Influence of osmotic stress on the respiration of potato tuber callus

Potato tuber ( Solanum tuberosum L. cv. Bintje) callus shows a decrease in fresh weight and an increase in dry weight upon transfer to nutrient medium supplemented with 0.3 or 0.5 M mannitol. The osmolarity of the intracellular fluid increases simultaneously. Probably mannitol is taken up from the medium till the osmolarity of the tissue is in equilibrium with that of the medium. After osmotic adaptation, on a medium with 0.5 M mannitol, growth is negligible, although the tissue retains its viability.
Respiration increases upon transfer to medium with extra mannitol, especially when expressed on a fresh weight basis. On this basis cytochrome and alternative pathway capacities do not change appreciably. The respiratory increase is exclusively caused by an increased engagement of the alternative pathway. The participation of this pathway in uninhibited respiration increases from about 10 to 90% upon transfer to medium with extra mannitol. The increase in respiration is partly correlated with the decrease in fresh weight upon transfer. Per disc, the capacities of the cytochrome and alternative pathway decline. Yet, total respiration per disc significantly increases due to the increased participation of the alternative pathway. This results in an almost equal ATP-production per disc before and after transfer. We suggest, that the alternative pathway functions as a reserve capacity in potato callus, which is switched on when ATP-production coupled to the cytochrome pathway is impaired.     

Effect of oxygen on growth and respiration of potato tuber callus

Growth and oxygen uptake of potato callus is faster in an oxygen-enriched atmosphere (70% oxygen, v/v; oxygen-callus) than in air (20% oxygen, v/v; air-callus). Especially the non-mitochondrial, so-called residual respiration is increased in oxygen-callus. The capacities of the mitochondrial respiratory pathways (cytochrome pathway, V_cyt and alternative pathway, V_alt) are also higher in this callus. In both callus types only a small part of the alternative pathway capacity is used in uninhibited respiration. The lower oxygen uptake of air-callus at normal air oxygen pressures is partially due to diffusional impedance. Measurement of the respiratory parameters of air-callus in oxygen-saturated medium leads to higher values than measurement in air-saturated medium, although these values are still lower than those of oxygen-callus.ATP-production was calculated from the oxygen-uptake data and compared with the dry weight production of the callus to give values of 10.0 and 10.8 g dry weight produced.-mol ATP^-1, for air-callus and oxygen-callus respectively. As no harmful side-effects are observed, cultivation of callus under elevated oxygen pressures may be useful, when rapid callus-growth is necessary.Abbreviations AA antimycin A; A; - BHAM benzohydroxamate - DW dry weight - FW fresh weight - 8-OHQ 8-hydroxyquinolin - RC respiratory control - SHAM salicylhydroxamate     

Alternative pathway activities in aged potato tuber slices measured by three methods

To find a simple and reliable oxygen electrode-based method to estimate the values of alternative pathway activity (V _alt) and its contribution to total respiration V _alt/V _t) in aged potato (Solanum tuberosum L.) tuber slices, we compared conventional hydroxamate-inhibiting method, improved hydroxamate-inhibiting method with 2,6-dichlorophenol indophenol (DCPIP), and the oxygen isotope discrimination (OID) method. The values of V _alt and V _alt/V _t obtained with an improved hydroxamate-inhibiting method with DCPIP in 12-h- and 24-h-aged slices were about twice higher than those with the conventional hydroxamate-inhibiting method. Only a relatively small difference in the values of V _alt and V _alt/V _t obtained by the OID method and the improved hydroxamate-inhibiting method with DCPIP in 12-h and 24-h-aged slices was observed. These results indicated that the improved hydroxamate-inhibiting method with DCPIP could be considered as a new, simple, and reliable technique for the noninvasive assay of the AP activity.From Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 311–315.Original English Text Copyright © 2005 by Hou, Zhou, Kong, Liang, Zhang.This article was submitted by the authors in English.This revised version was published online in April 2005 with a corrected cover date.     

Role of the pentose phosphate pathway during callus development in explants from potato tuber

Metabolic change during callus formation in explants from potatotuber (Solarium tuberosum L.) was investigated. Under the presentculture conditions, callus starts exponential growth (estimatedby the fresh weight increase) with a 5-day lag period, at whichtime marked production of DNA occurs. In the lag period, respirationis very much resistant to malonate, and the value of the C6/C1ratio and activities of both G6PDH 6PGDH pass their peaks. Onthe basis of these and relevant findings, glucose metabolismthrough the PP pathway is surmised to play a significant rolein the initial DNA multiplication phase of callus development. (Received October 15, 1969; )     

Alternative pathway respiration and lipoxygenase activity in aged potato slice mitochondria

Mitochondrial preparations isolated from aged white potato (Solanum tuberosum L.) slices exhibited classical cyanide-insensitive O(2) uptake which was inhibited by salicylhydroxamic acid and tetraethylthiuram disulfide (disulfiram). These mitochondria also possessed lipoxygenase activity, as determined by O(2) uptake in the presence of 4 millimolar linoleic acid. Purification of the mitochondrial preparation on a continuous Percoll gradient resulted in a large decrease in lipoxygenase activity whereas cyanide-insensitive (disulfiram sensitive) O(2) consumption was still observed. These data indicate that cyanide-insensitive O(2) consumption in mitochondrial preparations isolated from aged white potato slices is of mitochondrial origin and not due to lipoxygenase contamination.     

Effects of ethylene on potato tuber respiration

Treatment of potato tubers (Solanum tuberosum L.) with ethylene gas causes a rapid rise in their respiration rate, reaching 5 to 10 times the rate of untreated tubers over 30 hours of treatment and then falling slowly. The response shows a lag of 8 hours, and more than 24 hours of exposure is required for maximum effect; the temperature optimum is near 25 C. In sensitivity to low concentrations and dependence on temperature, the phenomenon is similar to the effect of ethylene on the respiration of climacteric and nonclimacteric fruits. Treated potato tubers returned to air recover their sensitivity to ethylene more slowly than do nonclimacteric fruits (e.g., mature green oranges). It is proposed that the respiratory rise characteristic of ripening in climacteric fruits and of the wound response in plant tissues is induced by a rise in endogenous tissue ethylene.     

Initiation and culture of potato tuber callus tissue with picloram

Callus cultures of 7 potato cultivars were initiated from tuber tissue and maintained on Gelrite-solidified media with 1–20 M picloram as the only PGR. Ten M picloram was the optimal concentration for callus induction. By 4–6 weeks after explanting, there was sufficient callus produced for subculture to maintenance media which contained 1–20 M picloram as the only PGR. When grown in the dark at 25°C, subcultured callus typically increased 10-fold in wet weight in 4–5 weeks. The callus produced was friable and a light grey to cream color. Callus cultures were used to establish cell suspension cultures. Callus and cell suspension cultures have been maintained for over 2 years on the picloram containing media.Abbreviations BA benzyladenine - 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige-Skoog - NAA naphthaleneacetic acid - PGR plant growth regulator Research paper #9053 of the Idaho Agricultural Experiment Station.     

The regulation of respiration and growth of potato tuber callus by endogenous ethylene. Suppression of ethylene action by 2,5-norbornadiene

The growth (fresh and dry weight increase) of potato tuber ( Solanum tuberosum L. cv. Bintje) callus discs was stimulated by incubation in air with 500 ppm 2,5-norbornadiene (NBD, a competitive inhibitor of ethylene action) and inhibited by incubation in air with 4 000 ppm NBD. Ethylene formation by the callus was stimulated by NBD. The development of the alternative pathway, measured in isolated mitochondria was inhibited by NBD in a concentration-dependent way. The alternative pathway capacity, measured in vivo, was inhibited by 4 000 ppm NBD, but not by 500 ppm. Uninhibited in vivo respiration, which consists of cytochrome path activity and alternative path activity, was stimulated by the treatment with 500 ppm NBD. The main contribution to this stimulation was made by the cytochrome pathway. In 4 000 ppm NBD-treated callus, uninhibited respiration seemed to be unaffected as a consequence of an inhibited cytochrome path activity, which was compensated by a stimulated alternative path activity. Both in 500 and 4 OIK) ppm NBD-treated callus the alternative path activity in vivo was stimulated.
The regulatory role for endogenous ethylene in potato tuber callus is discussed in relation to: 1) The induction of respiratory pathways, 2) the supply of reduction equivalents in vivo and 3) growth.     

Alternative pathway of respiration in Physarum polycephalum plasmodia

The external application of inhibitors of glycolysis in the presence of KCN shows a lethal effect on plasmodia of Physarum polycephalum. However, alpha-ketoglutarate, but not succinate, maintains the contraction-relaxation cycle of plasmodial actomyosin in spite of the fact that glycolysis and cytochrome oxidase are inhibited. The oscillations supported by ketoglutarate disappear in the presence of SHAM, an inhibitor of alternative oxidase. These results imply the existence of KCN-resistant, alternative pathway of electron transport in the mitochondria of Physarum polycephalum.     

Resistance of Escherichia coli grown at different temperatures to various environmental stresses

Aims:  To study the influence of growth temperature on the resistance of Escherichia coli to three agents of different nature: heat, pulsed electric field (PEF) and hydrogen peroxide.
Methods and Results:  Escherichia coli cells were grown to stationary phase at 10°C, 20°C, 30°C, 37°C and 42°C. Survival curves to a heat treatment at 57·5°C, to a PEF treatment at 22 kV cm⁻¹ and to 40 mmol l⁻¹ hydrogen peroxide were obtained and fitted to a model based on the Weibull distribution to describe and compare the inactivation. Time to inactivate the first log cycle of the population at 57·5°C of cells grown at 42°C was sixfold higher than that corresponding to cells grown at 10°C. On the contrary, cells grown at 10°C and 20°C were more resistant to PEF and hydrogen peroxide treatments.
Conclusions:  The influence of growth temperature on bacterial resistance depends on the stress applied. Cells grown at higher temperatures were more heat resistant, but more sensitive to PEF and hydrogen peroxide.
Significance and Impact of the Study:  Results obtained in this investigation help in understanding the physiology of bacterial resistance and the inactivation mechanisms of different technologies.     

Maintenance and growth respiration in shoots and roots of sunflower plants grown at different root temperatures

Continuous measurements of CO₂-evolution and dry matter accumulation were carried out on shoots and roots separately of intact Helianthus annuus L. cv. Autumn Beauty plants grown in nutrient solution at different root temperatures. The data were used to distinguish between growth and maintenance components of respiration. The maintenance and growth coefficients were higher in the root system than in the shoots. The overall efficiency of assimilate utilization was within the range reported in the literature. An increase in root temperature increased the maintenance part of root respiration and, to a lesser degree, also shoot maintenance respiration. Neither root nor shoot growth respiration coefficients were affected by root temperature. It is concluded that the study of whole-plant respiration masks differences in energy utilization between shoots and roots.     

Fatty acid fingerprints of Streptococcus mutans NCTC 10832 grown at various temperatures.

Fatty acid fingerprints were determined gas chromatographically for Strepcococcus mutans NCTC 1082 which had been grown in batch brain heart infusion at a series of nine temperatures ranging from 29.0 to 40.0 degrees C. The major acids at all temperatures were n-palmitic and octadecenoic acids. Other acids detected at all temperatures included n-myristic, palmitoleic, n-stearic, and eicosenoic acids. An increase in temperature resulted in a decrease in the proportion of unsaturated to saturated fatty acids, indicating the importance of accurate temperature control in such gas-liquid chromatographic, chemotaxonomic studies.     

Metabolic flux analysis of the phenylpropanoid pathway in elicitor-treated potato tuber tissue

The effects of beta-1,3-oligosaccharide elicitor on the metabolism of phenylpropanoids in potato tuber were analyzed quantitatively, by monitoring the time-dependent changes in the levels of seven compounds. The elicitor treatment caused an increase in the pool size of octopamine and tyramine amides (N-p-coumaroyloctopamine, N-feruloyloctopamine, N-p-coumaroyltyramine and N-feruloyltyramine), as well as a decrease in that of chlorogenic acid and putrescine amides (caffeoylputrescine and feruloylputrescine). An analysis of metabolic flux using stable isotope labeling and liquid chromatography-spectrometry (LC-MS) detection clearly demonstrated that the changes in the pool size of these compounds were correlated with the changes in their flux for biosynthesis (Jin) upon elicitor treatment. The increase in Jin in the cases of octopamine and tyramine amides was accompanied by an increase in flux for the transformation (Jout), indicating a rapid turnover of these compounds in the elicitor-treated tuber tissue. The result of the flux analysis indicated that the actual activation of the biosynthesis of octopamine and tyramine amides after the elicitor treatment was greater than that estimated from the changes in their levels in the potato tissue. These findings suggest that these amide compounds and their metabolic derivatives play an important role in the defense-related metabolism of phenylpropanoids in potato.     

Carbohydrate supplements to the callus culture medium modify the growth of potato tuber moth larvae feeding on Lycopersicon chmielewskii callus

Lycopersicon esculentum and L. chmielewskii are respectively susceptible and resistant to the potato tuber moth (Phthorimaea operculella Zeller) in the field. Feeding bioassays were conducted with the herbivore caterpillars reared on callus derived from both tomato species and grown in vitro, and the influence of carbohydrate supplements to the callus culture medium, on the insect's feeding behavior was investigated. Newly-hatched larvae fed with L. esculentum or L. chmielewskii callus raised on a medium with 88 mM sucrose, reached a weight of 12–15 mg and 1.5–3.0 mg, respectively, within 9 days. Restriction of larval weight increase in insects reared on L. chmielewskii callus, disappeared when the host tissue was transferred 24 h prior to the callus-insect assay to a medium supplemented with 264 mM of either sucrose, glucose, fructose or mannose. The capability of L. chmielewskii callus to restrict growth of larvae was restored in host tissue retransferred from a medium with 264 mM sucrose to a 24-h incubation on one supplemented with 264 mM of either mannitol, sorbitol, glycerol or myo-inositol, before the callus-insect bioassay. The larval growth response remained unaltered by callus incubated on a medium with 264 mM xylose. The ameliorating effect on insect growth of high sucrose in the callus medium was not due to sucrose as an ingredient of the insect's diet. The diverse response of L. chmielewskii callus, and its dependence on the type of carbohydrate in the medium, rule out effects of these substances as nonspecific medium osmotica. The swift callus responses to carbohydrates (within hours of a change in medium composition), as reflected in the insect's growth, were not accompanied by visible morphological variations in the host tissue. We suggest that suppression by high levels of exogenously applied saccharides and derepression by exogenous polyols and myo-inositol of the impedement to growth of the potato tuber moth larva, reflect the existence in L. chmielewskii of a carbon metabolic control mechanism of gene expression whose products affect insect growth.     

烟草愈伤组织继代培养期间呼吸途径与活性氧水平动态变化

继代培养期间的烟草愈伤组织总呼吸速率分别在第11天和第19天出现两次跃升,同时抗氰呼吸的发生与运行逐渐加强,在两呼吸高峰之间达到极大值,随后则逐渐下降,但愈伤组织的电子传递仍以细胞色素途径为主．通过对愈伤组织衰老过程中活性氧代谢变化分析,发现抗氰呼吸发生与H     

Phenol metabolism, phytoalexins, and respiration in potato tuber tissue treated with Fatty Acid

Potato (solanum tuberosum L. cv Katahdin) tuber discs treated with arachidonic acid become necrotic and accumulate sesquiterpenoid phytoalexins. The arachidonic acid also causes increases in both phenylalanine ammonia lyase and lignin, but no change in total alcohol-soluble phenols. Linoleic acid does not alter any of these parameters. A high concentration of nonanoic acid promotes both necrosis and accumulation of low levels of phytoalexins, but decreased levels of phenols, phenylalanine ammonia lyase, and lignin. The respiration of the control discs and those treated with linoleic acid declines by 24 hours after treatment, but the respiration of arachidonic acid-treated discs remains constant for at least 48 hours.     

Adventitious bud formation on leaf and stem segments of Heloniopsis orientalis grown at various temperatures

The effect of different temperatures on bud formation in excisedleaf fragments and in stem segments of Heloniopsis orientalis,a monocotyledonous plant, was investigated in light and in darkness.The optimal temperature for bud formation was 21?C to 25?C.16?C pretreatment for 7 to 21 days promoted bud formation inleaf segments. 30?C pretreatment for 7 days or more reducedthe number of buds in both young etiolated and mature greenleaf segments but not in young green leaf segments. In younggreen leaf segments grown in darkness, however, 30?C pretreatmentreduced the number of buds. Inhibition of bud formation dueto high temperature could not be reversed by BA. (Received November 15, 1978; )     

Motor units at various temperatures

This review focuses on the effects of temperature on the functioning of the neuromuscular system. The changes in environmental temperature could affect the contractile acts in both ectotherms and endotherms by changing the amplitude and velocity of contractions and, accordingly, the mechanical work of skeletal muscles. In this study, we summarize the data on the effects of hypo- and hyperthermia on the supraspinal and peripheral components of regulation of the neuromuscular function.