Showing papers on "Gibberellic acid published in 2001"

Release of Reactive Oxygen Intermediates (Superoxide Radicals, Hydrogen Peroxide, and Hydroxyl Radicals) and Peroxidase in Germinating Radish Seeds Controlled by Light, Gibberellin, and Abscisic Acid

Abstract: Germination of radish (Raphanus sativus cv Eterna) seeds can be inhibited by far-red light (high-irradiance reaction of phytochrome) or abscisic acid (ABA). Gibberellic acid (GA3) restores full germination under far-red light. This experimental system was used to investigate the release of reactive oxygen intermediates (ROI) by seed coats and embryos during germination, utilizing the apoplastic oxidation of 2′,7′-dichlorofluorescin to fluorescent 2′,7′-dichlorofluorescein as an in vivo assay. Germination in darkness is accompanied by a steep rise in ROI release originating from the seed coat (living aleurone layer) as well as the embryo. At the same time as the inhibition of germination, far-red light and ABA inhibit ROI release in both seed parts and GA3 reverses this inhibition when initiating germination under far-red light. During the later stage of germination the seed coat also releases peroxidase with a time course affected by far-red light, ABA, and GA3. The participation of superoxide radicals, hydrogen peroxide, and hydroxyl radicals in ROI metabolism was demonstrated with specific in vivo assays. ROI production by germinating seeds represents an active, developmentally controlled physiological function, presumably for protecting the emerging seedling against attack by pathogens.

A Role for Brassinosteroids in Germination in Arabidopsis

Abstract: This paper presents evidence that plant brassinosteroid (BR) hormones play a role in promoting germination. It has long been recognized that seed dormancy and germination are regulated by the plant hormones abscisic acid (ABA) and gibberellin (GA). These two hormones act antagonistically with each other. ABA induces seed dormancy in maturing embryos and inhibits germination of seeds. GA breaks seed dormancy and promotes germination. Severe mutations in GA biosynthetic genes in Arabidopsis, such as ga1-3, result in a requirement for GA application to germinate. Whereas previous work has shown that BRs play a critical role in controlling cell elongation, cell division, and skotomorphogenesis, no germination phenotypes have been reported in BR mutants. We show that BR rescues the germination phenotype of severe GA biosynthetic mutants and of the GA-insensitive mutant sleepy1. This result shows that BR stimulates germination and raises the possibility that BR is needed for normal germination. If true, we would expect to detect a germination phenotype in BR mutants. We found that BR mutants exhibit a germination phenotype in the presence of ABA. Germination of both the BR biosynthetic mutant det2-1 and the BR-insensitive mutant bri1-1 is more strongly inhibited by ABA than is germination of wild type. Thus, the BR signal is needed to overcome inhibition of germination by ABA. Taken together, these results point to a role for BRs in stimulating germination.

A Comparative Molecular-Physiological Study of Submergence Response in Lowland and Deepwater Rice

Abstract: Survival of rice (Oryza sativa) upon an extreme rise of the water level depends on rapid stem elongation, which is mediated by ethylene. A genomic clone (OS-ACS5) encoding 1-aminocyclopropane-1-carboxylic acid (ACC) synthase, which catalyzes a regulatory step in ethylene biosynthesis, has been isolated from cv IR36, a lowland rice variety. Expression was induced upon short- and long-term submergence in cv IR36 and in cv Plai Ngam, a Thai deepwater rice variety. Under hypoxic conditions, abscisic acid and gibberellin had a reciprocal opposite effect on the activity of OS-ACS5. Gibberellin up-regulated and abscisic acid down-regulated OS-ACS5 mRNA accumulation. Growth experiments indicated that lowland rice responded to submergence with a burst of growth early on, but lacked the ability to sustain elongation growth. Sustained growth, characteristic for deepwater rice, was correlated with a prolonged induction of OS-ACS5. In addition, a more pronounced capacity to convert ACC to ethylene, a limited ACC conjugation, and a high level of endogenous gibberellin(20) were characteristic for the deepwater variety. An elevated level of OS-ACS5 messenger was found in cv IR36 plants treated with exogenous ACC. This observation was concomitant with an increase in the capacity of converting ACC to ethylene and in elongation growth, and resulted in prolonged survival. In conclusion, OS-ACS5 is involved in the rapid elongation growth of deepwater rice by contributing to the initial and long-term increase in ethylene levels. Our data also suggest that ACC limits survival of submerged lowland rice seedlings.

Auxin promotes gibberellin biosynthesis in decapitated tobacco plants.

Abstract: Excision of the apical bud (decapitation) of tobacco (Nicotiana tabacum L.) plants reduced the endogenous levels of indole-3-acetic acid (IAA), gibberellin A20 (GA20), and GA1 (the bioactive GA), in internode tissue below the excision site. Application of IAA to the stump of decapitated plants dramatically increased GA20 content, to a level 3-fold greater than in intact plants. Gibberellin A1 content was also increased by IAA. Decapitation reduced the conversion of [14C]GA19 to [14C]GA20 and of [14C]GA20 to [14C]GA1, and appeared to promote the deactivation pathway [14C]GA20 to [14C]GA29 to [14C]GA29-catabolite. Application of auxin counteracted these effects, but did not restore the conversion of [14C]GA20 to [14C]GA1 to the level found in intact plants. The results indicate that auxin is necessary for normal GA biosynthesis in stems of tobacco.

Carbonic Anhydrase, Photosynthesis, and Seed Yield in Mustard Plants Treated with Phytohormones

Abstract: The leaves of 30-d-old plants of Brassica juncea Czern & Coss cv. Varuna were sprayed with 10−6 M aqueous solutions of indole-3-yl-acetic acid (IAA), gibberellic acid (GA3), kinetin (KIN), and abscisic acid (ABA) or 10−8 M of 28-homobrassinolide (HBR). All the phytohormones, except ABA, improved the vegetative growth and seed yield at harvest, compared with those sprayed with deionised water (control). HBR was most prominent in its effect, generating 32, 30, 36, 70, 25, and 29 % higher values for dry mass, chlorophyll content, carbonic anhydrase (E.C. 4.2.1.1) activity, and net photosynthetic rate in 60-d-old plants, pods per plant, and seed yield at harvest, over the control, respectively. The order of response to various hormones was HBR > GA3 > IAA > KIN > control > ABA.

Alleviation of salinity stress and the response to temperature in two seed morphs of Halopyrum mucronatum (Poaceae)

Abstract: Halopyrum mucronatum (L.) Stapf. is a coastal dune grass that produces seeds twice during each growing season. Seeds produced during May (summer seed) were black and heavier (2.8 ± 0.09 mg) than brown seeds (2.1 ± 0.04 mg; winter seed) that were produced in November. There was greater than 95% germination in both seed morphs in the non-saline controls at all temperature regimes, but germination was inhibited more by low than high temperatures in the salinity treatments. Summer seeds were more tolerant of salinity than the winter seeds. Highest germination was obtained in all salinity treatments at a 20/30°C (12-h night/12-h day) temperature regime for the winter seeds and at 25/35°C for the summer seeds. Gibberellic acid, thiourea and nitrate partially alleviated the effects of salinity in summer seeds and gibberellic acid, kinetin and betaine were able to alleviate the inhibitory effects of salinity on the germination of winter seeds. The seeds of Halopyrum mucronatum exhibited seed dimorphism and a difference in physiological response in the two seed morphs, which could provide them with multiple opportunities to germinate and establish in the hot, dry, saline and unpredictable maritime coastal-dune environment along the Arabian Sea coast of Karachi, Pakistan. Ge f um u Mn B0101

Effect of scarification, gibberellic acid and temperature on seed germination of two multipurpose Albizia species from Ethiopia

Abstract: Seeds of Albizia grandibracteata and Albizia gummifera possess seedcoat-imposed dormancy hampering complete, rapid and uniform germination. To overcome this dormancy, seeds of both species were pre-treated with mechanical scarification or concentrated sulphuric acid for 10, 20, 30, 40 and 60 minutes or hot water at 60, 70, 80, 90 and ca. 100°C. Besides, scarified seeds of A. grandibracteata were treated with three concentrations of gibberellic acid: 10 -3 , 10 -4 and 10 -5 M. To determine the effects of temperature on seed germination, pre-treated seeds from each species were germinated at 15, 20, 25, 30 and 35°C. All scarification treatments improved the germination capacity and vigour of A. gummifera seeds, the highest being after mechanical scarification followed by sulphuric acid and 80°C hot water treatments. Only mechanical scarification gave the highest germination in A. grandibracteata seeds. GA treatment of mechanically scarified seeds resulted in more than 50% germination, and GA 3 , 10 -4 M was better than the others were. Germination capacity and the speed of germination were higher at 20 and 25°C in both species; but A. gummifera seeds gerntinated well over a wider range of temperatures.

In vitro control of floral transition in tomato (Lycopersicon esculentum Mill.), the model for autonomously flowering plants, using the late flowering uniflora mutant

Abstract: In vitro control of floral transition in tomato (Lycopersicon esculentum Mill.), the model plant for autonomously flowering species has been investigated using the late flowering mutant uniflora (uf). Apices collected from truly vegetative plants were cultivated on solid media supplemented with different combinations of growth regulators and chemicals. Several chemical factors implicated in the promotion of floral transition of the uf mutant have been identified: sucrose, cytokinins and nitrogenous nutrients have all to be supplied at optimal concentrations. In contrast, gibberellic acid was found to be inhibitory. These results are discussed in relation to knowledge accumulated on the nature of the flowering signals circulating, at floral transition, in other plants, especially in photoperiodic species. This study suggests that tomato could constitute an adequate model to investigate the genetic and physiological control of floral transition and contribute in unravelling pathways which are constitutively regulating this important step of plant life cycle.

Plant Hormones Alter Fiber Initiation in Unfertilized, Cultured Ovules of Gossypium hirsutum

Abstract: Fiber initiation in two commercial cultivars of Gossypium hirsutum, MD51 and MAXXA GTO, was compared. MAXXA GTO produced significantly more fiber initials in ovules grown either in vivo or in vitro. Unfertilized ovules grown in culture without plant hormones exhibited a steady increase in fiber number over the experimental period. Exogenous applications of the plant hormones indole-3-acetic acid or gibberellic acid, either pre-anthesis to flower buds and developing flowers or post-anthesis to ovules, were examined in the MAXXA GTO cultivar. Unfertilized ovules treated pre-anthesis with 0.1 mg L -1 indole-3-acetic acid produced a greater number of fibers than did ovules treated with 1.0 mg L -1 gibberellic acid or water. Post-anthesis treatment with 1.0 mg L -1 gibberellic acid in the culture medium increased fiber production, compared with water or 0.1 mg L -1 indole-3-acetic acid applied in the culture medium. Application of either hormone (depending on concentration and time of treatment) resulted in an increase in fiber production, compared with controls. Fiber production in the absence of hormone treatment, either pre- or post-anthesis, suggests that hormones may not be a requirement for fiber initiation. Manipulation of the hormonal levels might cause an increase in the proportion of epidermal cells that differentiated as fibers. On the other hand, the hormone treatments might induce cell division, resulting in more epidermal cells and, consequently, a greater number of fiber initials. These results

Breaking dormancy in Arbutus andrachne L. seeds by stratification and gibberellic acid

Abstract: To break dormancy and allow germination of Arbutus andrachne L. (Eastern Strawberry tree) seeds, various methods were tested including scarification with hot water, sulphuric acid (H 2 SO 4 ), or potassium hydroxide (KOH), cold moist stratification and treatment of seeds with potassium nitrate (KNO 3 ), thiourea, or gibberellic acid (GA 3 ). None of the seeds in the control or those scarified with H 2 SO 2 or KOH, or treated with KNO 3 or thiourea germinated. Hot water scarification allowed some germination, the greatest being 36% when seeds were soaked in water at 60°C for three minutes. Stratification of seeds at 4°C for three to four months or treatment of seeds with 250 mg/liter GA, was successful as 86% of the seeds germinated for both treatments.

Differentiation in seed germination among populations of Capsicum annuum along a latitudinal gradient in Mexico

Abstract: Toinvestigate variation in germination capability of wild Capsicumannuum seeds, the effects of light, fluctuating temperature,gibberellic acid (GA), soaking and sulfuric acid were analyzed in samples from14 populations from northwest Mexico. Germination was inhibited by darkness inall populations studied. Darkness inhibition of germination was overcome byfluctuating temperature and GA, factors which also increased germinationpercentage but not germination rate. Soaking treatments did not significantlyincrease germination of C. annuum seeds, while sulfuricacid treatments had negative effects on the process. Populations showed highvariation in germination response in all treatments, except for continuousdarkness. Principal component analysis differentiated some populations withhighgermination percentage and slow germination rate. Such differences did notcorrelate with climatic variables from collection sites. Given the variation ingermination patterns observed, some of these totally contrasting, we have to becautious when considering the results of studies based on a single wildpopulation.

A new protein phosphatase 2C (FsPP2C1) induced by abscisic acid is specifically expressed in dormant beechnut seeds.

Abstract: An abscisic acid (ABA)-induced cDNA fragment encoding a putative protein phosphatase 2C (PP2C) was obtained by means of differential reverse transcriptase-polymerase chain reaction approach The full-length clone was isolated from a cDNA library constructed using mRNA from ABA-treated beechnut ( Fagus sylvatica ) seeds This clone presents all the features of plant type PP2C and exhibits homology to members of this family such as AthPP2CA (61%), ABI1 (48%), or ABI2 (47%), therefore it was named FsPP2C1 The expression of FsPP2C1 is detected in dormant seeds and increases after ABA treatment, when seeds are maintained dormant, but it decreases and tends to disappear when dormancy is being released by stratification or under gibberellic acid treatment Moreover, drought stress seems to have no effect on FsPP2C1 transcript accumulation The FsPP2C1 transcript expression is tissue specific and was found to accumulate in ABA-treated seeds rather than in other ABA-treated vegetative tissues examined These results suggest that the corresponding protein could be related to ABA-induced seed dormancy By expressing FsPP2C1 in Escherichia coli as a histidine tag fusion protein, we have obtained direct biochemical evidence supporting Mg 2+ -dependent phosphatase activity of this protein

Gibberellic acid and dwarfism effects on the growth dynamics of B73 maize (Zea mays L.) leaf blades: a transient increase in apoplastic peroxidase activity precedes cessation of cell elongation.

Abstract: The relationship between apoplastic peroxidase (EC 1.11.1.7) activity and cessation of growth in maize (Zea mays L.) leaf blades was investigated by altering elongation zone length. Apoplastic peroxidase activity in the elongation and secondary cell wall deposition zones of elongating leaf blades of the maize inbred line B73 was used as a control and compared to leaves of the dwarf mutant D8-81127, a near-isogenic line of B73 unresponsive to gibberellins, and to leaves of B73 plants to which gibberellic acid (GA(3)) had been applied via root uptake. Elongation zone length was increased by treatment with GA(3) through an increase in cell number as well as increased final cell length. The shorter elongation zone of dwarf leaves occurred primarily through reduced final cell length. Although elongation zone length differed among dwarf, control, and GA(3)-treated leaf blades, in all three treatments a transient increase in apoplastic peroxidase activity preceded a reduction in the segmental elongation rate in leaves. A peroxidase isoenzyme with pI 7.0 occurred in the leaf elongation zone during growth deceleration in all three treatments, and its activity decreased as growth displaced tissue into the region of secondary cell wall deposition. Growth cessation for all treatments coincided with the first appearance of peroxidase isozymes with pIs of 5.6 and 5.7. Based on the activity of particular isozymes relative to growth and differentiation, the pI 7.0 isoenzyme is most likely to be involved in cessation of cell elongation, while isozymes with pIs 5.6 and 5.7 are likely to be active in lignification.

Somatic embryogenesis on various potato tissues from a range of genotypes and ploidy levels

Abstract: Somatic embryos (SEs) formed on in vitro-cultured stem internodes, leaves, microtubers and roots of 18 tetraploid potato (Solanum tuberosum L.) cultivars, diploid and monoploid germplasm and three wild Solanum species. A two-step protocol with 6-benzylaminopurine or thidiazuron in the first medium, and zeatin, indoleacetic acid and gibberellic acid in the second medium produced SEs within 14–28 days. SEs developed through the globular, heart and torpedo stages to produce thin-stemmed plantlets resembling potato seedlings. Plantlets transferred to the greenhouse produced greenhouse tubers. Secondary SEs were observed at the base of germinating torpedo-stage SEs in culture. SEs formed on stem internode sections, leaves and microtuber slices of in vitro-grown plants. Genotypic differences in regenerative capacity were clearly evident.

Direct differentiation of shoot buds in leaf segments of white marigold (tagetes erecta l.)

Abstract: A protocol has been developed for differentiation of shoot buds directly from leaf segments of white marigold (Tagetes erecta L.). Leaf segments were taken from in vitro-proliferated shoots of white marigold established in aseptic culture from shoot tips of field-grown plants. Gibberellic acid (GA) played a significant role in the induction of shoot buds as well as in suppressing callus formation. Shoot buds were induced directly in Murashige and Skoog's (MS) medium supplemented with 14.43 μM GA and 4.44 μM 6-benzyladenine in the absence of any auxin. In this medium two to five shoot buds differentiated from the margins as well as leaf lamina of the lower petiolar segment within 4 wk of incubation. Differentiated shoots grew well and proliferated in the MS medium having 1.1 μM BA and 29.41 μM AgNO3, as it had a beneficial effect on the growth and proliferation of shoots. Shoots were excised, rooted in 0.27 μm α-naphthaleneacetic acid (NAA) and transplanted under glasshouse conditions, where they grew and flowered. Data on different morphological characters during flowering under field conditions were recorded for seed-grown control plants, tissue culture-raised primary regenerants (R0) and first-generation (R1) plants. It was found that all the economically desired characters of plant height, number and size of flowers per plant, number of viable seeds per flower, and days to full bloom, of the R1 generation plants were significantly better than the control, thus increasing the commercial value of the tissue culture-raised plants in successive generations.

Plant regeneration from zygotic embryo hypocotyls of Tunisian chili (Capsicum annuum L.)

Abstract: We report the regeneration of Tunisian pepper variety from zygotic embryos cultured in vitro. Zygotic embryos of the Tunisian cultivar D’hirat cultured in vitro develop adventitious buds. The best results for bud induction were obtained in Murashige and Skoog medium, supplemented with 6-benzylaminopurine (5 mg/l) and naphtaleneacetic acid (1 mg/l). Important effect of 6-benzylaminopurine in adventitious bud formation was demonstrated. Shoot bud development was enhanced by the addition of gibberellic acid to the medium. Plants were rooted in Murashige and Skoog medium at half strength and transferred into pots, containing loam. To test the stability of the regenerants, characters related to the fertility, fruit quality, leaf and flower were measured. Regenerants and their progeny were compared to control plants derived from seeds. Variance analysis and CANDISC were used in our investigation. We detected no significant differences between regenerants and control plants for the characters tested.

High frequency plant regeneration from immature cotyledons of mungbean

Abstract: An efficient and simple method for high frequency plant regeneration from immature cotyledons of mungbean is described. Immature cotyledons isolated from embryos, one week prior to harvest were cultured on MS medium with combinations of growth regulators such as benzyladenine (1 or 2 mg l−1), thidiazuron (0.1 or 0.5 mg l−1), gibberellic acid (0.1 mg l−1) and indole-3-acetic acid (0.1 or 0.5 mg l−1). A large number of greenish shoot primordia were initiated from the entire surface of the cotyledons in some of the growth regulators. Medium supplemented with benzyladenine (2 mg l−1) in combination with indole-3-acetic acid (0.5 mg l−1) produced the best response. On subculture to the same medium, well developed shoots were obtained. Addition of 0.5% activated charcoal to the shoot initiation medium completely inhibited initiation of shoot primordia. The shoot buds could be rooted on medium supplemented with 0.1 mg l−1 indole butyric acid and plants transferred to soil.

Effect of germination promoting compounds on the release of primary and salt-enforced seed dormancy in the halophyte Sporobolus arabicus Boiss

Abstract: Sporobolus arabicus Boiss., a perennial stoloniferous grass, is widely distributed in saline areas from Karachi to the plains of the Punjab, Pakistan. It is one of the important components of the vegetation of salt flats and deserts. Experiments were carried out to determine the ability of growth promoter substances to alleviate a primary and salinity- enforced dormancy in seeds of Sporobolus arabicus. Sporobolus arabicus exhibited primary seed dormancy, yielding less than 40% germination in the non-saline control. The growth regulators gibberellic acid (GA 3 ), kinetin and ethephon were unable to break the dormancy of seeds, but nitrate, thiourea, and fusicoccin partially alleviated dormancy. Salinity was not inhibitory at 100 mM NaCl but inhibited germination at higher concentrations, with no seeds germinating at 400 mM NaCl. Salinity-enforced dormancy was not alleviated by kinetin, GA 3 , and ethephon. Fusicoccin, nitrate, and thiourea significantly alleviated salinity-enforced dormancy and the velocity of germination also increased at all salinities in these treatments.

Regulation of alcohol dehydrogenase gene expression in barley aleurone by gibberellin and abscisic acid.

Abstract: The expression of the Adh1 gene (alcohol dehydrogenase, EC 1.1.1.1) was studied in the aleurone layer of barley (Hordeum vulgare cv. Himalaya). Expression increased markedly during grain development at the levels of activity, enzyme protein and mRNA. mRNA content, but not enzyme activity, could be increased further by exogenous abscisic acid (ABA) when isolated, de-embryonated developing grains were pre-treated with gibberellic acid (GA3) or fluridone. In isolated mature aleurone layers incubated with exogenous hormones, ADH mRNA was strongly up-regulated by ABA and down-regulated by GA3 within 6 h. With ABA, this increase in mRNA was followed by an increase in ADH protein and activity, peaking at 18 h. With GA3, the decrease in mRNA was accompanied by simultaneous decreases in protein and activity. In general, GA3 counteracted the effect of ABA and vice versa. In the aleurone of germinating grain, ADH activity decayed in a distal direction from the embryo, consistent with down-regulation by gibberellin(s) diffusing from it. It was concluded that ADH gene expression in the aleurone of the intact grain is regulated by an ABA/gibberellin interaction.

The expression of tgas118, encoding a defensin in Lycopersicon esculentum, is regulated by gibberellin

Abstract: A flower specific cDNA, tgas118, has been isolated after differential screening of a gib-1 anther cDNA library of Lycopersicon esculentum. The corresponding mRNA was present in all tissues analysed. Northern blot analysis revealed that in wild-type tomato the gene was predominantly expressed throughout flower development, while in the gibberellin (GA)-deficient mutant of tomato (gib-1) the abundance declined. Treatment of the mutant with GA resulted in an accumulation of the tgas118 mRNA within hours in leaf and bud tissues. In the leaf, GA 1 , GA3 and GA g were effective in enhancing the expression while GA4 was not. In addition to GA, wounding and dehydration also increased the accumulation of tgas118 mRNA in leaf tissue. In situ hybridization showed that application of 50 ng GA3 bud -1 induced a similar spatial expression of the tgas118 mRNA in gib-1 buds 24 h post treatment to that found in wild-type flower buds. The deduced TGAS118 protein displays up to 77% similarity with defensins and as its expression is up-regulated by stimuli such as wounding it is proposed that it may play a role in protection against pathogens.

Dormancy of yellow cedar seeds is terminated by gibberellic acid in combination with fluridone or with osmotic priming and moist chilling

Abstract: Following dispersal from the parent tree, seeds of yellow cedar (Chamaecyparis nootkatensis D. Don Spach) exhibit a low capacity for germination, primarily as a result of coat-imposed dormancy. Combined warm and cold stratification (generally 4 weeks and 8 weeks, respectively) is often used to break dormancy. Here we investigate the effectiveness of different chemical treatments in replacing warm stratification and in reducing the requirement for cold stratification (moist chilling). Treatments comprised of gibberellic acid (GA3) in combination with osmotic priming (using polyethylene glycol, PEG) or with other hormones (gibberellin 4+7 and benzylaminopurine) had a promotive effect on subsequent germination of whole seeds of yellow cedar after a 60-day moist chilling period. GA 3 had virtually no effect on germination when used alone and even when used with 60 days of moist chilling. Whole seeds exposed to GA 3 and to fluridone (the latter to diminish endogenous abscisic acid, ABA), exhibited increased germination with an increasing time of exposure to fluridone, even in the complete absence of moist chilling, but seedlings were abnormal and unable to survive. Embryos excised from mature seeds which had been subjected to dormancy-breaking treatments (osmotic priming, GA 3 , and moist chilling), exhibited a lowered sensitivity to ABA compared to embryos excised from mature seeds that had received only a 3-day water soak. A decline in ABA within the seed and/or reduced embryo sensitivity to ABA may be two critical factors leading to dormancy breakage of yellow cedar seed.

Indoleacetic acid, gibberellic acid, zeatin, and abscisic acid levels in NaCl-treated tomato species differing in salt tolerance

Abstract: Indoleacetic acid (IAA), gibberellic acid (GA3), zeatin, and abscisic acid (ABA) levels in cultivated tomato Lycopersicon esculentum (Mill.) cultivar Falcon 82 and its wild salt-tolerant relative L. pennellii (Correll) were examined over a range of 0 to 150 mM NaCl applied for 72 h. The treatment with 50 mM and 150 mM NaCl reduced relative water and protein contents in L. esculentum, but did not affect relative water content and increased protein content in L pennellii. Varietal differences between L. esculentum and L. pennellii were also observed in hormonal contents during the stress period. ABA levels in treated plants of both species increased significantly compared to the controls. However, the increase in the leaves of L. pennellii due to NaCl stress was not as pronounced as that of L. esculentum; it was significantly higher (p < 0.05) than that of salt-sensitive L. esculentum. In treated plants, zeatin concentrations in the leaves of L. esculentum decreased within 24-72 h after treatment. Neverthel...

Gibberellic acid-induced changes in glutathione metabolism and anthocyanin content in plant tissue

Abstract: Literature data point to a possible link between gibberellic acid (GA3) and glutathione metabolism in plant tissue, as both are connected to dormancy breakage. In order to study the influence of GA3 on glutathione metabolism, we treated an anthocyanin accumulating cell culture of periwinkle (Catharanthus roseus) and a shoot differentiated culture of pea (Pisum sativum) with GA3. Glutathione reductase (GR; E.C. 1.6.4.2) activity increased to 135% and 190% of the control in C. roseus and P. sativum, respectively. The level of oxidized glutathione (GSSG) decreased to 60% of the control in the C. roseus culture while no change in GSSG was observed in the P. sativum culture. No changes in the tissue concentration of total glutathione was observed in the cultures after GA3 treatment. Concomitant to the changes in GSSG and GR, an increase in anthocyanin accumulation was observed in the C. roseus culture in association with a strong increase in phenylalanine ammonia-lyase (PAL; E.C. 4.3.1.5) activity in response to GA3. These data strongly suggest a link between GA3 and glutathione metabolism.

Screening for strongly regenerative genotypes of spinach in tissue culture using subcultured root explants

Abstract: A system for subculture of spinach (Spinacia oleracea L.) roots was established, and differences in regeneration; namely, embryogenic competence, among individuals of the `Nippon' cultivar were examined. Root tissues, excised from seedlings, were grown on medium without growth regulators and subcultured on the same medium and then on medium that contained 10 μM naphthaleneacetic acid and 0.1 μM gibberellic acid to induce callus formation. Calli were transferred to medium without growth regulators. All explants formed calli. However, the frequency of embryo formation varied among lines. Higher concentrations of gibberellic acid in the callus-induction medium had limited effects on somatic embryogenesis from poorly embryogenic lines. These results indicate that inherent factors are important for somatic embryogenesis in spinach and that the root subculture system is useful for identifying strongly regenerative genotypes among individuals of a single cultivar.