Showing papers on "Gibberellic acid published in 2000"
TL;DR: The results suggest that GAs are required to overcome the germination constraints imposed both by the seed coat and ABA-related embryo dormancy.
Abstract: The mechanisms imposing a gibberellin (GA) requirement to promote the germination of dormant and non-dormant Arabidopsis seeds were analyzed using the GA-deficient mutant ga1, several seed coat pigmentation and structure mutants, and the abscisic acid (ABA)-deficient mutant aba1. Testa mutants, which exhibit reduced seed dormancy, were not resistant to GA biosynthesis inhibitors such as tetcyclacis and paclobutrazol, contrarily to what was found before for other non-dormant mutants in Arabidopsis. However, testa mutants were more sensitive to exogenous GAs than the wild-types in the presence of the inhibitors or when transferred to a GA-deficient background. The germination capacity of the ga1-1 mutant could be integrally restored, without the help of exogenous GAs, by removing the envelopes or by transferring the mutation to a tt background (tt4 and ttg1). The double mutants still required light and chilling for dormancy breaking, which may indicate that both agents can have an effect independently of GA biosynthesis. The ABA biosynthesis inhibitor norflurazon was partially efficient in releasing the dormancy of wild-type and mutant seeds. These results suggest that GAs are required to overcome the germination constraints imposed both by the seed coat and ABA-related embryo dormancy.
408 citations
TL;DR: It is suggested that in intact pea plants, auxin from the apical bud moves into the elongating internodes where it (directly or indirectly) maintains PsGA3ox1 transcript levels and, consequently, GA1 biosynthesis.
Abstract: In shoots of the garden pea, the bioactive gibberellin (GA1) is synthesised from GA20, and the enzyme which catalyses this step (a GA 3-oxidase –- PsGA3ox1) is encoded by Mendel's LE gene. It has been reported previously that decapitation of the shoot (excision of the apical bud) dramatically reduces the conversion of [3H]GA20 to [3H]GA1 in stems, and here we show that endogenous GA1 and PsGA3ox1 transcript levels are similarly reduced. We show also that these effects of decapitation are completely reversed by application of the auxin indole-3-acetic acid (IAA) to the ‘stump’ of decapitated plants. Gibberellin A20 is also converted to an inactive product, GA29, and this step is catalysed by a GA 2-oxidase, PsGA2ox1. In contrast to PsGA3ox1, PsGA2ox1 transcript levels were increased by decapitation and reduced by IAA application. Decapitation and IAA treatment did not markedly affect the level of GA1 precursors. It is suggested that in intact pea plants, auxin from the apical bud moves into the elongating internodes where it (directly or indirectly) maintains PsGA3ox1 transcript levels and, consequently, GA1 biosynthesis.
260 citations
TL;DR: Fluridone, a carotenoid biosynthesis inhibitor, is almost as efficient as GA3 in breaking dormancy and reveals an important role for ABA synthesis in dormancy maintenance in imbibed seeds.
Abstract: The physiological characteristics of seed dormancy in Nicotiana plumbaginifolia Viv are described The level of seed dormancy is defined by the delay in seed germination (ie the time required prior to germination) under favourable environmental conditions A wild-type line shows a clear primary dormancy, which is suppressed by afterripening, whereas an abscisic acid (ABA)-deficient mutant shows a non-dormant phenotype We have investigated the role of ABA and gibberellic acid (GA(3)) in the control of dormancy maintenance or breakage during imbibition in suitable conditions It was found that fluridone, a carotenoid biosynthesis inhibitor, is almost as efficient as GA(3) in breaking dormancy Dry dormant seeds contained more ABA than dry afterripened seeds and, during early imbibition, there was an accumulation of ABA in dormant seeds, but not in afterripened seeds In addition, fluridone and exogenous GA(3) inhibited the accumulation of ABA in imbibed dormant seeds This reveals an important role for ABA synthesis in dormancy maintenance in imbibed seeds
258 citations
TL;DR: It is hypothesize that LeEXP4 is involved in the regulation of seed germination by contributing to cell wall disassembly associated with endosperm cap weakening.
Abstract: Expansins are extracellular proteins that facilitate cell wall extension, possibly by disrupting hydrogen bonding between hemicellulosic wall components and cellulose microfibrils. In addition, some expansins are expressed in non-growing tissues such as ripening fruits, where they may contribute to cell wall disassembly associated with tissue softening. We have identified at least three expansin genes that are expressed in tomato (Lycopersicon esculentum Mill.) seeds during germination. Among these, LeEXP4 mRNA is specifically localized to the micropylar endosperm cap region, suggesting that the protein might contribute to tissue weakening that is required for radicle emergence. In gibberellin (GA)-deficient (gib-1) mutant seeds, which germinate only in the presence of exogenous GA, GA induces the expression of LeEXP4 within 12 hours of imbibition. When gib-1 seeds were imbibed in GA solution combined with 100 microM abscisic acid, the expression of LeEXP4 was not reduced, although radicle emergence was inhibited. In wild-type seeds, LeEXP4 mRNA accumulation was blocked by far-red light and decreased by low water potential but was not affected by abscisic acid. The presence of LeEXP4 mRNA during seed germination parallels endosperm cap weakening determined by puncture force analysis. We hypothesize that LeEXP4 is involved in the regulation of seed germination by contributing to cell wall disassembly associated with endosperm cap weakening.
227 citations
TL;DR: To improve vegetative multiplication, rhizome segments were treated with α-naphthaleneacetic acid (NAA) or indole-3-butyric acid (IBA) before planting; more than doubling in rooting percentage was observed with 100.0 μM IBA; other treatments were either ineffective or enhanced germination only marginally.
145 citations
TL;DR: It is hypothesized that PME plays a role in weakening of the megagametophyte, allowing radicle emergence and the completion of germination of yellow cedar seeds.
Abstract: Pectin methyl esterase (PME) (EC 31111) catalyzes the hydrolysis of methylester groups of cell wall pectins We investigated the role of this enzyme in dormancy termination and germination of yellow cedar (Chamaecyparis nootkatensis [D Don] Spach) seeds PME activity was not detected in dormant seeds of yellow cedar but was induced and gradually increased during moist chilling; high activity coincided with dormancy breakage and germination PME activity was positively correlated to the degree of dormancy breakage of yellow cedar seeds The enzyme produced in different seed parts and in seeds at different times during moist chilling, germination, and early post-germinative growth consisted of two isoforms, both basic with isoelectric points of 87 and 89 and the same molecular mass of 62 kD The pH optimum for the enzyme was between 74 and 84 In intact yellow cedar seeds, activities of the two basic isoforms of PME that were induced in embryos and in megagametophytes following dormancy breakage were significantly suppressed by abscisic acid Gibberellic acid had a stimulatory effect on the activities of these isoforms in embryos and megagametophytes of intact seeds at the germinative stage We hypothesize that PME plays a role in weakening of the megagametophyte, allowing radicle emergence and the completion of germination
138 citations
TL;DR: P pH, rice flour concentration and C:N ratio were the factors that most influenced the production of gibberellic acid; pH being the most important.
96 citations
TL;DR: Results show that K. paniculata seeds exhibit both exogenous and endogenous dormancy, and a combination of GA and chilling (GA-chilling) helped to alleviate seed dormancy in a relatively short period of time.
68 citations
TL;DR: The expression of the AtEPR1 gene appears to be under positive control of gibberellic acid, but is not downregulated by abscisic acid during seed germination, and no expression was detected in organs other than endosperm during Seed germination.
Abstract: Summary
Screening of 10 000 Arabidopsis transgenic lines carrying a gene-trap (GUS) construct has been undertaken to identify markers of seed germination. One of these lines showed GUS activity restricted to the endosperm, at the micropylar end of the germinating seed. The genomic DNA flanking the T-DNA insert was cloned by walking PCR and the insertion was shown to be located 70 bp upstream of a 2285 bp open reading frame (AtEPR1) sharing strong similarities with extensins. The AtEPR1 open reading frame consists of 40 proline-rich repeats and is expressed in both wild-type and mutant lines. The expression of the AtEPR1 gene appears to be under positive control of gibberellic acid, but is not downregulated by abscisic acid during seed germination. No expression was detected in organs other than endosperm during seed germination. The putative role of AtEPR1 is discussed in the light of its specific expression in relation to seed germination.
67 citations
TL;DR: In vitro seeds sown in pots under field conditions developed into flowering plants, and subsequently produced pods with viable seeds, which were germinable both in vitro and in vivo.
Abstract: Multiple shoots were efficiently regenerated from cotyledonary node and shoot tip explants of Pisum sativum within 15 days on MS medium containing B5 vitamins and supplelmented with 2.0 mgl-1 6-benzylaminopurine. The elongated shoots produced on the same medium were excised and transferred to MS medium containing half strength ammonium nitrate (8.25 gml-1) and supplemented with auxins (indole-3-butyric acid or naphthalene acetic acid) either alone or in combinations with gibberellic acid. Rooting and flowering were observed on the 7th and 15th day after their transfer to rooting medium. The flowers self-fertilised in vitro and produced mature pods within 25 days of rooting. These seeds were germinable both in vitro and in vivo. In vitro seeds sown in pots under field conditions developed into flowering plants, and subsequently produced pods with viable seeds.
66 citations
01 Jan 2000
TL;DR: In this paper, a combination of gibberellic acid (GA) and chilling (GA-chilling) was used to alleviate seed dormancy in a relatively short period of time.
Abstract: In contrast to scarified seeds, unscarified seed did not germinate in any of the treatments, indicating that Koelreuteria paniculata Laxm. seeds have hard, impermeable seed coat dormancy. Exogenous application of 100, 200 and 300 ppm GA increased germination of scarified seeds from 0 (control) to 17, 18 and 15%, respectively. Pre-chilling in distilled water (DW) for 60 days increased germination to 44%. Compared with DW-chilled seeds, the germination of seeds chilled in gibberellic acid (GA-chilled) was significantly increased after 15 days of chilling and maximum germination of seeds chilled in 100, 200 and 300 ppm GA was 60, 51 and 54%, respectively, achieved after 30 days. Longer duration of chilling in GA appeared harmful. Germination rate was positively correlated with germination percentage. These results show that K. paniculata seeds exhibit both exogenous and endogenous dormancy. A combination of GA and chilling (GA-chilling) helped to alleviate seed dormancy in a relatively short period of time. # 2000 Elsevier Science B.V. All rights reserved.
TL;DR: Cdc2Os-3 belongs to a group of CDKs that have no counterparts in animals, and may function in a plant-specific gibberellin-regulated cell division process, suggesting a distinct role in regulating G2/M phase progression.
Abstract: Internodal growth of deepwater rice (Oryza sativa L.) can achieve rates of up to 10 mm h−1. In submergence-induced plants, gibberellic acid activates the cell division cycle first at the G1 → S phase transition with a subsequent increase in mitotic activity. The proteins cycA1;1 and cdc2Os-3 are the regulatory and catalytic subunits, respectively, of cyclin-dependent protein kinases (CDKs) which are central to cell cycle regulation. Both genes are regulated by gibberellic acid in a coordinate manner with transcripts accumulating in the G2 phase prior to the B2-type mitotic cyclins described previously (M. Sauter et al. 1995, Plant J 7: 623–632), suggesting a distinct role in regulating G2/M phase progression. Since cdc2Os-3 belongs to a group of CDKs that have no counterparts in animals, it may function in a plant-specific gibberellin-regulated cell division process.
TL;DR: In vitro morphogenesis via organogenesis was achieved from callus cultures derived from hypocotyl explants of Acacia sinuata on MS (Murashige and Skoog, 1962) medium and Rooted plantlets were hardened and successfully established in the soil.
Abstract: In vitro morphogenesis via organogenesis was achieved from callus cultures derived from hypocotyl explants of Acacia sinuata on MS (Murashige and Skoog, 1962) medium. Calli were induced from hypocotyl explants excised from 7-day-old seedlings on MS medium containing 3% sucrose, 0.8% agar, 6.78 μM 2,4-dichlorophenoxyacetic acid and 2.22 μM 6-benzylaminopurine. Regeneration of adventitious buds from callus was achieved when they were cultured on MS medium supplemented with 10% coconut water, 13.2 μM 6-benzylaminopurine and 3.42 μM indoleacetic acid. Addition of gibberellic acid (1.73 μM) favored shoot elongation. Regenerated shoots produced prominent roots when transferred to half strength MS medium supplemented with 7.36 μM indolebutyric acid. Rooted plantlets, thus developed were hardened and successfully established in the soil. This protocol yielded an average of 20 plants per hypocotyl explant over a period of 4 months.
Journal Article•
TL;DR: The tetrazolium (Tz) staining pattern indicated that freshly collected seeds had high viability which decreased following storage at 4°C for 6 and 12 months and the combined treatments of gibberellin and cytokinin in general resulted in reduced ger mination in both species.
Abstract: Aconitum heterophyllum Wall, and A balfourii Stapf are important medicinal herbs of the Himalayan region The effect of plant growth substances (PGSs, namely, abscisic acid, 6-benzylaminopurine, gibberellic acid and zeatin riboside) and two nitrogenous compounds (thiourea and potassium nitrate) for enhancing and synchronising uniform germination was examined The tetrazolium (Tz) staining pattern indicated that freshly collected seeds had high viability which decreased following storage at 4°C for 6 and 12 months The treatments and time of seed germination were found to be significantly different (P <001) Gibberellic acid (GA 250 μM) significantly enhanced seed germination (425% compared to 275% in control) in A balfourii with in 15 weeks but was inhibitory in A heterohyllum, 6-Benzylaminopurine (BAP; 25 and 250 μM) and zeatin riboside (ZR; 25 and 250 μM) did not enhance germination in A balfourii; 250 μM ZR was actually inhibito ry In A hererophyllum the lower concentration of BAP was inhibitory (75% compared to 250% in control while 250 μM BAP enhanced germination (425% compared to 250% in control); the higher concentration of ZR was inhibitory The combined treatments of gibberellin and cytokinin in general resulted in reduced ger mination in both species Among the nitrogenous compounds, thiourea (CH 4 N 2 S) increased the rate and germination percentage in both species but potassium nitrate (KNO 3 ) enhanced germination in A baifourii only Seed germination was first detected in A balfourii in the 5th week (25%) Following treatment with 65 mM CH 4 N 2 S and this value increased to 225% in the 7th week and reached as high as 75% (compared to 275% in control) in the 15th week A higher dose of thiourea (130 mM) resulted in a rapid and high germination rate (40% compared to 0% in control) in the 7th week, reaching 75% in 10th and 12th weeks and a maximum 80% (compared to 275% in control) in the 15th week, In A heterophyllum, however, thiourea only marginally enhanced germination even up to the 15th week In A balfourii, KNO 3 (50 and 100 mM) significantly enhanced germination (62-70%) within 15 weeks
TL;DR: The results suggest that the black-spot symptoms caused by A. alternata, in persimmon, are related to the ability of the fungus to produce EG in developing lesions.
Abstract: Black-spot symptoms, caused by Alternaria alternata, developed in persimmon fruits during prolonged storage at -1°C. A preharvest treatment with gibberellic acid (GA3) extended the storage life of the fruit by delaying both black-spot development and fruit softening. Conversely, treatment of persimmon fruits with paclobutrazol (PBZ), an inhibitor of gibberellin (GA) synthesis, enhanced black-spot development and fruit softening during storage. Production of endo-1,4-β-glucanase (EC 3.2.1.4, EG) by A. alternata in culture and in the presence of cell walls from PBZ-treated fruits as the carbon source, was enhanced by 150% over production in the presence of cell walls from control fruits, whereas endoglucanase (EG) production in the presence of cell walls from GA3-treated fruits was reduced by 49% relative to controls. To determine the importance of EG in symptom development, A. alternata EG was purified from a culture-inducing medium. It had a molecular mass of 41 kDa, its optimal pH and temperatur...
TL;DR: Potassium citrate and citric acid (0.1% w/v in a 4:1 ratio) prevented oxidative browning and was superior to the untreated control or other antioxidant treatments tested.
Abstract: A micropropagation protocol was developed for the conservation of the critically endangered Western Australian shrub,Symonanthus bancroftii. It was necessary to screen antioxidant treatments to prevent the occurrence of lethal browning of explants upon excision. Potassium citrate and citric acid (0.1% w/v in a 4:1 ratio) prevented oxidative browning and was superior to the untreated control or other antioxidant treatments tested. Half strength Murashige and Skoog (MS) medium containing 0.5 μM kinetin and 0.25 μM benzyladenine produced three-fold multiplication compared to 1.75×, 1.5×, 1.8× and 1× multiplication for 2.5 μM kinetin + 0.25 μM benzyladenine, 0.5 μM kinetin + 5 μM gibberellic acid, 1 μM kinetin + 3 μM gibberellic acid and half strength MS with no plant growth regulators, over 4 weeks. Root production was achieved with indole-3-butyric acid (IBA) and α-naphthaleneacetic acid (NAA) at 0.5/0.5 μM (31% rooting) and 1.0/1.0 μM (36% rooting), after four weeks. Paclobutrazol (PBZ) at 0, 3.4 (1 mg 1−1), 10.2 (3 mg 1−1), or 17 μM (5 mg 1−1) improved tolerance to desiccation after transfer ofin vitro rooted shoots to soil. PBZ at 10.2 μM increased survival to 90% compared to 50% for those plantlets not treated with PBZ. The acclimatisation period from the glasshouse to the shadehouse was 1 week for plantlets treated with PBZ compared to 4 weeks for plantlets without any PBZ. PBZ at 3.4 μM increased the number of roots per shoot compared to untreated controls.
TL;DR: Seeds of Anthriscus sylvestris have physiologically dormant, underdeveloped embryos; thus, they have morphophysiological dormancy (MPD), and in situ germination could result in rapid depletion of seeds buried in the soil.
TL;DR: A system for regeneration of clary sage, (Salvia sclarea L.) via organogenesis using plant tissue culture techniques in a multistage culturing medium containing 2,4-dichlorophenoxyacetic acid (2, 4-D) is provided.
Abstract: The present work provides a system for regeneration of clary sage, (Salvia sclarea L.) via organogenesis using plant tissue culture techniques in a multistage culturing medium containing 2,4-dichlorophenoxyacetic acid (2,4-D) (9.05–181.00 μM). A higher frequency of organogenic tissue initiation was obtained from immature zygotic embryo cotyledons (IZEC) 2–3 wk after pollination on the medium supplemented with 9.05 μM 2,4-D. The organogenic tissues were then proliferated on media containing both indole-3-acetic acid (IAA) and 6-benzylaminopurine (BA). Organogenic lines were established via selection, isolation and continuous subculture of organogenic tissues on a medium containing 22.19 μM BA and 2.85 μM IAA. Shoots were regenerated from both the proliferated tissues and IZEC, and propagated in the presence of IAA or α naphthaleneacetic acid (NAA), BA and gibberellic acid (GA3). Although roots were induced from regenerated shoots on the media containing a low concentration of IAA, IBA (0.98 μM) in combination with desiccation of regenerated shoots with a stem ∼10 mm in length promoted more and stronger root formation. After the root system was well established (20 mm in length), the regenerated plants were transferred to soil in plastic pots for further growth and production of R1 seeds in the greenhouse.
TL;DR: Results suggested that root growth in L. minor is regulated by endogenous gibberellin, especially in epidermal cells, which are affected by inhibition of cell division.
Abstract: Hormonal control of root growth was studied in Lemna minor. Although addition of gibberellic acid (GA3) to the culture medium did not promote the root growth, a gibberellin biosynthesis inhibitor, uniconazole P (Un-P), significantly inhibited root growth. Both length and diameter of roots in Un-P-treated plants were significantly smaller than those in control plants, mainly caused by inhibition of cell division. In epidermal cells, the length was slightly decreased and the width increased by Un-P treatment, indicating inhibition of elongation growth. GA3 completely nullified the inhibition caused by Un-P. Transverse cortical microtubules (CMTs) of epidermal cells in the elongation zone were significantly fragmented by treatment with Un-P, but not by that in the presence of GA3. The cellulose microfibril array in the Un-P-treated cells was more random and more oblique than that in the control cells. These results suggested that root growth in L. minor is regulated by endogenous gibberellin.
Journal Article•
TL;DR: Gibberellins do not appear to be directly involved in seed abortion of the stenospermocarpic cultivars Emperatriz and Perlon, although their participation in a more complex scenario should not be rejected, taking into account that in Perlon germination rates are positively correlated with the number of clusters per plant.
Abstract: Hypothesizing that seed abortion in stenospermocarpic grapes (Vitis vinifera L.) is caused by high gibberellin levels in the seed during the first stages of its development, we studied the effect of gibberellic acid GA3 and uniconazol (a GAs biosynthesis inhibitor) on this phenomenon. In vitro germination was analyzed in the seedless cultivars Emperatriz and Perlon, which were treated with 60 and 120 mg.-l 1 uniconazol (5 and 15 days before bloom) and 100 mg.-l 1 GA3 (5 days after bloom). In addition, endogenous levels of free gibberellins in flowers and seeds of Emperatriz and Perlon were compared with their seedeed progenitor Emperador. Clusters were harvested at bloom and 20 days after bloom for gibberellin analysis and at commercial maturity for in vitro culture of the seeds. Considerable gibberellin activity was found in the three cultivars, but only small differences were detected between the seedless and the seeded genotypes. Exogenous applications of GA3 had a deleterious effect on seed growth and on in vitro germination. Uniconazol also inhibited in vitro germination, though not affecting the total number of germinating embryos plus those rescued from non-germinating seeds. In conclusion, gibberellins do not appear to be directly involved in seed abortion of the stenospermocarpic cultivars Emperatriz and Perlon, although their participation in a more complex scenario should not be rejected, taking into account that in Perlon germination rates are positively correlated with the number of clusters per plant. Treatments with growth regulators also modified berry number per cluster, berry weight and rachis morphology. Finally, the plant source was a determinant affecting germination rates in vitro.
TL;DR: Positive correlations were found between berry-size, invert enzyme activity andhexose content, suggesting that GA3 stimulation of invertase could be one of the factors involved in theberry sizing-effect of GA3.
Abstract: It is well known that post-bloom applications ofgibberellic acid (GA3) increase seedless grapeberry size by enhancing cell division, or cellenlargement, or both. As a consequence, total waterand sugar per berry are increased. Soluble invertaseis considered to be one of the key enzymes in theaccumulation of sugar in grape berries. To study apossible role of invertase in the GA3berry-sizing effect, different rates of post-bloomGA3 were applied to seedless grape cv. Sultanaand hexose concentration and invertase activity weremeasured. GA3 stimulated both parameters as earlyas 24 and 32 h after applications, respectively.Moreover, the increment in sugar content and enzymeactivity remained throughout the growing of the berries period and, at ripening, increases in hexosescontent (102%) and invertase activity (60%) weredetected when GA3 was applied at a rate of 45 ppm.At the same GA3 rate the pericarp cellsdoubled in size. Furthermore, positive correlationswere found between berry-size, invertase activity andhexose content, suggesting that GA3 stimulationof invertase could be one of the factors involved in theberry sizing-effect of GA3.
TL;DR: It was concluded that application of GA3 to the seedlings might be a useful method for promoting rapid shoot growth of beneh and kolkhong and reduce the expense of seedling production in glasshouse conditions.
Abstract: SummaryBeneh (Pistacia mutica F. & M.) and kolkhong (Pistacia khinjuk Stock) are wild species of pistachio which grow naturally with other trees in some parts of Iran. Because of their adaptibility to severe environmental conditions and their resistance to some pests and diseases, they can be used as rootstocks for pistachio cultivars. Poor germination and very low seedling vigour of these two species have been a major problem in using them as rootstocks for pistachio cultivars. In this study gibberellic acid (GA3), at five concentrations (100, 250, 500, 750 and 1000 mg l21), were used during and after stratification to enhance seedling growth. The results showed that GA3, applied during and after stratification, significantly increased the length, trunk diameter, internode length, leaf area and fresh and dry weight of seedlings of both beneh and kolkhong species. However, application of GA3 after stratification was more effective on seedling growth of beneh. GA3 applied at higher concentrations (500 and ...
01 Jan 2000
TL;DR: The har vest season could be extended from November-December into November, and the loss of juice in mature fruits in GA?- treated fruits was retarded.
Abstract: Foliar sprays of gibberellic acid (GA,) were used to control puffing of 'Sunburst' mandarin and to delay the har vest season under central Florida conditions. The application of 25 mg-L1 GA3 to trees of 'Sunburst' mandarin prior to color break, 6-8 weeks before the normal harvest season, delayed color change in the flavedo and prevented peel puffing. Peel thickness and weight were reduced and fruit firmness was higher in GA?- treated fruits. The treatment also retarded the loss of juice in mature fruits. Based on these results, the har vest season could be extended from November-December into
TL;DR: It is suggested that papaya seed presents an orthodox behavior, permitting germplasm conservation in conventional and cryogenic genebanks, and treatment with GA 3 enhanced germination rate in all treatments.
Abstract: The effects on germination of two lots of Carica papaya seed of dehydration at 25 °C, followed by exposure to -20 °C or -196 °C, were evaluated with and without gibberellic acid (GA 3 ) treatment. In the absence of GA 3 treatment, dehydration increased subsequent germination only in seed lot 1 when moisture content (m.c.) was reduced from 59% to 6.0% and 5.3%. In seed lot 2, dehydration followed by exposure to -196 °C increased germination compared with dehydration alone. Treatment with GA 3 enhanced germination rate in all treatments. Dehydration to 5.3% (lot 1) or 6.9% and 6.8% m.c. (lot 2), followed by exposure to subzero temperatures and treatment with GA 3 , were the most favorable combined treatments to enhance papaya seed germination. The results suggest that papaya seed presents an orthodox behavior, permitting germplasm conservation in conventional and cryogenic genebanks.
TL;DR: Results are consistent with the concept that rapid shoot growth is associated with synthesis of GAs leading to GA 1, and the role of GA 3 in delaying bud break in mango is proposed that it may enhance or maintain the synthesis or activity of endogenous auxin.
Abstract: Stems of mango (Mangifera indica L.) rest in a non-growing, dormant state for much of the year. Ephemeral flushes of vegetative or reproductive shoot growth are periodically evoked in apical or lateral buds of these resting stems. The initiation of shoot growth is postulated to be primarily regulated by a critical ratio of root-produced cytokinins, which accumulate in buds and by leaf-produced auxin, which decreases in synthesis and transport over time. Exogenously applied gibberellic acid (GA 3 ) delays initiation of bud break but does not determine whether the resulting flush of growth is vegetative or reproductive. We tested the hypothesis that endogenous GA 3 , which influences release of these resting buds, may decrease in stem tips or leaves with increasing age of mango stems. GA 3 and several other GAs in stem tip buds and leaves were identified and quantified in stems of different ages. The major endogenous GAs found in apical buds and leaves of vegetative mango stems were early 13-hydroxylation pathway gibberellins: GA 1 , epi-GA 1 , GA 3 , GA 19 , GA 20 , and GA 29 , as identified by gas chromatography-mass spectrometry (GC-MS). A novel but unidentified GA-like compound was also present. The most abundant GAs in apical stem buds were GA 3 and GA 19 . Contrary to the hypothesis, the concentration of GA 3 increased within buds with increasing age of the stems. The concentrations of other GAs in buds were variable. The concentration of GA 3 did not change significantly with age in leaves, whereas that of most of the other GAs declined. GA 1 levels were greatest in leaves of elongating shoots. These results are consistent with the concept that rapid shoot growth is associated with synthesis of GAs leading to GA 1 . The role of GA 3 in delaying bud break in mango is not known, but it is proposed that it may enhance or maintain the synthesis or activity of endogenous auxin. It, thereby, maintains a high auxin/cytokinin ratio similar to responses to GA 3 that maintain apical dominance in other plant species.
TL;DR: Addition of anti-auxins 2,3,5-triiodobenzoic acid and 2,4,6-trichlorophenoxy-acetic acid into proliferation medium increased number of shoots per explant and length of shoots in both rose cultivars.
Abstract: Shoots of rose cultivars Super Star and Sonia were multiplied for ten subcultures at 4-week intervals on solidified Murashige and Skoog's medium supplemented with 22.19 μM benzylaminopurine + 1.07 μM napthalene acetic acid + 0.05 μM gibberellic acid. Addition of anti-auxins 2,3,5-triiodobenzoic acid (TIBA; 2.0 μM) and 2,4,6-trichlorophenoxy-acetic acid (2,4,6-T; 0.39 μM) into proliferation medium increased number of shoots per explant and length of shoots in both cultivars. Treatment with TIBA increased also number of leaves per shoot and leaf chlorophyll content.
TL;DR: Well-developed somatic embryos were selected from a repetivively somatic embryo line derived from embryonic axes of immature zygotic embryos of English walnut ‘No. 120’ (Juglans regia L.) for germination and conversion studies.
Abstract: Well-developed somatic embryos were selected from a repetivively somatic embryo line derived from embryonic axes of immature zygotic embryos of English walnut ‘No. 120’ (Juglans regia L.) for germination and conversion studies. In germinating dishes, somatic embryos germinated into only shoots, only roots, or both shoots and roots. Without any pretreatment, 28% somatic embryos germinated, while those treated with 2.5–5.0 mg 1−1 (7.2–14.4 μmol) gibberellic acid (GA3) germinated at 25–28% and those receiving a cold treatment of 2–3 mo. at 3–4°C germinated at 30–43%. However, only 4–19% of the germinating embryos showed both shoots and roots. Treated with desiccation, either with CaCl2·6H2O or Ca(NO3)2·4H2O at 20°C in the dark for 3 d, somatic embryos germinated at 85–91%, 57–69% of which had both shoots and roots. Treatment with 2 mo. cold storage in combination with desiccation using Ca(NO3)2·4H2O resulted in 92% of somatic embryos germinating, 70% of which showed both shoots and roots. No significant differences were observed between solid and liquid germination media. After transferring the germinating embryos to plantlet development media, 52–63% of those with both shoots and roots developed into plantlets while 11% with only shoots or 9% with only roots converted into plantlets. Plantlet development was improved by using lower medium salts and sucrose concentrations. The addition of activated charcoal enhanced root development, particularly root branching. Of 131 plants transplanted, 91 plants were acclimatized to a greenhouse.
Journal Article•
TL;DR: Overall, both osmo-conditioning and matriconditioning hastened germination and total germination in switchgrass cultivars CIR and NJ and had the highest final germination at 56% and 37% respectively.
Abstract: Switchgrass (Panicum virgatum L) is being developed and evaluated as summer forage and for biomass production in eastern Canada Uneven germination and slow seedling growth in spring are some of the factors limiting its cultivation A study was conducted to reduce seed dormancy and to improve germination at suboptimal temperatures in switchgrass cultivars Cave-in-Rock (CIR), Dakota (DK) and New Jersey 50 (NJ) Seeds of these cultivars were conditioned either with 02% potassium nitrate (KNO 3 ) or 1mM gibberellic acid or osmo-conditioned with polyethylene glycol 8000 (PEG) solution with or without 02% KNO 3 or 1 mM gibberellic acid (GA 3 ); or matriconditioned with Micro-Cel E (MC) with either water, 02% KNO 3 or 1 mM GA 3 The seeds were conditioned at 8 or 16°C for 4 days and then germinated at 8, 16 or 24°C Conditioning treatment and temperature influenced germination For CIR seeds germinated at 8°C, conditioning with PEG at 8°C increased germination from 0 (control) to 22% All the conditioning treatments germinated earlier and the proportion of seeds that eventually germinated was higher than for the unconditioned control In the cultivar NJ conditioning at 16°C with water or 1 mM GA 3 increased germination to 12 and 17% respectively (0 for the control) when seeds were germinated at 8°C When germinated at 16°C treatments containing 1 mM GA 3 germinated earlier Osmoconditioning in PEG with 1 mM GA 3 had the highest final germination at 56% (37% for control) Cultivar DK did not significantly respond to the various conditioning treatments Overall, both osmoconditioning and matriconditioning hastened germination and total germination in switchgrass cultivars CIR and NJ