Diurnal variation of root respiration rates and nitrate uptake as influenced by nitrogen supply

Root respiration rates of Lolium multiflorum supplied with nitrate or ammonium were measured continuously during several days (Exp. A). Net uptake rate of nitrate was similarly measured by an ion selective nitrate electrode in a system of flowing nutrient solution (Exp. B). Diurnal variation of in vitro nitrate reductase activity and nitrate content of tops and roots were determined (Exp. C). Two levels of irradiance were applied throughout, with day:night of 16:8 h. Root respiration rates showed diurnal patterns, most pronounced in the nitrate treatment, with two peaks appearing about 6 and 16 h after commencement of the photoperiod. Respiration rates were highest in the nitrate treatment and at high irradiance. Respiration rates fell after removal of nitrogen, particularly in the nitrate supplied plant and at high irradiance. Net uptake rate of nitrate exhibited diurnal patterns, often with two peaks occurring at the same times as those of respiration rates. In vitro nitrate reductase activity of tops increased steeply 16 h after commencement of the photoperiod and remained at the high level during the following 8 h of darkness. Nitrate content of tops was highest during the 8 h dark period and fell at the start of the photoperiod. Possible controlling systems of the apparent coincidences of diurnal variation rates, net nitrate uptake and nitrate reduction are discussed.     

Effect of decreased irradiance on N and C metabolism in leaves and roots of maize

The effects of decreased irradiance on fresh and dry weight, root respiration, levels of carbohydrates and N-compounds, and extractable activities of enzymes involved in C and N metabolism were evaluated in maize ( Zea mays L. cv. Plauto) seedlings during the 7 days following transfer from 450 to 200 μmol m⁻² s⁻¹ PAR. The fresh weight of roots and stems, the initiation of new leaves, root respiration rate, and the accumulation of dry matter, soluble sugars, starch, malate and amino acids in both leaves and roots were strongly reduced at low irradiance. In contrast, the level of nitrate was increased in leaves and only marginally affected in roots. Leaf phosphoenolpyruvate carboxylase (EC 4.1.1.31) activity started to decrease after 24–34 h, whereas ribulose-1,5-bisphosphate carboxylase (EC 4.1.1.39) activity and chlorophyll content were unaffected or only slightly reduced. In both leaves and roots, the adjustment of N metabolism to low irradiance occurred through a relatively rapid (30% after 10 h) and large (60% after 3 days) decrease of nitrate reductase (NR; EC 1.6.6.1) activity, followed by slower and smaller changes in the activity of nitrite reductase (EC 1.7.7.1), glutamine synthetase (EC 6.3.1.2) and NAD-dependent glutamate dehydrogenase (EC 1.4.1.2). We suggest that the preferential decrease of NR activity relative to other N-assimilating enzymes may be important for preventing the accumulation of toxic N-compounds like ammonia in both leaf and root tissues.     

Partitioning of inorganic nitrogen assimilation between the roots and shoots of cerrado and forest trees of contrasting plant communities of South East Brasil

Summary Woody plants growing in cerrado and forest communities of south-east Brasil were found to have low levels of nitrate reductase activity in their leaves suggesting that nitrate ions are not an important nitrogen source in these communities. Only in the leaves of species growing in areas of disturbance, such as gaps and forest margins, were high levels of nitrate reductase present. When pot-grown plants were supplied with nitrate, leaves and roots of almost all species responded by inducing increased levels of nitrate reductase. Pioneer or colonizing species exhibited highest levels of nitrate reductase and high shoot: root nitrate reductase activities. Glutamine synthetase, glutamate synthase and glutamate dehydrogenase were present in leaves and roots of the species examined.¹⁵N-labelled nitrate and ammonium were used to compare the assimilatory characteristics of two species:Enterolobium contortisiliquum, with a high capacity to reduce nitrate, andCalophyllum brasiliense, of low capacity. The rate of nitrate assimilation in the former was five times that of the latter. Both species had similar rates of ammonium assimilation. Results for eight species of contrasting habitats showed that leaf nitrogen content increased in parallel with xylem sap nitrogen concentrations, suggesting that the ability of the root system to acquire, assimilate or export nitrate determines shoot nitrogen status. These results emphasise the importance of nitrogen transport and metabolism in roots as determinants of whole plant nitrogen status.     

Nitrate reductase and glutamine synthetase activities in relation to growth and nitrogen assimilation in red oak and red ash seedlings: effects of N-forms,N concentration and light intensity

The effects of growing seedlings of red oak (Quercus rubra) and red ash (Fraxinus pennsylvanica) with Hoagland solutions containing five N-regimes, differing in the N-forms (NH₄, NO₃) and concentrations (High and Low), in relation to light intensity were investigated by the utilization of enzymatic markers of the N assimilation pathway, nitrate reductase (NR) and glutamine synthetase (GS). Red oak and red ash showed different patterns of N-assimilation. Red oak seedlings assimilated NO₃ in low amounts in their roots and leaves, whereas red ash seedlings assimilated high amounts of NO₃, mostly in the leaves. A significant amount of constitutive NR activity was found in red oak seedlings supplied with NH₄ N-regime. This could be characteristic of a species adapted to soils that are poor in nitrogen. Root GS activity was lower in red oak seedlings than in red ash seedlings, indicating that the rate of NH₄ assimilation differed in these two hardwood species. Low irradiance reduced growth of both hardwood species, but greatly affected the specific leaf area of red ash and reduced NO₃ assimilation (when data are expressed per leaf area). Both species reacted similarly to N-regimes in terms of relative growth rate.     

ALLOCATION,GROWTH RATES AND GAS EXCHANGE IN SEEDLINGS OF STEPHANOMERIA EXIGUA SSP. CORONARIA AND ITS RECENT DERIVATIVE S. MALHEURENSIS

The annual diploid plant species Stephanomeria malheurensis is known only from a single locality where it grows interspersed with its progenitor S. exigua ssp. coronaria. S. malheurensis is thought to have originated recently at its present site and, consequently, serves as a model to study how the phenotype of a species is assembled following its origin. The following were examined in the present study: dry matter allocation, growth parameters, net photosynthesis, and dark respiration of seedlings under three temperatures in order to identify specific features of the new species that might relate to its ecological properties. Under each test condition, S. malheurensis had leaves with a significantly smaller surface area, greater dry weight per unit area, heavier roots, and a higher root/shoot ratio. Both species had similar relative growth rates during the measured period of rosette growth, but in S. malheurensis this resulted from the combination of a lower leaf area ratio and a higher net assimilation rate, whereas in ssp. coronaria it resulted from the opposite combination. The mean rates of apparent net photosynthesis and dark respiration were similar in both species. The differences between the species may reflect the establishment of genes in S. malheurensis which still are present in ssp. coronaria. The implications of this and the possible ecological significance are discussed.     

Effects of geminivirus infection and growth irradiance on the vegetative growth and photosynthetic production of Eupatorium makinoi

Eupatorium makinoi plants with or without geminivirus infection were grown in shading frames with 70, 15 and 5.5% sunlight. Growth characteristics of these plants in the early vegetative phase were compared by means of growth analysis. We also measured leaf photosynthetic gas exchange rates and examined relationships between leaf photosynthesis and whole-plant growth. Relative growth rate (RGR=(1/W)×(dW/dt), where W is plant dry mass) of virus-infected plants was lower than that of uninfected plants under all three light conditions. The reduction of RGR by infection was increased with irradiance. The net assimilation rate (NAR=(1/A)×(dW/dt), where A is total leaf area of the plant) was also reduced both by infection and shading. NARs that were estimated from light-response curves of leaf photosynthesis, in situ measurements of irradiance, and respiration rates of leaves, stems and below-ground parts, agreed very well with the values obtained by conventional growth analysis techniques. Decreases in the estimated NAR value from infection and shading were mostly explained by the decreases in leaf photosynthesis. These results clearly showed that lowered RGR in virus-infected plants was attributed mainly to impaired photosynthesis in virus-infected leaves.     

Growth and reproduction of Arabidopsis thaliana in relation to storage of starch and nitrate in the wild-type and in starch-deficient and nitrate-uptake-deficient mutants

We have investigated the interactions between resource assimilation and storage in rosette leaves, and their impact on the growth and reproduction of the annual species Arabidopsis thaliana. The resource balance was experimentally perturbed by changing (i) the external nutrition, by varying the nitrogen supply; (ii) the assimilation and reallocation of resources from rosette leaves to reproductive organs, by cutting or covering rosette leaves at the time of early flower bud formation, and (iii) the internal carbon and nitrogen balance of the plants, by using isogenic mutants either lacking starch formation (PGM mutant) or with reduced nitrate uptake (NU mutant). When plants were grown on high nitrogen, they had higher concentrations of carbohydrates and nitrate in their leaves during the rosette phase than during flowering. However, these storage pools did not significantly contribute to the bulk flow of resources to seeds. The pool size of stored resources in rosette leaves at the onset of seed filling was very low compared to the total amount of carbon and nitrogen needed for seed formation. Instead, the rosette leaves had an important function in the continued assimilation of resources during seed ripening, as shown by the low seed yield of plants whose leaves were covered or cut off. When a key resource became limiting, such as nitrogen in the NU mutants and in plants grown on a low nitrogen supply, stored resources in the rosette leaves (e.g. nitrogen) were remobilized, and made a larger contribution to seed biomass. A change in nutrition resulted in a complete reversal of the plant response: plants shifted from high to low nutrition exhibited a seed yield similar to that of plants grown continuously on a low nitrogen supply, and vice versa. This demonstrates that resource assimilation during the reproductive phase determines seed production. The PGM mutant had a reduced growth rate and a smaller biomass during the rosette phase as a result of changes in respiration caused by a high turnover of soluble sugars ( Caspar et al. 1986 ; W. Schulze et al. 1991 ). During flowering, however, the vegetative growth rate in the PGM mutant increased, and exceeded that of the wild-type. By the end of the flowering stage, the biomass of the PGM mutant did not differ from that of the wild-type. However, in contrast to the wild-type, the PGM mutant maintained a high vegetative growth rate during seed formation, but had a low rate of seed production. These differences in allocation in the PGM mutant result in a significantly lower seed yield in the starchless mutants. This indicates that starch formation is not only an important factor during growth in the rosette phase, but is also important for whole plant allocation during seed formation. The NU mutant resembled the wild-type grown on a low nitrogen supply, except that it unexpectedly showed symptoms of carbohydrate shortage as well as nitrogen deficiency. In all genotypes and treatments, there was a striking correlation between the concentrations of nitrate and organic nitrogen and shoot growth on the one hand, and sucrose concentration and root growth on the other. In addition, nitrate reductase activity (NRA) was correlated with the total carbohydrate concentration: low carbohydrate levels in starchless mutants led to low NRA even at high nitrate supply. Thus the concentrations of stored carbohydrates and nitrate are directly or indirectly involved in regulating allocation.     

Growth and carbon economy of a fast-growing and a slow-growing grass species as dependent on nitrate supply

In previous experiments systematic differences have been found in the morphology, carbon economy and chemical composition of seedlings of inherently fast- and slow-growing plant species, grown at a non-limiting nutrient supply. In the present experiment it was investigated whether these differences persist when plants are grown at suboptimal nutrient supply rates. To this end, plants of the inherently fast-growing Holcus lanatus L. and the inherently slow-growing Deschampsia flexuosa (L.) Trin. were grown in sand at two levels of nitrate supply. Growth, photosynthesis, respiration and carbon and nitrogen content were studied over a period of 4 to 7 weeks. At low N-supply, the potentially fast-growing species still grew faster than the potentially slow-growing one. Similarly, differences in leaf area ratio (leaf area:total dry weight), specific leaf area (leaf area:leaf dry weight) and leaf weight ratio (leaf dry weight:total dry weight), as observed at high N-supply persisted at low N-availability. The only growth parameter for which a substantial Species × N-supply interaction was found was the net assimilation rate (increase in dry weight per unit leaf area and time). Rates of photosynthesis, shoot respiration and root respiration, expressed per unit leaf, shoot and root weight, respectively, were lower for the plants at low N-availability and higher for the fast-growing species. Species-specific variation in the daily carbon budget was mainly due to variation in carbon fixation. Lower values at low N were largely determined by both a lower C-gain of the leaves and a higher proportion of the daily gain spent in root respiration. Interspecific variation in C-content and dry weight:fresh weight ratio were similar at low and high N-supply. Total plant organic N decreased with decreasing N-supply, without differences between species. It is concluded that most of the parameters related to growth, C-economy and chemical composition differ between species and/or are affected by N-supply, but that differences between the two species at high N-availability persist at low N-supply.     

Root Respiration and Growth in Plantago major as Affected by Vesicular-Arbuscular Mycorrhizal Infection

Effects of vesicular-arbuscular mycorrhizal (VAM) infection and P on root respiration and dry matter allocation were studied in Plantago major L. ssp. pleiosperma (Pilger). By applying P, the relative growth rate of non-VAM controls and plants colonized by Glomus fasciculatum (Thaxt. sensu Gerdemann) Gerdemann and Trappe was increased to a similar extent (55-67%). However, leaf area ratio was increased more and net assimilation rate per unit leaf area was increased less by VAM infection than by P addition. The lower net assimilation rate could be related to a 20 to 30% higher root respiration rate per unit leaf area of VAM plants. Root respiration per unit dry matter and specific net uptake rates of N and P were increased more by VAM infection than by P addition. Neither the contribution of the alternative respiratory path nor the relative growth rate could account for the differences in root respiration rate between VAM and non-VAM plants. It was estimated that increased fungal respiration (87%) and ion uptake rate (13%) contributed to the higher respiratory activity of VAM roots of P. major.     

Differential effect of irradiance and nutrient nitrate on the relationship of in vivo and in vitro nitrate reductase assay in chlorophyllous tissues

Growth at increasing continuous irradiance (at high nutrient nitrate) and nutrient nitrate concentrations (at high continuous irradiance) furnished increases in the in vivo and in vitro nitrate reductase activities of corn (Zea mays L.), field peas (Pisum arvense L.), wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), and globe amaranth (Gomphrena globosa L.) leaves and of marrow (Cucurbita pepo L.) cotyledons. Ratios of in vivo to in vitro activity declined exponentially in all species with increasing nitrate reductase levels promoted by nutrient nitrate. The ratios were more nearly independent of nitrate reductase levels generated by adjusting the irradiance; major exceptions were marrow and wheat at low (1.5 klux and less) irradiances and peas throughout the irradiance range, where decreases in the ratio were accompanied by increases in in situ nitrate concentration. The ratio also increased at the highest irradiance (39.2 klux) in wheat and barley, associated with a decline of in vitro nitrate reductase. These differences in response to irradiance and nutrient nitrate indicate that the in vivo assay does not provide a simple measure of nitrate reductase but rather yields a more composite measure of nitrate reduction, possibly related both to nitrate reductase level and to the supply of reductant for in vivo activity.     

Plasticity in relative growth rate and its components following a change in irradiance

A total of 244 plants from two species, Lythrum salicaria and Epilobium glandulosum, were grown individually in hydroponic sand culture from seed for 36 d. Until day 27 all plants experienced an irradiance of 550 μmol m^?2 s^?1 PFD and on day 27 half of the plants were subjected to a neutral shade treatment in which irradiance was reduced to 100 μmol m^?2 s^?1 photon fluy density (PFD). Measures of relative growth rate, net assimilation rate, specific leaf area, biomass partitioning to leaves, roots, structural tissues (i.e. stems, petioles and inflorescences) and tissue density were obtained from intensive harvests three or four times per day. The shade treatment caused an immediate decrease in relative growth rate and net assimilation rate. Within hours the specific leaf area of the shaded plants increased and leaf tissue density decreased, thus partially offsetting the decrease in relative growth rate. Biomass partitioning was not affected.     

Effect of withdrawal of phosphorus on nitrate assimilation and PEP carboxylase activity in tomato

Tomato plants (Lycopersicon esculentum) grown in a complete nutrient solution for 8 days were transferred to a P-free solution of pH 6.0. Within 2 days of transfer the rate of alkalinization of the nutrient solution declined and by 4 days the solution had become acid. Nitrate transferred from roots to leaves was depressed over this period, and the rate of nitrate reductase activity in the leaves (the main site of assimilation of nitrate in tomato) had declined by 60% within 5 days of transfer. The activity of PEP carboxylase in the leaves of the P-deficient plants increased after 3 days, eventually becoming 3 times greater than in the leaves of plants adequately supplied with P. The PEP carboxylase activity in the roots of the P-deficient plants increased within 2 days, becoming 4 times greater after 8 days' growth. These results are discussed in relation to mechanisms for enhancement of P acquisition and maintenance of cation and anion uptake during P-deficiency.     

Effect of irradiance during growth of Glycine max on photosynthetic capacity and percent activation of ribulose 1,5-bisphosphate carboxylase

The initial (in vivo) and total (activity present after preincubation with CO₂ and Mg²⁺) activities of ribulose bisphosphate carboxylase were both assayed in extracts of leaves of soybean (Glycine max) plants which had been grown under 4 different irradiance levels. The total carboxylase activity per unit leaf area decreased with decreased irradiance during growth but was not different on a dry weight basis. The initial activity as a percentage of the total activity was unchanged (approximately 95%) except in leaves of plants grown at the lowest irradiance (74%). When the plants grown at the lowest irradiance were exposed to high irradiance, the initial activity was increased to 93% of the total. Light saturated rates of photosynthesis per unit leaf area were lower and saturated at lower irradiance for plants grown at lower irradiances. Initial carboxylase activity was correlated closely (r²=0.84) with leaf photosynthesis rate on a dry weight basis.     

Assimilation of [N]Nitrate and [N]Nitrite in Leaves of Five Plant Species under Light and Dark Conditions

Light dependency of nitrate and nitrite assimilation to reduced-N in leaves remains a controversial issue in the literature. With the objective of resolving this controversy, the light requirement for nitrate and nitrite assimilation was investigated in several plant species. Dark and light assimilation of [¹⁵N]nitrate and [¹⁵N]nitrite to ammonium and amino-N was determined with leaves of wheat, corn, soybean, sunflower, and tobacco. In dark aerobic conditions, assimilation of [¹⁵N]nitrate as a percentage of the light rate was 16 to 34% for wheat, 9 to 16% for tobacco, 26% for corn, 35 to 76% for soybean, and 55 to 63% for sunflower. In dark aerobic conditions, assimilation of [¹⁵N]nitrite as a percentage of the light rate was 11% for wheat, 7% for tobacco, 13% for corn, 28 to 36% for soybeans, and 12% for sunflower. It is concluded that variation among plant species in the light requirement for nitrate and nitrite assimilation explains some of the contradictory results in the literature, but additional explanations must be sought to fully resolve the controversy.

In dark anaerobic conditions, the assimilation of [¹⁵N]nitrate to ammonium and amino-N in leaves of wheat, corn, and soybean was 43 to 58% of the dark aerobic rate while dark anaerobic assimilation of [¹⁵N]nitrite for the same species was 31 to 41% of the dark aerobic rate. In contrast, accumulation of nitrite in leaves of the same species in the dark was 2.5-to 20-fold higher under anaerobic than aerobic conditions. Therefore, dark assimilation of nitrite cannot alone account for the absence of nitrite accumulation in the in vivo nitrate reductase assay under aerobic conditions. Oxygen apparently inhibits nitrate reduction in the dark even in leaves of plant species that exhibit a relatively high dark rate of [¹⁵N]nitrite assimilation.

     

Growth Analysis of Sweet Pepper (Capsicum annuum L.): 1. The Influence of Irradiance and Temperature under Glasshouse Conditions in Winter

A growth analysis was carried out with sweet pepper grown ina glasshouse. The plants received natural daylight or additionalillumination applied either during or after the natural photopenod.All irradiance conditions were applied at three temperatureregimes. Additional illumination increased leaf number, leaf area andtotal dry weight. At all temperatures the long-day treatmentsshowed a smaller number of leaves, but a larger leaf area whencompared to the short-day treatments with the same daily radiationsum. A lower temperature progressively reduced leaf area. The derived growth analysis quantities showed strong ontogenetictrends. When comparing both methods of applying additional illuminationhigher mean relative growth rates were observed for the long-daytreatments, especially at the lowest temperature. No differencesin mean net assimilation rate were found, but the short-daytreatments showed a reduced mean leaf area ratio. A lower nighttemperature decreased RGR and NAR but did not affect LAR, alower day temperature increased NAR and decreased LAR. Changesin LAR were largely mediated by changes in specific leaf weight. Capsicum annuum L., sweet pepper, growth analysis, irradiance, temperature     

A dynamic whole-plant model of integrated metabolism of nitrogen and carbon. 2. Balanced growth driven by C fluxes and regulated by signals from C and N substrate

A whole-plant model of C and N metabolism is presented for the juvenile stage. It is aimed at comparing the growth performance of (wild) plant species in a range of environments with respect to irradiance and availability of nitrate (NO₃ ^-) and ammonium (NH₄ ⁺). State variables are the structural masses of leaves, stem and root, NO₃ ^- concentrations in root and shoot, non-structural carbohydrate (C) densities in leaves, stem and root and non-structural organic N concentration in the whole plant. Explicit expressions for NO₃ ^- influx, efflux, translocation and assimilation, and for NH₄ ⁺ uptake and assimilation have been formulated in an accompanying paper. Photosynthetic rate is derived from electron-transport rate which depends on irradiance and chlorophyll concentration on a leaf-area basis. The latter is proportional to non-structural organic N concentration. Photosynthetic N is considered non-structural. Unique features of the model are the use of metabolite signals and the treatment of C allocation and balanced growth. Metabolite signals are dimensionless functions of non-structural compounds (NO₃ ^-, C, organic N) and modify rate variables involved in N uptake and assimilation, C allocation and growth. Carbon allocation is driven by concentration differences of the cytosolic C pools in stem and root and is modified by the N status of the plant such that a high N status increases the apparent size of the shoot. Photosynthate is unloaded into C buffers which degrade at a constant specific rate. The sugar fluxes which arise from these buffers drive the growth rate of stem and root. No parameters are included for maximum specific growth or for activity or strength of sinks. Primary stem growth is proportional to growth of the leaf compartment: leaves arise from stems in a modular fashion. Leaves are autonomous with respect to their C balance. The model is presented as a system of differential equations which is integrated numerically. Parameter values, e.g., for uptake and assimilation capacities and costs of uptake, assimilation, maintenance and growth, are estimated for a grass species, Dactylis glomerata. Juvenile growth is simulated under optimal conditions with respect to irradiance and NO₃ ^- availability and compared with literature data. Diurnal and daily patterns of C utilisation and respiration, expressed as percentages of gross photosynthetic rate, are discussed. The model satisfactorily simulates typical responses to nutrient and light limitation and pruning, such as redirected C allocation, adjusted root and leaf weight ratios and compensatory growth. A sensitivity analysis is included for selected parameters. This revised version was published online in June 2006 with corrections to the Cover Date.     

Nitrogen Utilization in Lemna: I. Relations between Net Nitrate Flux, Nitrate Reduction, and in Vitro Activity and Stability of Nitrate Reductase

Cultures of Lemna gibba L. G3 were maintained at a constant, N-limited growth rate by adding nitrate daily in amounts calculated to sustain a rate of culture N increment of 0.20 day⁻¹. Nitrate added to the culture was consumed within 8 to 10 hours and the partitioning to reduction and accumulation during this phase corresponded to, on the average, 75 and 25% of net uptake, respectively. The calculated rate of nitrate reduction was stimulated by onset of net uptake without delay and decreased when net uptake ceased. NADH-nitrate reductase (NR) activity measured in vitro without inclusion of antiproteolytic agents more than doubled during the first hour after nitrate addition and then gradually fell to its original level over the rest of the 24 hour interval. In the presence of the proteinase inhibitor leupeptin during extraction, however, NR activity was in general much higher and without any apparent cycles. The relative stabilizing effect of leupeptin was greatest on NADH-NR and reduced flavin adenine mononucleotide-NR activities whereas the effect was less on NADH-cytochrome c reductase activity (diaphorase) and reduced methylviologen-NR activity. The constant nitrate reductase activity measured in the presence of proteinase inhibitors is assumed to reflect the physiological situation. It thus appeares that short-term changes in nitrate assimilation by N-limited Lemna is related to the flux of nitrate to the reducing site and not to changes in nitrate reductase activity.     

Phenology,irradiance and temperature characteristics of a freshwater red alga,Nemalionopsis tortuosa (Thoreales), from Kagoshima,southern Japan

Phenology, irradiance and temperature characteristics of a freshwater benthic red alga, Nemalionopsis tortuosa Yoneda et Yagi (Thoreales), were examined from Kagoshima Prefecture, southern Japan for the conservation of this endemic and endangered species. Field surveys confirmed that algae occurred in shaded habitats from winter to early summer, and disappeared during August through November. A net photosynthesis–irradiance (P–E) model revealed that net photosynthetic rate quickly increased and saturated at low irradiances, where the saturating irradiance (E_k) and compensation irradiance (E_c) were 10 (8–12, 95% credible interval (CRI)) and 8 (6–10, 95% CRI) μmol photon m^?2 s^?1, respectively. Gross photosynthesis and dark respiration was determined over a range of temperatures (8–36°C) by dissolved oxygen measurements, and revealed that the maximum gross photosynthetic rate was highest at 29.5 (27.4–32.0, 95%CRI) °C. Dark respiration also increased linearly when temperature increased from 8°C to 36°C, indicating that the increase in dark respiration at higher temperature most likely caused decreases in net photosynthesis. The maximum quantum yield (Fv/Fm) that was determined using a pulse amplitude modulated‐chlorophyll fluorometer (Imaging‐PAM) was estimated to be 0.51 (0.50–0.52, 95%CRI) and occurred at an optimal temperature of 21.7 (20.1–23.4, 95%CRI) °C. This species can be considered well‐adapted to the relatively low natural irradiance and temperature conditions of the shaded habitat examined in this study. Our findings can be applied to aid in the creation of a nature‐reserve to protect this species.