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Showing papers on "Gibberellic acid published in 1979"


Journal ArticleDOI
01 Jan 1979-Planta
TL;DR: Endo-β-mannanase (EC 3.2.1.78) is produced and secreted by the cells of the endosperm of lettuce “seeds” (achenes) and may be involved in the control by the axis of the rest of the seed.
Abstract: Endo-β-mannanase (EC 3.2.1.78) is produced and secreted by the cells of the endosperm of lettuce (lactuca sativa L.) “seeds” (achenes). In imbibed intact seeds, production is prevented by inhibitors. If the endosperm is incubated alone, these inhibitors can be removed by leaching, allowing mannanase production. Abscisic acid, a component of lettuce seeds, inhibits the production of mannanase in the isolated endosperm, and may be involved in regulation of mannanase production in intact seeds. During germination the inhibition is removed, beginning 4–8 h after red-light irradiation, which was given 4 h from sowing. The cotyledons participate in this process, and are controlled by events occuring in the axis within 4 h from red-light irradiation. This control by the axis apparently depends on the exchange of diffusible substances. Both benzyladenine and gibberellic acid can replace the influence of the axis if the latter is removed, and may therefore be involved in the control by the axis of the rest of the seed.

60 citations


Journal ArticleDOI
TL;DR: Benzyladenine and gibberellic acid were applied together as a foliar spray to young tomato plants growing in pots of well drained soil, waterlogged soil or in nutrient solution supplied with air (aerobic), nitrogen gas (anaerobic), or ethylene for up to 6 days and diminished the effectiveness of ethylene as a stimulator of epinastic curvature.
Abstract: Summary Benzyladenine (BA) and gibberellic acid (GA) were applied together as a foliar spray to young tomato plants growing in pots of well drained soil, waterlogged soil or in nutrient solution supplied with air (aerobic), nitrogen gas (anaerobic), or ethylene (20 or 100 ul 1−1 in air) for up to 6 days. BA and GA (10 fig ml−1) lessened the inhibitory effects of waterlogging on stem elongation, transpiration and the increase of fresh and dry wt of the shoots. In absolute terms the promotion of shoot growth by BA and GA was greater in plants growing in non-waterlogged than in waterlogged soil. Root growth was inhibited by BA and GA. The effect of waterlogging in promoting adventitious rooting at the base of the stem was reduced by BA and GA. Epinastic curvature by petioles was promoted by growing plants in waterlogged soil or anaerobic solution culture in association with an increase in the production of ethylene by the petioles. Applications of BA and of GA inhibited this epinastic growth but they did not lower the rate of ethylene production. However BA and GA diminished the effectiveness of ethylene as a stimulator of epinastic curvature. The application of ethylene to the roots inhibited the accumulation of dry wt by the root system and decreased slightly the growth promoting effects of BA and GA in the shoots. The inhibiting effect of waterlogging the root system on stem elongation could be offset if adventitious roots maintained in well aerated conditions were previously induced on the main stem above the primary roots. Epinastic curvature and ethylene production were not decreased by the presence of an adventitious root system. The extent to which applications of BA and GA may reflect the activity of endogenous hormones produced by aerobic roots is discussed.

49 citations


Journal ArticleDOI
15 Aug 1979-Botany
TL;DR: The seed coverings, including the pericarp and testa of the caryopsis and the hull, arc the main barriers to the exchange of gases and the penetration of exogenous gibberellic acid (GA3) for germination of wild oats (Avena fatua L.).
Abstract: The seed coverings, including the pericarp and testa of the caryopsis and the hull, arc the main barriers to the exchange of gases and the penetration of exogenous gibberellic acid (GA3) for germination of wild oats (Avena fatua L.). Dormancy was induced in seeds by immersing them in water for 15 minor longer. Dormancy induction was greater in those seeds immersed for up to 1 h in 6% sodium hypochlorite (NaOCl) and then 1 h in water than in those seeds immersed only in water for 1 h. The addition of GA3, to seeds subjected to NaOCl treatment for 15 min or less did not break dormancy, indicating a slow rate of entry, or the exclusion, of GA3, by the seeds. In the presence of GA3, germination increased with increasing exposure to NaOCl. Maximum germination was obtained by immersing dry seeds in NaOCl for 2 h, in water for 1 h, and then incubating the seeds in GA3. Gibberellic acid was not required for complete germination of imbibed, dehulled seeds immersed in NaOCl for 1 h then in water for 1 h, but it was...

48 citations


Journal ArticleDOI
TL;DR: Exogenously supplied indole-3-acetic acid (IAA)-amino acid conjugates promoted callus growth and inhibited regeneration more effectively than equivalent concentrations of free IAA, HV, HJ and HV×HJ exhibited similar patterns of media-induced callusgrowth and regeneration.

46 citations


Journal ArticleDOI
TL;DR: When cells or the culture filtrate of Azotobacter chroococcum grown on a medium without a source of fixed nitrogen were added to barley seeds, they sometimes stimulated the extension of seedling roots and inhibition of germination appears to be due to competition between viable bacteria and seed for available oxygen.
Abstract: When cells or the culture filtrate of Azotobacter chroococcumgrown on a medium without a source of fixed nitrogen were added to barley seeds, they sometimes stimulated the extension of seedling roots. The stimulation appeared to be due to a bacterial metabolite as the cells used were non-viable (due to a decrease in pH of the growth medium). There was no evidence that 3-indoleacetic acid or gibberellic acid, which were produced by the bacterium, were involved in the stimulation. When the bacterium was grown on a medium containing nitrate, the cells, but not the culture filtrate, always inhibited germination and the extension of seedling roots. This inhibition of germination appears to be due to competition between viable bacteria and seed for available oxygen.

44 citations



Journal ArticleDOI
01 Jan 1979-Planta
TL;DR: Measurements of the component transfer processes showed that GA3 was not acting to promote assimilate transfer by increasing the photosynthetic rate of, or the assimilate export rate from the source, nor by altering the mobilizing ability of the competing root sink.
Abstract: Gibberellic acid (GA3), applied as a dispersion in aqueous lanolin to the stumps of decapitated stems of P. vulgaris plants, was found to promote the transfer of 14C-and 32P-labelled assimilates to the site of hormone application. Measurements of the component transfer processes, operating between source and sink (site of hormone application), showed that GA3 was not acting to promote assimilate transfer by increasing the photosynthetic rate of, or the assimilate export rate from the source, nor by altering the mobilizing ability of the competing root sink. Here, it also was found that the time between GA3 application and detection of an enhanced transport flux was independent of the length of the transport pathway. Overall, the evidence obtained indicated that GA3 was not acting on any transfer process remote from its point of hormone application but was acting locally at this latter point.

41 citations


Journal ArticleDOI
01 Jan 1979-Planta
TL;DR: During germination, the transmembrane electric potential of cortical cells of the embryonal axis of radish seeds (Raphanus sativus L.) rises from-120mV initially to a maximum of-150 mV after 5 h incubation, then falls again to stable values of around-120 mV, while administration of uncoupling agents or low temperatures produces a marked fall of the PD transitory increase.
Abstract: During germination, the transmembrane electric potential (PD) of cortical cells of the embryonal axis of radish seeds (Raphanus sativus L.) rises from-120 mV initially to a maximum of-150 mV after 5 h incubation, then falls again to stable values of around-120 mV. Treatments inhibiting germination block the transitory PD increase. Administration of uncoupling agents or low temperatures, during the process of germination, produces a marked fall of the PD transitory increase. Abscisic Acid has a parallel inhibitory effect on PD and germination, while fusicoccin produces a rise in both; administration of abscisic acid with fusicoccin inhibits germination, while the PD remains at the high levels given by fusicoccin. These results are discussed in relation to ion exchange at membrane level.

39 citations



Journal ArticleDOI
01 Jan 1979-Planta
TL;DR: The presence of high levels of ABA until maturity could prevent early germination and premature production of α-amylase in kernels of triticale 6A190, and the relevance of changes in the capacity of kernels to respond to and produce GA and ABA is discussed in relation to problems of harvest dormancy in cereals.
Abstract: Abscisic-acid (ABA) levels were determined in triticale 6A190 kernels at various stages of development from anthesis to maturity. ABA reached a maximum at ca. 22 d post-anthesis and declined rapidly 12 d later. Associated with drying of the kernel at maturity there was a rapid increase in the endogenous level of α-amylase, apparently based upon de-novo synthesis. Simultaneously there were visible signs of degradation of the large starch grains in the starchy endosperm. Regulation of α-amylase production in the kernel by exogenous gibberellic acid (GA3) was only evident in the almost mature kernel (30–40 d after anthesis) and then only if these kernels were first dried artificially. Furthermore, little α-amylase mRNA could be detected prior to kernel maturity and water loss. Thus, the high levels of gibberellin (GA) that have been found early in kernel development in cereals do not appear to control the later production of α-amylase and onset of kernel germination in the ear of triticale. However, the presence of high levels of ABA until maturity could prevent early germination and premature production of α-amylase. Kernels of triticale 6A190 are characteristically shrivelled and non-dormant at maturity. The relevance of changes in the capacity of kernels to respond to and produce GA and ABA is discussed in relation to problems of harvest dormancy in cereals.

33 citations


Journal ArticleDOI
TL;DR: The optimum concentrations of naphthaleneacetic acid (NAA) and benzyladenine (BA) were determined for shoot and root initiation from hypocotyls and meristem-tip cultures differentiated shoots and roots in response to these concentrations.
Abstract: Hypocotyl sections and isolated meristem-tips from 7- to 10-day-old seedlings of flax were cultured on a Murashige and Skoog (1962) medium. The optimum concentrations of naphthaleneacetic acid (NAA) and benzyladenine (BA) were determined for shoot and root initiation from hypocotyls. Meristem-tip cultures differentiated shoots and roots in response to these concentrations. The frequency and yield of shoots, promoted by BA, decreased if NAA or gibberellic acid (GA3) was included in the medium. At high NAA concentration GA3 and BA inhibited root initiation. Morphological development of cultures differed depending on the growth regulators in the medium.

Journal ArticleDOI
TL;DR: The possibility is discussed that the synthesis of the protein portion of glycoproteins is specifically inhibited, when glycosylation is prevented, as well as tunicamycin, which may inhibit the rate of total protein synthesis.
Abstract: A crude membrane fraction was prepared from isolated aleurone layers, the secretory tissue of barley grains. The layers were pre-incubated in the presence or absence of the phytohormone gibberellic acid. The membranes catalyzed the transfer of [14C]mannose from GDP-[14C]mannose and of N-[14C]acetylglucosamine from UDP-N-[14C]acetylglucosamine to endogenous and exogenous dolichyl monophosphate. When gibberellic acid was present during the pretreatment the activity of the transferases was increased by a factor of two to three. A significantly increased activity was observable within four hours after the addition of gibberellic acid, whereas the gibberellic-acid-induced secretion of the glycoprotein alpha-amylase started only after 12 h. Tunicamycin inhibited the secretion of alpha-amylase by 60 to 80%. Intracellularly, however, no alpha-amylase was found to accumulate. On the other hand, tunicamycin did not inhibit the rate of total protein synthesis by more than 10%. The possibility is discussed that the synthesis of the protein portion of glycoproteins is specifically inhibited, when glycosylation is prevented.

Journal ArticleDOI
TL;DR: The application of 2,4-D and BA to inflorescences of cultivar ‘Fino’ increased fruit-setting and weight of the fruits, although not as efficiently as GA3, both the concentration and the time of application being more critical.

Journal ArticleDOI
TL;DR: In this paper, it was shown that growing barley aleurone cells with gibberellic acid produces a progressive increase in the RNA content of the cells, reaching a maximum ≈12 hours after hormone addition and declines thereafter.
Abstract: Incubation of barley aleurone cells with gibberellic acid produces a progressive increase in the RNA content of the cells. The activity of poly(A)-containing RNA, measured in an in vitro wheat germ protein-synthesizing system, reaches a maximum ≈12 hr after hormone addition and declines thereafter. The structurally intact functional mRNA content in these cells, measured as poly(A)-RNA with 5′ “caps,” also shows a maximum at 12 hr and correlates with the translational capacity of poly(A)-RNA. Activation of mRNA by guanylylation or methylation after addition of gibberellic acid is ruled out. Available evidence indicates that gibberellic acid stimulates protein synthesis by increasing the synthesis of mRNA. Studies with cycloheximide suggest that the induction of synthesis of α-amylase mRNA by gibberellic acid requires protein synthesis after hormone addition.

Journal ArticleDOI
TL;DR: The K + GA3 treatment, whilst promoting germination under high temperature or water stress, reduced radicle growth subsequent to germination, thus providing support for the possibility that, in gerulation, the initiation of cell elongation has a degree of metabolic independence of the other processes associated with growth.
Abstract: Summary Seeds of two cultivars of lettuce (Lactuca sativa L.), untreated or soaked in acetone containing kinetin and gibberellic acid (K + GA3), were germinated in light or dark at a range of (high) temperatures and at a range of water potentials. In addition, untreated and treated seeds were germinated at 20°C in the light and then transferred to the same high temperatures or to low water potentials. In both cvs light and K + GA3 promoted germination at high temperatures and at low water potentials, although the cvs differed quantitatively in their responses. The upper temperature limit of germination in the light, and of radicle growth after germination, were similar in treated and untreated seeds respectively, suggesting that light and K + GA3 in combination may have completely removed the specific high-temperature block to germination. Although light and K + GA3 increased the tolerance of germination to water stress, germinated, untreated seeds were able to grow at even lower water potentials. The K + GA3 treatment, whilst promoting germination under high temperature or water stress, reduced radicle growth subsequent to germination, thus providing support for the possibility that, in germination, the initiation of cell elongation has a degree of metabolic independence of the other processes associated with growth.

Journal ArticleDOI
15 Aug 1979-Botany
TL;DR: Callus formation and organogenesis have been induced on the internode culture of Cassava (Manihot esculenta Crantz) and the leaves which appear are typical of cassava; leaf differentiation is followed by shoot development.
Abstract: Callus formation and organogenesis have been induced on the internode culture of cassava (Manihot esculenta Crantz). Callusing was rapidly induced on the medium devised by Kartha, Gamborg, and Constabel for the shoot apical meristem culture of cassava. During culture, green protuberances appear on the callus followed by the differentiation of a leaf-like structure. The leaf-like structure degenerated after a month of differentiation. On the same medium, but lacking gibberellic acid (GA3), organogenesis is less frequent and precocious but the leaves which appear are typical of cassava; leaf differentiation is followed by shoot development.

Journal ArticleDOI
TL;DR: Development of the ability to respond to GA3 by increasing α-amylase activity depended on the duration of desiccation or isolation from the plant, and changes in metabolism emanating from the interruption to the supply of sucrose to the caryopsis may be involved.
Abstract: No change in the total β-amylase activity, attributable to the presence of 10-6 M gibberellic acid (GA3) in the incubation medium, was found in freshly harvested, de-embryonated, immature (11-38 days post-anthesis) caryopses of wheat. Significant amounts of GA3-induced α-amylase activity was found in 26-h incubates of similar caryopses which had been allowed to dry out either in the ear or detached from the ear. After 10 days of storage of detached immature caryopses in air of 99-100% relative humidity, de-embryonated half-caryopses responded to applied GA3 by producing α-amylase. More α-amylase was found in 26-h incubates if detached caryopses dried out slowly, but rapid desiccation led to little or no α-amylase being produced in the presence of GA3. Caryopses taken from ears cultured on 0.4 or 4% sucrose for 10 days did not respond to applied GA3 whereas those from ears cultured on water did respond, although the amount produced in 26-h incubates was not as large as those from slowly dried ears. Development of the ability to respond to GA3 by increasing α-amylase activity depended on the duration of desiccation or isolation from the plant. Changes in metabolism emanating from the interruption to the supply of sucrose to the caryopsis may be involved in the development of the ability of the aleurone to respond to GA3.


Journal ArticleDOI
TL;DR: Dormancy of field-grown wild oat seeds increased with increasing seed maturity and was affected by planting location and associated crop.
Abstract: Germination in response to gibberellic acid was used as an assay for wild oat seed dormancy. In growth chamber studies removal of glumes, a 5 °C reduction in night temperature (20 °C day/15 °C night vs. constant 20 °C), and a shorter photoperiod (12 vs. 18 h) during the period following panicle emergence reduced subsequent germination (increased dormancy) of mature seeds. Dormancy of field-grown wild oat seeds increased with increasing seed maturity and was affected by planting location and associated crop.

Journal ArticleDOI
15 Aug 1979-Botany
TL;DR: The hard coat seems to be the main factor in regulating wild buckwheat seed germination and Cow cockle, however, is regressive in this regard.
Abstract: Seed germination of wild buckwheat (Polygonum convolvulus L.) and cow cockle (Saponaria vaccaria L.) increased with increasing time of immersion in 6% sodium hypochlorite (NaOCl). Maximum germinati...

Journal ArticleDOI
TL;DR: In this article, the root stcklings of three cultivars of carrots (Daucus carota L) were vernalized 10 weeks at 5 C and subsequently grown at each of three greenhouse night/day temperature regimes: high (27/32 C), medium (21/27 C), and low (15/21 C).
Abstract: Stecklings (roots) of three cultivars of carrots (Daucus carota L.) were vernalized 10 weeks at 5 C and subsequently grown at each of three greenhouse night/day temperature regimes: high (27/32 C), medium (21/27 C), and low (15/21 C). Floral differentiation occurred first in the easy bolting cv. Scarlet Nantes, intermediate in cv. Danvers 126, and last in cv. Royal Chantenay. Stem elongation arising from the subapical meristematic region always preceded floral differentiation. Extractable gibberellin-like activity in carrot stem apices increased from harvest during the 10-week vernalization period, then remained constant even though floral differentiation and stem elongation occurred during an additional 20-week cold storage period. Low temperature had both an inductive and a direct effect on reproductive development depending on length of low temperature exposure.After 10 weeks vernalization at 5 C, high greenhouse temperature severely reduced ultimate seedstalk height and the endogenous gibberellinlike activity decreased rapidly during the first 3 weeks in the greenhouse. At the low greenhouse temperature, activity remained fairly constant during the 10-week sampling period. Changes in endogenous gibberellinlike activity were related with stem elongation, but not with floral initiation. Exogenous gibberellic acid (GA(3)) applied following vernalization prevented the inhibitory effect of high greenhouse temperature on seedstalk elongation and resulted in seedstalk heights comparable to untreated controls grown at the low greenhouse temperature. Exogenous applications of succinic acid-2,2-dimethylhydrazide and chlormequat reduced seedstalk height of carrot plants grown at the medium and low greenhouse temperatures to that of untreated controls grown at high temperature. Exogenous growth regulators and greenhouse temperature affected seedstalk elongation, but did not affect the number of plants that flowered.

Journal ArticleDOI
01 Dec 1979-Planta
TL;DR: Results show for the first time that in GA3-treated tissue enzyme activity is associated with the endoplasmic reticulum (ER) and it is suggested that this activity represents new enzyme synthesized on ER in response to GA3 and probably destined for secretion.
Abstract: A metal-salt precipitation method with p-nitrophenyl phosphate as substrate has been used to localize in the electron microscope acid phosphatase activity in isolated aleurone layers of barley (Hordeum vulgare L.), treated for 16 h in the presence or absence of gibberellic acid (GA3). The paper confirms results obtained earlier with an azo-dye precipitation method of enzyme localization. In addition the results show for the first time that in GA3-treated tissue enzyme activity is associated with the endoplasmic reticulum (ER), there being reaction product deposited in the ER cisternae. It is suggested that this activity represents new enzyme synthesized on ER in response to GA3 and probably destined for secretion.

Journal ArticleDOI
TL;DR: The forces required to puncture intact lettuce (Lactuca sativa) seed and pericarp, endosperm and embryo were measured by the Instron Universal Testing Machine and changes in the strength of theendosperm do not appear to be related directly to protrusion of the radicle.
Abstract: The forces required to puncture intact lettuce (Lactuca sativa) seed and pericarp, endosperm and embryo were measured by the Instron Universal Testing Machine. It required about 0.6 newton to puncture the endosperm in seeds imbibed in the dark at 6, 12 and 24 hours. Endosperm of seeds imbibed in the light or in dark with gibberellic acid required about 4.2 newtons at 6 and at 12 hours and only about 0.15 newton at 24 hours. Forces required to puncture embryo at all treatments and times remained constant at about 0.3 newton. Changes in the strength of the endosperm do not appear to be related directly to protrusion of the radicle.

Journal ArticleDOI
TL;DR: Comparison of the effects of gibberellic acid, abscisic Acid, and inhibitors of protein and RNA synthesis upon storage protein hydrolysis and their effects upon proteolytic activity indicated that storage protein Hydrolysis in germinating wheat is controlled by the rate of hormonally induced de novo synthesis of endoproteolytic enzymes.
Abstract: The effects of gibberellic acid, abscisic acid, cycloheximide, actinomycin D, and cordycepin upon exo- and endoproteolytic activities and storage (gluten) protein hydrolysis in germinating wheat and in incubated embryoless wheat seeds have been studied Early increases in endoproteolytic activity were insensitive to the addition of gibberellic acid and inhibitors of protein and RNA synthesis Later increases in endoproteolytic activity were enhanced by gibberellic acid, strongly inhibited by abscisic acid and cycloheximide, and partially inhibited by actinomycin D and cordycepin Increases in exoproteolytic activity were insensitive to the addition of gibberellic acid, abscisic acid, actinomycin D, and cordycepin but were inhibited in whole seeds when cycloheximide was added in the steeping medium However, cycloheximide did not inhibit increases in exoproteolytic activity when added to embryoless seeds, to germinating whole seeds, or to seeds which had been stored at 4 C for extended periods of time Comparison of the effects of gibberellic acid, abscisic acid, and inhibitors of protein and RNA synthesis upon storage protein hydrolysis and their effects upon proteolytic activity indicated that storage protein hydrolysis in germinating wheat is controlled by the rate of hormonally induced de novo synthesis of endoproteolytic enzymes

Journal ArticleDOI
TL;DR: The ABA and GA3 contents were investigated in barley seeds during maturation and after harvest and the results of quantitative determination corresponded to the growth effects in the test of the first leaf of oat.
Abstract: The ABA and GA3 contents were investigated in barley seeds during maturation and after harvest. The highest amount of ABA was found in milk and wax ripeness – 13 ng and 11 ng per seed respectively. The level decreased during the later stages of maturation and during release of dormancy and was 1 ng per seed 6 weeks after harvest. The content of gibberellic acid decreased in a similar way but in an earlier stage of maturation. The determined amounts of GA3 were: 0.4, 0.1, 0.03 and about 0.05 ng per seed respectively, in milk, wax and full ripeness and after harvest. The results of quantitative determination, obtained with the GLC method, corresponded to the growth effects in the test of the first leaf of oat.

Journal ArticleDOI
01 Jan 1979-Planta
TL;DR: The capacity of GA3 to induce flowering in sorghum, a short-day plant, seems to be enhanced by phytochrome being in the PR form at the beginning of the night when GA3 was applied, which promotes stem elongation equally whether floral initiation occurred or not.
Abstract: Combinations of far-red light (FR) (4 min) and gibberellic acid (GA3), given at the beginning of a daily 12-h dark period in a growth room, were used to study floral induction in four maturity genotypes of the milo group of sorghum (Sorghum bicolor (L.) Moench). The 12-h dark period without GA3 application or FR induced flowering in only the early genotype; FR hastened initiation in the early genotype, while GA3 hastened floral initiation in the two intermidiate-flowering genotypes. GA3 and FR together had a strong synergistic effect, hastening floral initiation by 30 to more than 80 d in the early and intermediate genotypes. Red light (R) did not hasten flowering; FR preceded by R gave the same effect as FR alone. GA3 promoted stem elongation equally whether floral initiation occurred or not; thus, its effect on stem elongation was independent of floral initiation. The capacity of GA3 to induce flowering in sorghum, a short-day plant, seems to be enhanced by phytochrome being in the PR form at the beginning of the night when GA3 was applied.

Journal ArticleDOI
Nobuo Okagami1
TL;DR: Effects of some environmental conditions (photoperiod, white and colored lights, temperature, partial oxygen pressure) and growth regulators (gibberellic acid, 2-chloroethyltrimethylammonium chloride) on induction and release of dormancy of the bulbils of Dioscorea batalas, Laportea bulbifera, Elatostema involucratum andSedum bulbiferum were investigated.
Abstract: Effects of some environmental conditions (photoperiod, white and colored lights, temperature, partial oxygen pressure) and growth regulators (gibberellic acid, 2-chloroethyltrimethylammonium chloride) on induction and release of dormancy of the bulbils ofDioscorea batalas, Laportea bulbifera, Elatostema involucratum andSedum bulbiferum were investigated. Bulbils were formed under short-day conditions inLaportea andElatostema, under long-day conditions inSedum, and irrespective of photoperiods inDioscorea. In all species exceptSedum, immature bulbils required light, particularly blue or far red, for sprouting (photo-sprouting stage), and mature bulbils required a cold treatment (thermo-sprouting stage). The duration of photo-sprouting and thermo-sprouting stages and the degree of dependency on light or low temperature of sprouting differed from species to species. Sprouting of chilled mature bulbils of these species was promoted by light, especially by red or green light. Both immature and mature bulbils ofSedum sprouted under short-day conditions. Continuous irradiation with blue, far-red and green light markedly inhibited their sprouting. Oxygen at high concentration inhibited the sprouting of immature bulbils inDioscorea; in the other species it promoted sprouting regardless of the maturation of the bulbils. Applications of gibberellic acid caused the sprouting of bulbils the absence of light, chilling or photoperiodic treatment in all species exceptDioscorea, in which gibberellic acid inhibited sprouting. Polyphenol oxidase activity was very high in the homogenates ofDioscorea bulbils, and increased further when the bulbils had been treated with gibberellic acid. In the other species, little or no such activity was observed.

Journal ArticleDOI
TL;DR: The enzymes from intact, wounded, and hormone-treated tissues possess similar characteristics: their activity is dependent on the presence of all four ribonucleotides and a divalent cation such as Mg(2+) or Mn(2+), but the sensitivity of the enzymes from different preparations toward alpha-amanitin differs.
Abstract: Chromatin-bound DNA-dependent RNA polymerases react upon wounding of white potato tuber tissues with an increase in activity, which is additionally enhanced to 300% in the presence of 0.1 micromolar gibberellic acid (GA 3 ). 2,4-Dichlorophenoxyacetic acid is only weakly effective and indoleacetic acid not at all. Wounding and treatment with GA 3 affect template availability of chromatin only slightly. The hormone has no effect on chromatin-bound RNA polymerases, if added in vitro. The enzymes from intact, wounded, and hormone-treated tissues possess similar characteristics: their activity is dependent on the presence of all four ribonucleotides and a divalent cation such as Mg 2+ or Mn 2+ . However, the sensitivity of the enzymes from different preparations toward α-amanitin differs. Total RNA polymerase activity of chromatin was inhibited by α-amanitin to about 44% in intact, to about 22% in wounded, and only 15% in GA 3 -treated tissues. The relative activities of polymerases I and II were estimated by varying the (NH 4 ) 2 SO 4 and α-amanitin concentrations in the assay system. It is evident that GA 3 preferentially stimulates polymerase I and hence ribosomal RNA synthesis. RNA polymerase II is but slightly affected by GA 3 . Nearest neighbor frequency analysis revealed that the RNA synthesized by the enzymes from the intact tuber is different from that of wounded or GA 3 -treated tissues.

Journal ArticleDOI
TL;DR: After applications of gibberellic acid tumbled, impacted and abraded grains formed α-amylase faster than untreated controls as discussed by the authors, and apical abrasion was not essential to achieve this enhanced response.
Abstract: After applications of gibberellic acid tumbled, impacted and abraded grains formed α-amylase faster than untreated controls. Apparently apical abrasion was not essential to achieve this enhanced response. The testae of treated grains appeared to be intact, and excluded externally applied gibberellic acid except at the base of the grains, where it normally gains entry. Essentially normal patterns of modification were observed in all grain samples, however treated. Tumbling and abrasion sometimes stimulate enzyme production in the absence of externally supplied gibberellic acid. It is deduced that these treatments do not alter the pattern of gibberellin penetration into grain. Physical treatments cause limited embryo-damage and create fissures in and between the grain's surface layers. The treatments appear to exert their beneficial effects on enzyme production by allowing better access of oxygen in the air to the living grain tissues. Normally the oxygen supply limits enzyme formation. Surface populations of microbes sometimes limit oxygen levels in grain and repress enzyme formation.

Journal ArticleDOI
TL;DR: It is suggested that flowering in this orchid hybrid is regulated by growth substances, both qualitatively and quantitatively.
Abstract: Summary The growth habit, axillary bud differentiation and flowering behaviour in a sympodial orchid hybrid, Dendrobium Louisae cv. ‘Dark’ were studied. Flowering occurred only after termination of vegetative growth in the pseudobulb. Intermediate shoots with both vegetative and reproductive growth were produced when plants were placed in the shade. Decapitation did not stimulate floral initiation. In mature pseudobulbs, Cytokinin (benzyladenine) stimulated flowering. Gibberellic acid enhanced the cytokinin effect but was itself not effective. It is suggested that flowering in this orchid hybrid is regulated by growth substances, both qualitatively and quantitatively.