Leaf Nitrogen Productivity Research Articles

Heterotic growth of hybrids of Arabidopsis thaliana is enhanced by elevated atmospheric CO2.

With the global atmospheric CO2 concentration on the rise, developing crops that can thrive in elevated CO2 has become paramount. We investigated the potential of hybridization as a strategy for creating crops with improved growth in predicted elevated atmospheric CO2. We grew parent accessions and their F1 hybrids of Arabidopsis thaliana in ambient and elevated atmospheric CO2 and analyzed numerous growth traits to assess their productivity and underlying mechanisms. The heterotic increase in total dry mass, relative growth rate and leaf net assimilation rate was significantly greater in elevated CO2 than in ambient CO2. The CO2 response of net assimilation rate was positively correlated with the CO2 response of leaf nitrogen productivity and with that of leaf traits such as leaf size and thickness, suggesting that hybridization-induced changes in leaf traits greatly affected the improved performance in elevated CO2. Vegetative growth of hybrids seems to be enhanced in elevated CO2 due to improved photosynthetic nitrogen-use efficiency compared with parents. The results suggest that hybrid crops should be well-suited for future conditions, but hybrid weeds may also be more competitive.

THE GROWTH STRATEGIES ANALYSIS OF TEN WOODY PLANT SPECIES FOR EFFECTIVE REVEGETATION

The growth strategies of plant species show the ecological role which is reflexed by their adaptation to environments and competitiveness. Those are essential in the study of the revegetation effectiveness. However, the growth strategies of plant species in various types of habitats have not yet been fully investigated. The objective of this study was to investigate the growth strategies of ten woody plant species which were naturalized from mangrove to lowland habitats in relation to their effectiveness for revegetation program. The seedling’s growth was recorded during 4 months in Purwodadi Botanic Garden-LIPI from October 2014 to February 2015. Complete randomized design with plant species as a treatment using 3 replications was carried out to examine the plant’s Relative Growth Rates (RGRs), their components, leaf nitrogen productivity and growth strategies.The study showed that RGRs of ten woody plants species varied across species. Based on the Pearson correlations, the plant’s Net Assimilation Rates (NAR) and two ecological traits related to the root trait i.e. Nitrogen productivity and Specific Root Length (SRL) were strongly correlated with the RGRs. Heritiera littoralis, Diospyros discolor, Antidesma bunius, Schleichera oleosa, Madhuca longifolia and Syzygium cumini have high RGRs but low Specific Leaf Area (SLA). B. asiatica has relatively low RGRs and SLA, while Dracontomelon dao have high RGRs and SLA. It showed that most of plant species studied, except D. dao achieve growth rates and competitiveness by developing strategies through forming fine roots to maximize its ecological function in nutrients uptake. Most of woody plant species are adaptive to dry lowland habitat and only D. dao potentially occupy the ecosystem. Furthermore, D. discolor and S. oleosa are highly recommended for revegetation in degraded tropical lowland areas.

Leaf-level nitrogen use efficiency: definition and importance

Nitrogen use efficiency (NUE) has been widely used to study the relationship between nitrogen uptake and dry mass production in the plant. As a subsystem of plant nitrogen use efficiency (NUE), I have defined leaf-level NUE as the surplus production (gross production minus leaf respiration) per unit amount of nitrogen allocated to the leaf, with factorization into leaf nitrogen productivity (NP) and mean residence time of leaf nitrogen (MRT). These concepts were applied to two herbaceous stands: a perennial Solidago altissima stand and an annual Amaranthus patulus stand. S. altissima had more than three times higher leaf NUE than A. patulus due to nearly three times longer MRT of leaf N. In both species, NUE and NP were higher at the leaf level than at the plant level, because most leaf N is involved directly in the photosynthetic activity and because leaf surplus production is higher than the plant net production. MRT was longer at the plant level. The more than twice as long MRT at the plant level as at the leaf level in S. altissima was due to a large contribution of nitrogen storage belowground in the winter in this species. Thus, comparisons between a perennial and an annual system and between plant- and leaf-level NUE with their components revealed the importance of N allocation, storage, recycling, and turnover of organs for leaf photosynthetic production and plant dry mass growth.

Leaf nitrogen productivity is the major factor behind the growth reduction induced by long-term salt stress

Plant growth response to salinity on a scale of years has not been studied in terms of growth analysis. To gain insights into this topic, 2-year-old Mediterranean Fan Palm (Chamaerops humilis L.) and Mexican Fan Palm (Washingtonia robusta H. Wendl) seedlings, each with its own distinct plant morphology, were grown for 2 years in a peat soil and irrigated with water of 2 dS m(-1) (control) or 8 dS m(-1) (saline). Plants were harvested on seven occasions and the time trends in relative growth rate (RGR, the rate of increase of biomass per unit of biomass already existing) and its components were analysed. In the long term, salinity produced a slight reduction in the mean RGR, values in both species. In the short term, salinity caused a reduction in RGR. However, during the second year, plants irrigated with 8 dS m(-1) grew somewhat more quickly than the control plants, probably as a result of delay in the growth kinetics due to salinity. Regarding RGR components, leaf nitrogen productivity (the rate of biomass gain per unit leaf N and time) was the major factor causing the differences in RGR resulting from salinity. Washingtonia robusta showed a relatively high plasticity in plant morphology by increasing root and decreasing stem biomass allocation in the presence of salinity. However, the long-term response of W. robusta to salinity, based to a great extent, on this morphological plasticity, was less effective than that of C. humilis, which is based mainly on the contribution of leaf N to RGR values.

Leaf nitrogen productivity as a mechanism driving the success of invasive annual grasses under low and high nitrogen supply

Invasion of the historically perennial-dominated landscapes in the Great Basin by exotic winter annual grasses is one of the most serious plant invasions in North America. Evidence suggests invasive annuals outperform native perennials under N-poor and N-rich conditions. The objective of this study was to identify key traits contributing to the success of invasive annual grasses in these environments. Three invasive annual grasses, two native perennial grasses and one introduced perennial grass were exposed to three levels of N supply. Root biomass, root length, root N uptake rate, root and leaf morphology, leaf nitrogen productivity (leaf NP) as well as biomass and N allocation were quantified over four harvests. Path analysis indicated that leaf NP was the key trait contributing to variation in N capture among the species. Species with a higher leaf NP produced more root length and consequently captured more N under a range of soil N availability. This suggests variation in leaf NP may be one critical trait determining the ability of the resident plant community to resist establishment of these invaders. Restoration programs may be able to increase weed resistance by specifically selecting for this trait in revegetation efforts.

Genetic basis of phenotypic correlations among growth traits in hybrid willow (Salix dasyclados×S. viminalis) grown under two water regimes

Phenotypic correlations and quantitative trait loci (QTL) for important growth traits and a surrogate of intrinsic water-use efficiency (leaf delta(13)C) were analysed in a willow pedigree of 92 full-sibling clones grown under two water regimes. The major objective was to examine the genetic basis of the phenotypic correlations. Cuttings of Salix were glasshouse-grown during one growing season. The relative growth rate (RGR) and underlying traits were assessed. QTL analysis was conducted based on an available linkage map for Salix. Leaf area productivity and leaf nitrogen productivity were more important in determining RGR than leaf area ratio and specific leaf area. However, phenotypic correlations among growth traits partly varied between the two environments. QTL were detected for most growth traits, among them many common QTL for different traits. The QTL pattern reflected the phenotypic correlation pattern. None of the QTL for the complex traits was consistent across the different environments. The results demonstrate a genetic basis for phenotypic correlations among growth traits in Salix, and provide evidence for the existence of 'master switches' regulating some of the traits.

The accumulation of terpenoid oils does not incur a growth cost in Eucalyptus polybractea seedlings.

The deployment of secondary metabolites, such as terpenes, as anti-herbivore defences is thought to be costly for plants in terms of primary metabolism. Moreover, it is assumed that the cost of this deployment is modified by resource availability. In this study we examined the impact of terpenoid oil accumulation on the growth of Eucalyptus polybractea R.T.Baker seedlings from four maternal half-sib families, under conditions of sufficient and limiting nitrogen. The foliar oil concentration measured was extremely variable, varying almost 20-fold to a maximum of 13% (w / DW). Oil concentration was higher in plants grown under high nitrogen than in low-nitrogen plants, and it was positively correlated with foliar nitrogen concentration. Oil concentration was related to maternal concentration, although this relationship was weak because of the variation encountered. The composition of oil, dominated by monoterpenes, was also extremely variable, although this variation could not be adequately explained by either nitrogen availability or the seedling parentage. Importantly, we detected no negative correlations between oil concentration and relative growth rate (RGR), net assimilation rate (NAR), or leaf nitrogen productivity (LNP). Rather, under nitrogen limiting conditions, positive correlations were detected between oil concentration and all three indices. We conclude that oil accumulation is associated with factors that promote growth and if there is a cost to oil deployment, it could not be detected using the experimental design employed here.

Understanding seedling growth relationships through specific leaf area and leaf nitrogen concentration: generalisations across growth forms and growth irradiance.

Seedling relative growth rate (RGR) achieved under favourable growth conditions can be thought of as a useful bioassay of the potential ability of species to take advantage of favourable growth opportunities; that is, of a species' growth strategy. The consistency of relationships between RGR and its component attributes leaf nitrogen productivity (LNP), leaf N per area (LNCa), specific leaf area (SLA) and leaf mass ratio (LMR) was assessed across 12 datasets comprising three growth forms (grasses, herbaceous dicots and woody plants; 250 species in total). These relationships were characterised in terms of scaling slopes (regressions on log-log axes, the slopes giving the proportional relationship between the variables). Mathematically, the expected scaling slope between RGR and each component is 1.0, giving an appropriate null hypothesis to test against (whereas the widely used null hypothesis of zero correlation is in fact inappropriate for this situation). Deviations below 1:1 scaling slopes indicate negative covariance between the components. Consequently, the correlation structure between the components of RGR should also be investigated. Biologically, RGR should scale 1:1 with SLA at a given LNCa and somewhat more weakly with LNCa at a given SLA. SLA and LNCa should themselves scale with a slope of between 0 and -1, with the actual slope indicating the extent to which between-species variation in SLA dilutes leaf N on an area basis versus the ability of species to maintain LNCa at a given growth irradiance. On average, across the 12 datasets RGR scaled close-to-proportionally with SLA, and 1:1 with SLA at a given LNCa. RGR scaled with LNCa with null or negative slopes, since SLA and LNCa scaled negatively (with slopes generally shallower than -1); however, RGR scaled positively (but less than proportionally) with LNCa at a given SLA. For these key relationships there were no qualitatively different conclusions with respect to the growth form under consideration or the growth irradiance at which the seedlings were grown. RGR also scaled close-to-proportionally with LNP, while LNP and LNCa were negatively associated. These relationships involving LNP are difficult to interpret since it can be shown that they are, at least potentially, the result of the interactions between RGR, SLA and LNCa, as well as reflecting intrinsic differences in the efficiency of nitrogen use in the growth process.

Cross‐species relationships between seedling relative growth rate, nitrogen productivity and root vs leaf function in 28 Australian woody species

Abstract1. Seedling relative growth rate (RGR) is often decomposed into the product of specific leaf area (leaf area per leaf mass, SLA), net assimilation rate (rate of mass increase per unit leaf area per unit time, NARa) and leaf mass ratio (ratio of leaf to total dry mass, LMR). Commonly, most cross‐species variation in RGR is accounted for by variation in SLA, while no general relationships occur between RGR and either NARa or LMR. NARa can be factored into the product of leaf nitrogen productivity (rate of mass increase per unit leaf nitrogen per unit time, LNP) and leaf nitrogen concentration (area basis, LNCa). In this way the influence on RGR of leaf nitrogen – how it is displayed, and how it is utilized – can be investigated.2. Seedlings of 28 Australian woody dicot species were grown under controlled, favourable conditions. Variation in SLA, LNP, LNCa and LMR explained c. 44%, 22%, 19% and 15% of variation in RGR, respectively. SLA and LNP were positively associated with RGR, while LNCa was negatively associated with RGR. LNP and LNCa were negatively correlated, the counteracting trends between RGR and each of these attributes resulting in no relationship between RGR and NARa. It is argued that this phenomenon may be widespread and may contribute to the inconsistency of reported relationships between NARa and RGR.3. The functional balance between leaves and roots can be described in terms of mass allocation and morphology (static ratios or allometric coefficients) or, alternatively, in terms of leaf ‘activity’ (NAR) and root ‘activity’ (nitrogen uptake rate, NUR). At any given time most species allocated greater mass to leaves than to roots, but species with low RGR tended to be partitioning a greater ongoing proportion of new biomass to the roots rather than to the leaves, resulting in a proportionally greater increase in root surface compared with leaf surface over time. Nitrogen uptake rate was correlated with leaf and whole‐plant nitrogen concentration, but not with other attributes. While it is clear that root and leaf functions must be co‐ordinated (and thus in balance) for growth to occur, there is little evidence that this balance varies systematically with RGR across all species.

Acquisition and allocation of carbon and nitrogen by Danthonia richardsonii in response to restricted nitrogen supply and CO2 enrichment

Dry weight (DW) and nitrogen (N) accumulation and allocation were measured in isolated plants of Danthonia richardsonii (Wallaby Grass) for 37 d following seed imbibition. Plants were grown at ≈ 365 or 735 μL L–1 CO2 with N supply of 0·05, 0·2 or 0·5 mg N plant–1 d–1. Elevated CO2 increased DW accumulation by 28% (low‐N) to 103% (high‐N), following an initial stimulation of relative growth rate. Net assimilation rate and leaf nitrogen productivity were increased by elevated CO2, while N concentration was reduced. N uptake per unit root surface area was unaffected by CO2 enrichment. The ratio of leaf area to root surface area was decreased by CO2 enrichment. Allometric analysis revealed a decrease in the shoot‐N to root‐N ratio at elevated CO2, while the shoot‐DW to root‐DW ratio was unchanged. Allometric analysis showed leaf area was reduced, while root surface area was unchanged by elevated CO2, indicating a down‐regulation of total plant capacity for carbon gain rather than a stimulation of mineral nutrient acquisition capacity. Overall, growth in elevated CO2 resulted in changes in plant morphology and nitrogen use, other than those associated simply with changing plant size and non‐structural carbohydrate content.

Growth response of grasses to elevated CO2: a physiological plurispecific analysis

summaryThe effect of CO2 enrichment on the growth and the economy of carbon and nitrogen of 11 Mediterranean grass species was investigated in order to determine the underlying causes of the large variation observed between species in their responses to elevated CO2. Plants were grown for 26–43 d (depending on species growth rate) under productive conditions at ambient (350 μmol mol−1) and elevated (700 μmol mol−1) concentrations of CO2. Plant parameters were determined at a common biomass of 0.15 g to determine the CO2 effect independent of ontogenic effects.The effect of CO2 on RGR ranged from −6.7 to 22.5%, with a mean stimulation of 10.3%. Averaged over the 11 species, the growth enhancement resulted from an increase in net assimilation rate per unit leaf d. wt. (narw) of 10.6 %. This was the result of a large increase (18.7%) in nar per unit leaf area (NARa) associated with a 8.1% decrease in the specific leaf area (sla). This decrease in sla was due to a large increase of the non‐structural carbohydrates. The increase in shoot activity was balanced by a 70.6% increase in the specific absorption rate of nitrogen (sar). AS a result, plant nitrogen content was not modified. Leaf nitrogen productivity was significantly increased (14.9%). Shoot vs. root allocation of biomass and nitrogen was not modified.An analysis across the 11 species of the relationships between the stimulation of rgb and the alteration in rgr components showed a significant correlation only with increases in narw, sar and nitrogen productivity. The co‐ordinated increase in these three parameters constitutes a single response syndrome, whose intensity is responsible for most of the species variability.

Nitrogen Productivity Depends on Photosynthetic Nitrogen Use Efficiency and on Nitrogen Allocation Within the Plant

The concept of plant nitrogen productivity was introduced at the end of the 1970s to interpret the dependency of plant growth on internal nitrogen. It is defined as the increase in plant dry matter per unit time and per unit plant nitrogen content. Recently, plant nitrogen productivity has been expressed as the product of two terms: the leaf nitrogen ratio, which is the proportion of the plant's nitrogen present in the leaves, and the leaf nitrogen productivity, which is defined as the increase in plant dry matter per unit time and leaf nitrogen content. In the present paper we use two data sets obtained from C3 herbaceous species to evaluate the relative importance of variation in leaf nitrogen ratio and leaf nitrogen productivity in determining interspecific variation in plant nitrogen productivity. Further, we analyse to what extent leaf and plant nitrogen productivities depend on photosynthetic nitrogen use efficiency. Results show that in all cases, photosynthetic nitrogen use efficiency is a major determinant of both plant and leaf nitrogen productivities. A positive relationship between leaf nitrogen ratio and plant nitrogen productivity was found only when comparisons were made over broad taxonomic groups.

Carbon and nitrogen content of congeneric annual and perennial grass species: relationships with growth

ABSTRACTSeven annual‐perennial pairs of grass species (six congeneric and one pair taken at random) were grown under productive conditions in the laboratory in order to investigate which plant characters were responsible for the higher relative growth rate (RGR) of annuals as compared to perennials under these conditions. The nitrogen and carbon concentrations of shoot organs and of the whole plant were higher in annuals than in perennials. This was also the case for the specific absorption rate for nitrate and nitrogen productivity (on whole plant and leaf basis). The range of RGR displayed by the 14 species was large enough (0.15–0.33d−1) to examine the general relationships between RGR and the various parameters measured in the present study. RGR was positively related to plant, leaf blade and sheath nitrogen concentrations, but there was no relationship between RGR and any of the carbon concentrations. RGR also strongly correlated with specific absorption rate for nitrate and with nitrogen productivity. A new factorization of this latter parameter led to the definition of the ‘leaf nitrogen productivity’ (NLP), which is likely to depend on photosynthetic nitrogen use efficiency. RGR was shown to be strongly correlated with NLP, but not with the second term of the factorization, namely the proportion of plant nitrogen allocated to the leaves.