Stimulatory effect of ethephon,ACC, gibberellin A3 and A4+7 on germination of methyl jasmonate inhibited Amaranthus caudatus L. seeds

Methyl jasmonate (JA-Me) inhibited or retarded germination of Amaranthus caudatus seeds in darkness at 24°C, Ethephon, ACC and gibberellins (GA₃ or GA₄₊₇) partially or completely reversed this inhibition depending on the concentration of JA-Me applied. Both ethephon and the gibberellins were more effective than ACC. Both GA₃ and GA₄₊₇ enhanced the stimulatory effect of ethephon or ACC on germination of seeds inhibited by JA-Me.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - JA jasmonic acid - JA-Me methyl jasmonate     

Endogenous ethylene and reversing methyl jasmonate inhibition of Amaranthus caudatus seed germination by benzyladenine or gibberellin

BA at 10^–5 M, GA₃ at 3×10^–4 M or GA₄₊₇ at 3×10^–5 M partially or largely reversed the inhibition of Amaranthus caudatus seed germination due to JA-Me. BA or GA₃ did not affect ethylene production and ACC oxidase activity in vivo in the presence of JA-Me before radicle protrusion. However, both increased ethylene production after 72 h of incubation, when the reversal of the JA-Me inhibition of seed germination was observed. AVG at 3×10^–4 M decreased ethylene production when it was applied simultaneously with BA and JA-Me or GA₃ and JA-Me, but it had no effect on seed germination. NBD almost completely reversed the stimulatory effect of BA, GA₃ or GA₄₊₇ on the germination of seeds in the presence of JA-Me. Exogenous ethylene reversed the inhibitory effect of NBD. The results indicate that action of endogenous ethylene is involved in the response of JA-Me inhibited seeds to BA or GA_s.     

Implication of Ethylene in the Release of Secondary Dormancy in Amaranthus caudatus L. Seeds by Gibberellins or Cytokinin

Ethephon (Eth), gibberellin A₃, A_{4 + 7} (GA₃, GA_{4 + 7}), and 6-benzyladenine (BA) removed secondary dormancy of Amaranthus caudatus seeds. The GAs and BA potentiated the effect of ethephon or 1-aminocyclopropane-1-carboxylic acid (ACC), an ethylene biosynthesis precursor, in terms of the rate or final percent of germination. Aminoethoxyvinylglycine (AVG), an ACC synthase activity inhibitor, was observed to simultaneously inhibit the release from dormancy effected by GA₃ or BA as well as the ethylene production stimulated by these regulators. Breaking of secondary dormancy by GA₃, GA_{4 + 7} or BA was prevented by 2,5-norbornadiene (NBD), an inhibitor of ethylene binding. Ethylene completely or markedly reversed the inhibitory effect of NBD. We thus conclude that the removal of secondary dormancy in Amaranthus caudatus seeds by gibberellin or benzyladenine involves ethylene biosynthesis and action.     

Effect of a plant-derived smoke extract, N6-benzyladenine and gibberellic acid on the thermodormancy of lettuce seeds

The effects of a plant-derived smoke extract, BA and GA₃ on the thermodormancy of Grand Rapids lettuce seeds were studied. Thermodormant lettuce seeds treated either with BA, GA₃ or smoke extract alone did not germinate. Combinations of BA with smoke extract and BA with GA₃ were most effective in overcoming induced thermodormancy. GA₃ plus smoke did not break the induced thermodormancy. The effects of the different treatments on germination were concentration dependent. BA was most effective at 10^–5 to 10^–3 M in combination with smoke dilutions 1:5,000 to 1:1,000,000 in overcoming thermodormancy.Abbreviations BA N⁶-benzyladenine; - GA₃ gibberellic acid; - SM smoke extract     

外源赤霉素对紫斑牡丹种子萌发的影响

以紫斑牡丹种子为试验材料,研究不同浓度的赤霉素(GA_3)处理对种子生根以及生根过程中营养物质、酶活性和内源激素水平变化的影响,为探讨紫斑牡丹种子萌发机制提供依据。结果表明:(1)GA_3处理能够促进种子生根,并以300 mg/L GA_3处理对种子生根效果最好,与对照相比可提前14.67 d生根,生根率可达71.00%。(2)与对照相比,GA_3处理可以在0～15 d时促进种子淀粉水解和可溶性糖的积累,并加速可溶性蛋白的消耗,在0～30 d促进过氧化物酶(POD)活性的提高,从而促进种子萌发生根。(3)在种子沙藏生根过程中,种子脱落酸(ABA)含量呈下降趋势,赤霉素(GA)、玉米素核苷(ZR)和吲哚乙酸(IAA)含量均表现出先上升后下降的趋势,与对照相比,GA_3处理可使种子GA、ZR和IAA的含量在沙藏前期明显上升,以解除种子休眠。研究发现,外源GA_3处理可以调控紫斑牡丹种子内源激素含量和POD活性的变化,促进营养物质转化,从而提前解除种子休眠使其萌发。     

Gibberellins in seeds of Arabidopsis thaliana: biological activities,identification and effects of light and chilling on endogenous levels

The activities of several gibberellins in stimulating germination of wild-type and GA-deficient gal seeds of Arabidopsis thaliana were compared. Of the six compounds tested GA₄ and GA₇-isolactone had the highest activity and GA₇ and GA₉ the lowest; activities of GA₁ and GA₃ were intermediate. Combined application of pure GAs presented no indications that more than one GA receptor is involved. Four GAs were identified in extracts from wild-type and GA-insensitive gai seeds by combined gas chromatography mass spectrometry: GA₁, GA₃, GA₄ and GA₉. Effects of light and chilling on levels of GA₁, GA₄ and GA₉ were studied using deuterated standards. Light increased both GA levels and germination in unchilled wild-type and gai seeds. As a result of irradiation GA levels in gai seeds were 7–10 times as high as in wild-type seeds. In the dark germination was 0%, in the light 14% of gai seeds and 95% of wild-type seeds germinated. A chilling pre-treatment of 7 days at 2°C was required to enhance further the germination of gai seeds in the light. Light did not increase GA levels of chilled seeds of either genotype; levels of GA₄ and GA₉ of chilled gai seeds, in the light were respectively 7 and 12 times lower than in non-chilled seeds, whereas the latter seeds germinated better. Slightly elevated levels of GA₄ were detected in darkness after chilling, but germination capacity was still 0%. These results strengthened the conclusion that GAs are required for germination of A. thaliana seeds, whereby GA₄ has intrinsic biological activity. However, it is unlikely that light and chilling stimulate germination primarily by increasing levels of GA. Instead GA sensitivity is a possible alternative.     

Responsiveness of Amaranthus retroflexus seeds to ethephon, 1-aminocyclopropane 1-carboxylic acid and gibberellic acid in relation to temperature and dormancy

Dormant Amaranthus retroflexus seeds do not germinate in the dark at temperatures below 35°C. Fully dormant seeds germinate only at 35–40°C whereas non-dormant ones germinate within a wider range of temperatures (15 to 40°C). Germination of non-dormant seeds requires at least 10% oxygen, but the sensitivity of seeds to oxygen deprivation increases with increasing depth of dormancy. 10^–6 to 10^–4 M ethephon, 10^–3 M 1-aminocyclopropane 1-carboxylic acid (ACC) and 10^–3 M gibberellic acid (GA₃) break this dormancy. In the presence of 10^–3 M GA₃ dormant seeds are able to germinate in the same range of temperatures as non-dormant seeds. The stimulatory effect of GA₃ is less dependent on temperature than that of ethephon, while ACC stimulates germination only at relatively high temperatures (25–30°C). The results obtained are discussed in relation to the possible involvement of endogenous ethylene in the regulation of germination of A. retroflexus seeds.Abbreviations ACC 1-aminocyclopropane 1-carboxylic acid - GA₃ gibberellic acid - SD standard deviation     

The effect of plant growth regulators, nitric oxide, nitrate, nitrite and light on the germination of dimorphic seeds of Suaeda salsa under saline conditions

Suaeda salsa, a leaf succulent shrub in the family Chenopodiaceae, is one of the most important halophytes in China. Suaeda salsa produces dimorphic seeds (soft brown seeds and hard black seeds). Seeds of S. salsa were collected from the coastal salt flats near Huanghua City, China. Experiments were conducted to determine the salinity-alleviating effect of plant growth regulators, nitric oxide, nitrate, nitrite and light on the germination of dimorphic seeds of S. salsa. Brown seeds had a higher germination rate than black seeds in all experiments. Black seeds were more sensitive to salt in the absence of light in comparison to brown seeds. Brown seeds absorbed water more quickly in comparison to black seeds and were found to be more tolerant of salt stress. Our results showed that 1-aminocyclopropane-1-carboxylate (ACC, the immediate precursor of ethylene), nitrite, GA₄ and BA improved seed germination in the presence of salt. However, nitrate, GA₁, GA₃ failed to alleviate salt stress. ABA inhibited seed germination and seedling growth. Possible mechanisms involved in the alleviation of salt stress in S. salsa seeds and the ecological adaptation of the seeds to the environment are discussed.     

Changes in concentrations of soluble carbohydrates during germination of <Emphasis Type="Italic">Amaranthus caudatus</Emphasis> L. seeds in relation to ethylene,gibberellin A<Subscript>3</Subscript> and methyl jasmonate

Unimbibed Amaranthus caudatus seeds were found to contain stachyose, raffinose, verbascose, sucrose, galactinol, myo-inositol, glucose and fructose, while no galactose, maltose and maltotriose was detected. During imbibition, seed concentrations of verbascose, stachyose, raffinose, galactinol, myo-inositol (temporary) and fructose (transient) were observed to decrease; concentrations of galactose and maltose remained fairly constant, while those of sucrose, glucose and maltotriose increased, the increase in sucrose concentration was only temporary. Effects of gibberellin A₃ (GA₃) at 3 × 10⁻⁴ M and ethephon at 3 × 10⁻⁴ M alone or in the presence of methyl jasmonate (Me-JA) at 10⁻³ M on concentrations of soluble sugars during germination of A. caudatus seeds were examined. Me-JA was found to inhibit seed germination and fresh weight of the seeds, but did not affect sucrose, myo-inositol, galactose and maltose concentrations during imbibition for up to 20 h. The exogenously applied GA₃ was observed to enhance germination, stachyose breakdown and glucose concentration after 20 h of incubation. Ethephon stimulated seed germination as well as utilisation of stachyose, galactinol (both after 14 and 20 h) and raffinose (after 14 h of incubation). Although the stimulatory effect of either GA₃ or ethephon on seed germination was blocked by Me-JA; these stimulators increased mobilisation of raffinose and stachyose, but only ethephon enhanced both glucose and fructose after 14 and/or 20 h of incubation in the presence of Me-JA. The maltose concentration was increased by both GA₃ and ethephon alone and in the presence of Me-JA. Of the growth regulators studied, ethephon alone and/or in combination with Me-JA significantly increased the concentrations of glucose, fructose, galactose, maltose and maltotriose. The differences in sugar metabolism appear to be linked to ethylene or GA₃ applied simultaneously with Me-JA.     

The control of seed germination in Trollius ledebouri A model of seed dormancy

Treatment of Trollius ledebouri seeds with gibberellins A₄+A₇ promotes germination. The efficacy of the treatment is dependent upon the duration of imbibition in distilled water prior to GA₄₊₇ application. Presoaking increases both the final percentage germination attained and also its rate of achievement. No presoaking effect is exhibited by seeds induced to germinate by testa removal in the absence of GA₄₊₇. Active washing of Trollius seeds enhances the presoaking effect and the eluent from washed seeds is inhibitory to germination. The results support the hypothesis that the presoaking effect exhibited by Trollius is the result of the leaching of a germination inhibitor from the seeds which is antagonistic to GA₄₊₇. Additionally, treatment of Trollius seeds with the gibberellin-biosynthesis inhibitor (2-chloroethyl)-trimethylammonium chloride (CCC) prior to testa removal retards germination. The inhibitory effect of CCC on germination is overcome by GA₄₊₇. Although CCC inhibits embryo growth during the presoaking of intact seeds, it does not affect the increased sensitivity of presoaked seeds to GA₄₊₇. Therefore, although endogenous gibberellins may be involved in the germination process, they do not contribute to the presoaking phenomenon. The expansion of isolated endosperm tissue is not affected by CCC. However, the chemical markedly inhibits endosperm expansion in intact seeds and implicates the embryo as both the site of production of the germination inhibitor and of gibberellin. These results are discussed in relation to previous studies and a model is presented to account for the characteristics of germination in Trollius.Abbreviations GA gibberellin - CCC (2-chloroethyl)-trimethylammonium chloride     

Germination of Tagetes minuta L. II. Role of gibberellins

The effect of the application of gibberellins to Tagetes minuta L. achenes (seeds) was determined at both 25°C, the optimal germination temperature, and 35°C, at which temperature the achenes are thermoinhibited. Both GA₃ and GA₄₊₇ accelerated germination at 25°C. Seed germination at 25°C was inhibited by paclobutrazol, but on subsequent application of GA₄₊₇ rapid germination was induced. Following application of GA₃ or GA₄₊₇ to thermoinhibited seeds, a significantly higher final germination percentage was observed than in the distilled water control. However, endogenous gibberellin levels in germinating and thermoinhibited seeds did not differ significantly.     

Tolerance of kikuyu grass to long term salt stress is associated with induction of antioxidant defences

Primary dormancy in A. retroflexus seeds wascompletely broken by dry storage or ethylene treatment and partially removedwith GA₃. Norbornadiene counteracted the dormancy breaking action ofethylene and GA₃. The GA₃ effect was lowered bycobaltous ions. ABA increased the ethylene requirement in primary dormant seeds.Dormant seeds had a similar or different ability to produce ethylene and ACCoxidase in vivo activity than did non-dormant seeds,depending on the period of incubation. Dormant seeds contained less endogenousACC than non-dormant seeds. Thus, ethylene seems to play an essential role inthe release of primary dormancy in A. retroflexus seeds.Ethylene also participates in the release of dormancy achieved by GA₃treatment. The results indicate that both ethylene biosynthesis and action isinvolved in the control of primary dormancy in Amaranthusretroflexus seeds.     

Reversing the inhibitory effect of paclobutrazol on seed germination of Amaranthus paniculatus by GA3, ethephon or ACC

The germination of Amaranthus paniculatus seeds was inhibited by applying paclobutrazol, a specific inhibitor of gibberellin biosynthesis. This inhibition was markedly counteracted by gibberellin A₃ (GA₃), suggesting that endogenous gibberellins are required for germination in this species. The inhibitory effect of paclobutrazol was also overcome by ethephon (2-chloroethylphosphonic acid) or the precursor of ethylene biosynthesis, ACC (1-aminocyclopropane-l-carboxylic acid). Thus the physiological effect of gibberellin can be mimicked by ethylene released from ethephon or synthesised from exogenous ACC. It is suggested, that endogenous gibberellins are involved in germination of Amaranthus paniculatus seeds and that action of GA₃ can be substituted by ethylene.Abbreviations ACC 1-aminocyclopropane-l-carboxylic acid - AMO-1618 (2-isopropyl-5methyl-4-trimethylammoniumchloride)-phenyl-l-piperidinium-carboxylate - ancymidol -cyclopropyl--(4-methoxyphenyl)-5-pyrimidine methanol - chloromequat chloride (2-chloroethyl)trimethylammoniumchloride - ethephon 2-chloroethylphosphonic acid - GA gibberellin A₃ - paclobutrazol (2RS, 3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-lyl)pentan-3-ol - Phosphon D 2,4,dichlorobenzyl-tributhylphosphoniumchloride - tetcyclacis 5,(4-chlorophenyl)-3,4,5,9,10-pentaaza-tetracyclo)5,4,1,0,Z,6,0^8,11 dodeca-3,9-diene     

Interaction between a plant-derived smoke extract,light and phytohormones on the germination of light-sensitive lettuce seeds

Plant-derived smoke extracts mimics the effect of red light on germination in light-sensitive lettuce seeds and partially overcomes the inhibitory effect of far-red light. Interaction between a smoke extract and gibberellins, cytokinins, abscisic acid and ethephon was investigated. Smoke acted synergistically with GA₃ and increased the sensitivity of the lettuce seeds to ABA. It seems likely that smoke affects membrane permeability or receptor sensitivity rather than influencing the phytochrome system of these seeds.Abbreviations R red light - FR far-red light - SM smoke extract     

Stimulation of Empress Tree Seed Germination by Liquid Smoke

The germination of Empress tree (Paulownia tomentosa Steud.) seeds is phytochrome-controlled. Liquid smoke could not induce germination in darkness but red light irradiation of liquid smoke imbibed seeds induced a high percentage of germination. Maximum germination was achieved at liquid smoke concentration of 0.1% (v/v) when present during the imbibition phase or during the phase of phytochrome activity. The light requirement of these seeds could be completely substituted by exogenously applied gibberellins. In the presence of liquid smoke, optimal concentrations of GA₃, GA₄, and GA₉ necessary for inducing germination were several times lower than in the controls, while that of GA₇ was equally active when applied at a concentration one order of magnitude lower. The inhibitory effect of the applied growth retardants was strongly reduced and liquid smoke, in the presence of retardants, allowed light-induced germination, if applied simultaneously or after retardants treatment.     

Uptake of Gibberellic Acid in Intact and Scarified Seeds of Barbarea vulgaris

Uptake of gibberellic acid as a function of duration of exposure, external concentration, and seed lot was measured in seeds of yellow rocket (Barbarea vulgaris R. Br.) by means of lettuce hypocotyl bioassays of the acidic, basic, or neutral fractions of seed extracts and by uptake of ¹⁴C-GA₃. In intact seeds, where mM levels of GA₃ promoted only 25% germination, uptake was completed within 24 h of exposure. The maximum uptake was about 0.2% of external amount. Although germination promotion by GA₃ differed among seedlots of yellow rocket, relative uptake (percentage of the external GA₃) was nearly the same. The relative rate of uptake of GA₃ was similar for scarified and intact seeds, but germination was promoted in scarified seeds by much lower levels of GA₃ than in intact seeds. Total uptake in scarified seeds was much higher, however (about 10% of the external amount). In seeds imbibed in H₂O, practically no endogenous GA-like activity was detected in either the acidic, basic, or neutral fractions. It was also apparent that intact seeds could take up quantities of GA₃ that failed to promote germination, but were comparable to quantities that promoted germination in scarified seeds.     

梾木种子低温层积过程中内源激素含量的动态变化特征

应用酶联免疫吸附测定法(ELISA)研究了梾木种子低温层积过程中内源激素含量的动态变化,分析了内源激素与种子休眠与发芽的关系。结果表明:(1)梾木种子中IAA含量在层积处理初期剧烈降低,持续一段时间后又显著升高,但后期下降,且IAA/ABA也出现同样的变化;种子中ABA含量在层积处理前期较高,但随着处理时间的延长趋于下降;种子内GA1/3含量以及GA1/3/ABA均随层积处理时间的延长逐渐增大;种子内ZRs和iPAs含量的变化相对较为平稳,尽管有一定的波动,但整体呈渐趋增高趋势。(2)梾木种子发芽率及发芽势在未经层积处理以及处理时间少于90d的条件下均为0,但随着层积处理时间的延长二者明显上升,层积处理的时间长短对梾木种子萌发有显著影响。(3)相关分析表明,梾木种子内GA1/3含量与种子的发芽率、发芽势均呈显著正相关关系,相关系数分别为0.688、0.662;种子内GA1/3/ABA增大有利于种子休眠解除和萌发。     

Effects of various pretreatments on seed germination of<Emphasis Type="Italic">Calystegia soldanella</Emphasis> (Convolvulaceae), a coastal sand dune plant

We tested various pretreatments to enhance the germination of ‘Sea bells’ (Calystegia soldanella Roem. et Schult). One experiment, which improved the germination rate by 70%, involved first scarifying the seed coats, then immersing the seeds in 50 ppm GA₃ for 24 h. A GA₃-alone pretreatment did not increase germination. However, the most effective method, with a 100% success rate, included 3 h of acid pretreatment with 98% H₂SO₄. We also used scanning electron microscopy (SEM) to examine the seed-coat surfaces and cross-sections of dry seeds. SEM showed structural differences between seeds that were not treated and those exposed to 98% H₂SO₄. The latter treatment allowed the seed coats to crack and break, thereby disrupting their physical dormancy.     

Responses of florence fennel (Foeniculum vulgare azoricum) seeds to light,temperature and gibberellin A4/7

The percentage and the rate of germination of seeds of three varieties of Florence fennel was higher in the dark than in the light, the high temperature cut-off points being between 27.2 and 29.4°C. The optimum temperature for germination was between 20 and 25°C. Seeds of all three varieties responded to incubation in solutions containing gibberellin A_4/7 mixture (GA_4/7; Regulex), giving higher germination in the light at temperatures from 20 to 30°C. Seeds steeped for 4 h at 25°C or for 24 h at 5°C in GA_4/7 solutions gave a higher percentage and increased rate of emergence as compared with untreated dry seeds, when sown in compost at 25°C; steeping in water alone was also beneficial. In general, drying the treated seeds before sowing reduced the rate but sometimes increased the percentage of germination as compared with seeds sown when still moist. Seeds harvested from secondary umbels of var. Zefa fino germinated better both in the light and dark than those taken from primary umbels.Abbreviations GA_4/7 a commercial mixture of the gibberellins A₄ and A₇ (trade name Regulex)