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     

Endogenous ethylene formation and the development of the alternative pathway in potato tuber discs

Callus-forming discs from potato ( Solanum tuberosum L. cv. Bintje) tubers grown on a nutrient medium containing an auxin and a cytokinin show both a higher ethylene formation and a higher capacity of the mitochondrial alternative pathway than nongrowing discs (on the same medium without auxin and cytokinin). Addition of 1-ami-nocyclopropane-1-carboxylic acid (ACC) to the nutrient medium of non-growing discs results in an enhancement of the ethylene formation as well as the alternative pathway capacity. In callus-forming tissue, the levels of both these parameters can be suppressed by adding aminoethoxyvinylglycine (AVG) to the nutrient medium without affecting growth. The effects on state 3-respiration of ACC (increase) and AVG (decrease) are relatively small. These results suggest that the alternative pathway capacity is controlled to a considerable extent by the endogenous ethylene formation of the tissues.     

Influence of ethanol on alternative oxidase in mitochondria from callus-forming potato tuber discs

Ethanol, when added to the incubation medium of callus-forming potato tuber discs, inhibits callus growth and causes an increase of the mitochondrial antimycin-A resistant respiration, expressed as a percentage of state III-respiration. This increase in resistance to antimycin-A is the result of a poor development of the cytochrome pathway in tissue discs treated with ethanol. The development of the antimycin-A resistant alternative oxidase sensitive to chelator is about the same for treated and untreated discs. The respiratory control (RC) ratio of the mitochondrial respiration increases after addition of a chelator, which inhibits the alternative pathway. The RC ratio of the uninhibited mitochondrial respiration appears to be inversely related to the capacity of the alternative pathway, when mitochondrial preparations with different capacities to transfer electrons via the alternative path are compared. From the experimentally observed relation between RC-ratio and alternative oxidase capacity, it was concluded that at least half of the capacity of the alternative path is used in uninhibited state IV respiration.     

Regulatory involvement of abscisic acid in potato tuber wound-healing

Rapid wound-healing is crucial in protecting potato tubers frominfection and dehydration. Wound-induced suberization and theaccumulation of hydrophobic barriers to reduce water vapourconductance/loss are principal protective wound-healing processes.However, little is known about the cognate mechanisms that effector regulate these processes. The objective of this researchwas to determine the involvement of abscisic acid (ABA) in theregulation of wound-induced suberization and tuber water vapourloss (dehydration). Analysis by liquid chromatography–massspectrometry showed that ABA concentrations varied little throughoutthe tuber, but were slightly higher near the periderm and lowestin the pith. ABA concentrations increase then decrease duringtuber storage. Tuber wounding induced changes in ABA content.ABA content in wound-healing tuber discs decreased after wounding,reached a minimum by 24 h, and then increased from the 3rd tothe 7th day after wounding. Wound-induced ABA accumulationswere reduced by fluridone (FLD); an inhibitor of de novo ABAbiosynthesis. Wound-induced phenylalanine ammonia lyase activitywas slightly reduced and the accumulation of suberin poly(phenolics)and poly(aliphatics) noticeably reduced in FLD-treated tissues.Addition of ABA to the FLD treatment restored phenylalanineammonia lyase activity and suberization, unequivocally indicatingthat endogenous ABA is involved in the regulation of these wound-healingprocesses. Similar experiments showed that endogenous ABA isinvolved in the regulation of water vapour loss, a process linkedto wax accumulation in wound-healing tubers. Rapid reductionof water vapour loss across the wound surface is essential inpreventing desiccation and death of cells at the wound site;live cells are required for suberization. These results unequivocallyshow that endogenous ABA is involved in the regulation of wound-inducedsuberization and the processes that protect surface cells fromwater vapour loss and death by dehydration. Key words: Abscisic acid, poly(aliphatic), poly(phenolic), potato, Solanum tuberosum L., suberin     

Droopy: a wilty mutant of potato deficient in abscisic acid

Abstract. Droopy mutant of potato ( Solanum tubero-sum L., group Pliureja ) wilts because of excessive stomatal opening (Waggoner & Simmonds, 1966). Progeny of the cross between potato clones C.P.C. 4461 and C.P.C. 4463 showed characteristics similar to those of the original droopy potato. These plants wilted at high vapour pressure deficit and their stomatal conductances in the light and the dark were higher than those of normal plants. Conductances were reduced by applied abscisic acid (ABA), but stomata remained partially open even when guard cells were plasmolysed. Leaves of droopy plants accumulated very little ABA when water-stressed.     

Photocontrol of chlorogenic acid biosynthesis in potato tuber discs

The appearance of phenylalanine ammonia-lyase activity and the accumulation of chlorogenic acid in potato tuber discs are stimulated by illumination with white light, whereas the appearance of cinnamic acid 4-hydroxylase activity is unaffected by illumination. The photosensitive step in chlorogenic acid biosynthesis may be by-passed by treatment of discs with exogenous supplies of cinnamic acid, whereas treatment of discs with phenylalanine does not isolate the photosensitive step. Therefore, the site of photocontrol of chlorogenic acid biosynthesis in potato tuber discs is the reaction catalysed by phenylalanine ammonia-lyase. Cinnamic acid 4-hydroxylase activity in vitro is unaffected by p-coumaric acid, caffeic acid or chlorogenic acid. Phenylalanine ammonia-lyase activity in vitro is sensitive to inhibition by cinnamic acid. The in vitro properties of the two enzymes are also consistent with the hypothesis that phenylalanine ammonia-lyase rather than cinnamic acid 4-hydroxylase is important in the regulation of chlorogenic acid biosynthesis in potato tuber discs.     

Influence of growth temperature on respiratory characteristics of mitochondria from callus-forming potato tuber discs

The uninhibited respiration of mitochondria, isolated from potato tuber discs (Solanum tuberosum L. cv. Bintje) incubated on a callus-inducing medium at 28°C, is higher than that of mitochondria from tissue incubated at 8°C. This respiration is composed of a CN-sensitive and a CN-resistant part. The capacity of the CN-resistant alternative oxidase pathway is larger in mitochondria from 28°C tissue than in mitochondria from 8°C tissue (35% and 8% of uninhibited respiration, respectively). The alternative pathway is operative both in mitochondria from 28°C tissue and 8°C tissue.

The observed difference in uninhibited respiration, is not only caused by lower values of respiration via the alternative pathway in mitochondria from 8°C tissue, but also by lower values of respiration via the cytochrome pathway.

A positive correlation has been demonstrated between the incubation temperature (ranging from 4-37°C) and the relative capacity of respiration via alternative pathway in the mitochondria. Induction of alternative pathway is not directly correlated with growth (in terms of increase in fresh weight) of the potato tuber discs.

     

Salt stress in cultured rice cells: effects of proline and abscisic acid

Abstract. The presence of 1 and 10 mol m⁻³ proline in media containing 100 and 200 mol m⁻³ of NaCl, had little effect on the growth of salt-adapted callus of rice. However, in such callus proline accumulation was stimulated by 10 mol m⁻³ proline in the presence of 100 mol m⁻³ NaCl. On the other hand, with 100 mol m⁻³ NaCl, both 1 and 10 mol m⁻³ proline significantly increased both the growth and proline content of salt-unadapted callus. On replacing NaCl with KCl (100 and 200 mol m⁻³), growth of saltadapted as well as unadapted callus was inhibited, but the presence of 10 mol m⁻³ proline had an ameliorating effect. Abscisic acid (ABA) supressed the growth of both salt-adapted and unadapted callus of rice in the absence of salt stress. ABA inhibited the growth of callus adapted to and grown in 100 and 200 mol m⁻³ of NaCl or when it was replaced by equimolar concentrations of KCl. Growth of 100 mol m⁻³ NaCl adapted cells was inhibited when they were transferred to a medium containing 200 mol m⁻³ of NaCl, but in the presence of ABA it was stimulated. ABA increased the growth of unadapted cells when subjected to different salts. Also, ABA accelerated the adaptation of cells exposed to salt but not to water deficits imposed by nonionic solutes.     

脱落酸对玉米胚芽和大豆子叶线粒体呼吸的影响

在提取玉米和大豆线粒体后,以ABA处理线粒体,发现在不同底物存在下,ABA均可增加线粒体的耗氧速率,呼吸速率随ABA浓度变化的结合常数（Kd）值为1．43μmol／L。ABA对4态呼吸的促进作用更为显著,因而导致呼吸控制下降,P／O比降低。蛋白质合成抑制剂环己酰亚胺不影响ABA的效应。以ABA预处理大豆子叶,虽然也促进了呼吸作用,但不改变呼吸控制和P／O.     

Adenine nucleotide contents in callus-forming potato tuber discs with different respiratory characteristics

ATP content (per g fresh weight) and energy charge were higher during incubation at 8°C than at 28°C in the early stages of callus induction of potato tuber discs ( Solanum luberosum L. cv. Bintje). After a transfer from 28°C to 8°C, ATP content increased while a sharp decline in ATP content was observed after a transfer from 8°C to 28°C. ADP and AMP pools did not increase correspondingly. When the callus discs had entered the logarithmic growth phase, the energy charge was maintained within relatively narrow limits (0.77–0.80) at all culture temperatures.     

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.     

A comparative study of the effects of abscisic acid and methyl jasmonate on seedling growth of rice

The effects of abscisic acid (ABA) and methyl jasmonate (MJ) on growth of rice seedlings were compared. The lowest tested concentration of ABA and MJ that inhibited seedling growth was found to be 4.5 and 0.9 µM, respectively. Growth inhibition by ABA is reversible, whereas that by MJ is irreversible. GA₃ was found to be more effective in reversing inhibition of shoot growth by ABA than by MJ. KCl partially relieved MJ-inhibited, but not ABA-inhibited, growth of rice seedlings. The beneficial effect of K⁺ on growth of rice seedlings in MJ medium could not be replaced by Li⁺, Na⁺ or Cs⁺. MJ treatment caused a marked release of K⁺ into the medium. In order to understand whether cell wall-bound peroxidase activity was inversely related to rice seedling growth, effects of ABA and MJ on cell wall-bound peroxidase activity were also examined. Results indicated that both ABA and MJ increased cell wall-bound peroxidase activity in roots and shoots of rice seedlings. Although MJ (4.5 µM) was less effective in inhibiting root growth than ABA (9 µM), MJ was found to increase more cell wall-bound peroxidase activity in roots than ABA.     

The effect of abscisic acid on root and shoot growth of cauliflower plants

Addition of abscisic acid (ABA) to the nutrient solution increased the root to shoot ratio of hydroponically-grown cauliflower plants by reducing the dry weight of the shoot and increasing that of the root. At concentrations higher than 10^–7 M, ABA increased root branching and root hair formation. Root extension was inhibited in plants kept continuously in solutions containing high ABA concentrations but following removal from the ABA solution root elongation was increased in comparison with plants given no ABA treatment. This elongation was greatest in plants with increased root branching caused by higher ABA concentrations.     

Effects of abscisic acid and its related compounds on rice seedling growth

Rice seedlings with the mesocotyl and coleoptile (the undeveloped leaves enclosed in the coleoptile) are here referred to as MC type seedlings and are considered to be suitable for deep sowing. We investigated the effects of abscisic acid (ABA) and several of its related compounds on the occurrence of MC type seedlings and on rice mesocotyl growth. Rice (Oryza sativa L. cv. JC 91) seedlings were grown on 0.8% agar medium in the presence or absence of various kinds of ABAs under aseptic conditions at 30 °C in the dark for 14 days. The activity of the R isomer of ABA (R-ABA) was slightly less than that of the naturally occurring S form (S-ABA) concerning the occurrence of MC type rice seedlings and the growth of the rice mesocotyl. In addition, the racemate of R-and S-ABA (RS-ABA) is less effective than R-ABA and S-ABA alone.Trans-ABA had no activity in relation to both percent occurrence of MC type seedlings and mesocotyl growth. The results of the present study suggest that the occurrence of MC type rice seedlings and the growth of rice mesocotyls were closely related to structure-activity relationships with analogs of ABA.     

Induction and activation of the alternative oxidase of potato tuber mitochondria

Potato tubers ( Solanum tubersum L. cv. Grata) were stored for atleast 1 week at room temperature and then incubated with an equal amount of apples ( Malus domestica L.) for 2 days. After this treatment, intact tuber mitochondria isolated by Percoll gradient centrifugation showed a high degree of induction of the alternative oxidase, measured as cyanide-resistant, salicylhydroxamic acid-sensitive respiration. With succinate as substrate an activity of more than 130 nmol O₂(mg protein) ¹ min ^t was obtained. An assay of the alternative oxidase using duroquinol as an electron donor was developed. To become reliable the assay required the presence of defatted bovine serum albumin (BSA) and catalase (EC 1. 11. 1. 6). Furthermore, a lowering of the assay temperature to 15°C improved the stability of the duroquinol-based activity. One remarkable finding was that with duroquinol (or external NADH) as substrate the alternative oxidase was synergistically activated by succinate (as well as by malate) even in the presence of the succinate dehydrogenase inhibitor malonate. Our interpretation is that succinate and malate (indirectly) activate the alternative oxidase and that this activation is part of a physiological mechanism for regulation of the alternative oxidase.     

Platanetin and 7-iodo-acridone-4-carboxylic acid are not specific inhibitors of respiratory NAD(P)H dehydrogenases in potato tuber mitochondria

Progress in understanding the role of NAD(P)H oxidation in plant respiration is restricted by the lack of access to specific inhibitors of each of the unknown number of NAD(P)H dehydrogenases in the inner mitochondrial membrane. Platanetin (3,5,7,8-tetrahydroxy-6-isoprenyl flavone) is known to be an inhibitor of extermal NADH oxidation by plant mitochondria, while 7-iodo-acridone-4-carboxylic acid (IACA) is an inhibitor of an internal, rotenone-insensitive NAD(P)H dehydrogenase isolated from yeast mitochondria.
Here we show that platanetin inhibits external NAD(P)H oxidation by intact potato ( Solanum tuberosum L. cv. Bintje) tuber mitochondria, deamino-NADH oxidation by Complex I assayed using inside-out submitochondrial particles from these mitochondria, and rotenone-insensitive NAD(P)H oxidation by these submitochondrial particles. IACA was found to inhibit the oxidation of external NADH and succinate by intact mitochondria with similar efficiency. However, IACA also inhibited NADPH and duroquinol oxidation by intact mitochondria as well as deamino-NADH and NAD(P)H oxidation by inside-out submitochondrial particles. This indicates that IACA has several sites of inhibition in the electron transport chain. The lack of specificity of both platanetin and IACA prevents these inhibitors from being used to shed more light on the identity of the NAD(P)H dehydrogenases in plant mitochondria.     

外源脱落酸对干旱胁迫下滇润楠幼苗生长及生理特性的影响

以滇润楠一年生实生苗为试验材料,研究在良好水分条件(土壤含水量为70%～75%田间持水量)、轻度干旱胁迫及重度干旱胁迫处理下(50%～55%和30%～35%田间持水量)进行外源脱落酸(ABA)喷施对其生长及生理特性的影响。结果表明: 干旱胁迫使得滇润楠幼苗叶片的相对含水量、株高和生物量显著下降,净光合速率及叶绿素荧光参数(PSⅡ最大光化学效率,F_v/F_m)有不同程度的下降,而根冠比、膜脂过氧化产物丙二醛(MDA)含量显著增加。外源ABA的喷施可提高干旱胁迫下滇润楠幼苗的适应性,尤其是重度干旱下,外源ABA显著提高了叶片相对含水量21.0%,同时增加了植株株高和生物量的累积,提高了根冠比,为良好水分条件的2.1倍;减少了干旱下膜脂过氧化产物MDA的累积,提高了抗氧化酶过氧化氢酶、超氧化物岐化酶的活性,显著增加了脯氨酸的含量,为良好水分条件的7.7倍。外源ABA的喷施显著缓解了干旱胁迫对植株光合器官的不利影响,减少干旱引起的叶片净光合速率及气孔导度的下降,并且减轻了PSⅡ受到干旱的伤害程度,重度干旱下喷施ABA的植株的F_v/F_m显著高于未喷施ABA的植株。外源ABA的喷施可以减轻干旱对滇润楠植株的伤害,提高其抗旱性。     

The biosynthesis of abscisic acid in Cercospora rosicola

1′-Deoxyabscisic acid (1′-deoxy-ABA) has been isolated from cultures of Cercospora rosicola which are actively synthesizing abscisic acid (ABA)     

Effect of temperature on carbohydrate content,ADP glucose pyrophosphorylase,and ATP- and PPi-dependent phosphofructokinase activity of potato tuber callus tissue

Callus derived from Lemhi Russet and Russet Burbank tuber tissue was incubated at 20°C and 30°C on a high sucrose medium for starch-formation and subjected to simulated storage and reconditioning treatments at 5°C and 25°C after transfer of the callus to a medium without a carbon source. Percent dry weight of callus from both cultivars averaged about 21% after starch formation and 5% after storage and reconditioning treatments. Total sugars were higher in callus incubated on the starch forming treatment. Lemhi Russet callus contained predominantly reducing sugars, while Russet Burbank callus contained mostly non-reducing sugars. Total sugar content was generally lower for both cultivars after the storage and reconditioning treatment in callus after starch formation at 20°C. Starch content was generally higher in Lemhi Russet tissue. After starch formation at 20°C Lemhi Russet had higher starch after the storage and reconditioning treatment than tissue from 30°C, while the opposite trend was found in Russet Burbank tissue. Total protein declined in Russet Burbank tissue during the storage and reconditioning treatment regardless of prior incubation conditions, while this decline only occurred in Lemhi Russet tissue initially incubated at 30°C during the starch formation treatment. In tissue of both cultivars, ATP- and PPi-dependent phosphofructokinase activities were inversely proportional to total sugar concentrations, while in RB callus ADP glucose pyrophosphorylase activities were proportional to starch content.Research Paper 91B1 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.