Functional analysis of the relative growth rate, chemical composition, construction and maintenance costs, and the payback time of Coffea arabica L. leaves in response to light and water availability

In this study, the combined effects of light and water availability on the functional relationships of the relative growth rate (RGR), leaf chemical composition, construction and maintenance costs, and benefits in terms of payback time for Coffea arabica are presented. Coffee plants were grown for 8 months in 100% or 15% full sunlight and then a four-month water shortage was implemented. Plants grown under full sunlight were also transferred to shade and vice versa. Overall, most of the traits assessed were much more responsive to the availability of light than to the water supply. Larger construction costs (12%), primarily associated with elevated phenol and alkaloid pools, were found under full sunlight. There was a positive correlation between these compounds and the RGR, the mass-based net carbon assimilation rate and the carbon isotope composition ratio, which, in turn, correlated negatively with the specific leaf area. The payback time was remarkably lower in the sun than in shade leaves and increased greatly in water-deprived plants. The differences in maintenance costs among the treatments were narrow, with no significant impact on the RGR, and there was no apparent trade-off in resource allocation between growth and defence. The current irradiance during leaf bud formation affected both the specific leaf area and leaf physiology upon transferring the plants from low to high light and vice versa. In summary, sun-grown plants fixed more carbon for growth and secondary metabolism, with the net effect of an increased RGR.     

ABIOTIC REGULATION OF INVESTMENT IN SEXUAL VERSUS VEGETATIVE REPRODUCTION IN THE CLONAL KELP LAMINARIA SINCLAIRII (LAMINARIALES,PHAEOPHYCEAE)1

Clonal kelp taxa may reproduce both sexually and vegetatively resulting in a potential trade‐off in the allocation of acquired carbon and nitrogen resources. Such trade‐offs may dictate a different response of clonal kelps to varying environmental conditions relative to aclonal kelp taxa. Laboratory temperature and nutrient manipulation experiments demonstrated that investment in sexual and vegetative reproduction in Laminaria sinclairii (Harv. ex Hook. f. et Harv.) Farl., C. L. Anderson et D. C. Eaton was regulated by different abiotic factors. Sorus production (investment in sexual reproduction) and blade growth were significantly higher at 12°C compared to 17°C, regardless of nutrient concentration. Net carbon storage and depletion in rhizomes were observed in the low‐ and high‐temperature treatments, respectively, suggesting that carbon stores were not responsible for increased growth. Rhizome elongation (investment in vegetative reproduction), on the other hand, was significantly higher in 12 μM NO₃^? than in 2 μM NO₃^?, irrespective of temperature. This increase in rhizome growth was concurrent with elevated rhizome percent tissue nitrogen levels also observed in treatments with higher nutrients, again indicating a growth response to treatment independent of previous nutrient stores. These results suggest that regulation of growth and investment in sexual reproduction in L. sinclairii is similar to that in aclonal kelps (i.e., warmer temperatures result in decreased reproductive output). Additionally, depletion of carbon and nitrogen from rhizomes in suboptimal conditions confirms the role of clonal kelp rhizomes in carbon and nutrient storage.     

Source of nitrogen associated with recovery of relative growth rate in Arabidopsis thaliana acclimated to sustained cold treatment

To determine (1) whether acclimation of carbon metabolism to low temperatures results in recovery of the relative growth rate (RGR) of plants in the cold and (2) the source of N underpinning cold acclimation in Arabidopsis thaliana, we supplied plants with a nutrient solution labelled with ¹⁵N and subjected them to a temperature shift (from 23 to 5 °C). Whole‐plant RGR of cold‐treated plants was initially less than 30% of that of warm‐maintained control plants. After 14 d, new leaves with a cold‐acclimated phenotype emerged, with the RGR of cold‐treated plants increasing by 50%; there was an associated recovery of root RGR and doubling of the net assimilation rate (NAR). The development of new tissues in the cold was supported initially by re‐allocation of internal sources of N. In the longer term, the majority (80%) of N in the new leaves was derived from the external solution. Hence, both the nutrient status of the plant and the current availability of N from external sources are important in determining recovery of growth at low temperature. Collectively, our results reveal that both increased N use efficiency and increases in nitrogen content per se play a role in the recovery of carbon metabolism in the cold.     

海草生物量和初级生产力研究进展

海草床是近岸重要的湿地生态系统,具有较高生物量和生产力。海草的生物量和生产力变化除了受到光照、无机碳源、营养盐、温度、盐度、水动力条件、铁限制和污染物等非生物因素制约外,还受到附生藻类和动物摄食等生物因素影响。非生物因素一般有最适合海草生长的范围,生物因素的影响具有两面性。海草生物量和生产力研究基本处于由定性向定量过渡阶段,准确便捷的方法、现场多因子围隔实验、更大时空尺度上的对比研究是今后研究的重点。     

Abiotic influences on bicarbonate use in the giant kelp,Macrocystis pyrifera,in the Monterey Bay

In the Monterey Bay region of central California, the giant kelp Macrocystis pyrifera experiences broad fluctuations in wave forces, temperature, light availability, nutrient availability, and seawater carbonate chemistry, all of which may impact their productivity. In particular, current velocities and light intensity may strongly regulate the supply and demand of inorganic carbon (Ci) as substrates for photosynthesis. Macrocystis pyrifera can acquire and utilize both CO₂ and bicarbonate (HCO₃^?) as Ci substrates for photosynthesis and growth. Given the variability in carbon delivery (due to current velocities and varying [DIC]) and demand (in the form of saturating irradiance), we hypothesized that the proportion of CO₂ and bicarbonate utilized is not constant for M. pyrifera, but a variable function of their fluctuating environment. We further hypothesized that populations acclimated to different wave exposure and irradiance habitats would display different patterns of bicarbonate uptake. To test these hypotheses, we carried out oxygen evolution trials in the laboratory to measure the proportion of bicarbonate utilized by M. pyrifera via external CA under an orthogonal cross of velocity, irradiance, and acclimation treatments. Our Monterey Bay populations of M. pyrifera exhibited proportionally higher external bicarbonate utilization in high irradiance and high flow velocity conditions than in sub‐saturating irradiance or low flow velocity conditions. However, there was no significant difference in proportional bicarbonate use between deep blades and canopy blades, nor between individuals from wave‐exposed versus wave‐protected sites. This study contributes a new field‐oriented perspective on the abiotic controls of carbon utilization physiology in macroalgae.     

Maximum Fruit Growth Potential Following Resource Limitation During Peach Growth

To achieve its maximum organ growth potential, an organ mustgrow at its potential relative growth rate (RGR) throughoutdevelopment. When resource availability limits growth, the RGRis reduced below the potential RGR. This study examines whether,following a period of resource-limited growth, the RGR is ableto increase to the potential RGR when sufficient resources areavailable. Fruit RGRs of a late maturing peach cultivar wereexamined following removal of most of the fruits (heavy thinning)from previously unthinned trees in Apr., May, and Jun. The fruitRGRs after imposition of the thinning treatments were higherthan those on unthinned trees during source-limited periodsof the growing season, suggesting that fruit RGR can increasein response to increased resource availability. In general,the RGRs of fruits of trees thinned in Apr., May, and Jun. didnot exceed those of fruits on trees thinned at bloom, suggestingthat heavy thinning at bloom provides a reasonable estimateof the potential RGR. There were times, however, when the effectsof competition with vegetative sinks were apparent, suggestingthat the RGR of fruits on trees that were heavily thinned atbloom may underestimate the potential RGR during these times.The absolute growth rates of fruits on thinned trees were greaterthan those on unthinned trees, but generally were not greaterthan those on trees that were thinned at bloom, suggesting thatpeach fruits are unable to recover potential growth lost duringresource-limited growth periods.Copyright 1995, 1999 AcademicPress Prunus persica (L.) Batsch, peach, maximum fruit growth potential, relative growth rate, absolute growth rate, thinning, fruit-fruit competition, resource availability, resource limitation, growth analysis     

The effects of calcium in mediating the inducible morphological defenses of a freshwater snail,Physa acuta

Predation risk is known to induce numerous, often adaptive, plastic changes in the morphology, life history, and behavior of prey. However, little is known about how abiotic factors such as environmental nutrient availability affect these responses. In this experiment, a freshwater pulmonate snail (Physa acuta) was used to determine how predator-induced shell morphology was affected by the availability of an abiotic nutrient important for shell growth (calcium). Each snail was reared individually in a factorial experiment consisting of two predator treatments (chemical cues from crayfish present or absent) and three calcium concentrations (20, 45, or 70 mg/L). Calcium induced larger, heavier, and thicker shells, while predator cues induced heavier and thicker shells. Importantly, the magnitude of the predator effect on shell thickness (i.e., the inducible defense) increased with additional calcium availability. Our results demonstrate the importance of nutrient availability in mediating and limiting the amount of adaptive predator-induced plasticity.     

CO2 enrichment reduces the relative contribution of latex and latex-related hydrocarbons to biomass in Euphorbia lathyris

The hypothesis that plants grown under elevated CO₂ allocate more carbon to the production of latex and C‐rich secondary compounds whereas nutrient addition counteracts this effect was tested. Two similar experiments were conducted in two different experimental facilities. In both facilities seedlings of Euphorbia lathyris were exposed to factorial combinations of two CO₂ concentrations and two levels of nutrient availability for 2 months. The CO₂ treatments and growth conditions differed substantially between these two experiments but treatment responses to elevated CO₂ and fertilizer addition were remarkably similar, underlining the robustness of our findings. Elevated CO₂ increased biomass to a greater extent in fertilized than in unfertilized plants and reduced the leaf biomass fraction by accelerating leaf senescence. Concentrations of non‐structural carbohydrates (NSC) increased in elevated CO₂. However, this apparent carbon surplus did not feed into the whole plant latex pool. The latex harvest per leaf (?25%) and the concentration of latex‐related hydrocarbons (?20%) even decreased under elevated CO₂ (both experiments P < 0.05). Fertilization reduced NSC concentrations (?25%) but neither affected latex yield per leaf nor the concentration of latex‐related hydrocarbons. It is concluded that latex and related hydrocarbons in CO₂‐enriched plants are a negligible sink for excess carbon irrespective of nutrient status and thus, vigour of growth.     

Effects of irradiance during growth on tolerance of geranium to sub- and supra-optimal boron supply

In our previous study on geranium, we showed that increases in growth irradiance from sub-optimal to near-optimal could delay boron deficiency effects on photosynthesis. In this study, we further investigated the effects of growth irradiance on tolerance to B stress by growing geranium (Pelargonium × hortorum cv. Maverick White) under sub- to supra-optimal B concentrations (4.5, 45, and 450 μM) and under three irradiances of 100, 300, or 500 μmol m^?2 s^?1 PAR for 30 d. In general, at low and medium irradiances, sub- and supra-optimal B availability decreased root and shoot dry masses, but at high irradiance, the B stress was prevented. Net photosynthetic rate decreased by the supra-optimal B concentration at the high irradiance only suggesting B-related photoinhibition. Tissue B content and root specific B uptake only modestly decreased by the low B treatment, but increased greatly by the high B availability, and the higher irradiance decreased the tissue B content and the root B uptake only at the low and medium B supplies. Interestingly, the increases in irradiance decreased the content and uptake of all other nutrients, except Fe uptake. Effects of the B stress on the content of other nutrients were variable, but the B stress often exacerbated decreases in nutrient content with the increasing irradiance which would be especially important under nutrient-limiting conditions. Hence, in this study, the B stress effects on growth were mitigated by the increases in growth irradiance, which offset negative effects on physiology, and the protective effects of irradiance were likely caused by its positive effects on plant carbon/energy status rather than on tissue B content or B uptake.     

Effects of nutrient enrichment and herbivory on morphology,reproduction and chemical content of Turbinaria conoides (Phaeophyceae)

The effects of nutrient enrichment and herbivory on resource allocation patterns among morphology, reproduction, and chemical content of the brown alga, Turbinaria conoides (J. Agardh) Kützing were tested in the shallow subtidal zone of the Gulf of Thailand. The field experimental design comprised 36 plots (50 × 50 cm²) with and without herbivores, and two nutrient levels. Cages (uncaged and fully caged plots) were used to exclude herbivorous fishes and two nutrients levels were achieved by experimental enrichment above ambient nutrient concentrations. For morphology of Turbinaria, the maximum length (holdfast to frond apex), the width of the base of the stipe, number of blades, holdfast and stipe diameter were measured. Biomass, reproductive output, and tissue nutrient (carbon: nitrogen: phosphorus) content of T. conoides were examined. Phlorotannin concentrations were examined using a modified Folin‐Ciocalteu method. The results showed that herbivory had no effect on morphology, reproduction, or phlorotannin concentrations. This could be due to the structural and morphological deterrents of alga, which might minimize grazing effects from herbivorous fishes. Nutrient enrichment had no effect on morphology and reproduction of T. conoides, possibly due to low nutrient demand in Turbinaria. However, nutrient enrichment did affect phlorotannin concentrations, as phlorotannins in the enriched plots were lower than the ambient plots. These results support, in part, the carbon–nutrient balance hypothesis that states algae will allocate fewer resources to production of anti‐herbivore chemical compounds when enriched with potential growth‐limiting nutrients.     

Epiphytic bromeliads in a changing world: the effect of elevated CO2 and varying water supply on growth and nutrient relations

• Global climate change is likely to impact all plant life. Vascular epiphytes represent a life form that may be affected more than any other by possible changes in precipitation leading to water shortage, but negative effects of drought may be mitigated through increasing levels of atmospheric CO₂.
• We studied the response of three epiphytic Aechmea species to different CO₂ and watering levels in a full‐factorial climate chamber study over 100 days. All species use crassulacean acid metabolism (CAM). Response variables were relative growth rate (RGR), nocturnal acidification and foliar nutrient levels (N, P, K, Mg).
• Both elevated CO₂ and increased water supply stimulated RGR, but the interaction of the two factors was not significant. Nocturnal acidification was not affected by these factors, indicating that the increase in growth in these CAM species was due to higher assimilation in the light. Mass‐based foliar nutrient contents were consistently lower under elevated CO₂, but most differences disappeared when expressed on an area basis.
• Compared to previous studies with epiphytes, in which doubling of CO₂ increased RGR, on average, by only 14%, these Aechmea species showed a relatively strong growth stimulation of up to +61%. Consistent with earlier findings with other bromeliads, elevated CO₂ did not mitigate the effect of water shortage.

     

The role of light availability and herbivory on algal responses to nutrient enrichment in a riparian wetland,Alaska

We investigated how the relative availability of solar radiation in the presence or absence of grazing alters the ability of benthic algae to respond to nutrient enrichment in an Alaskan marsh. We used a factorial mesocosm experiment that included nutrient enrichment (enriched or control), grazing (grazed or ungrazed), and light (unshaded or shaded) to simulate shading by macrophytes early and late in the growing season, respectively. We found stronger effects of grazers and nutrients compared to light on benthic algal biomass and taxonomic composition. Algal biomass increased in nutrient‐enriched treatments and was reduced by grazing. Shading did not have an effect on algal biomass or taxonomic composition, but the concentration of chl a per algal biovolume increased with shading, demonstrating the ability of algae to compensate for changes in light availability. Algal taxonomic composition was more affected by grazer presence than nutrients or light. Grazer‐resistant taxa (basal filaments of Stigeoclonium) were replaced by diatoms (Nitzschia) and filamentous green algae (Ulothrix) when herbivores were removed. The interacting and opposing influences of nutrients and grazing indicate that the algal community is under dual control from the bottom‐up (nutrient limitation) and from the top‐down (consumption by herbivores), although grazers had a stronger influence on algal biomass and taxonomic composition than nutrient enrichment. Our results suggest that low light availability will not inhibit the algal response to elevated nutrient concentrations expected with ongoing climate change, but grazers rapidly consume algae following enrichment, masking the effects of elevated nutrients on algal production.     

Effects of irradiance, water temperature and nutrients on the growth of sporelings of the crustose coralline alga Lithophyllum yessoense Foslie (Corallinales, Rhodophyceae)

Lithophyllum yessoense Foslie is a markedly dominant subtidal, crustose coralline alga in south–western Hokkaido, Japan. In this study, the effects of irradiance, water temperature and nutrients (nitrate and phosphate) on the growth of sporelings of the alga were examined. The relative growth rate (RGR) was saturated at 17.6% d^?1 at a high irradiance (240 umol photon m²s^?1). Even at a low irradiance (10.7–49.9 umol photon m^?2s^?1), RGR was 7.1–12.7% d^?1 The survival rate of sporelings was greater than 80% at irradiance above 10.7 μmol photon m^?2s^?1 throughout the culture period. The growth of L. yessoense sporelings was promoted at 15°C and 20°C, but inhibited at 5°C. The half‐saturation constants (Ks) for growth were about 0.5 umol L^?1 and 0.14 umol L^?1 for nitrate and phosphate, respectively. Saturated nitrate and phosphate concentrations for the growth were about 4.0 μmol L^?1 and 0.4 μmol L^?1, respectively, suggesting that L. yessoense is adaptable to a relatively high water temperature, a wide range of irradiance, and low ambient nitrate and phosphate concentrations. The results provide a possible explanation of why L. yessoense is dominant in the environments of south‐western Hokkaido.     

Effects of warming on annual production and nutrient‐use efficiency of aquatic mosses in a high Arctic lake

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Light availability regulates the response of algae and heterotrophic bacteria to elevated nutrient levels and warming in a northern boreal peatland

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Growth, cell walls, and UDP-Glc dehydrogenase activity of Arabidopsis thaliana grown in elevated carbon dioxide

The impact of elevated CO₂ (1000 μmol/mol) was assessed on the common weed,Arabidopsis thaliana (Landsberg erecta), which is used as a model plant system. Elevated CO₂ stimulated relative growth rate (RGR) and leaf area gain ofArabidopsis beginning from the cotyledon stage and continuing through the juvenile stage. This early advantage in growth enabled the plants grown in elevated CO₂ to gain more DW despite similar RGRs throughout the latter stages of development. The greater accumulation of DW in leaves grown in elevated CO₂ resulted in a lower specific leaf area (SLA). However, the amount of cell wall investment per unit of leaf area, specific “wall” area (SWA), was similar indicating that elevated CO₂ did not affect the distribution of cell carbon to the cell wall of leaves beyond that needed for cell and leaf expansion. Furthermore, cell wall composition changed with time due to developmental changes and was not affected by elevated CO₂. Associated with the increase in RGR by elevated CO₂ was a concomitant increase in the activity of UDP-Glc dehydrogenase (E.C. 1.1.1.22), a key enzyme in the nucleotide-sugar interconversion pathway necessary for biosynthesis of many cell-wall polysaccharides.     

Impacts of elevated terrestrial nutrient loads and temperature on pelagic food‐web efficiency and fish production

Both temperature and terrestrial organic matter have strong impacts on aquatic food‐web dynamics and production. Temperature affects vital rates of all organisms, and terrestrial organic matter can act both as an energy source for lower trophic levels, while simultaneously reducing light availability for autotrophic production. As climate change predictions for the Baltic Sea and elsewhere suggest increases in both terrestrial matter runoff and increases in temperature, we studied the effects on pelagic food‐web dynamics and food‐web efficiency in a plausible future scenario with respect to these abiotic variables in a large‐scale mesocosm experiment. Total basal (phytoplankton plus bacterial) production was slightly reduced when only increasing temperatures, but was otherwise similar across all other treatments. Separate increases in nutrient loads and temperature decreased the ratio of autotrophic:heterotrophic production, but the combined treatment of elevated temperature and terrestrial nutrient loads increased both fish production and food‐web efficiency. CDOM: Chl a ratios strongly indicated that terrestrial and not autotrophic carbon was the main energy source in these food webs and our results also showed that zooplankton biomass was positively correlated with increased bacterial production. Concomitantly, biomass of the dominant calanoid copepod Acartia sp. increased as an effect of increased temperature. As the combined effects of increased temperature and terrestrial organic nutrient loads were required to increase zooplankton abundance and fish production, conclusions about effects of climate change on food‐web dynamics and fish production must be based on realistic combinations of several abiotic factors. Moreover, our results question established notions on the net inefficiency of heterotrophic carbon transfer to the top of the food web.     

Effects of light and soil water availability on leaf photosynthesis and growth of Arisaema heterophyllum,a riparian forest understorey plant

The effects of soil-water availability on leaf light acclimation and whole-plant carbon gain were examined in Arisaema heterophyllum Blume, a riparian deciduous forest understorey plant. Photosynthesis, above-ground morphology and ramet biomass accumulation (relative growth rate: RGR of a corm for a full leaf life-span) were measured on plants raised under three light treatments combined with two soil water conditions. The two higher light treatments during growth (high: max. 550 μmol photons m^–2 s^–1; medium: 150 μmol photons m^–2 s^–1) resulted in a twofold increase in RGRs, 30% higher photosynthetic capacities and 20% less photosynthetic low-light use efficiency than those under a low light condition (50 μmol photons m^–2 s^–1). Leaf area was the smallest and leaf mass area ratio was the largest under the high light treatment. Water stress decreased both photosynthetic rate and leaf area and, hence, RGR in all the light regimes. However, water stress did not alter the general patterns of physiological and morphological responses to different light regimes. We estimated that higher photosynthetic low-light use efficiency and larger leaf area in the low light leaf would lead to a threefold carbon gain as compared with the high light leaf under simulated low light conditions. Both experimental and simulation results suggest that the physiological and morphological acclimations tend to be beneficial to carbon gain when light availability is low, whereas they favor increased water use efficiency when light availability is sufficiently high. Electronic Publication     

Chronic catchment nitrogen enrichment and stoichiometric constraints on the bioavailability of dissolved organic matter from leaf leachate

1. Chronic nitrogen (N) deposition may alter the bioavailability of dissolved organic matter (DOM) in streams by multiple pathways. Elevated N deposition may alter the nutrient stoichiometry of DOM as well as nutrient availability in stream water. 2. We evaluated the influence of a decadal‐scale experimental N enrichment on the relative importance of DOM nutrient content and inorganic nutrient availability on the bioavailability of DOM. We measured the consumption of dissolved organic carbon (DOC) and changes in nutrient concentration, DOM components and enzyme activity in a bottle incubation assay with different DOM and nutrient treatments. To evaluate the effect of DOM stoichiometry, we used leaf leachates of different carbon/N/phosphorus (C : N :P) ratio, made from leaf litter sourced in the reference and N‐enriched catchments at the Bear Brook Watershed in Maine (BBWM). We also manipulated the concentration of inorganic N and P to compare the effect of nutrient enrichment with DOM stoichiometry. 3. DOC from the N‐enriched catchment was consumed 14% faster than that from the reference catchment. However, mean DOC consumption for both leachates was more than doubled by the simultaneous addition of N and P, compared to controls, while the addition of N or P alone increased consumption by 42 and 23%, respectively. The effect of N and/or P enrichment consistently had a greater effect than DOM source for all response variables considered. 4. We subsequently conducted DOC uptake measurements using leaf leachate addition under ambient and elevated N and P in the streams draining the reference and N‐enriched catchments at BBWM. In both streams, DOC uptake lengths were shorter when N and P were elevated. 5. Although both DOM stoichiometry and inorganic nutrient availability affect DOM bioavailability, N and P co‐limitation appears to be the dominant driver of reach‐scale processing of DOM.     

Seedling growth of five tropical dry forest tree species in relation to light and nitrogen gradients

Aims Increasing anthropogenic nitrogen (N) deposition has been claimed to induce changes in species composition and community dynamics. A greenhouse experiment was conducted to examine the effect of increased N availability on growth and functional attributes of seedlings of five tree species with different life history characteristics under varying irradiances. The following questions have been addressed: (i) how do the pioneer and non-pioneer species respond in absolute growth and relative growth rate (RGR) to the interaction of light and nitrogen? (ii) how does the interaction between irradiance and nitrogen availability modulate growth attributes (i.e. functional attributes)? (iii) is there any variation in growth responses between leguminous and non-leguminous species along the light and nitrogen gradients?Methods Seedlings of five tree species (Acacia catechu, Bridelia retusa, Dalbergia sissoo, Lagerstroemia parviflora and Terminalia arjuna) were subjected to twelve combinations of irradiance and N levels. Various growth traits, including height (HT), basal area (BA), whole plant dry biomass (M D), leaf mass per unit area (LMA), leaf area ratio (LAR), net assimilation rate (NAR), RGR, biomass fractions, root-to-shoot ratio (R:S) and leaf nitrogen content, were studied to analyse intra- and inter-specific responses to interacting light and N gradients.Important findings Significant interactions for irradiance and N availability for majority of growth attributes indicates that growth and biomass allocation of seedlings were more responsive to N availability under high irradiance. However, species responded differentially to N addition and they did not follow successional status. Slow growers (B. retusa, a shade-tolerant species and L. parviflora, a light demander) exhibited greater response to N enrichment than the fast growers (A. catechu, D. sissoo and T. arjuna). However, N-mediated increment in growth traits was greater in non-legumes (B. retusa, L. parviflora and T. arjuna) compared with that of legumes (A. catechu and D. sissoo). Allocation of biomass to root was strongly suppressed at the highest N supply across species; however, at high irradiance and high N availability, a greater suppression in R:S ratio was observed for B. retusa. NAR was a stronger determinant of RGR relative to LAR, suggesting its prominent role in increased RGR along increasing irradiances. Overall, a higher growth response of slow-growing species to elevated N levels, particularly the non-pioneers (B. retusa and L. parviflora) suggests that future N deposition may lead to perturbations in competition hierarchies and species composition, ultimately affecting community dynamics in nutrient-poor tropical dry forests.