Leaf nitrogen distribution within canopies is (also) optimal

2020 ◽  
Author(s):  
Han Wang ◽  
Colin Prentice ◽  
Trevor Keenan ◽  
Ülo Niinemets ◽  
Nils Stenseth
Keyword(s):  
Photosynthetic Capacity ◽  
Temporal Distribution ◽  
Light Level ◽  
Leaf Nitrogen ◽  
Saturation Curve ◽  
Field Observations ◽  
Light Regimes ◽  
The Vertical Distribution ◽  
Global Datasets ◽  
Apparent Conflict

<p>The distribution of leaf nitrogen (N<sub>L</sub>) within canopies has been discussed for decades in relation to the optimality hypothesis that predicts coordination of carboxylation capacity with absorbed light. Although an optimal (that is, proportional) response of both carboxylation capacity and N<sub>L</sub>to light is extensively supported by field observations of variation among sites, the observed saturation curve of N<sub>L</sub>within canopies seems to challenge the generality of that response. By considering dynamic light regimes, we propose an optimality-based theory that successfully reconciles the apparent conflict of observed N<sub>L</sub>distribution within and between canopies. This theory proposes that due to the highly uneven temporal distribution of sun flecks, the light level to which understory leaves acclimate is much higher than the average light level. This proposition leads to a saturation curve for the vertical distribution of N<sub>L</sub>. Our within-canopy data analysis supports this theory. Understorey leaves require significantly less N<sub>L</sub>to achieve photosynthetic capacity as an acclimation to sun flecks. The contribution of structural and photosynthetic components to N<sub>L</sub>predicted by the theory is quantitatively and consistently supported by global datasets of variation both within and between canopies.</p>

scholarly journals Stock and Snapdragon as Influenced by Greenhouse Covering Materials and Supplemental Light

HortScience ◽  
1998 ◽  
Vol 33 (4) ◽  
pp. 668-671
Author(s):  
B. Dansereau ◽  
Y. Zhang ◽  
S. Gagnon ◽  
H.L. Xu
Keyword(s):  
Photosynthetic Capacity ◽  
Single Layer ◽  
Light Level ◽  
Dry Mass ◽  
Low Light ◽  
Polyethylene Films ◽  
Light Regimes ◽  
Covering Material ◽  
Flower Quality

We examined effects of single-layer glass and double-layer antifog polyethylene films on growth and flowering of stock (Matthiola incana L.) and snapdragon (Antirrhinum majalis L.) in a 3-year period. Stock produced more buds/spike with shorter but thicker stems under single-layer glass and under antifog 3-year polyethylene, and showed higher photosynthetic capacity (Pc) under single-layer glass than under other covers regardless of light regimes. Similarly, growth and flowering of snapdragon were significantly better under single-layer glass than in polyethylene houses. A supplemental light of 60 μmol·m-2·s-1 accelerated flowering by 20 to 25 days, improved flower quality, and eliminated differences in plant growth and quality of snapdragon between covering treatments. The Pc of stock was lower under all polyethylene covers than under single-layer glass. Among the three antifog polyethylene films, a slightly higher Pc was measured for plants under antifog 3-year polyethylene. However, there was no difference among covering treatments in the net photosynthetic rate (PN) at low light level (canopy level). Supplemental lighting reduced Pc of stock leaves, especially under single-layer glass, and diminished differences in Pc among covering treatments. Dry mass was more influenced by larger leaf area caused by higher leaf temperature than by PN. Overall, antifog 3-year polyethylene was a good covering material when both plant quality and energy saving were considered.

The Optimal Allocation of Nitrogen Within the C3 Photosynthetic System at Elevated CO2

1996 ◽  
Vol 23 (5) ◽  
pp. 593 ◽  
Author(s):  
BE Medlyn
Keyword(s):  
Elevated Co2 ◽  
Optimal Allocation ◽  
Co2 Concentration ◽  
Leaf Nitrogen ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Nitrogen Distribution ◽  
Photosynthetic System ◽  
Light Regimes ◽  
Nitrogen Contents

The distribution of nitrogen among compounds involved in photosynthesis varies in response to changes in environmental conditions such as photon flux density. However, the extent to which the nitrogen distribution within leaves adjusts in response to increased atmospheric CO2 is unclear. A model was used to determine the nitrogen distribution which maximises photosynthesis under realistic light regimes at both current and elevated levels of CO2, and a comparison was made with observed leaf nitrogen distributions reported in the literature. The model accurately predicted the distribution of nitrogen within the photosynthetic system for leaves grown at current levels of CO2, except at very high leaf nitrogen contents. The model predicted that, under a doubling of CO2 concentration from its current level, the ratio of electron transport capacity to Rubisco activity (Jmax : Vcmax) should increase by 40%. In contrast, measurements of Jmax : Vcmax taken from the literature show a slight but non-significant increase in response to an increase in CO2. The discrepancy between predicted and observed Jmax : Vcmax suggests that leaf nitrogen distribution does not acclimate optimally to elevated CO2. Alternatively, the discrepancy may be due to effects of CO2 which the model fails to take into account, such as a possible decrease in the conductance to CO2 transfer between the intercellular spaces and the sites of carboxylation at elevated CO2.

scholarly journals Leaf Photosynthetic Capacity of Sunlit and Shaded Mature Leaves in a Deciduous Forest

Forests ◽  
2020 ◽  
Vol 11 (3) ◽  
pp. 318
Author(s):  
Guangman Song ◽  
Quan Wang ◽  
Jia Jin
Keyword(s):  
Close Relationships ◽  
Deciduous Forest ◽  
Photosynthetic Capacity ◽  
Leaf Gas Exchange ◽  
Nitrogen Concentration ◽  
Leaf Traits ◽  
Leaf Nitrogen ◽  
Leaf Mass Per Area ◽  
Clear Understanding ◽  
Equivalent Water Thickness

A clear understanding of the dynamics of photosynthetic capacity is crucial for accurate modeling of ecosystem carbon uptake. However, such dynamical information is hardly available and has dramatically impeded our understanding of carbon cycles. Although tremendous efforts have been made in coupling the dynamic information of photosynthetic capacity into models, using “proxies” rooted from the close relationships between photosynthetic capacity and other available leaf parameters remains the popular selection. Unfortunately, no consensus has yet been reached on such “proxies”, leading them only applicable to limited cases. In this study, we aim to identify if there are close relationships between the photosynthetic capacity (represented by the maximum carboxylation rate, Vcmax) and leaf traits for mature broadleaves within a cold temperature deciduous forest. This is based on a long-term in situ dataset including leaf chlorophyll content (Chl), leaf nitrogen concentration (Narea, Nmass), leaf carbon concentration (Carea, Cmass), equivalent water thickness (EWT), leaf mass per area (LMA), and leaf gas exchange measurements from which Vcmax was derived, for both sunlit and shaded leaves during leaf mature periods from 2014 to 2019. The results show that the Vcmax values of sunlit and shaded leaves were relatively stable during these periods, and no statistically significant interannual variations occurred (p > 0.05). However, this is not applicable to specific species. Path analysis revealed that Narea was the major contributor to Vcmax for sunlit leaves (0.502), while LMA had the greatest direct relationship with Vcmax for shaded leaves (0.625). The LMA has further been confirmed as a primary proxy if no leaf type information is available. These findings provide a promising way to better understand photosynthesis and to predict carbon and water cycles in temperate deciduous forests.

scholarly journals The sensitivity of aerosol in Europe to two different emission inventories and temporal distribution of emissions

2006 ◽  
Vol 6 (12) ◽  
pp. 4287-4309 ◽  
Author(s):  
A. de Meij ◽  
M. Krol ◽  
F. Dentener ◽  
E. Vignati ◽  
C. Cuvelier ◽  
...  
Keyword(s):  
Emission Inventory ◽  
Dominant Role ◽  
Temporal Distribution ◽  
Temporal Variations ◽  
Anthropogenic Emissions ◽  
Emission Inventories ◽  
Global Transport ◽  
Modelling Uncertainties ◽  
The Vertical Distribution ◽  
Nitrate Aerosol

Abstract. The sensitivity to two different emission inventories, injection altitude and temporal variations of anthropogenic emissions in aerosol modelling is studied, using the two way nested global transport chemistry model TM5 focussing on Europe in June and December 2000. The simulations of gas and aerosol concentrations and aerosol optical depth (AOD) with the EMEP and AEROCOM emission inventories are compared with EMEP gas and aerosol surface based measurements, AERONET sun photometers retrievals and MODIS satellite data. For the aerosol precursor gases SO2 and NOx in both months the model results calculated with the EMEP inventory agree better (overestimated by a factor 1.3 for both SO2 and NOx) with the EMEP measurements than the simulation with the AEROCOM inventory (overestimated by a factor 2.4 and 1.9, respectively). Besides the differences in total emissions between the two inventories, an important role is also played by the vertical distribution of SO2 and NOx emissions in understanding the differences between the EMEP and AEROCOM inventories. In December NOx and SO2 from both simulations agree within 50% with observations. In June SO4= evaluated with the EMEP emission inventory agrees slightly better with surface observations than the AEROCOM simulation, whereas in December the use of both inventories results in an underestimate of SO4 with a factor 2. Nitrate aerosol measured in summer is not reliable, however in December nitrate aerosol calculations with the EMEP and AEROCOM emissions agree with 30%, and 60%, respectively with the filter measurements. Differences are caused by the total emissions and the temporal distribution of the aerosol precursor gases NOx and NH3. Despite these differences, we show that the column integrated AOD is less sensitive to the underlying emission inventories. Calculated AOD values with both emission inventories underestimate the observed AERONET AOD values by 20–30%, whereas a case study using MODIS data shows a high spatial agreement. Our evaluation of the role of temporal distribution of anthropogenic emissions on aerosol calculations shows that the daily and weekly temporal distributions of the emissions are only important for NOx, NH3 and aerosol nitrate. However, for all aerosol species SO4=, NH4+, POM, BC, as well as for AOD, the seasonal temporal variations used in the emission inventory are important. Our study shows the value of including at least seasonal information on anthropogenic emissions, although from a comparison with a range of measurements it is often difficult to firmly identify the superiority of specific emission inventories, since other modelling uncertainties, e.g. related to transport, aerosol removal, water uptake, and model resolution, play a dominant role.

Effect of leaf nitrogen and water regime on the photosynthetic capacity of kenaf (Hibiscus cannabinus L.) under field conditions

1990 ◽  
Vol 41 (5) ◽  
pp. 845 ◽  
Author(s):  
RC Muchow
Keyword(s):  
Water Deficit ◽  
Photosynthetic Capacity ◽  
N Uptake ◽  
Quantitative Information ◽  
Leaf Nitrogen ◽  
Hibiscus Cannabinus ◽  
High Rate ◽  
N Application ◽  
Area Index ◽  
The Relationship

To understand the influence of nitrogen (N) supply on the productivity of kenaf (Hibiscus cannabinus L.), the dependence of photosynthetic capacity, measured as light-saturated leaf CO2 assimilation rate (CA) and crop radiation use efficiency (RUE), on specific leaf nitrogen (SLN) was examined under well-watered conditions in the field. Photosynthetic capacity increased hyperbolically with SLN and was most responsive at SLN values less than c. 1.5 g m-2. The relationship reached a plateau at a maximum CA of 37 8mol m-2 s-1 and a maximum RUE of 1.5 g MJ-1 Increasing N application from 0 to 24 g N m-2 increased both RUE and SLN. Where ample N was applied, RUE and SLN were higher in those plots which previously experienced water deficit than in those that were always fully irrigated. The stimulation in growth following alleviation of water deficit was directly associated with the increase in SLN during water deficit. SLN varied according to differences in N uptake, the proportion of N allocated to leaves and the leaf area index. In particular, N application had much less effect on SLN and consequently RUE, than on N uptake, due to lower N partitioning to leaves and higher LAI where a high rate of N was applied. The importance of quantitative information on the relationship between photosynthetic capacity and SLN, in order to predict crop performance under varying environmental conditions, is discussed.

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