Nutrient translocation in the xylem of poplar ? diurnal variations and spatial distribution along the shoot axis

Siebrecht, S.; Herdel, K.; Schurr, Uli; Tischner, Rudolf

doi:10.1007/s00425-003-1041-4

Cited by 102 publications

(90 citation statements)

References 45 publications

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“…The lowest IR was in xylem tissues in all cultivars. The nutrient content of xylem tissues is lower than that of other tissues (Siebrecht et al, 2003;Yadeta and Thomma, 2014), which explains why few endophytes colonize this tissue. Xylem possesses highly structured and rigid secondary xylem walls and pit membranes with extremely small pores.…”

Section: Tissue Preferencementioning

confidence: 99%

Diversity of Tea Endophytic Fungi: Cultivar- And Tissue Preferences

Win¹,

Matsumura²,

Fukuda³

2018

Appl. Ecol. Env. Res.

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Abstract. Endophytic fungi were isolated from four healthy tissues (new leaf, old leaf, bark, and xylem) of three Japanese tea cultivars (Hokumei, Sayamakaori, and Yabukita) at the Saitama Tea Research Institute, Japan in July 2015. A total of 520 isolates was obtained from 600 segments and were classified into 44 fungal taxa; the majority (93.2%) belonged to the phylum Ascomycota. The lowest infection rate was found in the xylem tissue of all cultivars. The total infection rate did not differ significantly among the cultivars. Colletotrichum gloeosporioides f. sp. camelliae and Pleosporales sp. were the predominant endophytes in all tissue types and cultivars. Most of the dominant endophytes showed obvious cultivar and tissue preferences. Tissue type played a more important role in shaping community structure than did cultivar. Colletotrichum gloeosporioides f. sp. camelliae preferred bark and old leaf tissue while Pleosporales sp. preferred new leaf tissue. The colonization frequency of C. gloeosporioides f. sp. camelliae was significantly lower in the Yabukita cultivar. Stem tissues harbored more diverse endophytes than did leaf tissues.

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Section: Tissue Preferencementioning

confidence: 99%

Diversity of Tea Endophytic Fungi: Cultivar- And Tissue Preferences

Win¹,

Matsumura²,

Fukuda³

2018

Appl. Ecol. Env. Res.

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“…The sole source of nitrogen for the leaf model was nitrate import from the xylem based on the observation that nitrate represents the main form of nitrogen (80%) entering a leaf (Macduff and Bakken, 2003). The rate of nitrate import into the leaf during the day:night was constrained to be 3:2 based on measurements in various plant species (Delhon et al, 1995;Macduff and Bakken, 2003;Siebrecht et al, 2003). Other than the export of Suc and amino acids, cellular maintenance costs were accounted for by including generic ATPase and NADPH oxidase steps for maintenance and the requirement to satisfy a specified carbon conversion efficiency (Cheung et al, 2013).…”

Section: A Day-night Modeling Framework For Leaf Metabolismmentioning

confidence: 99%

A Diel Flux Balance Model Captures Interactions between Light and Dark Metabolism during Day-Night Cycles in C3 and Crassulacean Acid Metabolism Leaves

et al. 2014

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Although leaves have to accommodate markedly different metabolic flux patterns in the light and the dark, models of leaf metabolism based on flux-balance analysis (FBA) have so far been confined to consideration of the network under continuous light. An FBA framework is presented that solves the two phases of the diel cycle as a single optimization problem and, thus, provides a more representative model of leaf metabolism. The requirement to support continued export of sugar and amino acids from the leaf during the night and to meet overnight cellular maintenance costs forces the model to set aside stores of both carbon and nitrogen during the day. With only minimal constraints, the model successfully captures many of the known features of C 3 leaf metabolism, including the recently discovered role of citrate synthesis and accumulation in the night as a precursor for the provision of carbon skeletons for amino acid synthesis during the day. The diel FBA model can be applied to other temporal separations, such as that which occurs in Crassulacean acid metabolism (CAM) photosynthesis, allowing a system-level analysis of the energetics of CAM. The diel model predicts that there is no overall energetic advantage to CAM, despite the potential for suppression of photorespiration through CO 2 concentration. Moreover, any savings in enzyme machinery costs through suppression of photorespiration are likely to be offset by the higher flux demand of the CAM cycle. It is concluded that energetic or nitrogen use considerations are unlikely to be evolutionary drivers for CAM photosynthesis.Photosynthetic metabolism continues to be studied intensively because of its importance for crop performance and the global carbon cycle in relation to climate change. The metabolic pathways and enzymes involved in carbon fixation and related metabolic processes, such as the synthesis of Suc and starch, have been wellcharacterized. However, it is apparent that full appreciation of leaf metabolism requires these metabolic processes to be placed in the context of the wider metabolic network (Szecowka et al., 2013). This is particularly important for predicting how strategies for engineering improved photosynthesis (Maurino and Weber, 2013) may affect network properties, such as redox and energy balancing (Kramer and Evans, 2011).Flux balance analysis (FBA) has emerged as the method of choice for predicting fluxes in large metabolic network models (Sweetlove and Ratcliffe, 2011), and several flux balance models have explicitly considered photosynthetic metabolism in a variety of plants species and microorganisms, including cyanobacteria (Synechocystis sp. PCC 6803; Knoop et al

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“…This diurnal pattern suggests that the xylem loading rate of nitrate is high in the light period but low in the dark period. Indeed, several studies have shown that root-to-shoot nitrate translocation rates are high in the day and low in the night (Macduff and Bakken, 2003;Siebrecht et al, 2003). Thus, in addition to the high transpiration rate, the high xylem loading rate in the light period could lead to the pronounced diurnal variation in the nitrate translocation rate.…”

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confidence: 99%

Mutation of the Arabidopsis NRT1.5 Nitrate Transporter Causes Defective Root-to-Shoot Nitrate Transport

et al. 2008

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Little is known about the molecular and regulatory mechanisms of long-distance nitrate transport in higher plants. NRT1.5 is one of the 53 Arabidopsis thaliana nitrate transporter NRT1 (Peptide Transporter PTR) genes, of which two members, NRT1.1 (CHL1 for Chlorate resistant 1) and NRT1.2, have been shown to be involved in nitrate uptake. Functional analysis of cRNA-injected Xenopus laevis oocytes showed that NRT1.5 is a low-affinity, pH-dependent bidirectional nitrate transporter. Subcellular localization in plant protoplasts and in planta promoter-b-glucuronidase analysis, as well as in situ hybridization, showed that NRT1.5 is located in the plasma membrane and is expressed in root pericycle cells close to the xylem. Knockdown or knockout mutations of NRT1.5 reduced the amount of nitrate transported from the root to the shoot, suggesting that NRT1.5 participates in root xylem loading of nitrate. However, root-to-shoot nitrate transport was not completely eliminated in the NRT1.5 knockout mutant, and reduction of NRT1.5 in the nrt1.1 background did not affect rootto-shoot nitrate transport. These data suggest that, in addition to that involving NRT1.5, another mechanism is responsible for xylem loading of nitrate. Further analyses of the nrt1.5 mutants revealed a regulatory loop between nitrate and potassium at the xylem transport step. INTRODUCTIONNitrate and ammonium ions are the two major nitrogen sources for higher plants. Due to its toxicity, ammonium is preferentially assimilated in the root and then transported in an organic form to the aerial parts. By contrast, nitrate can be assimilated into ammonium and then amino acids in the root or shoot. Partitioning of nitrate assimilation between the root and shoot depends on the plant species, external nitrate concentration, temperature, and light intensity (reviewed in Smirnoff and Stewart, 1985). If there is sufficient light, nitrate assimilation in the leaf has a lower energy cost than in the root. However, some disadvantages of leaf nitrate assimilation include (1) if light is limited, nitrate assimilation and carbon dioxide fixation will compete directly for the reductants and ATP generated by photosynthetic electron transport (Canvin and Atkins, 1974), and (2) hydroxyl ions generated in the leaf need to be neutralized by the synthesis of organic acids (in the root, the pH balance may possibly be maintained by reducing proton excretion or increasing bicarbonate excretion). Due to these factors, the partition of nitrate assimilation between the root and shoot shows both seasonal and diurnal fluctuations, allowing the plant to sustain maximal growth. In turn, the partition of nitrate assimilation depends on the partition of nitrate between the root and shoot.To transport nitrate to the aerial parts of the plant, nitrate has to be loaded into the xylem vessels of the root vascular stele. In Arabidopsis thaliana roots, four layers of cells are found surrounding the xylem, these being the epidermis, cortex, endodermis, and pericycle (in the order external to ...

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Nutrient translocation in the xylem of poplar ? diurnal variations and spatial distribution along the shoot axis

Cited by 102 publications

References 45 publications

Diversity of Tea Endophytic Fungi: Cultivar- And Tissue Preferences

Diversity of Tea Endophytic Fungi: Cultivar- And Tissue Preferences

A Diel Flux Balance Model Captures Interactions between Light and Dark Metabolism during Day-Night Cycles in C3 and Crassulacean Acid Metabolism Leaves

Mutation of the Arabidopsis NRT1.5 Nitrate Transporter Causes Defective Root-to-Shoot Nitrate Transport

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