Leaf Elemental Concentrations Research Articles

Native and invaded-range surveys provide mixed support for enemy-release of Nymphoides peltata in the invaded range

Natural or anthropogenic movement of plant species outside their historical ranges may result in exposure to new environmental conditions and a lack of natural enemies, thus promoting their establishment and spread into new areas. A biogeographical comparison of native and invasive populations can provide insight into the mechanisms of successful invasions and guide effective management strategies, such as biological control, by targeting plant traits that promote invasiveness. We studied the Eurasian aquatic plant, Nymphoides peltata, in situ in the native (China, Korea) and invaded (USA) ranges to determine whether there were differences in natural enemy attack rates (percent leaf damage, frequency of leaf herbivory or disease), productivity (plant cover, reproduction), and leaf traits (leaf elemental content, leaf toughness, dry matter content, specific leaf area) between areas. We also investigated whether there was evidence of a tradeoff between natural enemy attack and growth or reproduction, as would be predicted by invasion theory. Plant cover (23–29 % higher) and reproductive output (eight times more seeds / m2) were consistently higher in the invaded range. Leaf traits consistently differed between ranges, which we would expect if plants in the invaded range had fewer herbivores or other pests. The amount of leaf damage present was similar between ranges, but the frequency of herbivory was 50 % greater, on average, in the native than invaded range. Although we did not quantify suppression of N. peltata by natural enemies, we found evidence of more frequent herbivory in Asia and reduced reproduction and plant cover compared to the USA, which supports further investigation into viability of biological controls.

Local‐Scale Controls Over Leaf N and P Stoichiometry of 121 Plant Species in the Inner Mongolia Grassland

AbstractNitrogen (N) and phosphorus (P) stoichiometry in plant leaves plays an important role in linking plant physiological processes with community assemblage and species distribution. Studies have revealed that temperature is a major driver of leaf stoichiometry, however, whether current global warming will alter leaf N and P stoichiometry on a local scale remain poorly understood. Taking advantage of an unique data set on leaf element concentrations of 122 plant species in the Xilingol Grassland National Reserve (established in 1979), we addressed this issue by resampling plant leaves of the same 121 species in 2018, and compared the leaf N, P, and N:P ratio between the 2 years. We found that leaf N, P, and N:P ratio of the 121 species all exhibited large variation, with a magnitude of 4.5‐fold for N, 5.8‐fold for P, and 6.3‐fold for N:P ratio, respectively. However, the mean leaf N, P, and N:P ratio of the 121 species, as well as for each family, each life form and each habitat type, did not significantly change over 40 years (1979 vs. 2018), though a 2°C increase in annual mean temperature occurred. We identified that taxonomic difference was the primary driver for variations in leaf N, P, and N:P ratio in this grassland reserve, which is different from those on the regional and global scales. These results suggest that controls over leaf stoichiometry are likely scale‐dependent. Thus, using leaf stoichiometry to explain community assemblage and species distribution should take into account the scale‐dependent drivers.

Physiological and molecular responses in phosphorus-hyperaccumulating Polygonum species to high phosphorus exposure.

Phosphorus (P)-hyperaccumulators for phytoextraction from P-polluted areas generally show rapid growth and accumulate large amounts of P without any toxicity symptom, which depends on a range of physiological processes and gene expression patterns that have never been explored. We investigated growth, leaf element concentrations, P fractions, photosynthetic traits, and leaf metabolome and transcriptome response in amphibious P-hyperaccumulators, Polygonum hydropiper and P. lapathifolium, to high-P exposure (5 mmol L-1), with 0.05 mmol L-1 as the control. Under high-P exposure, both species demonstrated good growth, allocating more P to metabolite P and inorganic P (Pi) accompanied by high potassium and calcium. The expression of a cluster of unigenes associated with photosynthesis was maintained or increased in P. lapathifolium, explaining the increase in net photosynthetic rate and the rapid growth under high-P exposure. Metabolites of trehalose metabolism, including trehalose 6-phosphate and trehalose, were sharply increased in both species by the high-P exposure, in line with the enhanced expression of associated unigenes, indicating that trehalose metabolic pathway was closely related to high-P tolerance. These findings elucidated the physiological and molecular responses involved in the photosynthesis and trehalose metabolism in P-hyperaccumulators to high-P exposure, and provides potential regulatory pathways to improve the P-phytoextraction capability.

Divergent Nitrogen, Phosphorus, and Carbon Concentrations among Growth Forms, Plant Organs, and Soils across Three Different Desert Ecosystems

Quantifying the dryland patterns of plant carbon (C), nitrogen (N), and phosphorus (P) concentrations and their stoichiometric values along environmental gradients is crucial for understanding ecological strategies. To understand the plant adaptive strategies and ecosystem nutrient concentrations across three desert ecosystems (e.g., desert, steppe desert, and temperate desert), we compiled a dataset consisting of 1295 plant species across three desert ecosystems. We assessed the element concentrations and ratios across plant growth forms, plant organs, and soils and further analysed the leaf vs. root N, P, and N:P scaling relationships. We found that the leaf N, P, and C concentrations were significantly different only from those of certain other growth forms and in certain desert ecosystems, challenging the generality of such differences. In leaves, the C concentrations were always greater than the N and P concentrations and were greater than those in soils depending on the soil chemistry and plant physiology. Thus, the element concentrations and ratios were greater in the organs than in the soils. The values in the leaf versus the root N, P, and N:P scaling relationships differed across the three desert ecosystems; for example, αN (1.16) was greater in the desert, αP (1.10) was greater in the temperate desert ecosystem, and αN:P (2.11) was greater in the desert ecosystem. The mean annual precipitation (MAP) and mean annual temperature (MAT) did not have significant effects on the leaf elemental concentrations or ratios across the desert ecosystems. This study advances our understanding of plant growth forms and organs, which support resource-related adaptive strategies that maintain the stability of desert ecosystems via divergent element concentrations and environmental conditions.

Incident Light Level Influences Elemental Budgets of Serianthes nelsonii Merr. Leaf Development

Recovery efforts for the endangered Serianthes nelsonii have been deficient. To learn more about leaf development costs, the content of biomass and essential elements were determined in the supportive and laminae tissue of leaves that were constructed under different levels of incident light. The biomass required to construct a leaf in 22% light transmission was 65% of that in full sun, and light treatment did not influence the balance between supportive and laminae tissues. Concentrations of carbon, phosphorus, iron, manganese, and boron were greatest for in full-sun laminae, but those of nitrogen, potassium, calcium, magnesium, and zinc were greatest in shaded laminae. The same patterns with regard to light were exhibited in supportive tissues for carbon, nitrogen, potassium, calcium, magnesium, and zinc. In contrast, the supportive tissue phosphorus content was greatest in shaded leaves, and the light level did not influence the supportive tissue concentrations of the remaining elements. The leaf laminae consistently exhibited greater concentrations of elements with the exception of potassium and nickel, which were greater in the supportive tissues. These results indicate that the construction of full-sun S. nelsonii leaves is more costly than that of shaded leaves, and the transfer of biomass and essential elements between the supportive and laminae tissues is not substantially influenced by the developmental light level. Identifying the drivers of S. nelsonii leaf element concentrations is crucial for understanding the role of this charismatic tree in community-level processes.

The genomic basis of nitrogen utilization efficiency and trait plasticity to improve nutrient stress tolerance in cultivated sunflower.

Maintaining crop productivity is challenging as population growth, climate change, and increasing fertilizer costs necessitate expanding crop production to poorer lands whilst reducing inputs. Enhancing crops' nutrient use efficiency is thus an important goal, but requires a better understanding of related traits and their genetic basis. We investigated variation in low nutrient stress tolerance in a diverse panel of cultivated sunflower genotypes grown under high and low nutrient conditions, assessing relative growth rate (RGR) as performance. We assessed variation in traits related to nitrogen utilization efficiency (NUtE), mass allocation, and leaf elemental content. Across genotypes, nutrient limitation generally reduced RGR. Moreover, there was a negative correlation between vigor (RGR in control) and decline in RGR in response to stress. Given this trade-off, we focused on nutrient stress tolerance independent of vigor. This tolerance metric correlated with the change in NUtE, plasticity for a suite of morphological traits, and leaf element content. Genome-wide associations revealed regions associated with variation and plasticity in multiple traits, including two regions with seemingly additive effects on NUtE change. Our results demonstrate potential avenues for improving sunflower nutrient stress tolerance independent of vigor, and highlight specific traits and genomic regions that could play a role in enhancing tolerance.

LEADER (Leaf Element Accumulation from DEep Roots): A nondestructive phenotyping platform to estimate rooting depth in the field

AbstractDeeper rooted crops are an avenue to increase plant water and nitrogen uptake under limiting conditions and increase long‐term soil carbon storage. Measuring rooting depth, however, is challenging due to the destructive, laborious, or imprecise methods that are currently available. Here, we present LEADER (Leaf Element Accumulation from DEep Roots) as a method to estimate in‐field root depth of maize plants. We use both X‐ray fluorescence (XRF) spectroscopy and ICP‐OES (inductively coupled plasma optical emission spectroscopy) to measure leaf elemental content and relate this to metrics of root depth. Principal components of leaf elemental content correlate with measures of root length in four genotypes (R2 = 0.8 for total root length), and we use linear discriminant analysis to classify plants as having different metrics related to root depth across four field sites in the United States. We can correctly classify the plots with the longest root length at depth (deeper than 30 or 40 cm) with high accuracy (accuracy >0.6) at two of our field sites (Hancock, WI and Rock Spring, PA). We also use strontium (Sr) as a tracer element in both greenhouse and field studies, showing that elemental accumulation of Sr in leaf tissue can be measured with XRF and can estimate root depth. We propose the adoption of LEADER as a tool for measuring root depth in different plant species and soils. LEADER is faster and easier than any other methods that currently exist and could allow for extensive study and understanding of deep rooting.

Responses of a common tropical epiphyte, Asplenium nidus, to changes in water and nutrient availability.

Epiphytes are highly dependent on atmospheric inputs of water and nutrients. Reductions in water availability associated with warming and climate change and continual atmospheric nitrogen (N) deposition can affect plant growth but few studies have evaluated the effects of changes in both water and nutrient availabilities on epiphytes. We experimentally tested whether epiphyte growth is more water- or nutrient-limited, if nutrient limitation was stronger for nitrogen or phosphorus, and whether nutrient limitation interacts with water availability. We applied watering (high and low) and nutrient addition (control, +N, +P, +N+P) treatments to greenhouse-grown Asplenium nidus, a common epiphytic fern found in many tropical and subtropical wet forests. We measured leaf area production and leaf elemental concentrations to assess how A. nidus growth and physiology respond to changes in water and nutrient availabilities. We found that leaf growth of A. nidus was more affected by water availability than nutrient addition and the effect of adding nutrients was not fully realized under low-water availability. Among the different nutrient treatments, +N+P had the greatest effects on A. nidus growth and physiology in both watering treatments. Watering treatment changed leaf elemental concentrations but not their ratios (i.e. C:N and N:P). Nutrient addition altered C:N and N:P ratios and increased the concentration of the added elements in leaves, with more pronounced increases in the high-watering treatment. We conclude that the growth of A. nidus is more water- than nutrient-limited. When nutrient limitation occurs (i.e. under high-water availability), nutrient co-limitation is stronger than limitation by N or P alone. This result taken together with studies of other epiphytes suggests greater water than nutrient limitation is likely widespread among epiphytic plants. The limited effects of nutrient addition in the low-water treatment suggest that the effect of atmospheric N deposition on epiphyte growth will be limited when water availability is low.

Sequentialremoval of cation/H+ exchangers reveals their additive role in elemental distribution, calcium depletionand anoxia tolerance.

Multiple Arabidopsis H+ /Cation exchangers (CAXs) participate in high-capacity transport into the vacuole. Previous studies have analysed single and double mutants that marginally reduced transport; however, assessing phenotypes caused by transport loss has proven enigmatic. Here, we generated quadruple mutants (cax1-4: qKO) that exhibited growth inhibition, an 85% reduction in tonoplast-localised H+ /Ca transport, and enhanced tolerance to anoxic conditions compared to CAX1 mutants. Leveraging inductively coupled plasma mass spectrometry (ICP-MS)and synchrotron X-ray fluorescence (SXRF), we demonstrate CAX transporters work together to regulate leaf elemental content: ICP-MS analysis showed that the elemental concentrations in leaves strongly correlated with the number of CAX mutations; SXRF imaging showed changes in element partitioning not present in single CAX mutants and qKO had a 40% reduction in calcium (Ca) abundance. Reduced endogenous Ca may promote anoxia tolerance; wild-type plants grown in Ca-limited conditions were anoxia tolerant. Sequential reduction of CAXs increased mRNA expression and protein abundance changes associated with reactive oxygen species and stress signalling pathways. Multiple CAXs participate in postanoxia recovery as their concerted removal heightened changes in postanoxia Ca signalling. This work showcases the integrated and diverse function of H+ /Cation transporters and demonstrates the ability to improve anoxia tolerance through diminishing endogenous Ca levels.

Different responses of macro- and microelement contents of 41 subtropical plants to environmental changes in the wet and dry seasons

AbstractDifferences in plant leaf elemental contents due to seasonal climate change reflect potential plant growth strategies. However, the distribution patterns of elements mediated by seasonal climate change remain unclear. This limits assessment of plant growth status and prediction of plant growth dynamics under global climate change. We collected 41 subtropical evergreen broadleaf plant leaves (31 tree species and 10 shrub species) during the wet and dry seasons, and determined foliar contents of macro- and microelements by inductively coupled plasma mass spectrometer. Our results showed that 41 plant leaves had significantly greater macroelement contents and significantly lower microelement contents in wet season than dry season. The highest macroelement content was in tree layer plants in wet season, followed by tree layer plants in dry season and shrub layer plants in wet season, the lowest was in shrub layer plants in dry season. The highest microelement content was in tree and shrub layer plants in dry season, followed by shrub layer plants in wet season, the lowest was in tree layer plants in wet season. Our results show that macro- and microelement contents of plant leaves with different vertical structures are affected by seasonal climate change. The transition from wet to dry season was detrimental to tree layer plants growth, but had less impact on shrub layer plants growth. These findings provide valuable evidence for predicting how different vertically structured subtropical evergreen broadleaf plants can adapt to changes in wet and dry season environments and to future global climate change.

Waterlogging effects on leaf element concentrations and cane weight of sugarcane genotypes

Aim: The aim of the present experiment was to examine whether waterlogging induced deficiency or excess of elements, is the cause for reduction in cane weight of sugarcane genotypes under waterlogged conditions. Methodology: The experiment was conducted in pots with eleven sugarcane genotypes grown under control and waterlogged conditions. Waterlogging treatment was imposed at 120 days crop age for a period of 60 days. Cane weight and element concentrations were measured at the end of waterlogging. Results: Compared to control, reduction in cane weight of sugarcane genotypes under waterlogging varied from 5.3% (A-46-11) to 32.3% (CoJ 64). Waterlogging caused a significant decrease in leaf N, P, K, S, Zn and Cu concentrations of sugarcane genotypes; the extent of decreases in leaf N and S were more and values for these elements dropped below their reported critical deficiency level for most genotypes. There was a significant inverse correlation between leaf K and S concentration, and reduction in cane weight of sugarcane genotypes, indicating that genotypes with high leaf K and S under waterlogging have relatively less reduction in cane weight. There were significant increase in the leaf Fe, Al, Mn and Na concentrations under waterlogging, however, increase in these elements were not correlated with reduction in cane weight of sugarcane genotypes. Interpretation: The results suggest that deficiencies of N, K and S rather than excess of Fe, Al and Mn is a major cause for reduction in cane weight of sugarcane genotypes under waterlogged condition. The genotypes tolerant to N, K and S deficiencies under waterlogging can be utilized in breeding program for developing sugarcane varieties with improved waterlogging tolerance. Key words: Cane weight, Element deficiencies, Element toxicities, Sugarcane, Waterlogging

Integrated diagnosis and time-series sensitivity evaluation of nutrient deficiencies in medicinal plant (Ligusticum chuanxiong Hort.) based on UAV multispectral sensors.

Nitrogen(N), phosphorus(P), and potassium(K) are essential elements that are highly deficient during plant growth. Existing diagnostic methods are not suitable for rapid diagnosis of large-scale planting areas. Near-ground remote sensing technology based on unmanned aerial vehicle (UAV) and sensor is often applied to crop growth condition monitoring and agricultural management. It has been proven to be used for monitoring plant N, P, and K content. However, its integrated diagnostic model has been less studied. In this study, we collected UAV multispectral images of Ligusticum chuanxiong Hort. in different periods of nutritional stress and constructed recognition models with different heights and algorithms. The optimal model variables were selected, and the effects of different sampling heights and modeling algorithms on the model efficiency under the time span were evaluated. At the same time, we evaluated the timeliness of the model based on leaf element content determination and SPAD. It was also validated in field crop production. The results showed that the LR algorithm's model had optimal performance at all periods and flight altitudes. The optimal accuracy of N-deficient plants identification reached 100%, P/K-deficient plants reached 92.4%, and normal plants reached 91.7%. The results of UAV multispectral diagnosis, chemical diagnosis, and SPAD value diagnosis were consistent in the diagnosis of N deficiency, and the diagnosis of P and K deficiency was slightly lagging behind that of chemical diagnosis. This research uses UAV remote sensing technology to establish an efficient, fast, and timely nutritional diagnosis method for L. Chuanxiong, which is applied in production. Meanwhile, the standardized production of medicinal plant resources provides new solutions.

Metallic mangroves: Sediments and in situ diffusive gradients in thin films (DGTs) reveal Avicennia marina (Forssk.) Vierh. lives with high contamination near a lead‑zinc smelter in South Australia

From 1889, aerial emissions and effluent from a coastal lead‑zinc smelter at Port Pirie, South Australia, have led to the accumulation of lead (Pb), zinc (Zn), arsenic (As), cadmium (Cd) and copper (Cu) in the surrounding marine environment. Despite this, extensive stands of grey mangrove (Avicennia marina) inhabit coastal areas at Port Pirie, right up to the smelter's boundary. To understand the contamination level the mangroves are living in there, elemental concentrations were measured in mangrove sediments, leaves, pneumatophores and fruits at sites 0.30–43.0 km from the smelter. Plant health was assessed via leaf chlorophyll content at four sites with contrasting contamination, as well as in situ labile elemental concentration using diffusive gradients in thin films (DGT). Sites < 1.7 km of the smelter exceeded Australian and New Zealand Environment and Conservation Council (ANZECC) & Agriculture and Resource Management Council of Australia and New Zealand (ARMCANZ) (2000) sediment quality guideline values for As (78.3–191 mg/kg), Cd (5.17–151 mg/kg), Cu (80.7–788 mg/kg), Pb (2,544–14,488 mg/kg) and Zn (281–62,097 mg/kg), while sites further away showed less enrichment above background. Similarly, elevated elemental concentrations in leaves and pneumatophores occurred closer to the smelter (up to 319 mg/kg Pb; 1,033 mg/kg Zn), while fruits had little contamination of non-essential elements (≤ 5.23 mg/kg). Relationship between sediment and leaf elemental concentration was isometric for Pb and anisometric for others. Labile As, Cd, Cu, Pb and Zn exceeded the 95% and 80% level of species protection in marine water by ANZECC & ARMCANZ (2000) near the smelter, but chlorophyll content did not vary significantly among sites (p > 0.05). These results reveal that A. marina tolerate high elemental contamination at Port Pirie, contributing to lesser but still high contamination in plants, warranting further investigation into non-lethal impacts on mangroves or additional biota inhabiting this ecosystem.

Influence of species functional strategy on leaf stoichiometric responses to fertilizer in a Bornean heath forest

Abstract The distribution of Bornean heath forest on white sand soils is believed to be due to element limitation and soil acidity. To determine the impact of both element limitation and soil acidity on tropical heath forest, we established a soil fertilization experiment to investigate the impact that increased soil N availability and reduced soil pH (using lime/CaCO3) had on a range of elements in tree leaves. We hypothesized that alterations in soil resource availability would cause changes in the tree leaf N:P ratio and concentrations of other elements and these changes would be influenced by species' functional strategies. The experiment was carried out in a Bornean heath forest on infertile soil over a 2‐year period. We selected 10 common tree species, spanning acquisitive to conservative strategies and tested whether tree species functional strategies influenced tree leaf elemental concentrations after the fertilization. Leaf N:P ratios showed considerable differences among co‐occurring species. Overall, we found that soil N addition treatments increased leaf N concentration, although leaf N:P ratios were not affected. Changes in leaf Al, Fe and S concentrations were correlated with species functional strategy: conservative species showed a greater increase in leaf Fe compared with acquisitive species, whereas acquisitive species showed a greater increase in leaf Al but a decrease in leaf S compared with conservative species. Synthesis. We show that soil elements uptake differs between acquisitive and conservative species and that acquisitive species may not take up soil elemental resources more effectively than conservative species. We suggest that the greater Fe acquisition by conservative species, in comparison to acquisitive species, might be due to a stress tolerance strategy. The overall increase in leaf N showed that, in this nutrient‐poor forest, N is a fundamental requirement irrespective of species functional strategies. Given the increased leaf Al and Fe concentration after liming, we also suggest that these elements are important, and possibly limiting (Fe), in this heath forest.

Leaf Stoichiometry of Potentilla fruticosa Across Elevations in China's Qilian Mountains.

As an individual plant species can develop its own leaf stoichiometry to adapt to environmental changes, this stoichiometry can provide critical information about a plant species’ growth and its potential management in the ecosystem housing it. However, leaf stoichiometry is largely undocumented in regions with large environmental changes arising from differences in elevation. The leaf stoichiometry of Potentilla fruticosa L., a major alpine shrub playing an important role in supporting ecosystem functions and services in China’s Qilian Mountains (Northeast Qinghai–Tibetan Plateau), was investigated at different elevations (2,400, 2,600, 2,800, 3,000, 3,200, 3,500, and 3,800 m). At each elevation, leaf elemental (C, N, and P) concentrations were measured in P. fruticosa leaves sampled from three plots (10 × 10 m), and edaphic properties were assessed in nine quadrats (1 × 1 m, three quadrats per plot). Temperature and precipitation were calculated using an empirical formula. Maximum and minimum leaf carbon (C) concentrations ([C]leaf) of 524 ± 5.88 and 403 ± 3.01 g kg–1 were measured at 2,600 and 3,500 m, respectively. Leaf nitrogen (N) concentration ([N]leaf) showed a generally increasing trend with elevation and peaked at 3,500 m (27.33 ± 0.26 g kg–1). Leaf phosphorus (P) concentration ([P]leaf) varied slightly from 2,400 to 3,200 m and then dropped to a minimum (0.60 ± 0.10 g kg–1) at 3800 m. The [C]leaf:[N]leaf, [C]leaf:[P]leaf, and [N]leaf:[P]leaf varied little from 2,400 to 3,000 m but fluctuated somewhat at higher elevations. The main factors affecting P. fruticosa leaf stoichiometry were soil organic C, pH, and soil total P, and the main limiting element for the growth of P. fruticosa in the study area was P. In conclusion, changes in elevation affected leaf stoichiometry of P. fruticosa mainly due to altered soil properties, and addressing phosphorus limitation, especially at higher elevations mainly due to losses caused by high precipitation and sparse vegetation, is a key measure to promote P. fruticosa growth in this region.

Carbon, nitrogen and phosphorus stoichiometry of two submerged macrophytes are more affected by plant species and organs than by light

Context Submerged macrophytes develop great phenotypic plasticity responding to light stress. However, the light effects on carbon (C), nitrogen (N) and phosphorus (P) stoichiometry of submerged macrophytes are unknown. Aims To determine the stoichiometric response of Myriophyllum spicatum and Vallisneria natans to a light gradient. Methods We determined the C, N and P stoichiometry of two aquatic plants grown in pots subjected to an incident light gradient ranging from 100 to 17% of incident light. Key results The C, N and P stoichiometry of V. natans (except C:N of root) were not significantly different among the light treatments, whereas those of M. spicatum (except leaf element concentrations and root element ratios) showed significant differences across the light gradient. The analysis of variance results implied that the species, plant organs and their interactions explained more than 75% of total variance of all measured indices (except C). Conclusions The C, N and P stoichiometry of the two studied submerged macrophytes are more affected by plant organs and species than by light irradiance. Implication Although C, N and P stoichiometry of submerged macrophytes was little affected by light irradiance, whether the stoichiometry of submerged macrophytes is stable under other environmental factors should be focused on in future investigation.

English

Field studies were conducted to evaluate the effect of various fertilizer placements on nutrient uptake, growth responses, storage root yield and leaf elemental concentration of Whatley/Loretan sweetpotato [Ipomoea batatas (L.) Lam.]. The fertilizer placement treatments comprised broadcast (Br), banded at two different widths (Ba), side dressing (Sd) or applied in various combinations of the above, and an untreated check. Fertilizer rates were 135, 35 and 133 kg.ha-1 each of N, P and K based on soil test. At nine weeks after planting, the fifth fully expanded leaf from the tip of five plants was collected and analyzed for elemental concentration. The plants were harvested 101 days after transplanting and biomass data were collected. Vine yield for all placement treatments was equal to or exceeded that of the full rate broadcast. Yield of US # 1 roots was increased 78 and 72%, respectively, when 2/3 of the fertilizer was banded and tended to increase total storage root yield compared to the same, full or 2/3 the rate broadcast. Leaf N was highest with 1/3 Ba at planting with two side dressings, while leaf P was reduced by all treatments compared to the check. Leaf K was highest with 2/3 the rate Br at planting. Storage root N was lower than foliar N while root K increased with 1/3 Br combined with 1/3 Ba. Root Ca, Mg, Fe and B were not significantly affected by placement. Root Mn was lower than foliar Mn suggesting that sweetpotato distributes more Mn to foliage relative to storage roots. Generally, these results suggest that placement rather than quantity of fertilizer applied enhanced yield and elemental concentration. Key words: Broadcast fertilizer, Ipomoea batatas, banded fertilizer, side-dressing, elemental concentration, storage roots, plant nutrition.

Leaf Elemental Concentrations, Stoichiometry, and Resorption in Guam’s Coastal Karst Forests

Greater knowledge concerning the interspecific diversity of the plant leaf ionome is required to effectively understand the spatiotemporal dynamics of biogeochemistry, but Micronesia has been ignored in this literature. The objectives of this study were to quantify the leaf ionome, resorption efficiency, and stoichiometry of leaves from 25 plant species representing Guam’s coastal karst forests. Carbon and nitrogen were quantified by dry combustion, and other minerals and metals were quantified by spectrometry. Nitrogen and calcium concentrations in Guam’s green leaves exceeded the published global means, but manganese and copper concentrations were less than the global means. The remainder of the elements were within the expected ranges. Nutrient resorption rates exhibited a decreasing order of potassium &gt; phosphorus &gt; nitrogen &gt; zinc &gt; copper. The term “accretion efficiency” is introduced to describe the accumulation of an element throughout leaf aging and senescence, and calcium and iron exhibited substantial accretion efficiency in this study. Stoichiometry relations indicated that Guam’s karst forest is most limited by phosphorus and then secondarily limited by nitrogen, although several individual taxa exhibited co-limitation by potassium. Five of the species are officially listed on extinction threat lists. Of these, the Malvaceae tree Heriteria longipetiolata exhibited leaf traits depicting the most recalcitrant litter characteristics, and the Fabaceae tree Serianthes nelsonii exhibited leaf traits depicting the most labile litter characteristics. The contributions of these two tree species to spatiotemporal diversity in biogeochemistry appear to be profound, indicating species recovery efforts are of paramount importance for maintaining ecosystem function and soil heterotroph biodiversity in northern Guam.

Global patterns in leaf stoichiometry across coastal wetlands

AbstractAimCoastal wetlands provide crucial ecosystem functions and services, such as coastal protection, nutrient retention and C sequestration. Despite the important roles in global C, N and P cycling, the global variation in leaf stoichiometry across coastal wetlands remains unclear.LocationGlobal.Time period1980–2018.Major taxa studiedVascular plants.MethodsBy compiling a global dataset of 698 data records in 205 sites, we carried out systematic analyses of the world‐wide trends and their determinants of leaf element contents and ratios of plants across coastal wetlands.ResultsLeaf N and P contents increased significantly, but C:N, C:P and N:P ratios decreased with increasing latitude in coastal wetlands. The mean annual temperature was the predominant driver of leaf N, P and C:N, whereas soil N:P was a good predictor of leaf C:P and N:P ratios. Furthermore, N increased faster with P in plant leaves of coastal wetlands compared with terrestrial ecosystems. Within coastal wetlands, herb‐dominated salt marshes had a significantly higher leaf P content, lower leaf N:P ratio and lower scaling exponent of leaf N to P than tree‐dominated mangroves.Main conclusionsThe similar latitudinal patterns of leaf stoichiometry in coastal wetlands compared with terrestrial ecosystems reflected the similar influences of temperature. However, different slopes of leaf P and N:P ratios and N and P scaling relationships between these two ecosystems suggested that different salinity and tidal inundation levels result in different strategies of N and P use in coastal wetland plants. These differences in leaf stoichiometry between ecosystems and between different types of coastal wetlands might need to be emphasized in future biogeochemical modelling owing to their different roles in global nutrient and carbon cycling.

Potential nutrient-response curves and sufficiency ranges of ‘Grande Naine’ banana cultivated in two environment

Abstract Adequate plant nutrition is essential to attain higher yields. The objective was to determine potential-nutrient response curves and sufficiency ranges using the boundary line approach and balance indices of Kenworthy for interpreting the nutritional status of ‘Grand Nain’ banana cultivated in two environments. The study was carried out using a database containing leaf nutrient concentrations and yields of bananas cultivated on two areas located in Missão Velha-CE, and Ponto Novo-BA, Brazil. Plots with high-yielding plants, which were those with yields above average plus 0.5 standard deviation, were used atem as reference population. The database was subdivided into two sets. One of them contained 46 leaf tissue samples and reference population with yield greater than 58.84 Mg ha-1 year-1, in Missão Velha-CE. The second data set contained 19 samples and reference population with yield greater than 76.12 Mg ha-1 year-1 in Ponto Novo-BA. Potential response curves were fitted to the relationship between relative yield and leaf element concentrations and balance indices of Kenworthy. Models expressed high predictive power. Sufficiency ranges for macro- and micronutrient concentrations and balance indices of Kenworthy were established. The ranges allow an improved nutritional status assessment of irrigated ‘Grand Nain’ bananas.