The Nitrogen Use Efficiency of C3 and C4 Plants III. Leaf Nitrogen Effects on the Activity of Carboxylating Enzymes in Chenopodium album (L.) and Amaranthus retroflexus (L.)

Department of Botany, University of California, Davis, California 95616.
Plant physiology (Impact Factor: 6.84). 11/1987; 85(2):355-9. DOI: 10.1104/pp.85.2.355
Source: PubMed


The relationships between leaf nitrogen content per unit area (N(a)) and (a) the initial slope of the photosynthetic CO(2) response curve, (b) activity and amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) and phosphoenolpyruvate carboxylase (PEPC), and (c) chlorophyll content were studied in the ecologically similar weeds Chenopodium album (C(3)) and Amaranthus retroflexus (C(4)). In both species, all parameters were linearly dependent upon leaf N(a). The dependence of the initial slope of the CO(2) response of photosynthesis on N(a) was four times greater in A. retroflexus than in C. album. At equivalent leaf N(a) contents, C. album had 1.5 to 2.6 times more CO(2) saturated Rubisco activity than A. retroflexus. At equal assimilation capacities, C. album had four times the Rubisco activity as A. retroflexus. In A. retroflexus, a one to one ratio between Rubisco activity and photosynthesis was observed, whereas in C. album, the CO(2) saturated Rubisco activity was three to four times the corresponding photosynthetic rate. The ratio of PEPC to Rubisco activity in A. retroflexus ranged from four at low N(a) to seven at high N(a). The fraction of organic N invested in carboxylation enzymes increased with increased N(a) in both species. The fraction of N invested in Rubisco ranged from 10 to 27% in C. album. In A. retroflexus, the fraction of N(a) invested in Rubisco ranged from 5 to 9% and the fraction invested in PEPC ranged from 2 to 5%.

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Available from: Robert W Pearcy, Sep 30, 2015
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    • "These regulatory networks extent organization from molecular, organelle, cell, and tissue levels to influence organism-level process such as N-uptake, N-allocation, and carbon assimilation rate. By way of relative importance , N is in greater demand by plants than any other mineral due to the large amount of N invested in the photosynthetic apparatus, especially in Rubisco that can account for up to 25% of leaf N (Sage et al. 1987). Plants need to balance the investment of N-containing proteins among different biological processes including photosynthesis , respiration, growth, and defense (Chapin et al. 1990; Evans and Poorter 2001; Xu et al. 2012). "
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    ABSTRACT: Understanding the consequences of elevated CO2 (eCO2; 800 ppm) on terrestrial ecosystems is a central theme in global change biology, but relatively little is known about how altered plant C and N metabolism influences higher levels of biological organization. Here, we investigate the consequences of C and N interactions by genetically modifying the N-assimilation pathway in Arabidopsis and initiating growth chamber and mesocosm competition studies at current CO2 (cCO2; 400 ppm) and eCO2 over multiple generations. Using a suite of ecological, physiological, and molecular genomic tools, we show that a single-gene mutant of a key enzyme (nia2) elicited a highly orchestrated buffering response starting with a fivefold increase in the expression of a gene paralog (nia1) and a 63% increase in the expression of gene network module enriched for N-assimilation genes. The genetic perturbation reduced amino acids, protein, and TCA-cycle intermediate concentrations in the nia2 mutant compared to the wild-type, while eCO2 mainly increased carbohydrate concentrations. The mutant had reduced net photosynthetic rates due to a 27% decrease in carboxylation capacity and an 18% decrease in electron transport rates. The expression of these buffering mechanisms resulted in a penalty that negatively correlated with fitness and population dynamics yet showed only minor alterations in our estimates of population function, including total per unit area biomass, ground cover, and leaf area index. This study provides insight into the consequences of buffering mechanisms that occur post-genetic perturbations in the N pathway and the associated outcomes these buffering systems have on plant populations relative to eCO2.
    Ecology and Evolution 06/2015; 5(14). DOI:10.1002/ece3.1565 · 2.32 Impact Factor
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    • "Nitrogen (N) is a crucial component of photosynthetic proteins, especially Rubisco (Field & Mooney, 1986). Total Rubisco activity and amount increase as leaf N increases (Sage et al., 1987), and across angiosperm, conifer and fern species, leaf photosynthetic rate tends to correlate with leaf N on an area and/or mass basis (Fig. 1) (Field & *These authors contributed equally to this work. "
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    ABSTRACT: * Cycads are the most ancient lineage of living seed plants, but the design of their leaves has received little study. We tested whether cycad leaves are governed by the same fundamental design principles previously established for ferns, conifers and angiosperms, and characterized the uniqueness of this relict lineage in foliar trait relationships. * Leaf structure, photosynthesis, hydraulics and nutrient composition were studied in 33 cycad species from nine genera and three families growing in two botanical gardens. * Cycads varied greatly in leaf structure and physiology. Similarly to other lineages, light-saturated photosynthetic rate per mass (Am) was related negatively to leaf mass per area and positively to foliar concentrations of chlorophyll, nitrogen (N), phosphorus and iron, but unlike angiosperms, leaf photosynthetic rate was not associated with leaf hydraulic conductance. Cycads had lower photosynthetic N use efficiency and higher photosynthetic performance relative to hydraulic capacity compared with other lineages. * These findings extend the relationships shown for foliar traits in angiosperms to the cycads. This functional convergence supports the modern synthetic understanding of leaf design, with common constraints operating across lineages, even as they highlight exceptional aspects of the biology of this key relict lineage.
    New Phytologist 01/2015; 206(2):n/a-n/a. DOI:10.1111/nph.13274 · 7.67 Impact Factor
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    • "The majority of nitrogen in a plant is contained in Rubisco, the primary enzyme in photosynthesis, which accounts for roughly 25% of leaf nitrogen in C3 plants. Rubisco content increases with leaf nitrogen and is sometimes, but not always, produced in excess of photosynthetic requirements as a means of nitrogen storage [64]. It is therefore possible that leaf nitrogen in P. macroloba is sufficiently limited, such that trade-offs between different cellular demands for nitrogen exist. "
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    ABSTRACT: One of the goals of chemical ecology is to assess costs of plant defenses. Intraspecific trade-offs between growth and defense are traditionally viewed in the context of the carbon-nutrient balance hypothesis (CNBH) and the growth-differentiation balance hypothesis (GDBH). Broadly, these hypotheses suggest that growth is limited by deficiencies in carbon or nitrogen while rates of photosynthesis remain unchanged, and the subsequent reduced growth results in the more abundant resource being invested in increased defense (mass-balance based allocation). The GDBH further predicts trade-offs in growth and defense should only be observed when resources are abundant. Most support for these hypotheses comes from work with phenolics. We examined trade-offs related to production of two classes of defenses, saponins (triterpenoids) and flavans (phenolics), in Pentaclethra macroloba (Fabaceae), an abundant tree in Costa Rican wet forests. We quantified physiological costs of plant defenses by measuring photosynthetic parameters (which are often assumed to be stable) in addition to biomass. Pentaclethra macroloba were grown in full sunlight or shade under three levels of nitrogen alone or with conspecific neighbors that could potentially alter nutrient availability via competition or facilitation. Biomass and photosynthesis were not affected by nitrogen or competition for seedlings in full sunlight, but they responded positively to nitrogen in shade-grown plants. The trade-off predicted by the GDBH between growth and metabolite production was only present between flavans and biomass in sun-grown plants (abundant resource conditions). Support was also only partial for the CNBH as flavans declined with nitrogen but saponins increased. This suggests saponin production should be considered in terms of detailed biosynthetic pathway models while phenolic production fits mass-balance based allocation models (such as the CNBH). Contrary to expectations based on the two defense hypotheses, trade-offs were found between defenses and photosynthesis, indicating that studies of plant defenses should include direct measures of physiological responses.
    PLoS ONE 10/2012; 7(10):e47554. DOI:10.1371/journal.pone.0047554 · 3.23 Impact Factor
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