The effect of photoperiod length on respiration in leaves of Saxifraga cernua L., an arctic herb

Abstract Rates of oxygen uptake were measured in leaves of Saxifraga cernua which had been exposed to an 18-h photoperiod. These rates were compared to those in plants which had been exposed to continuous light. Rates of total dark respiration and alternative pathway respiration measured at the end of the photoperiod gradually decreased over the initial 3 d of exposure to an 18-h photoperiod. Thereafter, respiratory rates were constant. Rates of total dark respiration and alternative pathway respiration decreased during the 6h dark period. Rates of normal and alternative pathway respiration are equally affected during the dark period. The respiratory rates had reached a new minimum level 3 d after the initiation of a dark period. These results suggest that respiration rates in arctic plants are high because of the long photoperiod in the arctic. The kinetics of photoperiod induced changes in respiration are slow enough to suggest the involvement of the biological clock in setting respiration rates. Indeed, total dark respiration and alternative pathway respiration show a definite circadian rhythm. Free-running experiments show that normal respiration changes much less (has a smaller amplitude of variation) than alternative pathway respiration and that alternative pathway respiration accounts for most of the rhythmicity of respiration.     

Cyanide-Resistant Root Respiration and Tap Root Formation in Two Subspecies of Hypochaeris radicata

Root respiration of the tap root forming species Hypochaeris radicata L. was measured during tap root formation. A comparison was made of two subspecies: H. radicata L. ssp. radicata L., a subspecies from relatively rich soils, and H. radicata L. ssp. ericetorum Van Soest, a subspecies from poor acidic soils. Root respiration was high and to a large extent inhibited by hydroxamic acid (SHAM) before the start of the tap root formation, indicating a high activity of an alternative non-phosphorylative electron transport chain. The rate of root respiration was much lower and less sensitive to SHAM when a considerable tap root was present. However, root respiration was also cyanide-resistant when a tap root was present, indicating that the alternative pathway was still present. A decreased rate of root respiration coincided with an increase of the content of storage carbohydrates, mainly in the tap root. The level of reducing sugars was constant throughout the experimental period, and it was concluded that the activity of the alternative oxidative pathway was significant in oxidation of sugars that could not be utilized for purposes like energy production, the formation of intermediates for growth or for storage. Root respiration decreased after the formation of a tap root. This decrease could neither be attributed to a gradual disappearance of the alternative chain, nor to a decreased level of reducing sugars. No differences in respiratory metabolism between the two subspecies have been observed, suggesting that a high activity of the alternative oxidative pathway is not significant in adaptation of the present two subspecies to relatively nutrient-rich or poor soils.     

Dark respiration in the marine macroalga Chondrus crispus (Rhodophyceae)

Dark respiration in the red macroalga Chondrus crispus was studied under a variety of conditions. The components of respiration were examined using selective inhibitors in order to characterise pathways of respiration and examine regulation of respiration in marine macroalgae.In comparison to respiration rates generally reported for higher-plant leaves and roots, the steady-state rate of O₂ consumption by this alga, after 30 min dark pretreatment, was found to be quite low (three- to sixfold lower than in higher plants). The addition of uncoupler had only a slight effect on the basal respiration rate, indicating that in these conditions, substrate supply could be limiting respiration. The addition of KCN inhibited respiration by approx. 60%, indicating the presence of alternative oxidase activity. The coefficient of engagement of the alternative pathway (calculated from the data herein) showed that under normal conditions there was little participation of the alternative pathway in O₂ consumption. The response of respiration to O₂ tension was examined with and without inhibitors and the apparent K _m was 17 to 21 M. The addition of KCN plus salicylhydroxamic acid almost completely blocked respiration in C. crispus. The hypothesis that respiratory substrate limits respiration in this alga was investigated by measuring respiration rates immediately after periods of photosynthetic activity. It was found that the respiration rate was dependent on the duration of the light period and could increase up to twofold. This stimulated rate of respiration declined in a first-order fashion during the next 20 to 30 min, finally reaching the basal, zero-order rate measured before illumination. These results strongly indicate a change in the nature of the respiratory substrates during this period. No change in the contribution of the alternative pathway of respiration could be detected following light pretreatment.Abbreviations CCCP carbonyl cyanide m-chlorophenylhydrazone - SHAM salicyl hydroxamic acid     

Alternative Respiration Pathways and Secondary Metabolism in Plants with Different Adaptive Strategies under Mineral Deficiency

The costs of adaptation respiration, the contribution of different biochemical pathways of respiration and alternative oxidases to the adaptation to mineral deficiency were compared in plant species representing different types of adaptive strategies: ruderal (Ru) (Amaranthus retroflexus L. and Leonurus quinquelobatus Gilib.) and predominantly stress-tolerant type (St) (Dactylis glomerata L. and Medicago sativa L.). The adaptation component of the total dark respiration was calculated on the basis of the relative growth rate and the ratio of dark respiration to gross photosynthesis. Adaptation costs were greater in less tolerant species. The inhibitory analysis showed that the contribution of glycolytic pathway decreased and the proportion of oxidative pentose phosphate pathway and residual respiration increased in the intolerant Ru-species under the conditions of abiotic stress. Conversely, in the tolerant St-species, the contribution of glycolysis increased. In all species studied, the contribution of the cytochrome pathway of substrate oxidation was reduced and the contribution of the alternative cyanide-insensitive and residual respiration increased under conditions of mineral deficiency; this phenomenon was particularly pronounced in a less tolerant species L. quinquelobatus. In the species characterized by Ru-strategy, stress increased the content of phenolic compounds and shikimic acid. We suppose that the adaptation respiration costs are associated with alternative biochemical pathways and alternative cyanide-resistant oxidase. The role of these pathways in the plants with St-strategy consists in maintaining the active state of oxidative pathways, whereas in the plants with Ru-strategy, they serve to burn excess metabolites and enhance the synthesis of secondary metabolites, which perform protective functions.     

Possible role of alternative respiration in temperature rise of water stressed plants

Role of alternative respiration, a thermogenic pathway, was evaluated in temperature rise of water stressed plants. Transpiration rate, plant temperature and respiratory dynamics were monitored in field grown irrigated and unirrigated sorghum(Sorghum vulgare Pers.) hybrid CSH 6 and pearl millet(Pennirelum typhoider (Burm. f.) Stapt and Hubbard) var. J 104 for 22 days. Transpiration rate of irrigated plants was always higher than the unirrigated plants. But the plant temperature and the alternative respiration activity of irrigated plants was always lower than unirrigated plants. The reduction in transpiration rate of unirrigated pearl millet was more as compared to unirrigated sorghum. Nonetheless, alternative respiration activity was higher in unirrigated sorghum as compared to unirrigated pearl millet. Temperature of unirrigated sorghum plants increased by 10.4°C during 22 days and it was 8.0°C higher than irrigated sorghum at day 22. Stressed pearl millet showed an increase of 3.9°C during 22 days and it was 2.9°C higher than the irrigated pearl millet at day 22. It is suggested that the heat released because of the alternative respiration activity also contributes towards temperature rise of water stressed plants.     

Induction of alternative oxidase chain under salt stress conditions

This paper describes the effect of NaCl on the respiration of Citrus cell suspensions namely on the induction of the alternative oxidase. The exposure of two Citrus (cvs. Carvalhal tangor and Valencia late) cell suspensions to 200 or 400 mM NaCl lead to a reduction on cell respiration rates. Under these conditions, the respiration rate decreased less in the presence of KCN indicating a stimulation of the capacity of the alternative oxidase (AOX). In addition, immunoblots showed an increase on the amount of AOX protein. Antibodies raised against the Sauromatum guttatum enzyme recognized the reduced form of the enzyme near the 35 kDa band. The protein accumulation was correlated with the significantly higher AOX capacity observed for cv. Carvalhal tangor.     

Cephalosporin-C production, morphology and alternative respiration of Acremonium chrysogenum in glucose-limited chemostat

Summary In this paper, the connection between morphology, cephalosporin-C production and alternative respiration of Acremonium chrysogenum is examined. As demonstrated by chemostat experiments, the ratio of the filamentous and the yeast-like forms depended on the growth rate. The yeast-like form, but not the filamentous form exhibited cyanide-resistant alternative respiration. As a consequence, the yeast-like form was regarded to be more suitable for antibiotic overproduction.     

The role of the alternative respiratory pathway in the stimulation of cephalosporin C formation by soybean oil in Acremonium chrysogenum

Addition of soybean oil to Acremonium chrysogenum cultures growing on sugars doubled the specific production of cephalosporin C during the idiophase of growth. While the addition of soybean oil had no effect on the total rate of respiration, the respiration that proceeded via the alternative, cyanide-insensitive pathway exhibited a more than twofold increase. Addition of soybean oil also stimulated the formation of isocitrate lyase activities. Inhibition of oxidative metabolism of one of the products of isocitrate lyase (succinate) by thenoyltrifluoroacetone completely inhibited the alternative respiratory pathway. The role of soybean-oil-stimulated alternative respiration in the stimulation of cephalosporin C production and the role of isocitrate lyase are discussed. Received: 13 October 1998 / Revised revision: 14 January 1999 / Accepted: 22 January 1999     

Respiration of crop species under CO2 enrichment

Respiratory characteristics of wheat (Triticum aestivum L. cvs Gabo and WW15), mung bean (Vigna radiata L. Wilczek cv. Celera) and sunflower (Helianthus annuus L. cv. Sunfola) were studied in plants grown under a normal CO₂ concentration and in air containing an additional 340 (or 250) μl l^?1 CO₂. Such an increase in global atmospheric CO₂ concentration has been forecast for about the middle of the next century. The aim was to measure the effect of high CO₂ on respiration and its components. Polarographic and, with wheat, CO₂ exchange techniques were used. The capacity of the alternative pathway of respiration in roots was determined polarographically in the presence of 0.1 mM KCN. The actual rate of alternative pathway respiration was assessed by reduction in oxygen consumption caused by 10 mM salicylhydroxamic acid. Each species responded differently. In wheat, growth in high atmospheric CO₂ was associated with up to 45% reduction in respiration by both roots and whole plants. Use of respiratory inhibitors in polarographic measurements on wheat roots implicated reduction in the degree of engagement of the alternative pathway as a major contributor to this reduced respiratory activity of high-CO₂ plants. No change was found in the total sugar content per unit wheat root dry weight as a result of high CO₂. In none of the species was there an increase in the absolute, or relative, contribution by the alternative pathway to total respiration of the root systems. Thus the improved photosynthetic assimilate supply of plants grown in high CO₂ did not lead to increased diversion of carbon through the non-phosphorylating alternative pathway of respiration in the root. On the contrary, in wheat grown in high CO₂ the reduced loss of carbon through that route must have contributed to their larger dry weight.     

Interactions between osmoregulation and the alternative respiratory pathway in Plantago coronopus as affected by salinity

Plantago coronopus L., a species from the coastal zone, was grown in culture solution with and without 50 mM NaCl. In addition it was transferred from a non-saline solution to a solution containing 50 mM NaCl. Short term effects of NaCl on growth and various aspects of energy metabolism, including photosynthesis, shoot dark respiration, root respiration and the contribution of the SHAM-sensitive alternative pathway to root respiration were investigated. The concentrations of soluble and insoluble non-structural carbohydrates and of sorbitol a compatible osmotic solute in Plantago, in both shoots and roots were also determined. Growth of shoots and roots was largely unaffected by addition of 50 mM NaCl. Net photosynthesis, shoot dark respiration and the concentration of non-structural carbohydrates in both shoots and roots were also unaffected by salinity. The rate of root respiration immediately decreased upon addition of 50 mM NaCl. This decrease was almost exclusively attributed to a decreased activity of the SHAM-sensitive alternative pathway. The concentration of sorbitol in the roots increased quickly after addition of 50 mM NaCl, whilst the increase in sorbitol concentration in the shoots started later. The time course of the increase of sorbitol concentration was similar to that of the decrease in activity of the alternative pathway. During the first 12 h after exposure to 50 mM NaCl, the amount of carbohydrates which was saved in respiration, due to the decreased activity of the alternative pathway, was the same as that used for sorbitol synthesis in the roots. It is concluded that the activity of the alternative pathway decreased due to increased utilization of carbohydrates for sorbitol synthesis, according to a proposed ‘energy overflow model’. After 24 h, the sorbitol concentration in the cytoplasm of the root cells of plants transferred to a saline solution reached a level that was sufficient to compensate for 50 mM NaCl, assuming a cytoplasmic volume of ca. 10% of the total cell volume. The sorbitol concentration in roots of plants grown in a saline environment for several weeks was lower than that in roots of plants transferred to a saline environment for c. 24 h. It is suggested that sorbitol accumulated in roots of Plantago coronopus as an immediate reaction upon salinity, whilst other adaptations may occur thereafter.     

Inheritance of cyanide-resistant respiration in two cultivars of pea (Pisum sativum L.)

Abstract Two pea cultivars (Pisum sativum L., cvs. Alaska and Progress No. 9) shown previously to differ with regard to the appearance of the cyanide-resistant (alternative) pathway of respiration in axis tissue, were found to show this same difference in mature leaf tissue and in epicotyl mitochondria. The possible relationship between dwarf growth form and lack of alternative respiration in cv. Progress No. 9 was tested in two ways. When dwarfism was alleviated in Progress No. 9 by application of exogenous gibberellin A₁, no appearance of the alternative pathway was observed. In a survey of eight other dwarf pea cultivars, five were found to have an alternative pathway comparable to that shown by the tall cv. Alaska, while three lacked the pathway (cf. Progress No. 9). In reciprocal crosses between Alaska and Progress No. 9, the alternative pathway capacity of F₁ progeny resembled that of the maternal parent. This pattern was maintained in all the F₂ generation, indicating maternal inheritance of the trait. These data suggest that alternative respiration in pea is, to some extent, under the control of an organellar genome.     

LIGHT RESPIRATION IN SIX ESTUARINE PHYTOPLANKTON SPECIES: CONTRASTS UNDER PHOTOAUTOTROPHIC AND MIXOTROPHIC GROWTH CONDITIONS1

The photoresponse of respiration was examined in six estuarine phytoplankton species grown at a limiting irradiance in the presence or absence of glucose. Cellular respiration rates in the dark, at the growth irradiance, and at saturating light levels were higher in glucose-grown cultures than in photoautotrophic cultures. Glucose uptake also affected the relationship between incident irradiance and gross respiration rate, and the specific respiratory pathways that contributed to the respiration versus irradiance (R vs. I) response. The energy-conseming Mehler reaction contributed largely to light-stimulated respiration in photoautotrophic (energy-limited) cultures. However, the energy-dissipating alternative pathway was the predominant form of respiration measured in mixotrophic (energy-sufficient) cultures. Based on these and previous observations, a model of phytoplankton R us. I response is presented, in which the relative contributions of different light respiratory processes (cytochrome pathway respiration, alternative pathway respiration, chlororespiration, Mehler reaction) are dependent on the incident irradiance and cellular energy content.     

Effects of light on respiration and oxygen isotope fractionation in soybean cotyledons

Light effects on electron flow through the cyanide-resistant respiratory pathway, oxygen isotope fractionation and total respiration were studied in soybean (Glycine max L.) cotyledons. During the first 12 h of illumination there was an increase in both electron partitioning through the alternative pathway and oxygen isotope fractionation by the alternative oxidase. The latter probably indicates a change in the properties of the alternative oxidase. There was no engagement of the alternative oxidase in darkness and its fractionation was 27‰. In green cotyledons 60% of the respiration flux was through the alternative pathway and the alternative oxidase fractionation was 32‰. Exposing previously illuminated tissue to continuous darkness induced a decrease in the electron partitioning through the alternative pathway. However, this decrease was not directly linked with the low cellular sugar concentration resulting from the lack of light because 5 min of light every 12 h was sufficient to keep the alternative pathway engaged to the same extent as plants grown under control conditions.     

Alternative respiration of fungus <Emphasis Type="Italic">Phycomyces blakesleeanus</Emphasis>

Respiratory characteristics of germinating spores, developing mycelium and mitochondria of the fungus Phycomyces blakesleeanus were investigated by means of oxygen Clark-type electrode. The effects of respiratory inhibitors and metabolic compounds on oxygen consumption were tested. It was demonstrated that P. blakesleeanus apart of cyanide-sensitive respiration, CSR, possess alternative respiration, (cyanide-resistant respiration, CRR) which is constitutive and whose capacity decreases during development. Maximum is observed for activated spores where CRR capacity is significantly greater than CSR. After treatment with antimycin A, a third type of respiration insensitive to antimycin A and low concentration of SHAM (sufficient for inhibition of CRR), but sensitive to cyanide and high concentration of SHAM, has been expressed.     

Mitochondrial function in the yeast form of the pathogenic fungus <Emphasis Type="Italic">Paracoccidioides brasiliensis</Emphasis>

Differences between the respiratory chain of the fungus Paracoccidioides brasiliensis and its mammalian host are reported. Respiration, membrane potential, and oxidative phosphorylation in mitochondria from P. brasiliensis spheroplasts were evaluated in situ, and the presence of a complete (Complex I–V) functional respiratory chain was demonstrated. In succinate-energized mitochondria, ADP induced a transition from resting to phosphorylating respiration. The presence of an alternative NADH–ubiquinone oxidoreductase was indicated by: (i) the ability to oxidize exogenous NADH and (ii) the lack of sensitivity to rotenone and presence of sensitivity to flavone. Malate/NAD⁺-supported respiration suggested the presence of either a mitochondrial pyridine transporter or a glyoxylate pathway contributing to NADH and/or succinate production. Partial sensitivity of NADH/succinate-supported respiration to antimycin A and cyanide, as well as sensitivity to benzohydroxamic acids, suggested the presence of an alternative oxidase in the yeast form of the fungus. An increase in activity and gene expression of the alternative NADH dehydrogenase throughout the yeast’s exponential growth phase was observed. This increase was coupled with a decrease in Complex I activity and gene expression of its subunit 6. These results support the existence of alternative respiratory chain pathways in addition to Complex I, as well as the utilization of NADH-linked substrates by P. brasiliensis. These specific components of the respiratory chain could be useful for further research and development of pharmacological agents against the fungus.     

基于代谢组学分析黑老虎植株不同部位黄酮类成分

黑老虎的根是常用中药,黄酮类化合物是药用植物的主要活性成分之一。为探究黑老虎植株叶和茎中可能含有与根类似或具有高度富集的类黄酮化合物,挖掘其利用价值。该文利用广泛靶向代谢组学技术,鉴定了黑老虎的叶、茎和根的代谢物,并根据结构配置分类,解析其中类黄酮的多样性和丰度。结果表明：(1)黑老虎叶中类黄酮数量(80个)>茎(73个)>根(67个),3个部位均有61个相同的黄酮类化合物,叶和茎中含有更多的黄酮醇类化合物,从而使类黄酮多样性高于根。(2)在3个部位积累量比较高的是黄酮醇类、黄酮类、黄烷醇类和查尔酮类,其中黄酮醇和黄酮在茎和根积累量下降,导致类黄酮丰度从叶(24.00×10⁷)-茎(13.45×10⁷)-根(9.05×10⁷)连续大幅度下调。(3)叶和茎中含有大量与根相同和多种根中没有的类黄酮,可以考虑替代或互补利用,3个部位儿茶素类化合物表达量都较高,叶中还富含槲皮素及其衍生物,具有较高的利用价值。     

The relationship between respiration and temperature in leaves of the arctic plant Saxifraga cernua

Abstract Saxifraga cernua, a perennial herb distributed throughout the arctic and subarctic regions, shows high levels of dark respiration. The amount of respiration exhibited by leaves and whole plants at any temperature is influenced by the pretreatment temperature. Plants grown at 10°C typically show higher dark respiration rates than plants grown at 20°C. The levels of alternative-pathway respiration (or cyanide-insensitive respiration) in leaves of S. cernua grown at high and low temperatures were assessed by treating leaf discs with 0.25 mol m^?3 salicylhydroxamic acid during measurements of oxygen consumption. Alternative pathway respiration accounted for up to 75% of the total respiration. Tissues from 20°C-grown plants yielded a Q₁₀ of 3.37 for normal respiration, and of 0.97 for alternative-pathway respiration. Tissues from 10°C-grown plants yielded a Q₁₀ of 2.55 for normal respiration, and of 0.79 for alternative-pathway respiration. The alternative pathway does not appear to be as temperature sensitive as the normal cytochrome pathway. A simple energy model was used to predict the temperature gain expected from these high rates of alternative-pathway respiration. The model shows that less than 0.02°C can be gained by leaves experiencing these high respiration rates.     

REGULATION OF ALTERNATIVE PATHWAY RESPIRATION IN CHLAMYDOMONAS REINHARDTH (CHLOROPHYCEAE)1

The inhibitor propyl gallate was used to estimate partitioning of respiratory electron flow between the cytochrome amd alternative pathways in Chlamydomonas reinhardtii Dangeard. Nutrient limitation (nitrogen or phosphorus resulted in a large increase in alternative pathway capacity relative to cytochrome pathway activity, without regulating in engagement of the alternative pathway. High rates of respiration, which could be induced in phosphate-starved cells by a combination of phosphate addition and uncoupler, resulted in alternative pathway activity. Osmotic stress resulted in decreased electron flow through the cytochrome pathway and increased flow through the alternative pathway, while high temperature also resulted in alternative pathway engagement. Incubation with exogenous carbon sources could increase the rate of respiratory O₂ consumption; the increase was mediated entirely by the alternative pathway. We suggest that the alternative pathway functions in these cells both to maintain respiration during environmentally induced stress and as on energy overflow.     

Relationship between root respiration and seedling age in tomato cultivars infested by Meloidogyne incognita

Measurements were made of respiration in the roots of tomato cultivars susceptible and resistant to Meloidogyne incognita. Nematode infestation of the susceptible cv. Roma VF caused an initial stimulation of the total respiration with an increase in the CN-sensitivity; the effect decreased and then disappeared as the seedlings aged. In the resistant cv. Rossol nematode infestation initially caused an inhibition of total respiration and a decrease in the CN-sensitivity; respiration and CN-sensitivity increased with seedling age. The activity of the alternative respiration pathway (m-chlorobenzhydroxamic acid-sensitive) was unchanged by nematode infestation in the resistant cultivar and increased markedly in the susceptible cultivar during the early stages of infestation.