scholarly journals Root growth and N dynamics in response to multi-year experimental warming, summer drought and elevated CO2 in a mixed heathland-grass ecosystem

2014 ◽  
Vol 41 (1) ◽  
pp. 1 ◽  
Author(s):  
M. F. Arndal ◽  
I. K. Schmidt ◽  
J. Kongstad ◽  
C. Beier ◽  
A. Michelsen
Keyword(s):  
Root Growth ◽  
Elevated Co2 ◽  
Environmental Changes ◽  
Nitrogen Concentration ◽  
N Uptake ◽  
Root Production ◽  
Summer Drought ◽  
Whole Plant ◽  
Grass Root ◽  
Biomass N

Ecosystems exposed to elevated CO2 are often found to sequester more atmospheric carbon due to increased plant growth. We exposed a Danish heath ecosystem to elevated CO2, elevated temperature and extended summer drought alone and in all combinations in order to study whether the expected increased growth would be matched by an increase in root nutrient uptake of NH4+-N and NO3– -N. Root growth was significantly increased by elevated CO2. The roots, however, did not fully compensate for the higher growth with a similar increase in nitrogen uptake per unit of root mass. Hence the nitrogen concentration in roots was decreased in elevated CO2, whereas the biomass N pool was unchanged or even increased. The higher net root production in elevated CO2 might be a strategy for the plants to cope with increased nutrient demand leading to a long-term increase in N uptake on a whole-plant basis. Drought reduced grass root biomass and N uptake, especially when combined with warming, but CO2 was the most pronounced main factor effect. Several significant interactions of the treatments were found, which indicates that the responses were nonadditive and that changes to multiple environmental changes cannot be predicted from single-factor responses alone.

scholarly journals Local root growth and death are mediated by contrasts in nutrient availability and root quantity between soil patches

2018 ◽  
Vol 285 (1886) ◽  
pp. 20180699 ◽  
Author(s):  
Peng Wang ◽  
Yan Yang ◽  
Pu Mou ◽  
Qingzhou Zhao ◽  
Yunbin Li
Keyword(s):  
Root Growth ◽  
Nutrient Availability ◽  
Environmental Changes ◽  
Nutrient Status ◽  
Root Production ◽  
Solution Versus ◽  
Hoagland Solution ◽  
Contrast Condition ◽  
Whole Plant ◽  
Local Root

Plants are thought to be able to regulate local root growth according to its overall nutrient status as well as nutrient contents in a local substrate patch. Therefore, root plastic responses to environmental changes are probably co-determined by local responses of root modules and systematic control of the whole plant. Recent studies showed that the contrast in nutrient availability between different patches could significantly influence the growth and death of local roots. In this study, we further explored, beside nutrient contrast, whether root growth and death in a local patch are also affected by relative root quantity in the patch. We conducted a split-root experiment with different splitting ratios of roots of Canada goldenrod ( Solidago canadensis ) individuals, as well as high- (5× Hoagland solution versus water) or low- (1× Hoagland solution versus water) contrast nutrient conditions for the split roots. The results showed that root growth decreased in nutrient-rich patches but increased in nutrient-poor patches when more roots co-occurred in the same patches, irrespective of nutrient contrast condition. Root mortality depended on contrasts in both root quantity and nutrients: in the high-nutrient-contrast condition, it increased in nutrient-rich patches but decreased in nutrient-poor patches with increasing root proportion; while in the low-nutrient-contrast condition, it showed the opposite trend. These results demonstrated that root growth and death dynamics were affected by the contrast in both nutrient availability and root quantity between patches. Our study provided ecological evidence that local root growth and death are mediated by both the responses of root modules to a nutrient patch and the whole-plant nutrient status, suggesting that future work investigating root production and turnover should take into account the degree of heterogeneity in nutrient and root distribution.

scholarly journals Effects of Elevated CO2 and Nitrogen Loading on the Defensive Traits of Three Successional Deciduous Broad-Leaved Tree Seedlings

Forests ◽  
2021 ◽  
Vol 12 (7) ◽  
pp. 939
Author(s):  
Yoko Watanabe ◽  
Kiyomi Hinata ◽  
Laiye Qu ◽  
Satoshi Kitaoka ◽  
Makoto Watanabe ◽  
...  
Keyword(s):  
Elevated Co2 ◽  
Environmental Changes ◽  
Total Phenolics ◽  
Condensed Tannin ◽  
N Uptake ◽  
Nitrogen Loading ◽  
Total Phenolic ◽  
Tree Seedlings ◽  
N Supply ◽  
Successional Species

To elucidate changes in the defensive traits of tree seedlings under global environmental changes, we evaluated foliar defensive traits of the seedlings of successional trees, such as beech, oak, and magnolia grown in a natural-light phytotron. Potted seedlings were grown under the combination of two CO2 concentrations (360 vs. 720 ppm) and two nitrogen (N) treatments (4 vs. 15 kg N ha−1 yr−1) for two growing seasons using quantitative chemical analyses and anatomical method. We hypothesized that the effects of CO2 and N depend on the successional type, with late successional species providing greater defense of their leaves against herbivores, as this species exhibits determinate growth. Beech, a late successional species, responded the most to both elevated CO2 concentration (eCO2) and high N treatment. eCO2 and low N supply enhanced the defensive traits, such as the high leaf mass per area (LMA), high carbon to N ratio (C/N ratio), and increase in the concentrations of total phenolic and condensed tannin in agreement with the carbon–nutrient balance (CNB) hypothesis. High N supply decreased the C/N ratio due to the high N uptake in beech leaves. Oak, a mid–late successional species, exhibited different responses from beech: eCO2 enhanced the LMA, C/N ratio, and concentration of total phenolics of oak leaves, but only condensed tannin increased under high N supply. Magnolia did not respond to all treatments. No interactive effects were observed between CO2 and N supply in all species, except for the concentration of total phenolics in oak. Although the amounts of phenolic compounds in beech and oak varied under eCO2 and high N treatments, the distribution of these compounds did not change. Our results indicate that the changes in the defensive traits of forest tree species under eCO2 with N loading are related to the successional type.

The Influence of Nitrogen on the Elevated CO2 Response in Field-Grown Rice

1996 ◽  
Vol 23 (1) ◽  
pp. 45 ◽  
Author(s):  
LH Ziska ◽  
W Weerakoon ◽  
OS Namuco ◽  
R Pamplona
Keyword(s):  
Elevated Co2 ◽  
Growth Response ◽  
Oryza Sativa L ◽  
N Uptake ◽  
Root Production ◽  
N Availability ◽  
Above Ground Biomass ◽  
Co2 Response ◽  
Ground Biomass ◽  
N Supply

Rice (Oryza sativa L. cv. IR72) was grown in the tropics at ambient (345 μL L-1) or twice ambient (elevated, 700 μL L-1) CO2, concentration at three levels of supplemental nitrogen (N) (no additional N (N0), 90 kg ha-1 (N1) and 200 kg ha-1 (N2)) in open-top chambers under irrigated field conditions from seeding until flowering. The primary objective of the study was to determine if N supply alters the sensitivity of growth and photosynthesis of field-grown rice to enriched CO2. A second objective was to determine the influence of elevated CO2 on N uptake and tissue concentrations. Although photosynthesis was initially stimulated at the leaf and canopy level with elevated CO2 regardless of supplemental N supply, with time the photosynthetic response became highly dependent on the level of supplemental N, increasing proportionally as N availability increased. Similarly, a synergistic effect was noted between CO2 and N with respect to above-ground biomass with no effect of elevated CO2 observed for the No treatment. Most of the increase in above-ground biomass with increasing CO2 and N was associated with increased tiller and, to a lesser extent, root production. The concentration of above-ground N decreased at elevated CO2 regardless of N treatment; however, total above-ground N did not change for the N1 and N2 treatments because of the greater amount of biomass associated with elevated CO2. For rice, the photosynthetic and growth response to elevated CO2 may be highly dependent on the supply of N. If additional CO2 is given and N is not available, lack of sinks for excess carbon (e.g. tillers) may limit the photosynthetic and growth response.

Managing nutrient regimes improves seedling root-growth potential of framework banksia-woodland species

2013 ◽  
Vol 61 (8) ◽  
pp. 600 ◽  
Author(s):  
Erin Griffiths ◽  
Jason C. Stevens
Keyword(s):  
Root Growth ◽  
Nutrient Loading ◽  
Slow Release ◽  
Growth Potential ◽  
Root Production ◽  
Summer Drought ◽  
Root Growth Potential ◽  
Application Rates ◽  
Root Shoot Ratio ◽  
Nursery Production

Limited success of restoring framework banksia-woodland species has been attributed to the failure of seedlings to establish deep root systems before the onset of the summer drought. The present glasshouse study investigated how optimising nutrient application during nursery production may increase new-root production after outplanting. Two experimental streams were established to (1) optimise nutrient application rates during nursery production and (2) utilise nutrient-loading techniques to improve root production of Banksia menziesii R.Br., Banksia attenuata R.Br. and Eucalyptus todtiana F.Muell after outplanting. Optimal nutrient-application rates were determined by measuring plant growth and internal nutrient responses to eight application levels of slow-release fertiliser (0–18 kg m–3, nitrogen (N) : phosphorus (P) : potassium (K) = 17 : 1.6 : 8.7). Nutrient-loading treatments utilised seedlings that had been grown under common industry fertiliser conditions (3 kg m–3 native Osmocote, N : P : K = 17 : 1.6 : 8.7) supplied with ‘low’ or ‘high’ loading doses of liquid Thrive continuously over 6 weeks, immediately before outplanting. Seedlings from both experiments were then outplanted to 1-m-deep poly-pipe tubes containing habitat soil. After 12 weeks, plants were harvested and new-root production and shoot growth were measured. Optimal concentrations of slow-release fertiliser for maximum outplanting success as indicated by increased root investment (root : shoot ratio and new-root production) were 8–12 kg m–3 for all species. Nutrient loading increased N and P concentrations of plants by up to 80% and 127%, respectively, by luxury nutrient consumption, and after planting, nutrient-loaded seedlings produced 1.5-fold the biomass of conventionally fertilised seedlings, this being the result of greater root productivity. In conclusion, optimising nursery nutrient regimes for framework species may increase root-growth potential, assisting in improving plant establishment in restoration programs.

Minirhizotron imaging reveals that nodulation of field-grown soybean is enhanced by free-air CO2 enrichment only when combined with drought stress

2013 ◽  
Vol 40 (2) ◽  
pp. 137 ◽  
Author(s):  
Sharon B. Gray ◽  
Reid S. Strellner ◽  
Kannan K. Puthuval ◽  
Christopher Ng ◽  
Ross E. Shulman ◽  
...  
Keyword(s):  
Environmental Change ◽  
Elevated Co2 ◽  
N2 Fixation ◽  
Root Length ◽  
Nitrogen Concentration ◽  
Global Environmental Change ◽  
Leguminous Plant ◽  
Root Production ◽  
Elevated Atmospheric Co2 ◽  
Global Environmental

The rate of N2 fixation by a leguminous plant is a product of the activity of individual nodules and the number of nodules. Initiation of new nodules and N2 fixation per nodule are highly sensitive to environmental conditions. However, the effects of global environmental change on nodulation in the field are largely unknown. It is also unclear whether legumes regulate nodulation in response to environment solely by varying root production or also by varying nodule density per unit of root length. This study utilised minirhizotron imaging as a novel in situ method for assessing the number, size and distribution of nodules in field-grown soybean (Glycine max (L.) Merr.) exposed to elevated atmospheric CO2 ([CO2]) and reduced precipitation. We found that nodule numbers were 134–229% greater in soybeans grown at elevated [CO2] in combination with reduced precipitation, and this response was driven by greater nodule density per unit of root length. The benefits of additional nodules were probably offset by an unfavourable distribution of nodules in shallow, dry soil in reduced precipitation treatment under elevated [CO2] but not ambient [CO2]. In fact, significant decreases in seed and leaf nitrogen concentration also occurred only in elevated [CO2] with reduced precipitation. This study demonstrates the potential of minirhizotron imaging to reveal previously uncharacterised changes in nodule production and distribution in response to global environmental change.

scholarly journals Why is plant-growth response to elevated CO2 amplified when water is limiting, but reduced when nitrogen is limiting? A growth-optimisation hypothesis

2008 ◽  
Vol 35 (6) ◽  
pp. 521 ◽  
Author(s):  
Ross E. McMurtrie ◽  
Richard J. Norby ◽  
Belinda E. Medlyn ◽  
Roderick C. Dewar ◽  
David A. Pepper ◽  
...  
Keyword(s):  
Stomatal Conductance ◽  
Elevated Co2 ◽  
Nitrogen Limitation ◽  
Growth Response ◽  
Nitrogen Concentration ◽  
N Uptake ◽  
Co2 Enrichment ◽  
Area Index ◽  
Oak Ridge ◽  
Leaf N

Experimental evidence indicates that the stomatal conductance and nitrogen concentration ([N]) of foliage decline under CO2 enrichment, and that the percentage growth response to elevated CO2 is amplified under water limitation, but reduced under nitrogen limitation. We advance simple explanations for these responses based on an optimisation hypothesis applied to a simple model of the annual carbon–nitrogen–water economy of trees growing at a CO2-enrichment experiment at Oak Ridge, Tennessee, USA. The model is shown to have an optimum for leaf [N], stomatal conductance and leaf area index (LAI), where annual plant productivity is maximised. The optimisation is represented in terms of a trade-off between LAI and stomatal conductance, constrained by water supply, and between LAI and leaf [N], constrained by N supply. At elevated CO2 the optimum shifts to reduced stomatal conductance and leaf [N] and enhanced LAI. The model is applied to years with contrasting rainfall and N uptake. The predicted growth response to elevated CO2 is greatest in a dry, high-N year and is reduced in a wet, low-N year. The underlying physiological explanation for this contrast in the effects of water versus nitrogen limitation is that leaf photosynthesis is more sensitive to CO2 concentration ([CO2]) at lower stomatal conductance and is less sensitive to [CO2] at lower leaf [N].

scholarly journals Nitrogen Requirements of Drip-irrigated Processing Tomatoes

HortScience ◽  
2009 ◽  
Vol 44 (7) ◽  
pp. 1988-1993 ◽  
Author(s):  
Timothy K. Hartz ◽  
Thomas G. Bottoms
Keyword(s):  
N Uptake ◽  
N Fertilization ◽  
Fruit Yield ◽  
N Availability ◽  
Total N ◽  
Whole Plant ◽  
Biomass N ◽  
Highly Correlated ◽  
Whole Plants ◽  
Processing Tomatoes

As growers of processing tomato (Lycopersicon esculentum Mill.) adopt drip irrigation, plant vigor and fruit yield typically increase, suggesting a need for re-evaluation of established nitrogen (N) fertilization practices. Trials were conducted in California in 2007–2008 to evaluate growth and N uptake dynamics of drip-irrigated processing tomatoes across N fertigation regimes ranging from deficient to excessive. Whole plants were collected at 2-week intervals for determination of biomass and N content, recently matured whole leaves for total N and petioles for NO3-N. Additionally, six commercial fields were sampled at 3- to 4-week intervals to document N uptake and crop N status under conditions representative of the industry. A seasonal N rate of ≈200 kg·ha−1 appeared adequate to maximize fruit yield across the range of field conditions encountered. The four highest-yielding fields (143 Mg·ha−1 mean fresh fruit mass) averaged 14 Mg·ha−1 of above-ground biomass with fruit representing 62%; these fields averaged 296 kg·ha−1 biomass N, of which 71% was in fruit. The rate of biomass development and N uptake peaked during the period between early fruit setting and early red fruit development (a period of ≈6 weeks) during which N uptake averaged 4 to 5 kg·ha−1·d−1. Leaf N concentration was highly correlated with whole plant N (r2 = 0.83) and provided a reliable indicator of plant N sufficiency throughout the season. Petiole NO3-N did not reliably discriminate between crops with adequate or deficient N availability; current petiole NO3-N sufficiency guidelines are unrealistically high.

scholarly journals Impact of Mycorrhization on Phosphorus Utilization Efficiency of Acacia gummifera and Retama monosperma under Salt Stress

Forests ◽  
2021 ◽  
Vol 12 (5) ◽  
pp. 611
Author(s):  
Abdessamad Fakhech ◽  
Martin Jemo ◽  
Najat Manaut ◽  
Lahcen Ouahmane ◽  
Mohamed Hafidi
Keyword(s):  
Salt Stress ◽  
Root Growth ◽  
N Uptake ◽  
P Uptake ◽  
Utilization Efficiency ◽  
Legume Species ◽  
Growth Responses ◽  
Phosphorus Utilization ◽  
Phosphorus Utilization Efficiency ◽  
Shoot And Root Growth

The impact of salt stress on the growth and phosphorus utilization efficiency (PUE) of two leguminous species: Retama monosperma and Acacia gummifera was studied. The effectiveness of arbuscular mycorrhizal fungi (AMF) to mitigate salt stress was furthermore assessed. Growth, N and P tissue concentrations, mycorrhizal root colonization frequency and intensity, and P utilization efficiency (PUE) in the absence or presence of AMF were evaluated under no salt (0 mM L−1) and three salt (NaCl) concentrations of (25, 50 and 100 mM L−1) using a natural sterilized soil. A significant difference in mycorrhizal colonization intensity, root-to-shoot ratio, P uptake, PUE, and N uptake was observed between the legume species. Salt stress inhibited the shoot and root growth, and reduced P and N uptake by the legume species. Mycorrhizal inoculation aided to mitigate the effects of salt stress with an average increase of shoot and root growth responses by 35% and 32% in the inoculated than in the non-inoculated A. gummifera treatments. The average shoot and root growth responses were 37% and 45% higher in the inoculated compared to the non-inoculated treatments of R. monosperma. Average mycorrhizal shoot and root P uptake responses were 66% and 68% under A. gummifera, and 40% and 95% under R. monosperma, respectively. Mycorrhizal inoculated treatments consistently maintained lower PUE in the roots. The results provide insights for further investigations on the AMF conferred mechanisms to salt stress tolerance response by A. gummifera and R. monosperma, to enable the development of effective technologies for sustainable afforestation and reforestation programs in the Atlantic coast of Morocco.

CO2 × Nitrogen Interaction on Seedling Growth of Four Species of Eucalypt.

1992 ◽  
Vol 40 (5) ◽  
pp. 457 ◽  
Author(s):  
SC Wong ◽  
PE Kriedemann ◽  
GD Farquhar
Keyword(s):  
Leaf Area ◽  
Elevated Co2 ◽  
Eucalyptus Camaldulensis ◽  
Fold Increase ◽  
Wide Distribution ◽  
Growth Responses ◽  
Seedling Vigour ◽  
Co2 Effects ◽  
Whole Plant ◽  
Large Trees

Four eucalypt species were selected to represent two ecologically disparate groups which would be expected to contrast in seedling vigour and in the nature of growth responses to CO2 × nitrogen supply. Eucalyptus camaldulensis and E. cypellocarpa were taken as examples of fast-growing species with a wide distribution, that develop into large trees. By contrast, E. pauciflora and E. pulverulenta become smaller trees, and show a more limited distribution. Seedlings were established in pots (5 L) of a loamy soil and supplied with nutrient solution containing either 1.2 or 6.0 mM NO3- in both ambient (33 Pa) and CO2-enriched (66 Pa) greenhouses. Analysis of growth response to treatments (2 × 2 factorial) was based on destructive harvest of plants sampled on four occasions over 84 days for E. carnaldulensis and E. cypellocarpa, and 100 days for E. pulverulenta and E. pauciflora. A positive CO2 × N interaction on plant dry mass and leaf area was expressed in all species throughout the study period. In E. carnaldulensis and E. cypellocarpa, plant mass was doubled by high N at 33 Pa CO2, compared with a three to four-fold increase at 66 Pa to reach 34g by final harvest. In E. pulverulenta and E. pauciflora, slower growth resulted in about 50% less mass at a given age, but relative increases due to CO2 and N were of a similar order. A distinction can be made between N and CO2 effects on growth processes as follows. When trees were grown on low N, elevated CO2 increased nitrogen-use efficiency (NUE) at both leaf and whole plant levels. On high N, leaf NUE was increased in E. camaldulensis and E. cypellocarpa, but decreased in E. pulverulenta and E. pauciflora. Whole plant NUE showed no consistent response to elevated CO2 when plants were supplied high N. Net assimilation rate (NAR) was increased by elevated CO2 in all species on either N treatment. Moreover, high N increased NAR under either CO2 treatment in all species. There was a positive N × CO2 interaction on NAR in E. carnaldulensis and E. cypellocarpa, but not in E. pulverulenta and E. pauciflora. Growth indices for E. carnaldulensis and E. cypellocarpa species, and especially E. carnaldulensis, generally exceeded those for E. pulverulenta and E. pauciflora in terms of NAR, leaf NUE, N-enhancement of CO2 effects on leaf area and biomass, and non-structural carbohydrate content of foliage.

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