Tissue Nutrient Status Research Articles

Soil and leaf tissue nutrient status relationships of Haskap (Lonicera caerulea L.) cultivars in Nova Scotia, Canada

• Haskap plant establishment, growth, and productivity vary widely among orchards in Nova Scotia due to growers’ management practices, and environmental and edaphic factors. • Haskap cv. Indigo gem had low leaf tissue P and K, but high Ca compared to the other cultivars. • Haskap cvs indigo gem and Tundra have similar nutrient uptake pattern. • Evidence of an antagonistic association among haskap leaf N, Mg, and K, and a synergistic association between haskap leaf K and Mg. Haskap ( Lonicera caerulea L.) is a rapidly emerging and promising berry crop and gaining popularity in Nova Scotia (NS). The establishment and productivity of haskap varies widely in NS and it is largely dependent on soil-plant interactions. A multi-locational field survey was carried out to evaluate and determine the relationship between soil and leaf nutrient concentrations of haskap cultivars grown in Nova Scotia. Soil samples were collected in mid-May, and leaf samples were collected starting from late June to early July in both years at the stage where 50% of the berries had turned color from green to blue. Among the studied cultivars, 44% were adequate in leaf N, 33% were adequate in leaf P, 45% had adequate leaf K, 52% adequate in Ca, and 74% adequate in leaf Mg. However, 26% had excessive leaf P and Mg content, while 47% was deficient in leaf K. Indigo Gem and Tundra cultivars had similar nutrient uptake response, while correlation analysis revealed significant negative relationships between leaf Mg versus leaf N and K. The relative comparison of Indigo Gem with other haskap cultivars revealed that Aurora had 48% more leaf P content, and Borealis had 39% more leaf Mn content than Indigo Gem. However, in most cases all cultivars were within 40% of the Indigo Gem value, and in many cases within 20%. It could be concluded that Indigo Gem can be used as a reference cultivar when assessing nutritional levels of Tundra and Borealis cultivars.

Protocol for salt stress screening of African marigold under hydroponic system

The present study was carried out at ICAR-IARI to standardize the protocol for screening of African marigold against saline stress under hydroponic system. Seedlings of African marigold cv. Pusa Narangi Gainda were grown under hydroponics system. They were treated with different levels of NaCl, viz. 0 mM 50 mM, 80 mM, 100 mM, 120 mM, 140 mM, 150 mM, 160 mM, 200 mM, after 7 days of transplanting to standardize the threshold level for the further rapid screening of germplasms at nursery stage. Observations on mortality, growth, morphological, physiological, biochemical parameters and tissue nutrient status were recorded and found to decrease with increasing in saline stress. Mortality in seedlings was not observed up to 80 m M NaCl stress. 150-160 mM qualified as the indicator concentration for the screening of African marigold genotypes based on the performance of marigold genotypes with regard to different morphological, physiological, biochemical parameters and tissue nutrient contents.

Nutrient availability predicts multiple stem frequency, an indicator of species resprouting capacity in tropical forests

Abstract Resprouting capacity is a key component of plant life history. While resprouting requires substantial nutrient reserves to support new growth, the influence of soil fertility on resprouting is largely unknown. We tested whether the frequency of multi‐stemmed trees, a potential indicator of resprouting history, is associated with low soil fertility, reflecting selection for conservative life histories that enhance survival, or with high fertility, reflecting greater resource availability to support regrowth. Data from the Barro Colorado Island (BCI) 50‐ha plot in Panama showed that multi‐stemmed trees are more likely to resprout during their lifetime than single‐stemmed trees, and that multiple stem frequency has a strong taxonomic signal for adult trees. To test how multiple stem frequency varies with demographic rates and nutrient allocation strategies, we compiled functional trait datasets for 71 species from lowland forest on BCI and 43 species from lower montane forest in western Panama. We also assessed environmental correlates of community‐wide multiple stem frequency in thirty‐seven 1‐ha lowland plots in the Panama Canal watershed and twelve 1‐ha montane plots in western Panama, spanning gradients of rainfall and soil fertility. Multiple stem frequency was not correlated with species demographic rates or wood density, suggesting that resprouting is unrelated to classical ‘persistence’ traits in neotropical tree species. Multiple stem frequency of tree species occurring on BCI was weakly but significantly positively correlated with regional soil phosphorus associations, but unrelated to foliar nutrient concentrations. Multiple stem frequency covaried strongly with soil and tissue nutrient status across fertility gradients. It was significantly positively correlated with nutrient allocation traits, including foliar phosphorus and wood nitrogen and phosphorus, among species sampled across soil habitats in western Panama. At the community level, the proportion of woody stems >10 cm DBH with at least one multiple stem increased with plant available soil phosphorus. Synthesis. These results suggest a novel mechanism by which soil phosphorus availability influences tree recruitment and forest dynamics by facilitating resprouting. Future experiments should seek to understand whether soil fertility mediates resprouting frequency through nutrient supply directly, or via the formation of enhanced wood nutrient reserves.

Impact of Chelated or Inorganic Manganese and Zinc Applications in Closed Hydroponic Bean Crops on Growth, Yield, Photosynthesis, and Nutrient Uptake

In this study, we investigated the effect of individual and combined applications of manganese (Mn) and zinc (Zn) chelates on common bean grown in hydroponics (nutrient film technique—NFT) on physiological and agronomical responses. Inorganic sulphate forms of Mn and Zn were compared to their synthetic chelate forms, in the replenishment nutrient solution (RNS). Nutrient (N, P, K, Ca, Mg, Fe, Mn, Zn and Cu) to water uptake ratios (termed uptake concentrations; UCs), growth, pods yield and quality, photosynthetic parameters and tissue nutrient status were evaluated in different cropping seasons (spring-summer and autumn-winter crops). Mean UCs of nutrients ranged as follows: 10.1–12.4 (N), 0.8–1.0 (P), 5.2–5.6 (K), 1.8–2.2 (Ca), 0.9–1.0 (Mg) mmol L−1; 12.2–13.4 (Fe), 5.2–5.6 (Mn), 4.4–4.9 (Zn), 0.9–1.0 (Cu) μmol L−1. Tissue macronutrient status remained unaffected in both seasons, however, Mn chelates in the RNS affected Fe within plants. Pod yield and quality, growth, photosynthesis and water uptake did not differ among treatments; however, seasonal variations are presented. Results suggest that the chelate forms of Mn and/or Zn in the refill solution for NFT-grown beans do not lead to any changes, adding superiority in the yield, photosynthesis, and nutritional status of the crops compared to their mineral forms.

Responses of macroalgal assemblages dominated by three Mediterranean brown macroalgae with different life strategies to nutrient enrichment

ABSTRACT Increase of nutrient concentrations in coastal waters is a worldwide phenomenon with ecological consequences for natural assemblages. Little is known about species-specific nutrient dynamics among macroalgae in the Mediterranean Sea, which may be key to understanding competitive strategies driving the structure of macroalgal assemblages. We conducted an in situ nutrient enrichment experiment to evaluate whether increasing nutrient availability modified the relative abundance of the three dominant brown macroalgae Cystoseira brachycarpa, Halopteris scoparia and Padina pavonica and whether any such modifications were related to different nutrient dynamics of the three macroalgae under different chronic enrichment regimes. Tissue nitrogen, carbon and phosphorus were determined 6 and 18 months after the first exposure to nutrient enrichment. Under nutrient-enriched conditions, C. brachycarpa decreased in abundance over the experimental period, while P. pavonica and H. scoparia increased (albeit with different trends), the former mostly in the earlier phase and the latter in the subsequent phase. Nutrient content of the three macroalgae responded positively to enrichment in the first year, although it was exploited differently: C. brachycarpa only increased its internal reserves, while H. scoparia and P. pavonica also used available nutrients for growth. A completely different pattern was observed in the second year, as nutrient content of all macroalgae was affected very little, if at all, by nutrient enrichment. However, the different responses in terms of abundance observed during the second year indicated changing nutrient dynamics across species over the longer timescale of nutrient exposure. The results of the study confirmed the existence of species-specific response patterns of nutrient dynamics in the three macroalgae. They also suggest that nutrient dynamics are habitat-specific, since nutrient response was strongly conditioned by macroalgal tissue nutrient status, which reflects the nutrient history of the site.

Nutrient sufficiency levels for haskap (Lonicera caeruleaL.) using the boundary-line approach

Adequate supply of plant nutrients is crucial for haskap plant growth and increased productivity. A study was carried out to determine the variability in haskap (Lonicera caerulea L. cv. Indigo Gem) plant characteristics in relation to soil and leaf tissue nutrient status. A total of 19 composite soil samples and corresponding plant leaf tissue samples were collected in 2016 from 12 locations in Nova Scotia. Plant parameters measured include growth rate, leaf size, leaf chlorophyll content, and visual observations. A boundary-line approach was used to determine nutrient sufficiency ranges in leaf tissues of 2.23%–2.96% for N, 0.22%–0.28% for P, 0.84%–1.32% for K, 1.63%–2.10% for Ca, and 0.14%–0.50% for Mg. Principal component and correlation analysis suggested a possible antagonistic interaction between leaf K and Mg. Negative associations were observed most frequently between Ca and Mg and other nutrients, especially K. Plant parameters such as bush volume, leaf size, and growth rate were closely related to soil and leaf K. Deficiencies in leaf tissue K and P were identified as potentially important factors limiting growth. Therefore, there is a need to adjust or balance the application of these nutrients. In conclusion, the sufficiency ranges derived can be used as a guiding principle in diagnosing the nutritional status of haskap cv. Indigo Gem on representative farms in Nova Scotia.

FERTILISER APPLICATION PRACTICES AND NUTRIENT DEFICIENCIES IN SMALLHOLDER OIL PALM PLANTATIONS IN INDONESIA

SUMMARYOil palm has become an important source of revenue for smallholders in Indonesia, but productivity of smallholder plantations is generally poor. Nutrient limitations have been suggested as an important agronomic constraint to yield. Our research aimed to quantify fertiliser use, soil and tissue nutrient status, and palm growth and yield in a sample of independent smallholder plantations. We selected 49 plantations in Indonesia in two provinces with contrasting soils. For all plantations, we obtained self-reported fertiliser use and yield data, collected soil and tissue samples, and analysed vegetative growth. More than 170 kg N ha−1year−1was applied in one site, and P was applied in excess of recommended quantities in both sites, but on average farmers applied less than 100 kg K ha−1year−1. Soils in the palm circle were poor in N, P and K in 29, 40 and 82% of the plantations, and deficiencies were measured in 57, 61 and 80% of the leaflet samples, respectively. We found statistically significant correlations between tissue nutrient concentrations and vegetative growth, but a large part of the variation in the data remained unaccounted for. Single leaf area was reduced in >80% of the plantations. Average yields were estimated to be 50‒70% of the water-limited potential. Our results demonstrate that widespread nutrient imbalances and deficiencies, especially potassium and phosphorus, occur in smallholder oil palm plantations, due to inadequate and unbalanced fertiliser application practices. These deficiencies may be an important underlying cause of the overall poor productivity, which threatens the economic and environmental sustainability of the smallholder sector.

Sulfate influx transporters in Arabidopsis thaliana are not involved in arsenate uptake but critical for tissue nutrient status and arsenate tolerance

Arsenic, a non-nutrient metalloid is toxic to plants but many details on the physiology of plant adaptation to arsenic stress are not well understood. This work provides new insights about the role of sulfur assimilation in arsenate uptake, growth and arsenic tolerance. Research reported here indicates that two high affinity sulfate transporters in Arabidopsis thaliana are not involved in root uptake of arsenate. Further this study revealed that sulfate status influenced thiol levels, elemental nutrients, growth and arsenate tolerance. The hypothesis that arsenate may be transported via sulfate transporters, SULTR1;1 and SULTR1;2 in Arabidopsis, was tested. The double mutant of sultr1;1 sultr1;2 exhibited significantly less growth than the wild-type or the single mutants. The double mutant's sulfur content was significantly lower than the wild-type but the single mutants were similar to the wild-type confirming the redundant functions of SULTR1;1 and SULTR1;2. Gene expression analyses indicated that the double mutant's sulfate uptake could be explained by the expressions of SULTR1;3, SULTR2;1, and SULTR2;2 in its roots. Following arsenate supply to the roots, the double mutant accumulated significantly less arsenic in the roots and the shoots than did the single mutants and the wild-type. The double mutant accumulated significantly less potassium and phosphorus also. (35)S sulfate supplied to wild-type or double mutant roots showed that sulfate uptake was not inhibited by arsenate. Taken together, these results indicate that root uptake of arsenate is probably not via sulfate transporters, but the poor growth of the double mutant of sultr1;1 and sultr1;2 was due to its poor sulfate status and decreased levels of thiols, which had pleiotropic effects on the root uptake and translocation of potassium and phosphorus and arsenic tolerance.

Enzyme Activities and Nutrient Status in Coconut (Cocos nuciferaL.) Seedling Rhizosphere Soil after Exposure to Elevated CO2and Temperature

The elevation of CO2 and temperature could affect soil microbial mineralization and nutrient cycling in perennial crop systems. To understand this, microbial enzyme activities in the rhizosphere soil and soilplant nutrient status in coconut (Cocos nucifera L.) seedlings were investigated. Coconut seedlings were grown in elevated CO2 at 550 ([CO2]550) and 700 ([CO2]700) μmol mol−1 and elevated temperature (2°C higher than ambient control; [T]+2°C) for three years (2007–2010) in controlled field facility called open top chambers (OTCs). Activities of soil dehydrogenase (62, 27 and 69%) and phosphatase (18, 47 and 49%) were reduced under [T]+2°C, [CO2]550 and [CO2]700, respectively, while activity of cellulase (5, 24 and 33%) was increased. Soil was more acidic in elevated CO2 conditions with higher activity of amylase (9 and 32%) and lower activity of urease (54 and 49%). Though elevated temperature did not influence soil pH, it increased the activities of soil urease (19%) and invertase (23%) but decreased the activity of amylase (32%). The soil electrical conductivity was increased (67, 64 and 53%, respectively), but total soluble sugars concentration was decreased (42, 21 and 39%, respectively) in [T]+2°C, [CO2]550 and [CO2]700, respectively. While soil respiration (6%) and total phenols (4%) increased in the [CO2]550 condition. At the same time soil free amino acids were decreased (3%) in [CO2]700. Reductions of soil potassium (K, 7%), iron (Fe, 9%) and sodium (Na, 6%) content at elevated temperature and calcium (Ca, 5%) content in elevated CO2 indicates higher uptake by plant as it is evident from leaf tissue nutrient status. Changes in concentration of other major and minor nutrients in leaf tissue and soil indicates effects of CO2 and temperature on soil organic matter mineralization, nutrient uptake, microbial community and pH. The study reveals that elevated CO2 and temperature can affect soil microbial mineralization and nutrient cycling and better soil management may be required in coconut plantations under future climatic conditions.

Assessment of the eutrophication status of the Great Barrier Reef lagoon (Australia)

Current scientific consensus is that inshore regions of the central and southern Great Barrier Reef, Australia, are at risk of impacts from increased nutrient (as well as sediment and pesticide) loads delivered to Reef waters. Increases in the discharge of water quality contaminants to the Reef are largely a consequence of the expansion of agricultural practices in northern Queensland catchments following European settlement in the 1850s. In particular, the presence of elevated chlorophyll a and nutrient concentrations in many parts of the inshore Great Barrier Reef together with intense and extensive phytoplankton blooms following the discharge of nutrient-rich river flood waters suggest that the central and southern inshore area of the Great Barrier Reef is likely to be significantly impacted by elevated nutrient loads. The biological consequences of this are not fully quantified, but are likely to include changes in reef condition including hard and soft coral biodiversity, macroalgal abundance, hard coral cover and coral recruitment, as well as change in seagrass distribution and tissue nutrient status. Contemporary government policy is centered around promotion and funding of better catchment management practices to minimize the loss of catchment nutrients (both applied and natural) and the maintenance of a Reef wide water quality and ecosystem monitoring program. The monitoring program is designed to assess trends in uptake of management practice improvements and their associated impacts on water quality and ecosystem status over the next 10 years. A draft set of quantitative criteria to assess the eutrophication status of Great Barrier Reef waters is outlined for further discussion and refinement.

Comparative phosphate acquisition in giant-celled rhizophytic algae (Bryopsidales, Chlorophyta): Fleshy vs. calcified forms

Phosphate uptake through above-ground thalli vs. subterranean rhizoids has been compared in siphonaceous rhizophytic green algal species from five globally distributed tropical genera: Avrainvillea nigricans Decaisne, Caulerpa lanuginosa J. Agardh, Halimeda incrassata (J. Ellis) J.V. Lamouroux, Penicillus capitatus Lamarck, and Udotea flabellum (J. Ellis & Solander) M. Howe. Plants were collected, acclimated to lab conditions for 3 days, and then incubated for 8 h at saturating light intensity with 30 μM PO 4 3− added to their above-ground thallus or below-ground rhizoids. Percent tissue phosphorus was then compared to control specimens, which were run simultaneously in the absence of phosphate. The two fleshy species, A. nigricans and C. lanuginosa, showed no significant differences in tissue nutrient status, and displayed much larger variation among controls than the three calcified species. Calcified species showed greater phosphorus content after being exposed to either above- or below-ground thallus portions, indicating that these seaweeds can respond to short term increases in nutrient availability and have a more regulated nutrient acquisition mechanism. Results suggest that calcification may play an important role in phosphorus absorption.

Effects of Nitrogen, Phosphorus, and Potassium Rates and Fertilizer Sources on Yield and Leaf Nutrient Status of Short-day Onions

This is a compilation of several studies that were performed to address specific grower concerns or questions about onion fertilization, to assess onion fertility, to make adjustments in soil test recommendations, and to test specific fertilizers for clients covering the 1999–2000 to 2004–2005 seasons. The synthesis of these studies was to evaluate levels of nitrogen (N), phosphorus (P), and potassium (K) fertilizers and their effect on yield, graded yield, and leaf tissue nutrient status in short-day onions over 6 years. In addition, various fertilizers were evaluated for their effect on these parameters. There was a significant increasing quadratic effect on yield from increasing N fertilizer from 0 to 336 kg·ha−1 with an R2 of 0.926. Maximum calculated yield was at 263 kg·ha−1 N fertilizer; however, the yield at this rate did not differ, based on a Fisher's least significant difference (P ≤ 0.05), from our current recommendations of 140 to 168 kg·ha−1 N. Jumbo (7.6 cm or greater) yield performed in a similar fashion. Phosphorus fertilizer rates from 0 to 147 kg·ha−1 had no effect on total yield, but did affect jumbo yields, which decreased linearly with an R2 of 0.322. Evaluations of P fertilizer in the 2001–2002 and 2002–2003 seasons only, when the exact same P fertilizer rates were used, showed a decreasing quadratic effect for jumbo yields with the lowest jumbo yields at 83 kg·ha−1 P fertilizer and jumbo yields increasing with 115 and 147 kg·ha−1 P fertilizer rates. Potassium fertilizer rates from 0 to 177 kg·ha−1 had a quadratic affect on total yield, with the highest yield of 52,361 kg·ha−1 with 84 kg·ha−1 K fertilizer rate. As would be expected, N and P fertilizer rates affected leaf tissue N and P levels, respectively. In addition, N fertilizer rates affected leaf tissue calcium (Ca) and sulfur levels. Potassium fertilizer rates had a significant linear effect on leaf tissue K 3 of 6 years. In addition, K fertilizer rates had a significant effect on leaf tissue P levels. Several fertilizers, including Ca(NO3)2 and NH4NO3, along with complete fertilizers and liquid fertilizers, were used as part of a complete fertilizer program and showed no differences for total yield or jumbo yield 4 of 5 years of evaluation when applied to supply the same amount of N fertilizer. Based on the results of this study, soil test P and K recommendations for onions in Georgia have been cut 25% to 50% across the range of soil test levels.

The role of alternative oxidase in modulating carbon use efficiency and growth during macronutrient stress in tobacco cells

When wild-type (wt) tobacco (Nicotiana tabacum cv. Petit Havana SR1) cells are grown under macronutrient (P or N) limitation, they induce large amounts of alternative oxidase (AOX), which constitutes a non-energy-conserving branch of the respiratory electron transport chain. To investigate the significance of AOX induction, wt cells were compared with transgenic (AS8) cells lacking AOX. Under nutrient limitation, growth of wt cell cultures was dramatically reduced and carbon use efficiency (g cell dry weight gain g(-1) sugar consumed) decreased by 42-63%. However, the growth of AS8 was only moderately reduced by the nutrient deficiencies and carbon use efficiency values remained the same as under nutrient-sufficient conditions. As a result, the nutrient limitations more severely compromised the tissue nutrient status (P or N) of AS8 than wt cells. Northern analyses and a comparison of the mitochondrial protein profiles of wt and AS8 cells indicated that the lack of AOX in AS8 under P limitation was associated with increased levels of proteins commonly associated with oxidative stress and/or stress injury. Also, the level of electron transport chain components was consistently reduced in AS8 while tricarboxylic acid cycle enzymes did not show a universal trend in abundance in comparison to the wt. Alternatively, the lack of AOX in AS8 cells under N limitation resulted in enhanced carbohydrate accumulation. It is concluded that AOX respiration provides an important general mechanism by which plant cells can modulate their growth in response to nutrient availability and that AOX also has nutrient-specific roles in maintaining cellular redox and carbon balance.

A Survey of Fertility Practices, Soil Fertility Status, and Tree Nutrient Status on Eastern North Carolina Christmas Tree Farms

“Choose and cut” Christmas tree production is gaining popularity in North Carolina, as well as the Southeastern United States. There are few recommendations concerning the fertility of Christmas trees except for the large Fraser fir (Abies fraseri) industry in the Appalachian mountain region. Outside of the mountains, Virginia pine (Pinus virginiana), eastern white pine (Pinus strobus), red cedar (Juniperus virginiana), and Leyland cypress (X Cupressocyparis leylandii) are commonly grown as “choose and cut” trees. This study was conducted in the piedmont and coastal plain of North Carolina with the objectives to determine (1) the fertility practices currently being used and (2) the current soil and tissue nutrient status of “choose and cut” Christmas tree fields. A mail survey was used to accomplish the first objective. Twenty farms, selected from survey respondents, were sampled to determine current soil and tissue nutrient status. Soil samples were taken at three depths to 45 cm. Survey data indicated that a wide variety of fertilization materials and practices were being used. Spring applications were somewhat common, but actual time of application varied. Tissue and soil levels of nutrients also varied. There was a poor relationship between soil test nutrient levels and tissue nutrient levels, indicating the need for routine tissue analysis. This study indicated the need for future research and extension programs focusing on eastern Christmas tree fertility. In particular, the survey indicated that Leyland cypress, for which no specific soil fertility recommendations exist, is grown widely enough to merit recommendation development.

Influence of initial tissue nutrient status of tropical marine algae on response to nitrogen and phosphorus additions

We conducted a 3-factor nutrient-enrichment experiment (factors: N, P, initial tissue- nutrient status) on common species of macroalgae collected from 2 sites along SW Puerto Rico. Our objective was to determine the relative importance of N- or P-limitation among species and sites and to investigate the role of tissue-nutrient status in the response to increased nutrient supply. Acan- thophora spicifera, Dictyota cervicornis, and Hypnea musciformis initially depleted in tissue nutrients responded strongly to either +N or +P alone and both nutrients together by increasing growth. In con- trast, growth of these macroalgae with enriched internal stores of nutrients was generally not as nutrient-limited. In our 3 d experiments, the calcified alga Halimeda incrassata never showed a growth response, perhaps due to the short duration or adaptation to sediment nutrient supply. Tissue N-stores in all algae with low internal nutrient concentrations increased in response to +N, whereas initially higher N-stores were diluted to support growth during the experiment. In addition, all algae depleted the added N and P from the water over the course of the experiment, regardless of tissue- nutrient status. Depleted algae also took up dissolved organic nitrogen (DON) as a secondary source of N, either directly or after mineralization, whereas enriched algae may have 'leaked' NH4. Our results demonstrated that prior storage of nutrients strongly influenced the response of a number of tropical algal species to increased nutrient supply. This variable response to nutrients within and among algae from 3 major algal divisions over small geographical scales may partially explain the mixed results in previous studies of N- and P-limitation.

Ammonium requirements of fast-growing ephemeral macroalgae in a nutrient-enriched marine embayment (Port Phillip Bay, Australia)

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 209:99-107 (2001) - doi:10.3354/meps209099 Ammonium requirements of fast-growing ephemeral macroalgae in a nutrient-enriched marine embayment (Port Phillip Bay, Australia) Stuart Campbell* Department of Life Sciences, Victoria University, PO Box 14428, MCMC, Victoria 8001, Australia *Marine Plant Ecology Group, Northern Fisheries Centre, PO Box 5396, Cairns, 4870, Australia. E-mail: campbes@dpi.qld.gov.au ABSTRACT: The observed high biomass of fast-growing macroalgae in Port Phillip Bay (PPB), Australia is of concern and may represent a shift from perennial macrophytes (e.g. kelps and seagrasses) to a dominance by fast-growing macroalgae. This study examined the limiting and optimum external ammonium-nitrogen concentrations for the growth of 3 fast-growing macroalgae that dominate reefs in northern Port Phillip Bay, Australia. The relationships between growth and tissue nutrients and the capacity of these algae to assimilate, store and survive on nutrients was examined. Winter and summer experiments aimed to determine the effects of tissue nutrient status on growth responses. An absence of any seasonal variation in critical N thresholds and N subsistence quotas in any of the species examined suggests that all species are able to tolerate low N availability. The utilisation of N reserves to support non-limited growth of Hincksia sordida (Clayton) and Polysiphonia decipiens (Montagne) was about 2- to 5-fold shorter in summer than winter, indicating potential N-limitation during summer. A high requirement for N by both H. sordida and Ulva sp. means that internal N reserves could support reduced growth for shorter periods compared to P. decipiens. Such high demands for N by H. sordida and Ulva sp. makes these taxa susceptible to N-limitation in summer, when inputs of N to coastal waters are low. Elevated nutrient inputs into PPB may allow these taxa to become nutrient-sufficient and colonise larger areas of nearshore reefs. KEY WORDS: Fast-growing macroalgae · Ammonium · Tissue nutrients · Nutrient storage · Eutrophication Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 209. Online publication date: January 05, 2001 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2001 Inter-Research.

Can the foliar nitrogen concentration of upland vegetation be used for predicting atmospheric nitrogen deposition? Evidence from field surveys

The deposition of atmospheric nitrogen can be enhanced at high altitude sites as a consequence of cloud droplet deposition and orographic enhancement of wet deposition on hills. The degree to which the increased deposition of nitrogen influences foliar nitrogen concentration in a range of upland plant species was studied in a series of field surveys in northern Britain. A range of upland plant species sampled along altitudinal transects at sites of known atmospheric nitrogen deposition showed marked increases in foliar nitrogen concentration with increasing nitrogen deposition and altitude (and hence with decreasing temperature). For Nardus stricta L., Deschampsia flexuosa (L.) Trin., Calluna vulgaris (L.) Hull, Erica cinerea L. and Hylocomium splendens (Hedw.) Br. Eur. on an unpolluted hill, foliar nitrogen increased by 0.07, 0.12, 0.15, 0.08 and 0.04% dry weight respectively for each 1 kg ha −1 year −1 increase in nitrogen deposition. Most species showed an approximately linear relationship between foliar nitrogen concentration and altitude but no trend with altitude for foliar phosphorus concentration. This provided evidence that the tissue nutrient status of upland plants reflects nutrient availability rather than the direct effects of climate on growth. However, differences in the relationship between foliar nitrogen concentration and atmospheric nitrogen deposition for N. stricta sampled on hills in contrasting pollution climates show that the possibility of temperature-mediated growth effects on foliar nitrogen concentration should not be ignored. Thus, there is potential to use upland plant species as biomonitors of nitrogen deposition, but the response of different species to nitrogen addition, in combination with climatic effects on growth, must be well characterised.

Ginsenosides in Roots and Leaves of American Ginseng

The six major ginsenosides, Rg1, Re, Rb1, Rc, Rb2, and Rd, in roots and leaves of American ginseng have been isolated and quantified by high-performance liquid chromatography. In 4-year-old roots, the main ginsenosides were Re and Rb1, and together they accounted for >75% of the total ginsenosides. In leaves, the concentration and composition of ginsenosides varied with the maturity of the leaf tissue. One-month-old leaves contained 1.33−2.64 g ginsenoside/100 g dry weight, and the ginsenoside Re accounted for >50% of the total concentration. In mature, 4-month-old leaves, the total ginsenoside content ranged from 4.14 to 5.58 g/100 g dry weight, and the ginsenosides Re and Rd each accounted for ∼40% of the total ginsenosides. The production site of ginseng influenced the ginsenoside contents of roots and leaves. However, few significant correlations were found between root and leaf ginsenosides and between ginsenoside levels and mineral composition of the leaves and soil. Keywords: Panax quinquefolium; saponins; ginsenosides; HPLC analysis; soil fertility; leaf tissue nutrient status

Nutritional Controls Over Nitrogen and Phosphorus Resorption From Alaskan Birch Leaves

Little is known about factors that control nutrient loss from plants. We measured N (nitrogen) and P (phosphorus) resorption from leaves of Alaskan birch (Betula papyrifera) trees that differed strongly in their tissue nutrient status. We then experimentally manipulated those factors that we thought were most likely to control nutrient resorption. Trees of high nutrient status had larger maximum leaf N and P pools, translocated more N and P out of leaves, and left larger N and P pools in abscised leaves than did trees on infertile soils. However, plant nutrient status had no effect on the efficiency of N or P resorption (i.e., the proportion of the maximum nutrient pool resorbed from leaves during autumn senescence) except for low efficiency of P resorption in the highly fertile lawn. Prolonging the time that a leaf remained attached to the tree had no effect on N and P resorption efficiency. Leaching by autumn rains accounted for 25% of the N disappearance and 55% of the P disappearance from senescing leaves in a high—fertility field. Weakening of source—sink interactions by shading senescing leaves in a high—fertility field. Weakening of source—sink interactions by shading senescing leaves or by removing catkins (a sink for carbohydrates and nutrients) significantly reduced resorption efficiency. On the basis of our results and previous work, we conclude that nutrient resorption efficiency is influenced more strongly by carbohydrate flux from leaves (i.e., source—sink interactions) than by factors governing hydrolysis of nutrient—containing fractions in leaves.

Lime and Phosphorus Effects on American Ginseng: I. Growth, Soil Fertility, and Root Tissue Nutrient Status Response

Soil applications of dolomitic limestone and P fertilizer before seeding American ginseng (Panax quinquefolium L.) affected root weight (RW) gain during the first 4 years of growth. At the end of each growing season, root size was greatest with the intermediate liming rate and with the high P rate. Lime resulted in positive linear responses in soil pH, K, Ca, and Mg and in root N, P, Ca, and Mg and curvilinear responses in soil Mn and Zn and in root K, Mn, and Zn. Applied P had a positive linear effect on soil Na and on root N, Ca, and Fe and a curvilinear effect on soil P and on root P and Ca. Terminal RW was positively correlated with soil pH, K, Ca, Mg, and Na and with root P, K, Ca, and Mg; RW was negatively correlated with root Mn and Zn. Regression analyses implicated only soil Ca and Na and root Mg and Zn as significant terms in prediction equations,