Showing papers on "Gibberellic acid published in 1973"

Effects of plant growth substances on in vitro fiber development from unfertilized cotton ovules

Abstract: Fertilization of cotton ovules was prevented by removal of styles and stamens on the morning of anthesis. Forty-eight hr later ovaries were harvested and ovules were aseptically transferred to liquid culture medium supplemented with various plant growth substances. In the absence of phytohormones, ovules browned and failed to increase in size or produce fibers. Indoleacetic acid and gibberellic acid provided for ovule growth and fiber development. Kinetin provided for ovule growth only. The ovule's capacity for indoleacetic acidor gibberellic acid-stimulation of fiber development was reduced by high concentrations of kinetin or abscisic acid. Low concentrations of kinetin partially reversed the inhibitory effect of

Regulation of Invertase Levels in Avena Stem Segments by Gibberellic Acid, Sucrose, Glucose, and Fructose

Abstract: Gibberellic acid and sucrose play significant roles in the increases in invertase and growth in Avena stem segments. About 80% of invertase is readily solubilized, whereas the rest is in the cell wall fraction. The levels of both types of invertase change in a similar manner in the response to gibberellic acid and sucrose treatment. The work described here was carried out with only the soluble enzyme. In response to a treatment, the level of invertase activity typically follows a pattern of increase followed by decrease; the increase in activity is approximately correlated with the active growth phase, whereas the decrease in activity is initiated when growth of the segments slows. A continuous supply of gibberellic acid retards the decline of enzyme activity. When gibberellic acid was pulsed to the segments treated with or without sucrose, the level of invertase activity increased at least twice as high in the presence of sucrose as in its absence, but the lag period is longer with sucrose present. Cycloheximide treatments effectively abolish the gibberellic acid-promoted growth, and the level of enzyme activity drops rapidly. Decay of invertase activity in response to cycloheximide treatment occurs regardless of gibberellic acid or sucrose treatment or both, and it is generally faster when the inhibitor is administered at the peak of enzyme induction than when given at its rising phase. Pulses with sucrose, glucose, fructose, or glucose + fructose elevate the level of invertase significantly with a lag of about 5 to 10 hours. The increase in invertase activity elicited by a sucrose pulse is about one-third that caused by a gibberellic acid pulse given at a comparable time during mid-phase of enzyme induction, and the lag before the enzyme activity increases is nearly twice as long for sucrose as for gibberellic acid. Moreover, the gibberellic acid pulse results in about three times more growth than the sucrose pulse. Our studies support the view that gibberellic acid, as well as substrate (sucrose) and end products (glucose and fructose), play a significant role in regulating invertase levels in Avena stem tissue, and that such regulation provides a mechanism for increasing the level of soluble saccharides needed for gibberellic acid-promoted growth.

Hormonal regulation of growth in unfertilized cotton ovules.

Abstract: Exogenous plant growth regulators can substitute for pollination, fertilization, and subsequent embryo development in cotton. Isolated, unfertilized, immature ovules enlarge in the presence of kinetin, and both enlarge and produce fibers in the presence of indoleacetic acid or gibberellic acid or both. An extract of germinating cotton pollen qualitatively mimics the effect of exogenous hormones.

Seed and Embryo Germination in Syringa vulgaris and S. reflexa as Affected by Temperature during Seed Development

Abstract: Effects of controlled temperature conditions during seed development on seed and embryo germination of Syringa vulgaris were studied using vegetatively propagated mother plants. Seeds from mother plants grown at 18–24°C were partially dormant at low (15°C) but not at high (21°C) germination temperature, while seeds from outdoors or from plants grown at 12°C were not dormant at all. Seed dormancy at low temperatures was induced as well when branches from outdoor plants were kept at 18–24°C for the last two-three weeks before harvesting. The dormancy induced by 24°C during seed development was not broken by keeping branches at 12°C for the last two-three weeks. In most cases the induced seed dormancy was broken completely by gibberellic acid. Embryo germination at 24 or 15°C was not affected by mother plant temperature. Part of the embryos from plants grown at 24°C were, however, dormant at 9°C. The ability of embryos to germinate in osmoticum was only slightly affected by mother plant temperature. The mechanical resistance of the endosperm was significantly higher in the seeds from plants grown at 24°C than in seeds from 12°C. Both the embryos and the seeds of S. reflexa were dormant at the time of termination of embryo elongation. Experiments with three seed-propagated mother plants indicated that the water potential of embryos may be reduced by high mother plant temperature.

An improved bio‐assay for abscisic acid and other antitranspirants

Abstract: SUMMARY A greatly improved method is described for the bio-assay of abscisic acid (ABA) and other compounds that possess ‘antitranspirant’ activity. As in the previous method, the stomatal responses are observed on pieces of isolated epidermis of Commelina communis immersed in small volumes of solution containing the compounds to be assayed. In new media, it is now possible to obtain linear responses to ABA concentrations over the range 10-4-10-8 M in PIPES buffer at pH 6.8, and over the range 10-7-10-10 M in citrate buffer at pH 5.5. In citrate buffer, it is possible to detect as little as 26 pg of ABA. In both media, the assay is unaffected by the presence of six other growth regulators (auxin, gibberellic acid, kinetin, coumarin, xanthinin and scopoletin) but the stomata closed partially in response to 10-3 M chlorogenic acid.

Spring Shoot Growth in Douglas-Fir May Be Initiated by Gibberellins Exported from the Roots

Abstract: Trials conducted under controlled environments demonstrated that the delay of bud activity of Douglas-fir (Pseudotsuga menziesii) seedlings occasioned by low temperature of the soil could be eliminated by application of gibberellic acid. Analyses of field-grown plants showed a parallel increase in bud activity, level of gibberellin-like compounds in xylem sap, and soil temperature during February and March.

Effects of Kinetin, Gibberellins and (±) Abscisic acid on the Germination of Lettuce (Lactuca sativa)

Abstract: Germination responses of achenes of lettuce (Lactuca sativa L, cv. Arctic King) to treatment with kinetin, gibbe-rellins and abscisic acid were examined over a range of temperatures: in both light and dark. Kinetin (0.1–10 mg/l) strongly promoted germination at temperatures above 27±C in continuous light or after short periods of illumination during the early stages of imbibition. It also relieved the inhibitory affects of abscisic acid in these conditions. In total darkness however kinetin treatment resulted in only a minor promotive effect. Treatment with gibberellic acid (A3) or a mixture of gibberellins A4 and A7 were much less effective in promoting germination at higher temperatures of lettuce achenes exposed to light but were strongly promotive in the dark.

Hormonal Control of Orthophosphate Incorporation into Phospholipids of Barley Aleurone Layers

Abstract: Gibberellic acid added to isolated barley aleurone layers enhances orthophosphate incorporation into chloroform-methanol-soluble compounds. The effect is measurable at 4 to 6 hours after the addition of gibberellic acid and reaches a maximum after 8 to 12 hours. The increase in the rate of orthophosphate incorporation is 3- to 5-fold over the rate in control layers incubated without gibberellic acid. The gibberellic acid enhancement of the rate of phospholipid labeling is inhibited within 1 to 2 hours by cycloheximide, 6-methylpurine, and abscisic acid. The increase in labeling of phospholipids occurs throughout the subcellular fractions rather than being restricted to a specific fraction or organelle. The increase in radioactivity in phospholipids as shown by thin layer chromatography is due to a proportional increase in all phospholipids. The enhancement by gibberellic acid of the rate of phospholipid labeling may be required for the subsequent production of gibberellic acid-induced hydrolases.

Influence of gibberellic and abscisic acids and the growth retardant, CCC, upon plastid development

Abstract: Gibberellic acid (GA3) enhances ultrastructural morphogenesis of plastids in greening cereals whilst abscisic acid (ABA) and CCC have the reverse effect over a shorter period. GA3 application counteracts the ABA and CCC inhibition of membrane development and, over longer periods of greening, the fastest rate of chloroplast development is shown in the presence of both GA3 and ABA. Experiments with isolated etioplasts show that the ABA inhibition of development also occurs and can be counteracted with GA3 treatment but no individual enhancement of plastid morphogenesis by GA3 was detected. Ribulose 1,5-diphosphate carboxylase (RuDPC) acitvity was also increased with applications of GA3 and reduced with ABA treatment. The initial levels of RuDPC activity in the presence of CCC were concentration dependant; high in 10-3 M CCC and low in 10-6 M CCC but activity returned to normal levels after CCC application was stopped. Experiments with isolated etio-chloroplasts gave similar results but levels of RuDPC activity declined rapidly in both illuminated and un-illuminated incubated suspensions of intact etioplasts.

Changes in Endogenous Cytokinins of Lettuce Seed during Germination

Abstract: Using the soybean callus bioassay it has been shown that dormant lettuce seeds (Lactuca sativa L. cv. Grand Rapids) contain large amounts of water soluble cytokinins and small amounts of butanol soluble ones. When the seeds are irradiated with red light, or imbibed with 5 mg/1 gibberellic acid in the dark, the total cytokinin content of the seeds decreases, the level of water soluble cytokinins decreases, and the level of the butanol soluble cytokinins increases. Far-red light does not reverse this effect completely although cytokinin activity in the butanol extracts decreases following such irradiation. It is proposed that the interconversion of cytokinins initiated by red light, or gibberellic acid in the dark, is one of the primary events leading to radicle elongation in light-sensitive lettuce seed.

Effects of gibberellic Acid and sucrose on the growth of oat (Avena) stem segments

Abstract: Gibberellic acid induced growth in Avena (oat) stem segments within 35 minutes after hormone application. The total elongation elicited by gibberellic acid was greater than 15 times the control growth. The sensitivity of the segments to low concentrations of gibberellic acid (1 pmole) and the specificity of the segments to the gibberellin class of hormones suggest that oat stem segments would be a valuable tool for gibberellin bioassays. Both gibberellic acid-induced growth and control growth are temperature-dependent and showed a Q10 of two or greater. Although the most apparent effect of gibberellic acid was to promote the uptake of water into the internode, the hormone also promoted transport of endogenous substrate and the uptake of exogenous substrate into the growing region. The growth promotion was accomplished without an apparent increase in osmotic pressure.

In vitro tuberization of potato sprouts as affected by ethrel and gibberellic acid

Abstract: In vitro tuberization of etiolated potato sprouts was considerably advanced by a dose of 50 ppm ethrel (2-chloro-ethyl-phosphonic acid). The adition of ethrel also increased the number of tubers, produced shorter and thicker stolons and reduced root development. Some of these effects are opposite to those induced by gibberellic acid which is known to retard tuberization and to promote elongation. When both substances were simultaneously supplied to the medium, they showed a clear antagonistic interaction.

Interactions between Gibberellic Acid, Ethylene, and Abscisic Acid in Control of Amylase Synthesis in Barley Aleurone Layers

Abstract: Gibberellic acid-induced α-amylase synthesis in barley (Hordeum vulgare L.) aleurone layers was inhibited by abscisic acid, and the inhibition was partly removed by additional gibberellic acid alone and by ethylene alone. Together additional gibberellic acid and ethylene almost eliminated abscisic acid inhibition of amylase synthesis. Time course studies of these phenomena showed that the effect of abscisic acid, ethylene, and varying concentrations of gibberellic acid on the course of amylase synthesis were either to speed up or slow down the whole process and not to affect the lag phase or the linear phase separately. The data are discussed in relation to previous studies of abscisic acid-gibberellic acid interaction.

Gibberellic Acid and Ion Release from Barley Aleurone Tissue Evidence for Hormone-dependent Ion Transport Capacity

Abstract: The release of potassium, magnesium, and phosphate ions from aleurone cells of barley (Hordeum vulgare L. cv. Himalaya) is a gibberellic acid-dependent process. The release of these ions is preceded by a lag period of 6 to 8 hours after gibberellic acid addition. The effect of gibberellic acid on the release of ions is not mediated through an effect on ion solubilization. Thus, gibberellic acid does not apreciably affect the sum of extracted and released ions relative to controls. Rather, the effect of the hormone is on the release process itself. Inhibitors of oxidative phosphorylation when added with gibberellic acid or at times up to 6 hours after gibberellic acid inhibition release. When these inhibitors are added after ion release has begun, however, rapid efflux of ions occurs. These results suggest a strong correlation between energy levels and ion transport capacity. Inhibitors of RNA and protein synthesis also inhibit gibberellic acid-stimulated ion release. Evidence suggests that RNA and protein synthesis are required to establish and maintain ion release capacity of aleurone cells.

Synthesis and release of sucrose by the aleurone layer of barley: Regulation by gibberellic acid

Abstract: Aleurone layers of barley contain large amounts of a soluble oligosaccharide which was identified as sucrose (30–40 μg/mg fresh weight). Treatment of the layers with gibberellic acid (GA3) causes the release of sucrose from the cells. This release requires the participation of metabolic processes, including protein synthesis. When embryoless half-seeds are incubated sucrose accumulates in the aleurone layers, but when seeds are germinated the sucrose content of the aleurone layers declines. Labeling experiments with radioactive glucose and fructose show that aleurone layers continuously synthesize sucrose and that the release, but not the synthesis of sucrose is enhanced by GA3.

Shoot differentiation in callus cultures of Datura innoxia

Abstract: Datura innoxia Mill. callus cultures formed shoots in 2–4 weeks on media containing; a) gibberellic acid, b) indoleacetic acid, c) low concentrations of naphthylacetic acid, d) low concentrations of 2,4-dichlorophenoxyacetic acid, e) benzylaminopurine, f) no growth substance. Benzylaminopurine promoted shoot differentiation. Gibberellic acid inhibited shoot formation weakly, but inhibited proper leaf blade formation. Root differentiation was rare. The callus cultures of Datura innoxia grew rapidly (100-fold in 4 weeks) on a slightly modified Murashige and Skoog medium (0.5 mg/l thiamin · HCl, pH 5.5, no glycine) in light at 30°C. Callus grew well on any single one of the growth substances NAA (10−5M), 2,4-D (10−6M) or BAP (3 × 10−6M). Growth was less and more erratic on GA or IAA. The callus cultures did not grow significantly better when BAP was combined with one of the auxins or with GA.

Effect of Hormone-Directed Presoaking on Emergence and Growth of Osmotically Stressed Wheat (Triticum aestivum L.) Seeds

Abstract: The water potential gradient between a planted seed and the surrounding soil largely controls water absorption by the seed. Salinity of soil water affects this balance, which in turn lowers germination and seedling growth. Overcoming the inhibition of water intake by presoaking and the use of auxins and gibberellins has been shown to be advantageous for certain crops,but studies with wheat are limited. This approach constitutes the objectives of this investigation. The effects of presoaking wheat seeds in 10, 20, 50, and 100 ppm each of GA, IB A, IAA, and NAA at O, 3, 6, and 9 atm osmotic pressure on seedling development were observed. Auxins had little influence on emergence at 0 atm but promoted emergence at 3, 6, and 9 atm. Three-indole acetic acid (IAA) and α — naphthalene acetic acid (NAA) at 50 ppm produced maximum shoot length, whereas gibberellic acid (GA) and three-indole-butyric acid (IBA) gave better results at 100 ppm. Increased concentrations of GA and NAA significantly reduced primary root length, whereas IAA increased root length. All hormones increased proliferation of lateral roots, but auxins produced more lateral roots at all salinity levels. Root/shoot ratio was decreased by NAA and GA. Water absorption was increased by all treatments. IAA and NAA at 50 ppm gave the better results. The data support the hypothesis that the beneficial effects of hormones may be the result of increased water absorption, which improves plant growth even under high salt concentrations hi the growth medium.

Seed Dormancy in Acer CHANGES IN ENDOGENOUS GERMINATION INHIBITORS, CYTOKININS, AND GIBBERELLINS DURING THE BREAKING OF DORMANCY IN ACER PSEUDOPLATANUS L.

Abstract: Changes in germination inhibitors, cytokinins, and gibberellin-like substances during the breaking of coat-imposed dormancy of sycamore seeds at low temperature suggest that dormancy may be controlled by the presence of endogenous germination inhibitors. Stratification at 5 °C led to a greater loss of neutral inhibitor(s) from the embryo than did incubation at 20 °C. No marked differences were observed in the level of cytokinins and gibberellin-like substances between treatments. However, a gradual decrease in the level of cytokinins was observed during stratification. Whether a cytokinin-inhibitor interaction is involved in the control of dormancy of sycamore seeds, as was previously suggested, remains to be determined. INTRODUCTION Experiments with dormant sycamore (Acer pseudoplatanus L.) fruits indicated that fruits and seeds with the testa intact require a period of chilling at 5 °C to break dormancy, whereas isolated embryos germinated immediately at 20 °C on moist filter-paper without pretreatment (Webb and Wareing, 1972a). Results from leaching experiments suggested that dormancy was the result of the restric tion, by the testa, of the outward diffusion of germination inhibitors present in the embryo. Inhibitors extracted from dormant sycamore seeds have also been shown to inhibit the germination of non-dormant sycamore seeds at relatively low concentrations (Webb and Wareing, 19726). A comparison with the effects of applied abscisic acid (ABA) indicated that the level of endogenous ABA alone could not account for the inhibition observed by the seed extracts. Both ABA and neutral compounds present in the embryo appeared to be involved. Leaching treatments that removed dormancy also led to a decrease in the level of inhibitors present in the basic and neutral ethyl acetate fraction. Application of kinetin to dormant sycamore seeds increased germination 1 Present address : Great Lakes Forest Research Centre, Canadian Forestry Service, P.O. Box 490, Sault Ste. Marie, Ontario, Canada. 2 Present address : Botany Department, University of Natal, Pietermaritzburg, Republic of South Africa. This content downloaded from 40.77.167.104 on Sun, 24 Jul 2016 04:18:58 UTC All use subject to http://about.jstor.org/terms 742 Webb, van Staden, and Wareing—Seed Dormancy in Acer whereas gibberellic acid (GA3) had no effect. A similar response was obtained with lettuce seeds in which germination was inhibited by the basic and neutral ethyl acetate fraction obtained from dormant sycamore seeds. These results led to the suggestion that a possible inhibitor-cytokinin interaction may be involved in the dormancy of sycamore seeds (Webb and Wareing, 19726). Similarly, the work of Pinfield and Stobart (1972) supports this hypothesis. The results of Van Staden, Webb, and Wareing (1972) with Acer saccharum suggested that endogenous cyto kinins may play an important role in embryo-dormant seeds. Stratification led to a marked increase in the level of cytokinins and gibberellin-like compounds with a concomitant loss of ABA. In sycamore seeds which show a coat-imposed dormancy, the natural means of dormancy removal is by moist low-temperature after-ripening as the fruit over winters on the ground. Thus, it was of interest to examine the possible involvement of endogenous germination inhibitors and promoters during the breaking of coat imposed dormancy of sycamore seeds at low temperatures. MATERIALS AND METHODS Seed storage and germination conditions A. pseudoplatanus L. fruits were collected from single, open-grown trees in the Botany Gardens, Aberystwyth, in November 1970 and 1971. The fruits were air-dried to remove surface water only and stored in sealed containers at 2-5 °C. In these studies seeds were used within 2 months from the dated collection since it is difficult to store sycamore fruits in a dormant state without loss of viability (Jahnel, 1955). Seeds were germinated on filter-paper in Petri-dishes at 20 °C (Webb and Wareing, 1972a). Protrusion of the radicle through the covering structures was used as the criterion for germination. Stratification conditions Whole fruits were presoaked in distilled water for 24 h and placed in plastic bags. Any excess moisture was drained off and the sealed bags stored at 5 °C for approximately 80-100 d. At 10-d intervals the bags were opened and checked for moisture. Extraction and bioassay of growth regulators Germination inhibitors and gibberellin-like substances were extracted as previously described (Webb, Van Staden, and Wareing, 1972). The seed material was homogenized and extracted in 80 per cent redistilled methanol at 2-5 °C. The aqueous fraction was partitioned four times at pH 8-0 with redistilled ethyl acetate. The aqueous fraction was then adjusted to pH 2-5 and again partitioned with ethyl acetate. Cytokinins were extracted using the methods of Van Staden et al. (1972). The partitioned extracts were dried under vacuum at 35 °C and strip-loaded on to Whatman No. 1 chromatography paper. The chromatograms were developed in a descending manner in iso-propanol: ammonia iwater (10:1:1 v/v/v) in the case of extracts to be assayed for inhibitors or gibberellins, and in water-saturated sec butanol for extracts to be assayed for cytokinins. Germination inhibitors in the acidic ethyl acetate fraction and in the basic ethyl acetate fraction (which would also contain any neutral compounds) were determined using the lettuce-seed germination bioassay (Webb and Wareing, 19726). In all experiments recorded the results are the means of at least two bioassays seen at different times. The lettuce hypo cotyl bioassay was used to determine gibberellin-like activity (Loveys, 1970). Cytokinin activity was determined using the soybean callus bioassay (Miller, 1965). RESULTS Whole fruits from the 1970 seed crop were stratified at 5 °C and a second control sample was incubated at 20 °C (a temperature that normally does not lead to This content downloaded from 40.77.167.104 on Sun, 24 Jul 2016 04:18:58 UTC All use subject to http://about.jstor.org/terms Webb, van Staden, and Wareing—Seed Dormancy in Acer 743 Fig. 1. The effect of stratification on the level of acidic germination inhibitors in sycamore seeds. The equivalent of 0-5 g dry weight of i material in the acidic ethyl acetate fraction was chromatographed on paper in '10:1:1' and assayed with the lettuce seed germination bioassay. r

Effects of Gibberellic Acid and Abscisic Acid on Shoot Formation in Tobacco Callus Cultures

Abstract: Tobacco (Nicotiana tabacum L. cv. W. 38) callus grown on a shoot-forming medium was exposed to gibberellic acid (GA3) and abscisic acid (ABA) for varying lengths of time and at different periods during culture. The results suggest that if the tissue accumulated sufficient GA3 prior to the initiation of meristemoids and shoot primordia, repression of shoot formation occurred. This repression was not reversed by increasing the levels of auxin or cytokinin in the medium, but ABA could partially overcome the GA3 repression of shoot formation.

Interaction between ethylene, abscisic acid and gibberellic acid in elongation of rice mesocotyl.

Abstract: Combined application of ethylene, abscisic acid and gibberellic acid produced marked partly synergistic stimulation of mesocotyl growth of japonica rice in darkness.

Induction of morphogenetic changes and acceleration of leaf initiation by gibberellic acid in xanthium pennsylvanicum

Abstract: One application of gibberellic acid (GA3) to young internodes significantly accelerated the rate of leaf initiation and caused an increase in the number of internodes in shoots of Xanthium pennsylvanicum. The average duration of one plastochron was reduced from 3.3 to 1.9 days. The rate of growth of the GA3-treated internodes, and also of those positioned above and below, was at least twice that of the control. It appeared that the growth substance was translocated both acropetally and basipetally from the locus of application and that it significantly accelerated the rate of stem elongation. Gibberellic acid also had a pronounced morphogenetic effect on the leaves. It induced the development of lanceolate leaves instead of typical deltoid leaves. The area and the leaf length of the treated plants were both significantly reduced. Each response may be regulated by increasing or decreasing the concentration of gibberellic acid. The induced morphogenetic changes were not permanent. A reversion to the original condition was noticeable about 8 wk after treatment.

Factors affecting the culture in vitro of potato meristem tips

Abstract: Meristem tips of an Italian cultivar were cultured in a modification of Murashige and Skoog's medium. Light spectrum and intensity affected rooting and vigour of plantlets. The best results were obtained with 4000-lux fluorescent lamps with a spectrum roughly similar to that of daylight but richer in red. Agar did not affect the proportion of explants rooting but changed the root system appearance. The presence of gibberellic acid was important for rooting. Rooting of plantlets cultured on liquid substrates devoid of gibberellic acid was not dependent on the size of the explants. Sometimes teratomata developed in liquid substrates and occurred together with a small downward pH shift, while the normal development was always accompanied by a stronger pH shift to acid values

Effect of extracellular products ofAulosira fertilissima on the growth of rice seedlings

Abstract: The effect of extracellular products fromAulosira fertilissima on the growth of rice seedlings (IR-8) has been studied. There is indication of liberation of a root-promoting hormone from the alga. The growth pattern of rice seedlings, treated with algal filtrate, parallels that of seedlings treated with gibberellic acid. An increased growth of rice seedlings results when they are treated with algal filtrate obtained from the exponential phase of the alga. The amino acid-treated seedlings do not show any marked increase in growth. Filtrate fromAnacystis nidulans, on the other hand, do not show any growth promoting response. The possibility of liberation of kinins byA. fertilissima does not appear to be involved.

Early Actions of Gibberellic Acid on the Embryo and on the Endosperm of Avena fatua Seeds

Abstract: Gibberellic acid at 0.1 μm stimulates amylase synthesis in dormant Avena fatua seeds without inducing germination; at 0.5 mm it enhances biosynthesis of proteins and RNA in both the embryo and the endosperm and utilization of the endosperm sugars by the embryo. These events occur in early hours (0-14th hour) and prior to germination, which begins 24 hours after gibberellic acid application. These observations are in agreemeent with the concept that in cereal grains gibberellic acid has two morphological sites of actions: the embryo and the endosperm, and that germination (radicle protrusion) is not caused by gibberellic acid-induced amylase synthesis in the endosperm.

Bud Sprouting and Growth of Purple Nutsedge Altered by Benzyladenine

Abstract: Varying concentrations of benzyladenine (BA), in- doleacetic acid (IAA), gibberellic acid (GA), abscisic acid (ABA), and 2-chloroethylphosphonic acid (ethephon) were used to induce sprouting of dormant purple nutsedge (Cyperus rotundus L.) tubers. BA at 50 to 300 ppm stimulated sprout- ing. The continuous presence of BA during the sprouting period was necessary to give significant sprout stimulation. Neither IAA at 1, 10, or 100 ppm; GA at 10, 100, or 1000 ppm; nor ethephon at 10, 100, or 1000 ppm had stimulatory effects on sprouting. ABA counteracted the stimulatory effects of BA when tubers were treated with ABA following BA treatment. Sprouting was markedly greater at 33 C day, 25 C night than at 24 C day, 17 C night. Growth of plants originat- ing from tubers pretreated with 100 ppm BA did not differ significantly from the controls. Sustained BA applications at 100 and 200 ppm produced numerous plants with tuft-type growth habit, delayed flowering, and reduced the number of inflorescences. Numerous short, diageotropic rhizomes were produced.