Retranslocation Of Nutrients Research Articles

Global scaling the leaf nitrogen and phosphorus resorption of woody species: Revisiting some commonly held views

Leaf nutrient resorption is one of the important mechanisms for nutrient conservation in plants. Element stoichiometry is crucial to characterizing nutrient limitations and terrestrial ecosystem function. Here, we use nitrogen (N) and phosphorus (P) resorption efficiencies (NRE and PRE) and their stoichiometry to evaluate the response patterns of leaf nutrient resorption efficiency (NuRE) to plant functional groups, species traits, climate, and soil nutrients on the global scale. In light of the findings from the global data set of published literature on N and P resorption by woody plants, we revisit the commonly held views that: The strong N fixation ability of N-fixers weakened the NRE, which was consistent with the general views. The NuRE was linearly negatively correlated with plant growth rate. The higher NuRE of evergreen species than deciduous plants revealed how leaf life span constrains nutrient conservation. From the perspective of NRE, PRE and their ratios, woody plants were limited by P in the tropical zone and the limiting nutrient gradually transformed into N in the temperate zone (23.43–66.57°). The NuRE of woody plants in the frigid zone was the largest than that of others implied that low temperature may limit the nutrient absorption by plant roots, thereby enhancing the retranslocation of nutrients by senesced leaves. Furthermore, Akaike weights analysis found that mean annual precipitation (MAP) and temperature (MAT), N-fixers, soil nutrients, and leaf life span have significant effects on nutrient resorption patterns, sequentially. Overall, these results showed that the plasticity of plant nutrient resorption patterns was strongly sensitive to plant functional groups and soil nutrients, but the regularity of NuRE on a global scale was controlled by temperature and precipitation. And the resorption stoichiometry pattern better interprets plant nutrient limitation and the synergy effect of N and P in plant and soil on multiple scales.

Retranslocation of nutrients in coffee leaves of cultivars Red Catuaí IAC 144 and IAC 125 RN

Knowledge of the retranslocation of nutrients in plants can help in the management of coffee fertilization, especially with regard to the ideal time and method of application and the need for installments. The aim of this study was to evaluate the retranslocation of nutrients in coffee leaves of two varieties. The treatments consisted of two varieties of coffee (Red Catuaí IAC 144 and IAC 125 RN) and coffee leaves in four phenological stages (young leaves, diagnostic, senescent and deciduous). The index leaf of Catuaí Vermelho IAC 144 showed the highest photosynthetic rate and stomatal conductance, while the internal conductance of CO2 was higher in young and senescent leaves, and the index and senescent leaves showed the highest efficiencies in the use of water. The chlorophyll a, b and total chlorophyll has higher concentrations in the index leaf, while the highest carotenoids occurred in young and senescent leaves. The highest levels of N, P, K and Zn in Catuaí Vermelho IAC 144 was occurred in young leaves and the highest Ca and Fe in senescent leaves. The highest levels of N, P and K in the IAC 125 RN variety was occurred in young leaves, Ca and Mg in deciduous leaves and S in senescent and deciduous leaves. Nutrients with low mobility in the plant must be parceled, the application of Zn leaves is an alternative method of supplying this nutrient, as it has retranslocation via phloem

Short-Term Magnesium Deficiency Triggers Nutrient Retranslocation in Arabidopsis thaliana.

Magnesium (Mg) is essential for many biological processes in plant cells, and its deficiency causes yield reduction in crop systems. Low Mg status reportedly affects photosynthesis, sucrose partitioning and biomass allocation. However, earlier physiological responses to Mg deficiency are scarcely described. Here, we report that Mg deficiency in Arabidopsis thaliana first modified the mineral profile in mature leaves within 1 or 2 days, then affected sucrose partitioning after 4 days, and net photosynthesis and biomass production after 6 days. The short-term Mg deficiency reduced the contents of phosphorus (P), potassium, manganese, zinc and molybdenum in mature but not in expanding (young) leaves. While P content decreased in mature leaves, P transport from roots to mature leaves was not affected, indicating that Mg deficiency triggered retranslocation of the mineral nutrients from mature leaves. A global transcriptome analysis revealed that Mg deficiency triggered the expression of genes involved in defence response in young leaves.

An Age-Dependent Sequence of Physiological Processes Defines Developmental Root Senescence.

Aging-related processes in plant tissues are associated with changes in developmental and physiological processes relevant for stress tolerance and plant performance. While senescence-regulated processes have been extensively characterized in leaves, they remain poorly described in roots. Here, we investigated the physiological processes and molecular determinants underlying the senescence of seminal roots in hydroponically grown barley (Hordeum vulgare). Transcriptome profiling in apical and basal root tissues revealed that several NAC-, WRKY-, and APETALA2 (AP2)-type transcription factors were upregulated just before the arrest of root elongation, when root cortical cell lysis and nitrate uptake, as well as cytokinin concentrations ceased. At this time point, root abscisic acid levels peaked, suggesting that abscisic acid is involved in root aging-related processes characterized by expression changes of genes involved in oxidative stress responses. This temporal sequence of aging-related processes in roots is highly reminiscent of typical organ senescence, with the exception of evidence for the retranslocation of nutrients from roots. Supported by the identification of senescence-related transcription factors, some of which are not expressed in leaves, our study indicates that roots undergo an intrinsic genetically determined senescence program, predominantly influenced by plant age.

Seasonal nutrient retranslocation in reforested Pinus halepensis Mill. stands in Southeast Spain

Retranslocation, resorption and relocation of nutrients are important adaptive mechanisms developed by plants to acquire the amount of the nutrients required for growth. They are usual mechanisms in deciduous and conifer trees that occur in Mediterranean regions where drought periods are usual. Soil factors, environmental characteristics and species factors are key drivers of nutrient retranslocation in conifers but is not well understood how soil fertility or intraspecific competition influences the process. We studied retranslocation in Pinus halepensis Mill. stands showing different site quality (differences in climate and intraspecific competition) occurring in Southeast Spain. We monitored reforested mature Aleppo pine forests in stands with differences in site quality, climate and intraspecific competition. Stands were characterised, the content of nutrients of soil and green samples (twigs and pine needles) were recorded, and seasonal nutrient retranslocation was obtained. Site characteristics were related to growth rate and nutrient content of foliage and soil. We evaluated whether the retranslocation of nutrients from older to younger foliage was related to the current-year growth rate and to the nutritional status of the plant as influenced by intraspecific competition. Foliar macronutrient concentrations and the amount of retranslocated macronutrients were seasonal, with differences related to site quality and tree density. As a general trend, nutrient concentrations increased after drought (autumn) and decreased during the growth period (spring). However, some micronutrients (mainly Na and Fe) decreased during both periods. The retranslocation pattern in Aleppo pine reinforced the hypothesis that pine adaptations to drought- and fire-prone habitats are linked to the resilience of these forest types. We developed scientific knowledge to assist decision making in adaptive forest management; e.g. fertilizer recommendations or reforestation programmes.

Retranslocation of foliar nutrients of deciduous tree seedlings in different soil condition under free-air O3 enrichment

Retranslocation is the amount of an element that is depleted from old plant components and is provided for new growth. Leaf senescence is usually accelerated at elevated O3 (eO3), and leaf shedding is influenced by soil nutrient availability (and acidification). In this study, we focused on the net retranslocation and allocation dynamics of foliar nutrients (N, P, Mg, K, Ca, Mn, Fe and Al) to investigate the effect of eO3 on birch (Betula platyphylla var. japonica), oak (Quercus mongolica var. crispula), and beech (Fagus crenata) seedlings grown in different soil conditions. Seedlings of the 3 species were planted in a free-air O3 enrichment system under 3 soil types (brown forest soil, serpentine soil, volcanic ash soil) for one growing season. All tree species were grown with 3 replications per each plot at elevated O3 (about 80 ppb) and ambient condition (O3 ranging 25-35 ppb). Leaf samples were taken from the top part of seedlings during the growing season in mid-September, and senescing leaves were sampled in mid-November. Both were collected for chemical composition analysis. Retranslocation rate of P was markedly increased by eO3 in birch and significantly differed among soil types in oak seedlings, while was constant across treatments in beech seedlings. Retranslocation of N in oak seedlings was significantly affected by soil type. Retranslocation of other elements was most sensitive to both eO3 and soil type in beech seedlings. The influence of differential growth patterns among species in modulating the physiological response of seedlings to high levels of ozone and different soil conditions are discussed.

Dynamic change of mineral nutrient content in different plant organs during the grain filling stage in maize grown under contrasting nitrogen supply

Abstract The introduction of new hybrids and integrated crop-soil management has been causing maize grain yield to increase. However, less attention has been paid on the nutrient concentration of the grain; this aspect is of great importance to supplying calories and nutrients in the diets of both humans and animals worldwide. Increasing the retranslocation of nutrients from vegetative organs to grain can effectively increase the nutrient concentration of grain and general nutrient use efficiency. The present study involved monitoring the dynamic change of macro- and micronutrients in different organs of maize during the grain filling stage. In addition, the mobility of different elements and their contribution to grain nutrient content were evaluated in a 2-year experiment under low (LN, no N supplied) and high N (HN, 180 kg N ha−1) supply. Under HN supply, the net remobilization efficiency (RE) of the vegetative organs as a whole (calculated as nutrient remobilization amount divided by nutrient content at silking) of N, P, K, Mn, and Zn were 44%, 60%, 13%, 15%, and 25%, respectively. The other nutrients (Mg, Ca, Fe, Cu, and B) showed a net accumulation in the vegetative organs as a whole during the grain filling stage. Among the different organs, N, P, and Zn were remobilized more from the leaves (RE of 44%, 51% and 43%, respectively) and the stalks (including leaf sheaths and tassels) (RE of 48%, 71% and 43%, respectively). K was mainly remobilized from the leaves with RE of 51%. Mg, Ca, Fe, Mn, and Cu were mostly remobilized from the stalks with the RE of 23%, 9%, 10%, 42%, and 28%, respectively. However, most of the remobilized Mg, Ca, Fe, Mn, Cu, and Zn were translocated to the husk and cob, which seemingly served as the buffer sink for these nutrients. The REs of all the nutrients except for P, K, and Zn were vulnerable to variations in conditions annually and were reduced when the grain yield and harvest index were lower in 2014 compared with 2013. Under LN stress, the RE was reduced in P and Zn in 2013, increased in Cu and unchanged in other nutrients. The concentration of these nutrients in the grain was either unchanged (P, K, Ca, Zn, and B) or decreased (N, Mg, Fe, Mn, and Cu). It is concluded that grain N, P, K, Mn, and Zn, but not Mg, Ca, Fe, Cu, and B concentration, can be improved by increasing their remobilization from vegetative organs. However, enhancing the senescence of maize plant via LN stress seems unable to increase grain mineral nutrient concentration. Genetic improvement aiming to increase nutrient remobilization should take into account the organ-specific remobilization pattern of the target nutrient.

<b>Nutrient retranslocation in forest species in the Brazilian Amazon

Internal retranslocation is an important mechanism for nutrient conservation in plants, which depends on different factors. However, there are little data about this subject, especially on tropical forest species. This study aimed to evaluate the macronutrient retranslocation dynamic and the influence of ecological (P: pioneer x NP: non-pioneer) and phenological (ND: non-deciduous x D: semideciduous / deciduous) characteristics on the macronutrient content of leaves of five tree species on monospecific plantations in the Brazilian Amazon: Acacia mangium Willd., Parkia decussata Ducke, Dipteryx odorata (Aublet) Willd., Jacaranda copaia (Aubl.) D. Don and Swietenia macrophylla King. Photosynthetically active green leaves and senescent leaves (leaf litter) were collected. Retranslocation was estimated through an equation proposed by Attiwill, Guthrie and Leuning (1978). The pioneer species presented higher foliar contents of N; the non-pioneer species presented higher contents of K, Ca and S; and the results were inconclusive for P and Mg. The deciduous species presented higher foliar contents of K and of P, whereas the foliar contents of N, Ca, Mg and S were virtually identical between the phenological groups. The internal retranslocation of foliar nutrients in pioneer and non-deciduous species was higher than that of non-pioneer and deciduous species.

Increasing air humidity – a climate trend predicted for northern latitudes – alters the chemical composition of stemwood in silver birch and hybrid aspen

We studied the physicochemical properties of stemwood in saplings of silver birch ( Roth) and hybrid aspen ( L. × Michx.), grown for four years under artificially elevated relative air humidity (on average by 7%) in field conditions, using the Free Air Humidity Manipulation (FAHM) research facility in Estonia. Altogether 91 sample trees from three experimental plots with manipulated air humidity and from three control plots were cut in the dormant season and sampled for the analysis of cellulose, hemicellulose, acid detergent lignin, macronutrients (N, P, K), ash content, density, and calorific value of wood. The analysed trees grew significantly more slowly under elevated humidity conditions, with a more pronounced effect on aspens. Significantly higher concentrations of N and P were observed in the stemwood of both aspens and birches grown under elevated humidity. This could be the result of a change in the content of living parenchyma cells and/or enhanced retranslocation of nutrients into wood parenchyma. Additionally, humidification resulted in a significantly higher concentration of cellulose and a lower concentration of hemicellulose in aspen stemwood, and in significantly lower concentrations of cellulose and K in birch stemwood. Elevated humidity did not affect lignin concentration, ash content, basic density and calorific value of stemwood. Results from the FAHM experiment suggest that the increasing air humidity accompanying global warming at northern latitudes will affect the growth and functioning of deciduous trees and forests, with obvious consequences also for forest management and industry.Betula pendulaPopulus tremulaP. tremuloides

Prerequisites for evolution: variation and selection in yellow autumn birch leaves

Prerequisites for evolution: variation and selection in yellow autumn birch leaves

Retranslocation of nutrients in relation to boron availability during leaf senescence of Betula pendula Roth

Boron (B) is an essential micronutrient, whose deficiency is common in boreal forests. Our aim was to investigate the effects of the B supply on the retranslocation of micro- and macro nutrients in seedlings of Betula pendula Roth. One-year-old seedlings were grown under three different levels of B: 0%, 30% and 100% of the standard level for complete nutrient solution. Half of the seedlings were harvested after summer period and another half when leaves abscised. Boron was not resorbed in significant amounts from senescing birch leaves prior to abscission. The only micronutrients resorbed were Zn and Ni. Three macronutrients, N, P, and S, were resorbed efficiently from senescing leaves and accumulated into the stems. The resorption of nutrients was the mostly pronounced in B0 seedlings and minimal in B30 seedlings, which, however, showed the highest accumulation of nutrients during autumn period at least partly independently from the resorption from senescing leaves. Boron was shown to be an immobile element in silver birch seedlings that was not withdrawn from senescing leaves prior to abscission. This may increase the B availability for other tree species but also increase the potential for its leaching.

Impacts of the invasive plant Fallopia japonica (Houtt.) on plant communities and ecosystem processes

Fallopia japonica (Japanese knotweed) invades riparian areas and roadsides in New England. This large clonal species drastically alters the appearance of habitats by forming highly productive near-monocultures. To understand how these invasions affect ecosystem processes in New England, we quantified the impacts of F. japonica on species diversity, primary productivity, and nitrogen cycling at five locations in central Massachusetts, USA. In stands of F. japonica and in adjacent uninvaded areas, we recorded the cover of each plant species and measured the aboveground biomass and nitrogen (N) concentrations in plants, along with N retranslocation from F. japonica leaves and several soil characteristics. In addition, we severed rhizomes of peripheral F. japonica shoots to determine if clonal integration contributes to the species’ rapid spread and dominance. Stands of F. japonica had lower species diversity, but greater aboveground biomass and standing N than uninvaded areas. Nitrogen and carbon concentrations in biomass and N mineralization rates in soil did not differ between stands and adjacent areas. Rhizome severing temporarily reduced growth of F. japonica, suggesting that retranslocation of photoassimilates and/or nutrients between shoots via rhizomatal connections may maximize stand level growth rates and facilitate dominance by F. japonica.

Yield, Uptake, and Retranslocation of Nutrients in Banana Plants Cultivated in Upland Soil of Central Amazonian

ABSTRACT Banana cultivation is considered one of the most important agricultural activities of economic and social importance in Brazil. The objective of this work was to investigate the uptake, retranslocation and the effect of fertilization on the yield and uniformity of banana bunches (Musa spp.) cultivated in Central Amazonian, region with approximately 1.5 million km2 or 150 million hectares. Two experiments were conducted in a Xanthic Ferralsol (dystrophic Yellow Latosol), the predominant soil of the region, examining: i) the nutrient uptake and translocation rate in twelve plants; and ii) the efficiency of zinc use, in a completely randomized blocks in a 4×2 factorial scheme in split plot design with four zinc sulfate (ZnSO4) rates (0, 30, 60, and 120 g plant−1 cycle−1) and two application times (in the hole together with the seedling or as surface broadcast in the fifth month after planting), with four replicates. Uptake of macronutrients was in the order of potassium (K) > nitrogen (N) > calcium (Ca) > magnesium (Mg) > phosphorus (P) and micronutrients in the order of manganese (Mn) > iron (Fe) > boron (B) > zinc (Zn) > copper (Cu). The N, P, K, Mg, and Cu have a high retranslocation rate compared to other nutrients investigated. The bunch yield increased significantly in a quadratic fashion with increasing Zn rate and hole application method of zinc was more efficient compared to broadcast application. At high concentration, Zn presents a low mobility in the phloem from the leaves to the fruits. The critical leaf concentration of zinc at the start of inflorescence was 12.9 mg kg−1.

Retranslocation of foliar nutrients in evergreen tree species planted in a Mediterranean environment

Internal nutrient recycling through retranslocation (resorption) is important for meeting the nutrient demands of new tissue production in trees. We conducted a comparative study of nutrient retranslocation from leaves of five tree species from three genera grown in plantation forests for commercial or environmental purposes in southern Australia--Acacia mearnsii De Wild., Eucalyptus globulus Labill., E. fraxinoides H. Deane & Maiden, E. grandis W. Hill ex Maiden and Pinus radiata D. Don. Significant amounts of nitrogen, phosphorus and potassium were retranslocated during three phases of leaf life. In the first phase, retranslocation occurred from young leaves beginning 6 months after leaf initiation, even when leaves were physiologically most active. In the second phase, retranslocation occurred from mature green leaves during their second year, and in the third phase, retranslocation occurred during senescence before leaf fall. Nutrient retranslocation occurred mainly in response to new shoot production. The pattern of retranslocation was remarkably similar in the leaves of all study species (and in the phyllodes of Casuarina glauca Sieber ex Spreng.), despite their diverse genetics, leaf forms and growth rates. There was no net retranslocation of calcium in any of the species. The amounts of nutrients at the start of each pre-retranslocation phase had a strong positive relationship with the amounts subsequently retranslocated, and all species fitted a common relationship. The percentage reduction in concentration or content (retranslocation efficiency) at a particular growth phase is subject to many variables, even within a species, and is therefore not a meaningful measure of interspecific variation. It is proposed that the pattern of retranslocation and its governing factors are similar among species in the absence of interspecies competition for growth and crown structure which occurs in mixed species stands.

Retranslocation of nutrients and zinc sulphate fertilization of banana plants in central Amazon

Banana cultivation is ranked as one of the agricultural activities of greatest economic importance and social signi cance in Brazil. The area under banana cultivation in Brazil (516,000 ha) is larger than India and Ecuador, leading countires in production, but with rather lower productivity due to lack of adequate crop management, particularly fertilizer application. The objective of this work was to investigate the rate of nutrient retranslocation and the effect of fertilization on the yield and uniformity of banana bunches cultivated in central Amazon region. Two  eld experiments were conducted in a xanthic Ferralsol (dystrophic Yellow Latosol) - predominant soil of the region, examining: a) the nutrient translocation rate in twelve plants; and b) the ef ciency of zinc use, in a completely randomized blocks in split plot design with four rates of ZnSO 4 (0, 30, 60 and 120 g plant -1 cycle -1 ) and two application times (in the hole together with the seedling or applied in the  fth month after planting), with four replicates. Under the local edaphoclimatic conditions, the results show that N, P, K, Mg and Cu have a high retranslocation rate. The plant yield was in uenced by the rates of ZnSO 4 , with the most ef cient application method being in the planting hole. Results indicated that at high concentrations, zinc had mobility in the phloem from the leaves to the fruits. The proposed critical leaf zinc concentration at the start of in orescence was 12.9 mg kg -1 for the third leaf.

Effect of salinity on tissue architecture in expanding wheat leaves

Salinity greatly reduces the leaf cross-sectional area of wheat (Triticum aestivum L.) during its development, which may lead to variation in the architectural properties of growing leaves that would result in a change in leaf physiological functions. Our objective was to characterize the effect of salinity on the spatial distribution of the cross-sectional area and the anatomy of large and small veins of a growing wheat leaf. Spring wheat was grown in a growth chamber in soils with or without 120 mM NaCl. Leaf 4 in both treatments was harvested 2-3 days after its emergence and then cut into five transverse segments. Examination of the transverse sections revealed that salinity significantly reduced the cross-sectional area, width, and radii of both epidermal and mesophyll cells along the leaf axis. Reduction in the cross-sectional area and width occurred mainly at the leaf base, indicating that these reductions occur during the period of leaf initiation. The reduction in cross-sectional area was attributed to a decrease in the size of the vein segments and a reduced number of medium and small veins. The thickness of the leaf was also reduced under the 120 mM NaCl treatment. A greater intercellular air space in the large vein segments under saline conditions was also found. The approximately 35% reduction observed in the number of veins under saline conditions (mainly in the number of small veins) may suggest that salinity reduces the capacity for re-translocation of mineral nutrients and assimilates. The reduced area of protoxylem and metaxylem in midrib and large vein segments in growing tissues may be responsible for lower water deposition into the growth zone under saline conditions.

Growth, allocation and tissue chemistry of Picea abies seedlings affected by nutrient supply during the second growing season.

One-year-old Norway spruce (Picea abies (L.) Karst.) seedlings were grown hydroponically in a growth chamber to investigate the effects of low and high nutrient availability (LN; 0.25 mM N and HN; 2.50 mM N) on growth, biomass allocation and chemical composition of needles, stem and roots during the second growing season. Climatic conditions in the growth chamber simulated the mean growing season from May to early October in Flakaliden, northern Sweden. In the latter half of the growing season, biomass allocation changed in response to nutrient availability: increased root growth and decreased shoot growth led to higher root/shoot ratios in LN seedlings than in HN seedlings. At high nutrient availability, total biomass, especially stem biomass, increased, as did total nonstructural carbohydrate and nitrogen contents per seedling. Responses of stem chemistry to nutrient addition differed from those of adult trees of the same provenance. In HN seedlings, concentrations of alpha-cellulose, hemicellulose and lignin decreased in the secondary xylem. Our results illustrate the significance of retranslocation of stored nutrients to support new growth early in the season when root growth and nutrient uptake are still low. We conclude that nutrient availability alters allocation patterns, thereby influencing the success of 2-year-old Norway spruce seedlings at forest planting sites.

The unusual vascular structure of the corm of Eriophorum vaginatum: implications for efficient retranslocation of nutrients.

Eriophorum spp. are abundant perennial graminoids in the Arctic tundra and boreal peatlands. Because ecological studies indicated that some plants are unusually productive on infertile and cold sites, the anatomy of the overwintering corms of Eriophorum vaginatum (L.) and Eriophorum scheuchzeri (Hoppe) were examined to determine their involvement in nutrient uptake and storage. Components of the long-distance transport pathways were identified within the plants by using histochemical techniques and transport of apoplastic and symplastic dyes. E. scheuchzeri produced a rhizome that consisted mainly of storage parenchyma cells within which collateral vascular bundles were centrally located and arranged in a circle. By contrast, E. vaginatum developed a ring of horizontally arranged xylem and phloem, in addition to axial amphivasal vascular bundles leading to the leaves, all of which were bordered by transfer cells. As shown by the transport of fluorescein in the phloem and Safranine O in the xylem, each axial bundle and adventitious root contacted the horizontal ring of vascular tissues so that solutes from one vascular bundle were translocated into the vascular ring and circulated to another vascular bundle and/or to the roots. In addition, special groups of sclereids that functioned in both phloem and xylem transport were found at the base of the leaf traces and within junctions of senescing roots. These sclereids were named 'vascular sclerenchyma' and it was hypothesized that they provide a moving end for the vascular system because the corm dies progressively from the distal end as it grows upward from the apical meristem. It was concluded that this unusual vascular system of E. vaginatum is efficient in recycling nutrients internally, which may account for its competitive advantage in infertile and cold sites.

The Influence of Phytophthora citricola on Rhizosphere Soil Solution Chemistry and the Nutritional Status of European Beech Seedlings

AbstractIn a rhizotron experiment the influence of Phytophthora citricola on root development, rhizosphere chemistry and nutritional status of beech seedlings was studied. After infection, the fine root system was seriously damaged and 6 weeks after inoculation some seedlings died. Plants infected with Phytophthora citricola had less steep concentration gradients of K+, Ca2+, Mg2+ and NO in the rhizosphere soil solution as compared with uninfected seedlings, which indicates reduced activity in nutrient uptake. It is concluded that plants try to compensate their deficit in fine root biomass and nutrient acquisition by retranslocation of nutrients.

Growth and nutrition of three conifer species across site gradients of north coastal British Columbia

We compared height growth and nutrition (foliar nutrient concentrations and retranslocation rates from 1-year-old needles) of second-growth plantations on imperfectly drained, lower productivity cedar–hemlock–salal forests with those of more productive ecosystems of north coastal British Columbia. Soils ranged from deep organic profiles to well-drained mineral soils derived from igneous to metamorphic bedrock. Leader increments on imperfectly drained sites were smaller than on well-drained sites, averaging 42% less for western hemlock (Tsuga heterophylla (Raf.) Sarg.), 56% less for Sitka spruce (Picea sitchensis (Bong.) Carrière), and 32% less for western redcedar (Thuja plicata Donn ex D. Don). Strong linear correlations were found between leader increment and foliar N, P, and S concentrations for all three tree species, and baseline foliar data for productive sites were presented. The foliar N ratios with P, S, and K were consistent across sites and indicated that many key foliar nutrients increased proportionally to the availability of N. A comparison of nutrient concentrations between current and 1-year-old foliage generally showed little difference on poorer sites, which suggested that there had been no retranslocation of nutrients from young needles within trees to compensate for low soil nutrient availability. This study confirmed the inherently low productivity of cedar-hemlock-salal forests, especially on granodiorite and gneissic diorite bedrock types, and suggested the need for site treatments or long rotations for sustainable management.