onthe effect of P supply (0, 20, 40 and 60 kg P ha-1) on P uptake, P use efficiency, dry matter production, N-fixation, AMF infection and N balance. Dry matter production, shoot/root ratio, total shoot N, and total N-fixed of the non-P-responder line, IT81D-715, were strongly related to P uptake efficiency. The P-responder IT81D-849 had a significant (95%) correlation between AMF and P-use efficiency.The cowpea lines fixed on average 22 kg N ha-1, which was70% of the plant total N. The N balance based on the difference between the amount of N2 fixed and N exported through the harvest, ranged between ?10.6 kg N ha-1 and +7.7 kg N ha-1. Based on its adaptability to grow in low P soils and overallpositive N balance, the cowpea line IT81D-715 should be recommended for cultivation when P is the limiting factor." [ABSTRACT FROM AUTHOR]