Showing papers on "Gibberellic acid published in 2004"

The Effect of α -Amanitin on the Arabidopsis Seed Proteome Highlights the Distinct Roles of Stored and Neosynthesized mRNAs during Germination

Abstract: To investigate the role of stored and neosynthesized mRNAs in seed germination, we examined the effect of α-amanitin, a transcriptional inhibitor targeting RNA polymerase II, on the germination of nondormant Arabidopsis seeds. We used transparent testa mutants, of which seed coat is highly permeable, to better ascertain that the drug can reach the embryo during seed imbibition. Even with the most permeable mutant (tt2-1), germination (radicle protrusion) occurred in the absence of transcription, while subsequent seedling growth was blocked. In contrast, germination was abolished in the presence of the translational inhibitor cycloheximide. Taken together, the results highlight the role of stored proteins and mRNAs for germination in Arabidopsis and show that in this species the potential for germination is largely programmed during the seed maturation process. The α-amanitin-resistant germination exhibited characteristic features. First, this germination was strongly slowed down, indicating that de novo transcription normally allows the synthesis of factor(s) activating the germination rate. Second, the sensitivity of germination to gibberellic acid was reduced 15-fold, confirming the role of this phytohormone in germination. Third, de novo synthesis of enzymes involved in reserve mobilization and resumption of metabolic activity was repressed, thus accounting for the failure in seedling establishment. Fourth, germinating seeds can recapitulate at least part of the seed maturation program, being capable of using mRNAs stored during development. Thus, commitment to germination and plant growth requires transcription of genes allowing the imbibed seed to discriminate between mRNAs to be utilized in germination and those to be destroyed.

Glucose delays seed germination in Arabidopsis thaliana

Abstract: Here we report that glucose delays germination of Arabidopsis thaliana (L.) Heynh. seeds at concentrations below those known to inhibit early seedling development. This inhibition acts on embryo growth and is independent of hexokinase (HXK) function. Hormones and hormone inhibitors were applied to the germination media and several hormone biosynthesis and signalling mutants were tested on glucose media to investigate a possible role of abscisic acid (ABA), gibberellin and ethylene in the glucose-induced germination delay. Results indicate that the germination inhibition by glucose cannot be antagonized by ethylene or gibberellin and is independent of the HXK1/ABA/ABI4 signalling cascade. These findings suggest that there is a separate regulatory pathway independent of ABI2/ABI4/ABI5. Thus, in a relatively short time frame sugars utilize different signalling cascades to inhibit germination and post-germination growth, underlining the complexity of sugar responses.

Separation of Abscisic Acid, Indole-3-Acetic Acid, Gibberellic Acid in 99 R (Vitis berlandieri x Vitis rupestris) and Rose Oil (Rosa damascena Mill.) by Reversed Phase Liquid Chromatography

Abstract: Plant hormones, specialized chemical substances produced by plants, are the main internal factors controlling growth and development. In this study the pH and polarity of the mobile phase were taken into consideration to optimize the mobile phase for the chromatographic separation of 3 important plant hormones: abscisic acid (ABA), indole-3-acetic acid (IAA) and gibberellic acid (GA3). pKa values of ABA, IAA and GA3 were determined using retention factors. These 3 hormones were extracted from 99 R (Vitis berlandieri x Vitis rupestris) and rose oil (Rosa damascena Mill.) and the chromatographic method developed was used for the separation of these hormones.

Characterization of a Xyloglucan Endotransglucosylase Gene That Is Up-Regulated by Gibberellin in Rice

Abstract: Xyloglucan endotransglucosylases/hydrolases (XTHs) that mediate cleavage and rejoining of the β (1-4)-xyloglucans of the primary cell wall are considered to play an important role in the construction and restructuring of xyloglucan cross-links. A novel rice (Oryza sativa) XTH-related gene, OsXTH8, was cloned and characterized after being identified by cDNA microarray analysis of gibberellin-induced changes in gene expression in rice seedlings. OsXTH8 was a single copy gene; its full-length cDNA was 1,298 bp encoding a predicted protein of 290 amino acids. Phylogenetic analysis revealed that OsXTH8 falls outside of the three established subfamilies of XTH-related genes. OsXTH8 was preferentially expressed in rice leaf sheath in response to gibberellic acid. In situ hybridization and OsXTH8 promoter GUS fusion analysis revealed that OsXTH8 was highly expressed in vascular bundles of leaf sheath and young nodal roots where the cells are actively undergoing elongation and differentiation. OsXTH8 gene expression was up-regulated by gibberellic acid and there was very little effect of other hormones. In two genetic mutants of rice with abnormal height, the expression of OsXTH8 positively correlated with the height of the mutants. Transgenic rice expressing an RNAi construct of OsXTH8 exhibited repressed growth. These results indicate that OsXTH8 is differentially expressed in rice leaf sheath in relation to gibberellin and potentially involved in cell elongation processes.

Determination of endogenous hormones, sugars and mineral nutrition levels during the induction, initiation and differentiation stage and their effects on flower formation in olive

Abstract: Olive (Olea europaea L.) is one of the most important crop plants grown in the Mediterranean region. Varying levels of hormones, sugars and mineral nutrient are thought to influence flower bud formation. The objective of this study was to evaluate the changes in endogenous sugar, mineral nutrition and hormone levels in leaf, node and fruit samples of ‘Memecik’ olive during the induction, initiation and differentiation periods in on (bearing) and off (non-bearing) years. Leaf, node and fruit samples of mature 15-year-old Memecik olive were used. The samples were taken during the induction, initiation and differentiation periods of olive in on (2000) and off (2001) years. Sugar (glucose, fructose and sucrose), mineral nutrient (N, P, K, Ca, Mg, Fe, Zn, Mn and Cu) and hormone [abscisic acid (ABA), indole acetic acid (IAA), gibberellic acid (GA3, GA4) and zeatin (Z)] levels were determined in on and off years. Hormone and sugar levels were measured by gas chromatography and high-performance liquid chromatography. The K, Ca, Mg, Fe, Mn, Zn and Cu levels were quantified by an atomic absorption spectrophotometry. Nitrogen was determined by the Kjeldahl procedure, and P by a spectrophotometric method. The differences in any of the sugar concentrations, with the exception of fructose, were not significant in on and off years. Hormone levels, however, were significantly different in on and off years. Glucose had the highest concentrations in both years, followed by sucrose and fructose, respectively. The highest macro and micro element concentrations were found to be Ca and Fe, respectively. Thus, the results suggest that carbohydrates and mineral nutrients may not have a direct effect to induce flower initiation. However, high GA3 level exhibited an inhibitory effect on floral formation during the induction and initiation periods. On the other hand, the high concentrations of GA4, ABA and certain cytokinin levels may have a positive effect on flower formation in olive during the induction and initiation periods.

Action of plant growth regulators and salinity on seed germination of Ceratoides lanata

Abstract: Ceratoides lanata (Pursh) J.T. Howell is a shrub with numerous annual branchlets from the family Chenopodiaceae and is widely distributed in brackish water playas of northern Utah. Seeds had no dormancy, and about 90% of the seeds germinated in nonsaline control. Seed germination decreased with the increase in salinity, and more than 10% of the seeds germinated at 900 mmol/L NaCl. Almost all seeds germinated in less than 24 h, and no additional seed germinated after this time. Gibberellic acid had no effect in alleviating salinity effects; however, kinetin and fusicoccin substantially alleviated the effect of salinity on germination, while ethephon almost completely reverted the effect of salinity.Key words: Ceratoides lanata, gibberellic acid, ethephon, fusicoccin, halophytes, kinetin.

Smoke exposure alters endogenous gibberellin and abscisic acid pools and gibberellin sensitivity while eliciting germination in the post-fire annual, Nicotiana attenuata

Abstract: Exposure to smoke is required for the germination of seeds from dormant genotypes of Nicotiana attenuata, a post-fire annual of the Great Basin Desert. Germination can be elicited by GA1,3,4,7 treatments and inhibited by the GA biosynthesis inhibitor, paclobutrazol (PAC), abscisic acid (ABA) and terpenes leached from unburned litter of the plant’s natural habitat. We analysed the endogenous GA and ABA dynamics during the 22 h after imbibition, when smoke-treated dormant seeds commit to germination. Extractable GA1+3 pools decreased in all seeds, but the decrease was more dramatic within 2 h of smoke exposure, which was followed by an increase between hours 2 and 4. Extractable ABA pools increased shortly after imbibition and remained stable in control, water-treated seeds, but decreased sharply in smoke-treated seeds. PAC completely inhibited smoke-induced germination when seeds were treated for 12 h after smoke exposure, consistent with the requirement of de novo GA synthesis for germination. Smoke treatment in the dark did not result in germination, whereas GA3 treatment did, a result consistent with phytochrome-mediated GA biosynthesis. Smoke exposure dramatically increased the sensitivity of seeds to exogenous GA3 treatments in both the light and dark, and light exposure increased this sensitivity an additional tenfold. Taken together, these results suggest that while germination requires endogenous GA synthesis, the effects of smoke treatment increase GA sensitivity, which is correlated with a decrease in endogenous ABA pools.

Fluridone and norflurazon, carotenoid-biosynthesis inhibitors, promote seed conditioning and germination of the holoparasite Orobanche minor.

Abstract: Fluridone and norflurazon, two carotenoid-biosynthesis inhibitors, shortened the conditioning period required by seeds of Orobanche minor in order to respond to the germination stimulant strigol. Neither fluridone nor norflurazon alone induced seed germination of O. minor, they promoted strigol-induced germination. In addition, these compounds restored the conditioning and germination of seeds at a supraoptimal temperature (30 degrees C) as well as in the light. Gibberellic acid (GA(3)) showed similar promotive and protective effects on the conditioning and germination of O. minor seeds. Although fluridone and norflurazon are known to prevent abscisic acid (ABA)-biosynthesis, and stresses such as supraoptimal temperatures have been reported to induce ABA accumulation in plants, the amount of ABA in the seeds or that released from the seeds into the conditioning media was not affected by the fluridone treatment and by exposure to the supraoptimal temperature. These results indicate that the promotive and protective effects of fluridone and norflurazon on the conditioning and germination of O. minor seeds would be attributed to other perturbations rather than the inhibition of ABA-biosynthesis.

Growth, metabolic profiling and enzymes activities of Catharanthus roseus seedlings treated with plant growth regulators

Abstract: The effect of different growth regulators on growth and the production of terpenoid indole alkaloids as well as some enzymes involved in the biosynthesis were studied in Catharanthus roseus seedlings. The seedlings were grown on MS solid medium containing different concentrations of each growth regulator for a period of one month. Extracted alkaloids were analyzed by HPLC for determination of terpenoid indole alkaloid quantities. Continuous availability of growth regulators induced different alkaloids with variable effects among the regulators. Gibberellic acid at concentration of either 5.8 μM or 11.6 μM resulted in elongation of shoots with lowering the number of leaves. Abscisic acid has a retardant effect on growth. Ethylene did not effect the growth pattern at concentration of 100 μM but seedlings were not tolerant to higher concentrations. Methyljasmonate reduced the growth of the root system. Methyljasmonate was a general inducer for all alkaloids and increased the activity of strictosidine glucosidase. Ethylene applications promoted the pathways towards ajmalicine, serpentine, tabersonine and vindoline. Similar effect as for ethylene was observed for abscisic acid. Salicylic acid treatment increased the production of serpentine, tabersonine and higher concentration of salicylic acid induced vindoline accumulation. Peroxidase activity was also induced by salicylic acid. Gibberellic acid has little effect on alkaloid levels.

Effects of 1-methylcyclopropene and gibberellic acid on ripening of Chinese jujube (Zizyphus jujuba M) in relation to quality

Abstract: Overripening of Chinese jujube (Zizyphus jujuba M) fruit at the postharvest stage usually results in a dramatic decline in quality. The role of 1-methylcyclopropene (1-MCP) and gibberellic acid (GA) in fruit ripening of Chinese jujube during storage in relation to quality was investigated. Fruit ripening of jujube was significantly enhanced by ethylene, whereas rates of respiration and ethylene production of the fruit were reduced by 1-MCP. Treatment with 1-MCP or GA delayed the decreases in firmness and vitamin C and reduced the level of ethanol. Furthermore, the effectiveness of 1-MCP was improved by replicate treatments during storage at 20 or 2 °C. In addition, treatment with GA + 1-MCP resulted in additive beneficial effects on ripening inhibition of the fruit. Copyright © 2003 Society of Chemical Industry

In vitro propagation of Oroxylum indicum Vent. a medicinally important forest tree

Abstract: In vitro propagation of Oroxylum indicum Vent. was carried out using cotyledonary node explants. Among the different types of cytokinins used for culture establishment, 6-benzyladenine exhibited the best response with higher concentrations (8.87 µM or above) for inducing multiple shoots. Inclusion of indole-3-acetic acid (2.85 µM) into 6-benzyladenine-supplemented medium triggered a high frequency of response as well as a proliferation of shoots. The best medium for proliferation was Murashige-Skoog (MS) medium with 6-benzyladenine (8.87 µM) and indole-3-acetic acid (2.85 µM). However, incorporation of gibberellic acid (1.44 µM) was mandatory to enhance shoot elongation. Repeated subculturing of cotyledonary node and in vitro developed nodal segments in MS medium with 6-benzyladenine (4.44 µM) at 4-week intervals resulted in continuous mass multiplication of shoots without any evidence of decline. Root induction was best (91.6%) when MS strength was reduced to one-quarter and combined with α-naphthalene acetic acid (2.69 µM) and indole-3-acetic acid (5.71 µM), with a high survival rate (70–72%) of plantlets hardened in either soil rite or soil : sand : soil rite (1 : 1 : 2).

Spectrophotometric method for determining gibberellic acid in fermentation broths

Abstract: A novel method for the quantitative determination of gibberellic acid in fermentation broths has been developed. It is based on the kinetic of the reaction of conversion of gibberellic acid to gibberellenic acid. The method is simple, reliable, faster than most of methods known, and free of the interferences which commonly affect spectrophotometric methods currently in use. Its threshold sensitivity is 0.1 g and its accuracy is greater than 97% for concentrations of gibberellic acid ranging from 0.1 to 1 g l−1.

Variations in abscisic acid, indole-3-acetic acid, gibberellic acid and zeatin concentrations in two bean species subjected to salt stress

Abstract: Common bean (Phaseolus vulgaris L.) is sensitive to drought and salinity, while an ancestral legume, tepary bean (P. acutifolius A. Gray) is cultivated successfully where high temperature and drought are common (Lazcano-Ferrat and Lovatt, 1999). Hence, P. acutifolius is a potential source of stress tolerant traits for P. vulgaris through interspecific hybrids. This study comparatively evaluated the effects of salt stress on leaf relative water content (RWC), soluble protein, the phytohormones indole acetic acid (IAA), gibberellic acid (GA3), zeatin, and abscisic acid (ABA) levels in P. vulgaris and P. acutifolius. With the exception of ABA, stress-induced changes in hormonal levels putatively related to stress tolerance have not been investigated previously in either species. Treatment with 50 mM, 100 mM and 150 mM NaCl reduced relative water and protein content in P. vulgaris, but did not affect relative water content and increased protein content in P. acutifolius. Varietal differences between P. vulgaris and P. acutifolius were also observed in hormonal content during the stress period. ABA levels in salt-treated plants of P. vulgaris increased but did not change in P. acutifolius versus the controls. Both IAA and gibberellin levels increased in leaves of P. acutifolius but decreased in P. vulgaris under salt stress. In salt-treated plants, zeatin concentrations in leaves of P. vulgaris decreased within 24–72 h after treatment. However, P. acutifolius responded to all tested NaCl levels by increasing zeatin concentrations after short-term NaCl treatment.

Improving In Vitro Plant Regeneration from Leaf and Petiole Explants of `Marion' Blackberry

Abstract: Additional index words. Rubus, tissue culture, thidiazuron Abstract. Experiments focusing on plant growth regulatorsʼconcentrations and combina- tions, mineral salt formulations, and TDZ pretreatment formations were conducted to optimize in vitro shoot regeneration from leaf and petiole explants of ʻMarionʼ black- berry. Optimum shoot formation was obtained when stock plants were incubated in TDZ pretreatment medium for 3 weeks before culturing leaf explants on regeneration medium (Woody Plant Medium with 5 µM BA and 0.5 µM IBA) in darkness for 1 week before transfer to light photoperiod (16-hour photoperiod at photosynthetic photon flux of ≈50 µmol·m-2 ·s -1 ) at 23 °C ± 2 °C for 4 weeks. Under these conditions, ≈70% of leaf explants formed ≈40 shoots per petri dish that could be harvested and rooted to form plantlets. Chemical names used: N6 -benzyladenine (BA); 2,4-dichlorophenoxyacetic acid (2,4-D); gibberellic acid (GA 3); indole-3-acetic acid (IAA); indole-3-butyric acid (IBA); α-naph- thaleneacetic acid (NAA); N-phenyl-Nʼ-1,2,3-thidiazol-5-ylurea (thidiazuron (TDZ)).

Factors influencing regeneration of soybean from mature and immature cotyledons

Abstract: Soybean (Glycine max L.) plantlets were e?ciently regenerated from mature and immature cotyledons of?ve different genotypes by studying various parameters affecting regeneration. Green organogenic noduleswere induced at the proximal end, which subsequently differentiated into shoot buds on modi?ed MS(Murashige T. and Skoog F. 1962. Physiol. Plant. 15: 473-497) medium. The presence of 6-benzylaminopurine(BAP) and thidiazuron (TDZ) in the medium exerted a synergistic effect, in that regenerationeffciency was higher than for either cytokin alone. The regenerated shoot buds elongated and rooted onMS medium containing 0.29 lM gibberellic acid (GA3) and 2.69 lM a-naphthaleneaceticacid (NAA),respectively. Rooted plants were established in the greenhouse with 87% success and produced viable seeds.Preliminary studies with Agrobacterium show great promise for soybean transformation based on theregeneration protocol reported here.

SENESCENCE OF CUT LEAVES OF Zantedeschia aethiopica AND Z. elliottiana. PART I. CHLOROPHYLL DEGRADATION

Abstract: Chlorophyll degradation occurring during leaf senescence in under control of plant hormones. Changes in the chlorophyll content and the effects of BA (benzyladenine) and GA3 (gibberellic acid) on this process were analyzed during senescence of cut leaves of Zantedeschia aethiopica Spr. and Zantedeschia elliottiana Engl., two species grown for the florists' green. Both growth regulators were applied as 24 h pulse treatment: 0.25 mmol·dm -3 and 0.1 mmol·dm -3 for GA3 and BA, respectively. Gibberellic acid was more effective than benzyladenine in delaying senescence of both Zantedeschia species leaves by retarding chlorophyll loss. A standard preservative solution used to prolong longevity of cut flowers (8-HQC /citrate of hydroxyquinoline/ +2% S /sucrose/) radically accelerated chlorophyll loss of Z. aethiopica leaves but had no effect on pigment degrada- tion in leaves of Z. elliottiana. However, in both species the preservative diminished the positive effect of GA3 treatment on final chlorophyll content.

Factors affecting somatic embryogenesis in Prunus incisa cv. February Pink.

Abstract: Factors affecting somatic embryogenesis from root explants of Prunus incisa Thunb. cv. February Pink were investigated. Using a medium containing Murashige and Skoog salts and vitamins supplemented with 10 μM 2,4-dichlorophenoxyacetic (2,4-D), we evaluated the effects of light, growth regulators, amino acids, carbohydrate source, and root induction medium. Explants cultured under light or dark conditions both resulted in the formation of embryos. Embryogenesis was inhibited by the addition of 6-benzyladenine, thidiazuron, or gibberellic acid to the medium. Amino acids were not effective in promoting embryogenesis, with high levels of amino acids actually inhibiting it. Sucrose and glucose effectively induced embryogenesis, while sorbitol and mannitol completely inhibited it. Sucrose and glucose also promoted secondary embryogenesis. Embryos that formed in medium containing 4% or 5% sucrose were abnormally shaped and did not fully develop, while those that formed in medium with sucrose concentrations of 2% or 3% were much more vigorous. Root explants that were induced on medium containing 1.0 μM indole-3-butyric acid (IBA) produced more somatic embryos than explants induced on medium without IBA. Approximately 50% of the roots induced on medium containing 1.0 μM IBA produced somatic embryos on medium containing 10 μM 2,4-D and 3% sucrose.

Effect of gibberellic acid on the post-harvest flower longevity of Zantedeschia elliottiana [W.Wats] Engl.

Abstract: Two experiments were carried out to determine the effect of gibberellic acid on the longevity of cut flowers of two Zantedeschia elliottiana (W. Wats./Engl.) cultivars: 'Black Magic' and 'Florex Gold'. The flowers were conditioned for 2, 4 and 20 hours in water solutions of 8-hydroxyquinoline citrate at concentrations of 200 mg l -1 , and then kept in water and gibberellic acid solutions at concentrations of 50 and 100 mg l -1 . Gib- berellic acid enhanced the post-harvest longevity of Z. elliottiana flowers. Those of the 'Black Magic' cultivar lasted the longest when not conditioned, but merely stored in gib- berellic acid solutions. 8-hydroxyquinoline citrate shortened their longevity by a week. The post-harvest longevity of flowers of the 'Florex Gold' cultivar significantly depended on the concentration of gibberellic acid and conditioning time. The longest-lasting flowers were those conditioned in 8-hydroxyquinoline citrate for 2 hours.

Rapid in vitro adventitious shoot propagation of Scopolia parviflora through rhizome cultures for enhanced production of tropane alkaloids.

Abstract: A rapid micropropagation system for Scopolia parviflora Nakai (Solanaceae), a rare medicinal plant native to Korea, was established using rhizome cultures. Shoots that originated from adventitious shoots of the rhizome were multiplied when the rhizomes were cultured on half-strength B5 liquid medium supplemented with various growth regulators. Optimum shoot multiplication was observed in half-strength B5 medium containing 3% (w/v) sucrose and 5.77 μM gibberellic acid (GA3). Each rhizome gave rise to an average of 12 shoots. Shoot elongation and root induction from multiple shoots occurred on growth regulator-free half-strength B5 solid medium. Healthy plantlets were transferred to a peat moss:vermiculite mixture for acclimatization, which was successful. The concentrations of tropane alkaloids, hyoscyamine and scopolamine were determined in different tissues of native growing plants, in vitro-propagated plants and acclimatized plants by high-performance liquid chromatography. The analysis revealed that the levels of hyoscyamine and scopolamine were higher in in vitro-propagated plants than in the native growing plants. When the rhizome was cut into segments and transferred to optimal culture conditions for multiple shoot propagation, only 12 weeks were required to produce a mature plant. We conclude that in vitro propagation techniques through rhizome cultures provide an efficient and rapid method for shoot propagation of S. parviflora.

EFFECT OF GIBBERELLIC ACID ON THE POST-HARVEST FLOWER LONGEVITY OF Zantedeschia elliottiana (W. WATS) ENGL.

Abstract: Two experiments were carried out to determine the effect of gibberellic acid on the longevity of cut flowers of two Zantedeschia elliottiana (W. Wats./Engl.) cultivars: 'Black Magic' and 'Florex Gold'. The flowers were conditioned for 2, 4 and 20 hours in water solutions of 8-hydroxyquinoline citrate at concentrations of 200 mg l -1 , and then kept in water and gibberellic acid solutions at concentrations of 50 and 100 mg l -1 . Gib- berellic acid enhanced the post-harvest longevity of Z. elliottiana flowers. Those of the 'Black Magic' cultivar lasted the longest when not conditioned, but merely stored in gib- berellic acid solutions. 8-hydroxyquinoline citrate shortened their longevity by a week. The post-harvest longevity of flowers of the 'Florex Gold' cultivar significantly depended on the concentration of gibberellic acid and conditioning time. The longest-lasting flowers were those conditioned in 8-hydroxyquinoline citrate for 2 hours.

Enhancing Germination of Eastern Gamagrass Seed with Stratification and Gibberellic Acid

Abstract: Eastern gamagrass (Tripsacum dactyloides, L.), a warm season, perennial grass with great potential for forage and conservation uses, has a high level of seed dormancy, making establishment difficult. Stratification at 4°C for 6 wk is a standard method for providing germinable gamagrass seed. Earlier research showed that gibberellic acid (GA 3 ) increased germinability of gamagrass caryopses removed from the cupule, but was less effective when the caryopses remained in the cupule. We hypothesized that gibberellic add together with stratification may increase germination of seed above levels obtained by stratification or gibberellic add alone. This study assessed the germination of three seed lots of eastern gamagrass to 1 mM GA 3 and exposure to 4°C for 0 to 7 wk. Seed soaked in GA 3 solution averaged 43% germination during the first 3 wk of stratification and was significantly higher than the germination of water soaked seed averaging 35% germination. Seed reached peak germinability after 4 wk of stratification and remained at this level during the final weeks. After 4 wk of stratification, germination levels of GA 3 and water treated seed were similar at 64 to 70%. The most pronounced effect of GA 3 was more rapid germination of seed in all of the stratification durations tested.

Maturity and temperature stratification affect the germination of Styrax japonicus seeds

Abstract: SummaryThe effect of seed maturity, warm (18°C) or cold (5.5°C) temperature, and gibberellic acid (GA3) on Styrax japonicus seed germination was investigated. Morphological changes during fruit development were observed using magnetic resonance imaging (MRI) and to correlate changes in germination behaviour with time. Internal structures of fruits were identified using MRI, which showed tissues that contained water with different mobility in early growth stages. In the pericarp, the seed coat, and the endosperm of fruits harvested 17 weeks after anthesis, spin-lattice relaxation time T1 decreased with maturation of the fruits. This finding indicated the termination of the physiological role of the pericarp due to a loss of free water, and of water that existed in bound form in the endosperm and the cotyledons as seeds became dry. Magnetic resonance images of Styrax japonicus ‘Pink Chime’ fruits harvested 11 weeks after anthesis showed the formation of cotyledons and endosperm. Fruits were fully developed ...

A Study on the use of carrot juice in the tissue culture of Daucus carota

Abstract: Effects of using carrot juice in the in vitro growth of Daucus carota were investigated. Callus was the only form of growth obtained after five weeks in culture. The increase in fresh weight, dry weight and moisture content of the explants with increasing concentration of carrot juice in the medium was much lower when compared to either the cytokinin benzyladenine (BA) and/or the auxin picloram. Spectrophotometric and chromatographic analyses revealed the presence of both indole-3-acetic acid (IAA) and abscissic acid (ABA) in the carrot juice, while gibberellic acid was absent. Key Words: Carrot juice; auxin; abscissic acid. African Journal of Biotechnology Vol. 3 (4), 2004: 248-252

Micropropagation of Dianthus gratianopolitanus

Abstract: Meristem culture and/or thermotherapy were used to eliminate viruses from ornamental Dianthus gratianopolitanus Vill. ('Spotti' and 'Frosty Fire') mother plants. Shoot tip, leaf, node, and ovary explants collected from greenhouse-maintained, virus-free plants were cultured in vitro for shoot initiation on Murashige and Skoog (MS) medium containing BAP, kinetin, or 2-iP with or without IAA or NAA. Culture of shoot tips in MS with 0.57 µM IAA and node explants in MS with 2.46 µM 2-iP is recommended for 'Spotti' cultivar. In 'Frosty Fire', optimum number of axillary shoots was obtained from shoot tip and node explants in MS without plant regulators. Leaves and ovaries were not adequate explants for D. gratianopolitanus micropropagation because none or only a low percentage of explants regenerated shoots. High levels of cytokinins increased the number of shoots per explant but also increased the production of aberrant phenotypes and induced hyperhydricity. Adventitious shoots rooted in vitro with auxins, but maximum rooting was 97% ex vitro without auxins. This study demonstrated that D. gratianopolitanus can be successfully micropropagated. Chemical names used: 6-benzyladenine (BAP); kinetin (KIN); 6-(γ,γ-dimethylallylamino)-purine (2iP); indole-acetic acid (IAA); indole-3-butyric acid (IBA); α-naphthaleneacetic acid (NAA); gibberellic acid (GA3).

Rapid seed-based propagation method for the threatened African cherry (Prunus africana)

Abstract: Studies on the germination characteristics of various seed groups, extent of seedling and wildling establishment, as well as measurements on early seedling growth, were conducted on Prunus africana (Hook. f.) Kalkm. (syn. Pygeum africanum Hook. f.) (Rosaceae). Germination of seeds gathered en masse (together with soil and litter) from beneath Prunus trees was significantly greater (P < 0.01) compared to those collected in pure form from the ground (with or without fruit flesh) or those picked from the trees. Treating seeds with 10 or 100 µmol gibberellic acid (GA3) showed better germination than the control, but the difference was not statistically significant. Gibberellic acid at 1000 µmol (10−3 M) inhibited germination significantly (P = 0.02). Seedlings survived better in the glasshouse (90%) than in the nursery (87%). Whereas 60% of the 280 wildlings between 2.5 and 4.0 cm successfully established, only 10% of the 220 wildlings between 8.0 and 13.0 cm survived 3 mo after these had been maintained in the glasshouse. Seedlings derived from the GA3-treated seeds showed higher initial growth than the control owing to rapid hypocotyl elongation. Transferring seedlings to larger pots enhanced growth significantly after a lag period of about two weeks. Seedlings maintained in the glasshouse grew better than those in the nursery (P < 0.01). The study found that germination of seeds/fruits (gathered en masse from beneath trees) on a seedbed is convenient, technically less demanding, and is cost-effective.