Temporal separation of nitrogen fixation and photosynthesis in the filamentous,non-heterocystous cyanobacterium Oscillatoria sp.

When growing in laternating light-dark cycles, nitrogenase activity (acetylene reduction) in the filamentous, non-heterocystous cyanobacterium Oscillatoria sp. strain 23 (Oldenburg) is predominantly present during the dark period. Dark respiration followed the same pattern as nitrogenase. Maximum activities of nitrogenase and respiration appeared at the same time and were 3.6 mol C₂H₄ and 1.4 mg O₂ mg Chl a ^-1·h^-1, respectively. Cultures, adapted to light-dark cycles, but transferred to continuous light, retained their reciprocal rhythm of oxygenic photosynthesis and nitrogen fixation. Moreover, even in the light, oxygen uptake was observed at the same rate as in the dark. Oxygen uptake and nitrogenase activity coincided. However, nitrogenase activity in the light was 6 times as high (22 mol C₂H₄ mg Chl a ^-1·h^-1) as compared to the dark activity. Although some overlap was observed in which both oxygen evolution and nitrogenase activity occurred simultaneously, it was concluded that in Oscillatoria nitrogen fixation and photosynthesis are separated temporary. If present, light covered the energy demand of nitrogenase and respiration very probably fulfilled a protective function.     

Light control of the respiration of exogenous glycerol in the red macroalga Grateloupia doryphora

Heterotrophic activity in macroalgae has been little studied, but the red macroalga Grateloupia doryphora is known to grow in light at a higher rate in a glycerol-containing medium than in seawater. The effects of 0·1 M exogenous glycerol in seawater (SW90-gly) on the respiration rate of G. doryphora and the role played by light were investigated. The algae pretreated for 2 h in the light and in SW90-gly evolved oxygen and fixed carbon dioxide (H¹⁴CO₃ ^?), but also evolved radioactive ¹⁴CO₂ from [¹⁴C]glycerol. The rate of oxygen evolution was lower than that of samples in seawater, due to a high respiration rate and/or a partial inhibition of photosynthesis induced by glycerol. In contrast, the rate of inorganic carbon fixation was higher in SW90-gly than in control samples in seawater, suggesting that non-photosynthetic patterns were operating. In darkness, after pretreatment in the light in SW90-gly, samples showed a high oxygen uptake rate just after the light was turned off. Twenty minutes of darkness were enough to decrease this high respiration rate to that of samples in seawater. The oxygen uptake observed in all experiments with glycerol was mitochondrial as it was inhibited by potassium cyanide and salicylhydroxamic acid (SHAM). Pretreatment of samples in the light in SW90-gly with the photosynthetic inhibitor DCMU did not inhibit ensuing dark respiration, thus providing evidence for a non-photosynthetic effect of the light. The highest dark respiration rate was observed after the samples were pretreated in monochromatic blue light in glycerol-containing media.     

Predicting the impact of climatic warming on the carbon balance of the moss <Emphasis Type="Italic">Sanionia uncinata</Emphasis> on a maritime Antarctic island

The effects of climatic factors, especially those of temperature, on the carbon balance of the moss Sanionia uncinata were examined on King George Island in the maritime Antarctic. Net photosynthesis (P _n ) and dark respiration rates of two colonies (A and B) were measured with a portable infrared gas analyzer. Colony A showed small P _n compared with its dark respiration rates throughout the growing season. Colony B showed much higher net photosynthetic rates, but the dark respiration rates of the two colonies did not differ significantly. Net photosynthetic rate determined at light saturation was almost constant over a wide temperature range, from 5° to 15°C, while the dark respiration was strongly affected by temperature. To assess the impact of warming on the carbon balance of the moss, cumulative carbon gain of the moss was calculated using a simulation model for the main part of the growing season. The results suggest that climatic warming may cause a reduction of carbon gain in some relatively photosynthetically inactive moss colonies. Received: April 13, 2001 / Accepted: November 5, 2001     

Community structure and photosynthetic activity of epilithon from a highly acidic (pH≤2) mountain stream in Patagonia,Argentina

We explored a benthic community living on stones in an acidic (pH2) stream of active volcanic origin from Patagonia, Argentina, by combining in situ measurements (temperature, pH, conductivity, dissolved oxygen), photosynthesis of intact biofilms (measured with microsensors by the light–dark shift method), pure-culture experiments on isolated algae, and confocal laser scanning microscopy on the biofilms. The epilithon of the Agrio River was dominated (99% of total biomass) by one species: Gloeochrysis (Chrysophyceae). This species was observed as brown, mucilaginous, 200-m-thick films on stones, growing in clumps in a dense matrix of fungal hyphae, bacteria, and inorganic particles held together by extracellular polymeric substances. Gloeochrysis was isolated and cultivated. The photosynthetic rate measured at saturation irradiance was 120 mol oxygen (mg chlorophyll a)^–1h^–1 under laboratory conditions, and the saturation rate of photosynthesis by carbon dioxide was 90 mol oxygen (mg chlorophyll a)^–1 h^–1 for oxygen evolution. Photosynthetic activity of the biofilm was light-dependent and saturated above 200 mol photons m^–2 s^–1. In the dark, the stone surface became anoxic. Our data suggest that primary production in the Agrio River was not limited by light, carbon, or phosphorus but instead, nitrogen-limited.     

Studies on the Biochemistry and Fine Structure of Silica Shell Formation in Diatoms. Photosynthesis and Respiration in Silicon-Starvation Synchrony of Navicula pelliculosa

Rates of photosynthesis, measured by oxygen electrode or by ¹⁴CO₂ fixation, dark respiration and ³²P-phosphate incorporation are reported for the silicon-starvation synchrony of the fresh water diatom Navicula pelliculosa. During late exponential growth the rates were consistent with increase in carbon mass. During silicon starvation, rates of carbon dioxide fixation, oxygen evolution and ³²P incorporation fell, and the saturating light intensity decreased from 27,000 lux to 5000 lux. Reintroduction of silicon led to immediate transients in all parameters studied, followed by a prolonged increase in rate of dark respiration and a gradual increase in apparent photosynthesis. During release of daughter cells, the rates of dark respiration decreased as photosynthesis and ³²P incorporation increased. These results are discussed in relation to effects of silicon on the energy metabolism of the diatom.     

Crassulacean acid metabolism in the shade. Studies on an epiphytic fern,Pyrrosia longifolia,and other rainforest species from Australia

Summary Crassulacean acid metabolism (CAM) was studied in a tropical epiphytic fern, Pyrrosia longifolia, from a fully sun-exposed and from a very shaded site in Northern Queensland, Australia. Measurements of instantaneous net CO₂ exchange showed carbon gain via CO₂ dark fixation with some net CO₂ uptake also occuring during late afternoon, in both sun and shade fronds. Maximum rates of net CO₂ uptake and the nocturnal increase in titratable acidity were lower in shade than in sun fronds. ¹³C values of sun and shade fronds were not significantly different, and ranged between-14 and-15 suggesting that, in the long term, carbon gain was mainly via CO₂ dark fixation. Sun fronds had a higher light compensation point of photosynthesis than shade fronds but the same quantum yield. Yet there was no acclimation of photosynthetic O₂ evolution, (measured at 5% CO₂) in sun and shade fronds and photosynthesis saturated at between 200 and 400 mol quanta m^-2 s^-1. Use of higher light intensities for photosynthesis of sun fronds was probably precluded by low nutrient availability. Total nitrogen was less than 1% of dry weight in fully expanded sun and shade fronds. Exposure of shade fronds to full sunlight for 6 h led to a 60% decline in the quantum yield of photosynthesis and to a decline in variable fluorescence measured at room temperature. Photoinhibition by high light was also observed in Hoya nicholsoniae, a rainforest climber growing in deep shade. This species also exhibited CAM as demonstrated by nocturnal net CO₂ uptake, nocturnal acidification and a ¹³C value of-14. Photosynthetic O₂ evolution in this species was saturated at 2.5% of full sunlight. Two species of Dendrobium (Orchidaceae) from sun-exposed sites, one species exhibiting CAM and the other one exhibiting net CO₂ uptake exclusively during daytime via conventional C₃ photosynthesis, showed similar light response curves and the same quantum yield for photosynthetic O₂ evolution.     

Photosynthetic acclimation to variability in the light environment of early and late successional plants

Summary Fourteen plant species from early-, mid-, and late-successional habitats were grown for a period of 25 to 50 days in each of two light environments, i.e. full sunlight and in deep shade. The rate of photosynthesis for newly formed leaves was measured as a function of light intensity for plants from each light environment. Photosynthetic flexibility, measured as the difference in response between sun- and shade-grown plants, was determined for each of 5 parameters including dark respiration, quantum yield, light compensation, half-saturating irradiance for photosynthesis, and the photosynthetic rate at 1,400 E m^-2 s^-1. We found photosynthetic flexibility to be high for early successional annuals, intermediate for midsuccessional species, and low for late successional species.     

Photosynthetic performance of freshwater Rhodophyta in response to temperature, irradiance, pH and diurnal rhythm

Responses of net photosynthetic rates to temperature, irradiance, pH/inorganic carbon and diurnal rhythm were analyzed in 15 populations of eight freshwater red algal species in culture and natural conditions. Photosynthetic rates were determined by oxygen concentration using the light and dark bottles technique. Parameters derived from the photosynthesis–irradiance curves indicated adaptation to low irradiance for all freshwater red algae tested, confirming that they tend to occur under low light regimes. Some degree of photo‐inhibition (β= ‐0.33–0.01 mg O₂ g^?1 DW h^?1 (μmol photons m^?2 s^?1)^?1) was found for all species/populations analyzed, whereas light compensation points (Ic) were very low (≤ 2 μmol photons m‐ photons s^?1) for most algae tested. Saturation points were low for all algae tested (Ik = 6–54 μmol photons m^?2 s^?1; Is = 20–170 umol photons m^?2 s^?1). Rates of net photosynthesis and dark respiration responded to the variation in temperature. Optimum temperature values for net photosynthesis were variable among species and populations so that best performances were observed under distinct temperature conditions (10, 15, 20 or 25°C). Rates of dark respiration exhibited an increasing trend with temperature, with highest values under 20–25°C. Results from pH experiments showed best photosynthetic performances under pH 8.5 or 6.5 for all but one species, indicating higher affinity for inorganic carbon as bicarbonate or indistinct use of bicarbonate and free carbon dioxide. Diurnal changes in photosynthetic rates revealed a general pattern for all algae tested, which was characterized by two relatively clear peaks, with some variations around it: a first (higher) during the morning (07.00–11.00 hours.) and a second (lower) in the afternoon (14.00–18.00 hours). Comparative data between the ‘Chantransia’ stage and the respective gametophyte for one Batrachospermum population revealed higher values (ca 2‐times) in the latter, much lower than previously reported. The physiological role of the ‘Chantransia’ stage needs to be better analyzed.     

Responses of Two Coastal Algae (Skeletonema costatum and Chlorella vulgaris) to Changes in Light and Iron Levels1

Iron (Fe) is essential for phytoplankton growth and photosynthesis, and is proposed to be an important factor regulating algal blooms under replete major nutrients in coastal environments. Here, Skeletonema costatum, a typical red-tide diatom species, and Chlorella vulgaris, a widely distributed Chlorella, were chosen to examine carbon fixation and Fe uptake by coastal algae under dark and light conditions with different Fe levels. The cellular carbon fixation and intracellular Fe uptake were measured via ¹⁴C and ⁵⁵Fe tracer assay, respectively. Cell growth, cell size, and chlorophyll-α concentration were measured to investigate the algal physiological variation in different treatments. Our results showed that cellular Fe uptake proceeds under dark and the uptake rates were comparable to or even higher than those in the light for both algal species. Fe requirements per unit carbon fixation were also higher in the dark resulting in higher Fe: C ratios. During the experimental period, high Fe addition significantly enhanced cellular carbon fixation and Fe uptake. Compared to C. vulgaris, S. costatum was the common dominant bloom species because of its lower Fe demand but higher Fe uptake rate. This study provides some of the first measurements of Fe quotas in coastal phytoplankton cells, and implies that light and Fe concentrations may influence the phytoplankton community succession when blooms occur in coastal ecosystems.     

16O2/18O2 analysis of oxygen exchange in Dunaliella tertiolecta. Evidence for the inhibition of mitochondrial respiration in the light

A mass spectrometric ¹⁶O₂/¹⁸O₂-isotope technique was used to analyse the rates of gross O₂ evolution, net O₂ evolution and gross O₂ uptake in relation to photon fluence rate by Dunaliella tertiolecta adapted to 0.5, 1.0, 1.5, 2.0 and 2.5 M NaCl at 25°C and pH 7.0.At concentrations of dissolved inorganic carbon saturating for photosynthesis (200 M) gross O₂ evolution and net O₂ evolution increased with increasing salinity as well as with photon fluence rate. Light compensation was also enhanced with increased salinities. Light saturation of net O₂ evolution was reached at about 1000 mol m^-2s^-1 for all salt concentrations tested. Gross O₂ uptake in the light was increased in relation to the NaCl concentration but it was decreased with increasing photon fluence rate for almost all salinities, although an enhanced flow of light generated electrons was simultaneously observed. In addition, a comparison between gross O₂ uptake at 1000 mol photons m^-2s^-1, dark respiration before illumination and immediately after darkening of each experiment showed that gross O₂ uptake in the light paralleled but was lower than mitochondrial O₂ consumption in the dark.From these results it is suggested that O₂ uptake by Dunaliella tertiolecta in the light is mainly influenced by mitochondrial O₂ uptake. Therefore, it appears that the light dependent inhibition of gross O₂ uptake is caused by a reduction in mitochondrial O₂ consumption by light.Abbreviations DCMU 3-(3, 4-dichlorophenyl)-1, 1-dimethylurea - DHAP dihydroxy-acetonephosphate - DIC dissolved inorganic carbon - DR_a rate of dark respiration immediately after illumination - DR_b rate of dark respiration before illumination - E₀ rate of gross oxygen evolution in the light - NET rate of net oxygen evolution in the light - PFR photon fluence rate - RubP rubulose-1,5-bisphosphate - SHAM salicyl hydroxamic acid - U₀ rate of gross oxygen uptake in the light     

Adaptation and acclimation of growth and photosynthesis of five Antarctic red algae to low temperatures

Temperature requirements for growth, photosynthesis and dark respiration were determined for five Antarctic red algal species. After acclimation, the stenothermal species Gigartina skottsbergii and Ballia callitricha grew at 0 or up to 5 °C, respectively; the eurythermal species Kallymenia antarctica, Gymnogongrus antarcticus and Phyllophora ahnfeltioides grew up to 10 °C. The temperature optima of photosynthesis were between 10 and 15 °C in the stenothermal species and between 15 and 25 °C in the eurythermal species, irrespective of the growth temperature. This shows that the temperature optima for photosynthesis are located well below the optima from species of other biogeographical regions, even from the Arctic. Respiratory rates rose with increasing temperatures. In contrast to photosynthesis, no temperature optimum was evident between 0 and 25 °C. Partial acclimation of photosynthetic capacity to growth temperature was found in two species. B. callitricha and Gymnogongrus antarcticus acclimate to 0 °C, and 5 and 0 °C, respectively. But acclimation did in no case lead to an overall shift in the temperature optimum of photosynthesis. B. callitricha and Gymnogongrus antarcticus showed acclimation of respiration to 5 °C, and P. ahnfeltioides to 5 and 10 °C, resulting in a temperature independence of respiration when measured at growth temperature. With respect to the acclimation potential of the species, no distinction can be made between the stenothermal versus the eurythermal group. (Net)photosynthetic capacity:respiration (P:R) ratios showed in all species highest values at 0 °C and decreased continuously to values lower than 1.0 at 25 °C. In turn, the low P:R ratios at higher temperatures are assumed to determine the upper temperature growth limit of the studied species. Estimated daily carbon balance reached values between 4.1 and 30.7 mg C g⁻¹ FW day⁻¹ at 0 °C, 16:8 h light/dark cycle, 12–40 μmol m⁻² s⁻¹. Received: 4 November 1999 / Accepted: 7 March 2000     

Photosynthetic capacity in microalgae associated with Antarctic pack ice

Summary Previous studies of primary production in Antarctic seas have concluded that microalgae associated with sea ice make only a minor contribution to the carbon budget; however, production estimates for sea ice algae have been based almost exclusively on microalgae from nearshore fast ice. We measured biomass and rates of photosynthesis (at saturating irradiances) in microalgae collected from offshore pack ice during four cruises to the Weddell-Scotia Sea and the region west of the Antarctic Peninsula. Chlorophyll a concentrations in pack ice (0.089 to 260 g 1^-1) were as high as reported from fast ice. Photosynthetic rates typically ranged (median 75%) from 0.3 to 3.6 C g chl a ^-1 h^-1 (n=127; arithmetic mean = 1.7, S D =1.9). These photosynthetic capacities are approximately an order of magnitude greater than previously reported for fast ice microalgae, but are similar to rates reported for Antarctic phytoplankton. Because pack ice constitutes more than 90% of the ice cover in Antarctic seas and indigenous microalgae have a higher photosynthetic capacity than previously realized, we raise the question: has the importance of sea ice algae to primary product: on in the southern ocean been underestimated?     

Photosynthetic metabolism and cell-wall polysaccharide accumulation inGelidium sesquipedale (Clem.) Born. et Thur. under different light qualities

The influence of different light qualities on the photosynthetic rate, dark respiration, intracellular carbon and nitrogen content, and accumulation of photosynthetic pigments and cell-wall polysaccharides during short-term incubation (5 h) of the red algaGelidium sesquipedale was investigated. The same photon irradiance of 50mol m^–2 s^–2 below the light saturation point of photosynthesis was applied in each case. Blue light stimulated photosynthesis, dark respiration and the accumulation of chlorophyll and biliproteins, phycoerythrin in particular. The accumulation of internal carbon and nitrogen was greater under blue light than under the other light qualities. In contrast, the percentage of cell-wall polysaccharides was higher in red light. The content of cell-wall polysaccharides decreased during the time of incubation in all light treatments except in red light. The action of a non-photosynthetic photoreceptor in the control of cell-wall polysaccharide synthesis is suggested because the accumulation of cell-wall polysaccharides was not correlated with net photosynthesis in contrast to what occurred with carbon, chlorophyll and phycoerythrin accumulation.     

Predicting the impact of climatic warming on the carbon balance of the moss Sanionia uncinata on a maritime Antarctic island

The effects of climatic factors, especially those of temperature, on the carbon balance of the moss Sanionia uncinata were examined on King George Island in the maritime Antarctic. Net photosynthesis (P(n)) and dark respiration rates of two colonies (A and B) were measured with a portable infrared gas analyzer. Colony A showed small P(n) compared with its dark respiration rates throughout the growing season. Colony B showed much higher net photosynthetic rates, but the dark respiration rates of the two colonies did not differ significantly. Net photosynthetic rate determined at light saturation was almost constant over a wide temperature range, from 5 degrees to 15 degrees C, while the dark respiration was strongly affected by temperature. To assess the impact of warming on the carbon balance of the moss, cumulative carbon gain of the moss was calculated using a simulation model for the main part of the growing season. The results suggest that climatic warming may cause a reduction of carbon gain in some relatively photosynthetically inactive moss colonies.     

RATES OF PHOTOSYNTHESIS AND RESPIRATION OF THE MOSS BRYUM SANDBERGII AS INFLUENCED BY LIGHT INTENSITY AND TEMPERATURE

Using differential respirometry and air enriched to 3% CO₂ (v/v), the rates of photosynthesis and dark respiration of the moss Bryum sandbergii were measured as influenced by temperature and light intensity. The optimal temperature for net (apparent) photosynthesis was between 24 to 30 C; however, the photosynthesis/respiration ratio was about 11 to 27 between 4 to 24 C and dropped to lower values at 34 C., which indicates a wide temperature tolerance for this moss in short-term experiments. The maximum temperature for photosynthesis was about 41 C and the minimum was below –5 C. At 20 C light saturation was approached at 6.2 mw cm^–2 (ca. 700 ft-c) but not completely reached at 12 mw cm^-2; the light compensation point was estimated to be 0.4 mw cm^-2 (ca. 40 ft-c). At 4 C light saturation and the compensation point were at lower levels and apparently solarization occurred at 12 mw cm^-2. Light intensity had little or no apparent effect on dark respiration. However, respiration increased with temperature over various ranges extending from –5 to 39 C with temperature quotients of about 2.5 to 1.2. The significance of these characteristics is discussed with respect to the ecological relationships of the species.     

LIGHT INDEPENDENT CARBON FIXATION BY MARINE MACROALGAE1

Several marine macroalgae representative of the Chlorophyceae, Rhodophyceae and Phaeophyceae were investigated for their potentials of photosynthesis and light independent (dark) carbon fixation. In addition, the activities of ribulose-1,5-bisphosphate carboxylase (RubP-C; EC 4.1.1.39) and of phosphoenolpyruvate carboxykinase (PEP-CK; EC 4.1.1.32) were studied. In contrast to the green and red algae investigated, all brown algae exhibited comparably high rates of dark fixation accounting for up to 20% of photosynthetic carbon uptake. These observations are confirmed by the activities of RubP-C and PEP-CK measured after extraction from different species and thallus regions. Dark fixed ¹⁴C was mainly recovered from aspartate, citrate, malate, glutamate, and alanine. Appreciable amounts of ¹⁴C were incorporated into insoluble (polymeric) constituents even after relatively short periods of dark fixation.     

Photosynthesis and respiration of Griffithsia monilis (Rhodophyceae): Effect of light,salinity, and oxygen

The giant-celled alga Griffithsia monilis has a low light compensation point and saturates photosynthesis at 60–90 mol photons m^-2s^-1 (oxygen evolution and CO₂ fixation). Under dark and low light intensities ¹⁴C is preferentially incorporated into amino acids (mainly aspartate and alanine). With increasing light a gradual change was observed and, under light saturation, compounds of the anionic fraction (digeneaside and hexosephosphates) were the most strongly labeled compounds, together with the amino acids glycine and serine. To a large extent (30–40% of the total) ¹⁴C was fixed into EtOH-insoluble products, the hydrolysates of which consisted mainly of glucose and mannose. In the steady state the rates of photosynthesis and respiration decreased with increasing salinity. Changes in the rates after hyperosmotic shocks were less severe in cells adapted to high salinities. Photorespiration exists in Griffithsia: Glycine and serine are the major labeled compounds in O₂-saturated media.     

Remarks on mixotrophic and autotrophic carbon nutrition of Vitis plantlets cultured in vitro

Two Vitis species were cultured in vitro under photoautrophic (sucrose-free culture medium) and photomixotrophic (sucrose 15 g l^-1) conditions during the period following microcutting rooting (day 34 to day 120). Several parameters were measured at the end of the culture: growth, plant dry weight, carbohydrate uptake from the medium and rates of photosynthesis and dark respiration. The two species behaved very differently. Under photoautotrophic conditions, dark respiration, net photosynthesis and daily CO₂ fixation were higher in Vitis vinifera than in Vitis rupestris. Culture under mixotrophic conditions caused increase in growth, respiration and photosynthesis in Vitis rupestris. In contrast, photosynthesis decreased in Vitis vinifera under the same conditions.     

Effects of temperature on the gas exchange of leaves in the light and dark

Summary Evolution of CO₂ into CO₂-free air was measured in the light and in the dark over a range of temperatures from 15 to 50°. Photosynthetic rates were measured in air and O₂-free air over the same range of temperatures. Respiration in the light had a different sensitivity to temperature compared with respiration in the dark. At the lower temperatures the rate of respiration in the light was higher than respiration in the dark, whereas at temperatures above 40° the reverse was observed. For any one species the maximum rates of photosynthesis and photorespiration occur at about the same temperature. The maximum rate for dark respiration generally is found at a temperature about 10° higher. Zea mays and Atriplex nummularia showed no enhancement of photosynthesis in O₂-free air nor any evolution of CO₂ in CO₂-free air at any of the temperatures.     

Comparative physiology and demography of three Neotropical forest shrubs: alternative shade-adaptive character syndromes

A suite of functionally-related characters and demography of three species of Neotropical shadeadapted understory shrubs (Psychotria, Rubiaceae) were studied in the field over five years. Plants were growing in large-scale irrigated and control treatments in gaps and shade in old-growth moist forest at Barro Colorado Island, Panama. Irrigation demonstrated that dry-season drought limited stomatal conductance, light saturated photosynthesis, and leaf longevity in all three species. Drought increased mortality of P. furcata. In contrast, irrigation did not affect measures of photosynthetic capacity determined with an oxygen electrode or from photosynthesis-CO₂ response curves in the field. Drought stress limited field photosynthesis and leaf and plant survivorship without affecting photosynthetic capacity during late dry season. Leaves grown in high light in naturally occurring treefall gaps had higher photosynthetic capacity, dark respiration and mass per unit area than leaves grown in the shaded understory. P. furcata had the lowest acclimation to high light for all of these characters, and plant mortality was greater in gaps than in shaded understory for this species. The higher photosynthetic capacity of gap-grown leaves was also apparent when photosynthetic capacity was calculated on a leaf mass basis. Acclimation to high light involved repackaging (higher mass per unit leaf area) as well as higher photosynthetic capacity per unit leaf mass in these species. The three species showed two distinct syndromes of functionally-related adaptations to low light. P. limonensis and P. marginata had high leaf longevity (3 years), high plant survivorship, low leaf nitrogen content, and high leaf mass per unit area. In contrast, P. furcata had low leaf survivorship (1 year), high plant mortality (77–96% in 39 months), low leaf mass per unit area, high leaf nitrogen content, and the highest leaf area to total plant mass; the lowest levels of shelf shading, dark respiration and light compensation; and the highest stem diameter growth rates. This suite of characters may permit higher whole-plant carbon gain and high leaf and population turnover in P. furcata. Growth in deep shade can be accomplished through alternative character syndromes, and leaf longevity may not be correlated with photosynthetic capacity in shade adapted plants.