Dark Leaf Respiration in Light and Darkness of an Evergreen and a Deciduous Plant Species

Dark respiration in light as well as in dark was estimated for attached leaves of an evergreen (Heteromeles arbutifolia Ait.) and a deciduous (Lepechinia fragans Greene) shrub species using an open gas-exchange system. Dark respiration in light was estimated by the Laisk method. Respiration rates in the dark were always higher than in the light, indicating that light inhibited respiration in both species. The rates of respiration in the dark were higher in the leaves of the deciduous species than in the evergreen species. However, there were no significant differences in respiration rates in light between the species. Thus, the degree of inhibition of respiration by light was greater in the deciduous species (62%) than in the evergreen species (51%). Respiration in both the light and darkness decreased with increasing leaf age. However, because respiration in the light decreased faster with leaf age than respiration in darkness, the degree of inhibition of respiration by light increased with leaf age (from 36% in the youngest leaves to 81% in the mature leaves). This suggests that the rate of dark respiration in the light is related to the rate of biosynthetic processes. Dark respiration in the light decreased with increasing light intensity. Respiration both in the light and in the dark was dependent on leaf temperature. We concluded that respiration in light and respiration in darkness are tightly coupled, with variation in respiration in darkness accounting for more than 60% of the variation in respiration in light. Care must be taken when the relation between respiration in light and respiration in darkness is studied, because the relation varies with species, leaf age, and light intensity.     

Leaf Respiration in Light and Darkness (A Comparison of Slow- and Fast-Growing Poa Species)

We investigated whether leaf dark respiration (nonphotorespiratory mitochondrial CO2 release) is inhibited by light in several Poa species, and whether differences in light inhibition between the species are related to differences in the rate of leaf net photosynthesis. Four lowland (Poa annua L., Poa compressa L., Poa pratensis L., and Poa trivialis L.), one subalpine (Poa alpina L.), and two alpine (Poa costiniana Vick. and Poa fawcettiae Vick.) Poa species differing in whole plant relative growth rates were grown under identical controlled conditions. Nonphotorespiratory mitochondrial CO2 release in the light (Rd) was estimated according to the Laisk method. Photosynthesis was measured at ambient CO2 partial pressure (35 Pa) and 500 [mu]mol photons m-2 s-1. The rate of photosynthesis per unit leaf mass was positively correlated with the relative growth rate, with the slow-growing alpine Poa species exhibiting the lowest photosynthetic rates. Rates of both Rd and respiration in darkness were also substantially lower in the alpine species. Nonphotorespiratory CO2 release in darkness was higher than Rd in all species. However, despite some variation between the species in the level of light inhibition of respiration, no relationship was observed between the level of inhibition and the rate of photosynthesis. Similarly, the level of inhibition was not correlated with the relative growth rate. Our results support the suggestion that rates of leaf respiration in the light are closely associated with rates in darkness.     

Responses of Respiration to Increases in Carbon Dioxide Concentration and Temperature in Three Soybean Cultivars

The purpose of this experiment was to determine how respirationof soybeans may respond to potential increases in atmosphericcarbon dioxide concentration and growth temperature. Three cultivarsof soybeans (Glycine max L. Merr.), from maturity groups 00,IV, and VIII, were grown at 370, 555 and 740cm³m^-3carbon dioxideconcentrations at 20/15, 25/20, and 31/26°C day/night temperatures.Rates of carbon dioxide efflux in the dark were measured forwhole plants several times during exponential growth. Thesemeasurements were made at the night temperature and the carbondioxide concentration at which the plants were grown. For thelowest and highest temperature treatments, the short term responseof respiration rate to measurement at the three growth carbondioxide concentrations was also determined. Elemental analysisof the tissue was used to estimate the growth conversion efficiency.This was combined with the observed relative growth rates toestimate growth respiration. Maintenance respiration was estimatedas the difference between growth respiration and total respiration.Respiration rates were generally sensitive to short term changesin the measurement carbon dioxide concentration for plants grownat the lowest, but not the highest carbon dioxide concentration.At all temperatures, growth at elevated carbon dioxide concentrationsdecreased total respiration measured at the growth concentration,with no significant differences among cultivars. Total respirationincreased very little with increasing growth temperature, despitean increase in relative growth rate. Growth respiration wasnot affected by carbon dioxide treatment at any temperature,but increased with temperature because of the increase in relativegrowth rate. Values calculated for maintenance respiration decreasedwith increasing carbon dioxide concentration and also decreasedwith increasing temperature. Calculated values of maintenancerespiration were sometimes zero or negative at the warmer temperatures.This suggests that respiration rates measured in the dark maynot have reflected average 24-h rates of energy use. The resultsindicate that increasing atmospheric carbon dioxide concentrationmay reduce respiration in soybeans, and respiration may be insensitiveto climate warming. Glycine max L. (Merr.); carbon dioxide; respiration; temperature; climate change     

Methionine Sulfoximine Effects on C4 Plant Leaf Discs: Comparison with C3 Species

Methionine sulfoximine caused ammonia accumulation and photosyntheticrate inhibition in leaf discs from two C₄ species, Zea maysL. cv. F. M. Cross (Hybrid) and Sorghum bicolor L. Moench cv.NC-70X, as well as one C₃ plant species, Datura stramonium L.cv. stramonium. Similar results were obtained earlier with theC₃ species Spinacia oleracea L. The effect occurred in the absenceof inorganic nitrogen reduction and was light dependent. Ammoniaaccumulation rates were similar in all four species examined.The results support a role for glutamine synthetase in leafammonia recycling in both C₄ and C₃ leaves. ¹ Current address: Cetus Madison Corporation, 2208 Parview Road,Middleton, WI 53562, U.S.A. (Received November 2, 1981; Accepted April 28, 1982)     

Direct and Indirect Effects of Atmospheric Carbon Dioxide Enrichment on Leaf Respiration of Glycine max (L.) Merr

Long-term and short-term effects of CO2 enrichment on dark respiration were investigated using soybean (Glycine max [L.] Merr.) plants grown at either 35.5 or 71.0 Pa CO2. Indirect effects, or effects of growth in elevated CO2, were examined using a functional model that partitioned respiration into growth and maintenance components. Direct effects, or immediate effects of a short-term change in CO2, were examined by measuring dark respiration, first, at the CO2 partial pressure at which plants were grown, and second, after equilibration in the reciprocal CO2 partial pressure. The functional component model indicated that the maintenance coefficient of respiration increased 34% with elevated CO2, whereas the growth coefficient was not significantly affected. Changes in maintenance respiration were correlated with a 33% increase in leaf total nonstructural carbohydrate concentration, but leaf nitrogen content of soybean leaves was not affected by CO2 enrichment. Thus, increased maintenance respiration may be a consequence of increased nonstructural carbohydrate accumulation. When whole soybean plants were switched from low CO2 to high CO2 for a brief period, leaf respiration was always reduced. However, this direct effect of CO2 partial pressure was approximately 50% less in plants grown in elevated CO2. We conclude from this study that there are potentially important effects of CO2 enrichment on plant respiration but that the effects are different for plants given a short-term increase in CO2 partial pressure versus plants grown in elevated CO2.     

Leaf Conductance as Related to Xylem Water Potential and Carbon Dioxide Concentration in Sitka Spruce

Current year shoots of Sitka spruce [Picea sitchensis Bong. (Carr.)] from the forest canopy were equilibrated in a leaf chamber. The shoots were excised in air, and removed at differing times in order to establish a relationship between stomatal conductance and xylem water potential. The experiment was repeated at five ambient CO₂ concentrations. A second set of excised forest shoots, and shoots excised from 2-year- old nursery seedlings were allowed to evaporate freely in a controlled environment wind tunnel until a constant rate of transpiration was measured, to establish a relationship between cuticular conductance and xylem water potential. Cuticular conductance was estimated to be 0.012 cm s^-1 at high water potential and declined linearly to 0.007 cm s^-1 at ?3.5 MPa. The implication of this decline in the subsequent calculation of stomatal and mesophyll conductance is considered. Stomatal conductance remained constant at water potentials above ?1.4 MPa and was not affected by ambient carbon dioxide concentrations between 20 and 600 cm^-3. At lower water potentials, stomatal conductance declined and approached zero at ?2.5 to ?2.6 MPa. The results suggest that stomatal aperture is not controlled by either ambient or intercellular space carbon dioxide concentration, and that stomatal closure at low water potential is unlikely to be mediated by carbon dioxide.     

Carbon Dioxide Efflux from Leaves in Light and Darkness

Efflux of carbon dioxide in light and darkness was measured at low ambient CO₂ concentrations in leaves of Rumex acetosa. Light carbon dioxide production (photo-respiration) was found to depend on irradiance and to differ from dark production as to the response to temperature and ambient concentrations of O₂ and CO₂. These observations support previously made suggestions that photorespiration follows a different metabolic pathway to dark respiration.     

Effects of Prolonged Exposure to Darkness on Circadian Photic Responsiveness in the Mouse

Circadian rhythms in mammals are generated by an endogenous pacemaker but are modulated by environmental cycles, principally the alternation of light and darkness. Although much is known about nonparametric effects of light on the circadian system, little is known about other effects of photic stimulation. In the present study, which consists of a series of five experiments in mice, various manipulations of photic stimulation were used to dissect the mechanisms responsible for a variation in the magnitude of light-induced phase-shifts that results from prolonged exposure to darkness. The results confirmed previous observations that prolonged exposure to darkness causes an increase in the magnitude of phase shifts (both phase advances and phase delays) evoked by discrete light pulses. The results also indicated that the increase in responsiveness results from the lack of exposure to light per se and not from collateral effects of exposure to constant darkness such as the lack of previous entrainment. The lack of exposure to light causes the circadian system to undergo a process of dark adaptation similar to dark adaptation in the visual system but with a much slower temporal course. The results suggest that circadian dark adaptation may take place at the retinal level, but it is not clear whether it involves a change in the sensitivity or maximal responsiveness of the system.     

Effects of Anoxia on Phloem Loading in C3 and C4 Species

Changes in phloem loading rate were inferred from observationsof ¹¹C export from attached leaves of C₃ and C₄ monocots anddicots. Loading decreased under anoxia in C₃ leaves, but notin general in the leaves of either C₄ monocots or dicots inthe light. However, loading rate in the C₄ leaves did reduceif the leaf was also darkened or received no CO₂. We suggestthat insensitivity to anoxia in C₄ leaves is due to oxygen fromphotosynthesis which is retained in the bundle sheath at a concentrationsufficient to energize a phloem loading system. There may alsobe another system which is insensitive to anoxia since the effectsof shade and CO₂ deprivation were not always seen, and loadingwas not completely stopped by these treatments. Key words: Phloem loading, C₃, C₄     

Effects of Various Concentrations of Carbon Dioxide on Respiration and Potassium Uptake in Barley Roots

Barley roots contain a CO₂ sensitive respiratory fraction which is inhibited in 50 per cent CO₂ and is partially restored upon subsequent exposure to air. The residual O₂ consumption occurring at CO₂ concentrations between 50 per cent and 95 per cent amounts to about 40 per cent of the O₂ uptake in air and can support K⁺ uptake for a limited time at a rate equal to or higher than occurs in air. Above 95 per cent CO₂ both O₂ and K⁺ uptakes decrease rapidly. 2,4-dinitrophenol (DNP), in the range of 10^?6 to 10^?5M, stimulates O₂ uptake by the roots in air. The stimulation is absent when roots are treated with DNP in 80 per cent CO₂, presumably because of the reduced demand for inorganic phosphate and phosphate acceptor at the lower respiratory level in high CO₂. In either air or CO₂, K⁺ uptake is strongly inhibited by DNP. A comparison of the respiratory and K⁺ uptake data indicates that O₂ consumption is a necessary requirement for the uptake process in high CO₂. Protoplasmic streaming in the root cells is rapidly stopped by high CO₂ although K⁺ uptake and O₂ consumption continue. The cation uptake mechanism in high CO₂ appears to be limited to the stationary cytoplasm. It is also possible that a similar mechanism may be involved in cation uptake in air.     

Carbon Isotopic Fractionation Does Not Occur during Dark Respiration in C3 and C4 Plants

The magnitude of possible carbon isotopic fractionation during dark respiration was investigated with isolated mesophyll cells from mature leaves of common bean (Phaseolus vulgaris L.), a C3 plant, and corn (Zea mays L.), a C4 plant. Mesophyll protoplasts were extracted from greenhouse-grown leaves and incubated in culture solutions containing different carbohydrate substrates (fructose, glucose, and sucrose) with known [delta]13C values. The CO2 produced by protoplasts after incubation in the dark was collected, purified, and analyzed for its carbon isotope ratio. From observations of the isotope ratios of the substrate and respired CO2, we calculated the carbon isotope discrimination associated with metabolism of each of these substrates. In eight of the 10 treatment combinations, the carbon isotope ratio discrimination was not significantly different from 0. In the remaining two treatment combinations, the carbon isotope ratio discrimination was 1[per mille (thousand) sign]. From these results, we conclude that there is no significant carbon isotopic discrimination during mitochondrial dark respiration when fructase, glucose, or sucrose are used as respiratory substrates.     

Effects of Carbon Dioxide Concentration on the Growth of Callistephus chinensis cultivar Johannistag

Carbon dioxide enrichment to 600 ppm increased the amount ofdry matter produced by Callistephus chinensis plants in growthcabinets with negligible mutual shading over a period of 18weeks. Further enrichment to 900 ppm showed smaller and morevariable increases. These effects were the result of a higherunit leaf rate of the treated plants. The direct effect on unitleaf rate was partly offset by a reduction in leaf-area ratio,and this was due almost entirely to the effect on specific leafarea with hardly any effect on leaf-weight ratio. Carbon dioxideaccelerated flower development by about a week at 600 ppm andsomewhat less at 900 ppm. The proportion of the total plantweight in the form of flowers showed a similar trend with timein all treatments and the relationship between flower-weightratio and dry-matter content of flowers was likewise similarfor all treatments, with the highest dry-matter contents ofabout 19 per cent associated with the highest flower-weightratios of about 0.44 for mature flowers. Carbon dioxide enrichmentsignificantly increased the dry-matter content of leaves. Theefficiency of energy conversion based on incident light anda twenty-four-hour cycle of 8 h light and 16 h dark for smallplants of 140–300 mg total dry weight (leaf areas of 50–120cm²) was about 4.7 per cent for the 325 ppm treatment, 6.3 percent for 600 ppm, and 5.5 per cent for 900 ppm. By referenceto some further experiments on the growth of C. chinensis cultivarJohannistag in glasshouse conditions, considerable adaptiveresponse to high and low light intensity was also demonstrated.     

Temperature and Time-course of the Carbon Balance of Vegetative Tomato Plants During Prolonged Darkness: Examination of a Method of Estimating Maintenance Respiration

In order to examine the suitability of estimating maintenancerespiration in prolonged darkness, the variation of structuraldry matter (SDM) was calculated on vegetative tomato plantsduring 48 h of darkness. For that purpose, the time-coursesof respiration rate and carbohydrate content were recorded inshoots and roots at temperatures of 10, 15, 20, and 25 °C Two exponential declines of respiration rate, separated by ashort resumption, were observed in shoots and roots, differentcarbohydrate pools might be involved. Respiration rate was alwayshigher in roots than in shoots: the part played by energy costsof mineral absorption has to be investigated. After 14 h ofdarkness, a fall in respiration rate was associated with a progressiveexhaustion of sucrose and starch - which was quicker at highertemperatures - and a decrease in shoot to root carbon translccation.After 24 h of darkness, respiration stabilized at all temperatures.However, structural growth persisted throughout the dark periodat 10 °C, stopped after about 14 h darkness at. 15 and 20°C, and became negative beyond 24 h at 25 °C The hypothesis of maintenance of SDM after a period of darknesscan thus be invalidated. The simple observation of the time-courseof respiration rate does not allow complete inferences to bemade concerning biomass maintenance Lycopersicon esculentum Mill., tomato, respiration, maintenance respiration, carbohydrate reserves, translocation, structural dry matter, temperature     

Effects of Elevated Carbon Dioxide Concentration in the Dark on the Growth of Soybean Seedlings

Previous work has shown that elevated carbon dioxide (CO₂) concentrationsin the dark reversibly reduce the rate of CO₂ efflux from soybeans.Experiments were performed exposing soybean plants continuallyto concentrations of 350 or 700 cm³ m^-3 for 24 h d^-1, or to350 during the day and 700 cm³ m^-3 at night, in order to determinethe importance of the reduced rate of dark CO₂ efflux for plantgrowth. High CO₂ applied only at night conserved carbon andincreased dry mass during initial growth compared with the constant350 cm³ m^-3 treatment. Long-term net assimilation rate was increasedby high CO₂ in the dark, without any increase in daytime leafphotosynthesis. However, leaf area ratio was reduced by thedark CO₂ treatment to values equal to those of plants continuallyexposed to the higher concentration. From days 14-21, leaf areawas less for the elevated night-time CO₂ treatment than foreither the constant 350 or 700 cm³ m^-3 treatments. For the days7-21-period, relative growth rate was significantly reducedby the high night CO₂ treatment compared with the 350 cm³ m^-3continuous treatment. The results indicate that some functionallysignificant component of respiration was reduced by the elevatedCO₂ concentration in the dark.Copyright 1995, 1999 AcademicPress Glycine max L. (Merr.), carbon dioxide, plant growth, respiration     

Acclimation of Leaf Dark Respiration to Temperature in Alpine and Lowland Plant Species

Acclimation to temperature in terms of dark respiration by leavesis a missing link in current efforts to predict the effectsof global warming on plant communities. We studied the acclimationof plants from alpine or lowland areas and asked two questions:(1) do plants acclimate to a change in temperature and doesacclimation depend on the plants' origin; and (2) have alpineplants adapted to low temperatures by respiring faster thanlowland plants at any given temperature? Nineteen alpine andcorresponding lowland species, collected in Switzerland, weregrown at 10 and 20°C for 5 weeks. Night-time leaf dark respirationrates were measured at the growth temperature of each plant.Acclimation patterns ranged from full to no acclimation. Fullacclimation to temperature, defined as the equality betweenrespiration measured at 20°C of plants grown at 20°Cand respiration measured at 10°C of plants grown at 10°C,occurred in only three out of 19 species. Dark respiration ofleaves was stimulated by a 10 K warming, but on average, byabout 50% less than predicted by the instantaneous temperatureresponse, i.e. Q₁₀. Acclimation did not depend on the alpineor lowland origin of the plant, but rather on its genus. Prostratealpine plants displayed the lowest acclimation potential. Weconclude that predictions at the community level cannot be madebased on single species because of the variety observed in therespiration responses.Copyright 1995, 1999 Academic Press Acclimation, alpine and lowland, climate warming, comparative ecology, dark respiration, grassland, Q₁₀, temperature     

Effects of Carbon Dioxide on Coccidian Oocysts from 6 Host Species*

SYNOPSIS Activation of sporozoites in oocysts of Eimeria acervulina (chicken), E. intricata (sheep), and E. scabra (swine) occurred after pretreatment in aqueous 0.02 M cysteine hydrochloride under an atmosphere of CO₂, followed by incubation in a trypsin-bile mixture. Sporozoites of E. stiedae (rabbit), E. bilamellata (squirrel), and Isospora canis (dog) became activated when incubated in trypsin and bile with or without prior CO₂-pretreatment of oocysts; however, when CO₂-pretreatment was used, activation of these species in trypsin and bile was greatly enhanced. For E. acervulina, 12% of the oocysts were activated after 4 hr CO₂-pretreatment and 10 hr incubation in trypsin and bile at 43 C; higher temperatures or longer pretreatment times did not cause greater activation. Eimeria intricata oocysts became activated after 1 hr pretreatment and 10 hr incubation in trypsin and bile at 37, 39 or 41 C, respectively. The highest activation (31%) occurred after 20 hr pretreatment and 10 hr incubation in trypsin and bile at 41 C. Ninety percent of E. scabra oocysts contained active sporozoites after 1 hr CO₂-pretreatment and 10 hr incubation in trypsin and bile at 37 C. At 39 or 41 C, 100% activation occurred with this species after similar pretreatment and treatment periods. With E. bilamellata, 64% activation occurred in nonpretreated oocysts incubated 10 hr in trypsin and bile at 41 C, whereas 100% activation occurred if oocysts were pretreated with CO₂ for 1 hr before treatment with trypsin and bile. Thirty-one, 35, and 36% of CO₂-pretreated E. stiedae oocysts were activated after 1 hr incubation in trypsin and bile at 37, 39 or 41 C, respectively, whereas 1, 2, and 20% activation occurred in nonpretreated oocysts incubated at the same temperatures. Sporozoites in 99-100% of I. canis oocysts were activated after 10 hr treatment in trypsin and bile with or without 1 hr CO₂-pretreatment at 23, 37, 39 or 41 C.