The role of hormones in regulating the germination of polymorphic seeds and early seedling growth of Atriplex triangularis under saline conditions

Germination of the polymorphic seeds and seedling growth of Atriplex triangularis under various salinity, gibberellic acid and kinetin treatments were determined. Gibberellic acid (GA₃; 2.9 m M ) promoted germination and growth at high NaCl concentrations (345 m M ). Kinetin (4.7 μ M ) stimulated germination at all salinities and seed sizes tested. GA₃ and kinetin generally increased seedling growth at all concentrations of salinity studied. Higher concentrations of kinetin were found to be inhibitory.     

珍稀药用植物云南萝芙木种子休眠与萌发特性

研究了云南萝芙木（Rauvolfia yunnanensis）种子吸水及内源萌发抑制物特性,探讨了赤霉素浓度、温度和光照对种子萌发的影响。结果表明：云南萝芙木新鲜饱满种子28℃和31℃／22℃光照或黑暗下1个月内不萌发,种子胚已分化发育完全,种皮透水,种仁含有萌发抑制物,GA可促进种子萌发,说明云南萝芙木种子具有浅度生理休眠。400-1800mg·L-1是打破云南萝芙木种子休眠的适宜GA处理浓度范围。云南萝芙木种子的适宜萌发温度范围为22～2822和31℃／22℃变温,28％发芽指数最高,1023种子不萌发。云南萝芙木种子在周期性光照和全黑暗下均可萌发,但31℃和31℃／22℃下周期性光照促进种子萌发。     

INTERACTION OF GIBBERELLIN, KINETIN AND POTASSIUM NITRATE IN THE GERMINATION OF LIGHT-SENSITIVE TOBACCO SEEDS

1. The effects of gibberellin, kinetin, potassium nitrate, andtheir interactions in the germination of light-sensitive tobaccoseeds were studied. 2. Gibberellin was very effective in inducing the dark germinationof tobacco seeds, and a linear relation was found to exist betweenthe germination rate and the concentration of gibberellin ifa suitable temperature was chosen for germination. This linearrelation was, however, changed by illumination and by a raisedtemperature in the manner that the germination on lower concentrationsof gibberellin was increased by the former and decreased bythe latter. 3. Kinetin was effective in promoting the tobacco seed germinationonly when the seeds were irradiated. This light effect was,however, limited only to the longer wavelengths in the visibleregion. The red effect was found to be reversed by infra-redirradiation under the influence of kinetin. 4. The combination of gibberellin and kinetin was synergisticin promoting the tobacco seed germination both in the lightand in the dark, whereas the combination of potassium nitrateand gibberellin or kinetin was synergistic only in the light. (Received November 1, 1960; )     

林线树种太白红杉种子萌发的生理生态特性

 太白红杉(Larix chinensis)是太白山的高山林线树种。通过在人工气候室内的试验,研究了太白红杉种子在6种不同的光照与温度组合处理条件下的萌发特性。结果表明：在恒温和变温两种条件下,交替光照对于种子吸胀后的脱落酸（ABA）和赤霉素 (GA)有刺激作用。在恒温条件下,持续光照对于种子吸胀后的生长素 (IAA)有刺激作用,而变温条件下交替光照对生长素有刺激作用。细胞分裂素（CTK）的变化情况与IAA相反。光照条件相同时,恒温条件下的植物激素含量要高于变温条件下的含量,说明恒温对于各种激素有刺激作用。在25 ℃环境下种子的萌发率高于在12 ℃环境下的萌发率,说明温度对于种子的萌发有重要作用。太白红杉种子的萌发受交替光照（12 h光照/12 h黑暗）的刺激;恒温（25 ℃）条件下的种子萌发率高于变温（12 ℃/25 ℃）条件下的种子萌发率。实验结果反映了内源激素在太白红杉种子萌发过程中起着重要作用。     

Effets de l'acide gibbérellique et de la kinétine sur le développement de l'activitéα-amylasique durant la croissance de l'Orge

Effects of gibberellic acid and kinetic on α-amylase production during the germination of barley. - The action of gibberellic acid and kinetin, alone or combined at different concentrations, has been studied on α-amylase production in whole barley seedlings and in embryoless endosperms in course of the six first days of development in the dark. The classic activation of α-amylase synthesis by gibberellic acid has been confirmed both in whole seeds and in embryoless endosperms. Kinetin inhibits α-amylase synthesis after the third day of germination but has no effect on isolated endosperms. When gibberellic acid and kinetin are given simultaneously gibberellic acid stimulated during the three first days just as it does alone, kinetin inhibits after the third day also as it was alone so that the two regulators act, without interactions, at different stages in the time. These effects of kinetin are be independent. A critical examination of the techniques used in the literature in the stud of amylase is made.     

SOME FACTORS AFFECTING THE GERMINATION OF SEED OF THE SAGUARO CACTUS (CARNEGIEA GIGANTEA)

Alcorn , Stanley M. (U. S. Dept. of Agric., Tucson, Ariz.), and Edwin B. Kurtz , Jr . Some factors affecting the germination of seed of the saguaro cactus (Carnegiea gigantea). Amer. Jour. Bot. 46(7): 526–529. 1959.—Germination of saguaro cactus seeds is stimulated by red light (approx. 6550 A) or daylight and far-red light (approx. 7350 A) counteracts this effect. About 0.1% germinate in continuous darkness. A single exposure to red light was most effective when the seeds were imbibed 24 hr., but maximum germination resulted from multiple exposures to red light during a 72-hr. imbibition period. The optimum temperature for germination was 25°C.; no germination occurred at 15°C. and only slight germination at 35°C. Imbibition of light-treated seeds in 0.05 to 0.2% KNO₃ increased germination. Germination of seeds in either light or dark was increased by imbibing the seeds in 500 to 1000 p.p.m. gibberellic acid.     

Germination Promotion of Loblolly Pine and Baldcypress Seeds by Stratification and Chemical Treatments

The effects of 4 chemicals on the germination promotion of stratified and unstratified seeds of loblolly pine (Pinus taeda) and baldcypress (Taxodium distichum) were studied. The chemicals used were gibberellic acid, kinetin, potassium nitrate and thiourea, each at 3 different concentrations. Stratification promoted the germination of both seed species. Certain concentrations of gibberellic acid, potassium nitrate and thiourea improved the germination of unstratified loblolly pine and baldcypress seeds while kinetin had no stimulatory effect. All 4 chemicals at specific concentrations promoted the germination of loblolly pine seeds stratified for a short period of time. Considering both speed and completeness of germination, best results were obtained when 21-day stratified seeds were treated with either gibberellic acid (100 mg/1) or kinetin (10 mg/1). In baldcypress, on the other hand, none of these chemicals had any stimulatory effect on the germination of stratified seeds. Germination of both species of seeds was either partially or completely inhibited by the highest concentration of thiourea (30,000 mg/1) used.     

Reversal of induced dormancy in lettuce by ethylene, kinetin, and gibberellic Acid

The germination of lettuce seeds (Lactuca sativa L., cv. Premier Great Lakes) was significantly inhibited by high temperature (32 C), 0.1 mM abscisic acid or 0.4 M mannitol. Ethylene (16 μl/1 of air) partially reversed the dormancy induced by all three inhibitors but only in the presence of 1 mM gibberellic acid (GA) or light. Neither ethylene plus GA nor ethylene plus light were able to promote germination when thermal inhibition was imposed at 36 C. Addition of 0.01 mM kinetin to the ethylene plus GA or light reversed thermodormancy at 36 C. The dormancy imposed by abscisic acid was also reversed by kinetin. Kinetin was unable to reverse the osmotic dormancy imposed by mannitol. The reversal of osmotic dormancy by ethylene or ethylene plus GA was actually inhibited by kinetin but only in the light. Kinetin apparently stimulates cotyledonary growth in the presence of light, and this growth may compete for certain metabolites critical to radicle growth and subsequent germination. Kinetin and ethylene, as demonstrated primarily in the thermodormancy at 36 C and in osmotic dormancy, appear to regulate a common event(s) leading to germination but through mechanisms unique to each respective growth regulator. The regulation of germination by ethylene is absolutely dependent upon an interaction with GA and/or light.     

Nitric oxide accelerates seed germination in warm-season grasses

The nitric oxide (NO) donor sodium nitroprusside (SNP) significantly promoted germination of switchgrass (Panicum virgatum L. cv Kanlow) in the light and in the dark at 25°C, across a broad range of concentrations. SNP also promoted seed germination in two other warm-season grasses. A chemical scavenger of NO inhibited germination and blocked SNP stimulation of seed germination. The phenolic (+)-catechin acted synergistically with SNP and nitrite in promoting seed germination. Acidified nitrite, an alternate NO donor also significantly stimulated seed germination. Interestingly, sodium cyanide, potassium ferricyanide and potassium ferrocyanide at 200 μM strongly enhanced seed germination as well, whereas potassium chloride was without effect. Ferrocyanide and cyanide stimulation of seed germination was blocked by an NO scavenger. Incubation of seeds with a fluorescent NO-specific probe provided evidence for NO production in germinating switchgrass seeds. Abscisic acid (ABA) at 10 μM depressed germination, inhibited root elongation and essentially abolished coleoptile emergence. SNP partially overcame ABA effects on radicle emergence but did not overcome the effects of ABA on coleoptile elongation. Light microscopy indicated extension of the radicle and coleoptiles in seeds maintained on water or on SNP after 2 days. In contrast, there was minimal growth of the radicle and coleoptile in ABA-treated seeds even after 3–4 days. These data indicate that seed germination of warm-season grasses is significantly influenced by NO signaling pathways and document that NO could be an endogenous trigger for release from dormancy in these species.     

Inhibition of cottonseed germination with abscisic Acid and its reversal

Germination of cottonseed (Gossypium hirsutum L.) was inhibited by abscisic acid. Inhibition was greater when seeds were soaked in abscisic acid for 5 hours and dried prior to germination than when abscisic acid was applied in the germination medium. (2-Chloroethyl)phosphonic acid, gibberellic acid, and kinetin partially overcame the inhibitory action of abscisic acid. Combinations of (2-chloroethyl)phosphonic acid with gibberellic acid or kinetin were more effective than the individual substances. Germination also was partially restored by removal of seed coats. Fusicoccin completely restored germination of abscisic acidtreated seeds.     

Additive and synergistic effects of kinetin and ethrel on germination, thermodormany, and polyribosome formation in lettuce seeds

The inhibition of germination of Grand Rapids lettuce (Lactuca sativa L.) seeds at 35 C was removed to a marked extent by kinetin and 2-chloroethylphosphonic acid (ethrel). When both compounds were used together, an additive effect was observed. A synergistic effect was, however, noted when ethrel promoted the kinetin reversal of abscisic acid inhibition of seed germination (light- as well as gibberellic acid-, induced). Both kinetin and ethrel increased the total ribosomal material and the percentage of polyribosomes in lettuce seeds imbibed in the light for 24 hours. A combination of the two compounds showed a synergism in polyribosome formation only at high ethrel concentration. The inability of ethrel to reverse abscisic acid inhibition indicates that kinetin action cannot always be substituted by ethrel. The possible mechanisms involved in the enhanced response by a combination of kinetin and ethrel are discussed.     

The germination characteristics of <Emphasis Type="Italic">Scrophularia marilandica</Emphasis> L. (Scrophulariaceae) seeds

Investigations on seeds of Scrophularia marilandica L. were undertaken to determine their germination requirements. Seeds were collected from three naturally occurring sites and one greenhouse-grown population in London, Ontario in September and October of 1997. Some were set to germinate immediately after collection; others were stored in or on soil outside and/or under controlled laboratory conditions before testing. Germination was assessed under two light/temperature regimes (35°C 14 h light, 20°C 10 h dark and 25°C 14 h light, 10°C 10 h dark), in continuous darkness, and in the presence of two germination-promoting chemicals (GA₃ and KNO₃). Fresh seeds germinated best at 35/20°C, while stored seeds germinated best at 25/10°C. No differences in percent germination were found among three seed-maturity stages. All chemical treatments, except 0.01 M KNO_3, increased percent germination. Significant differences were found both among and within sites for most chemical treatments, but exposure to 3 × 10⁻⁴ M GA₃ caused almost every seed to germinate. When compared to the control, both the gibberellic acid and the soil-storage treatments contributed to faster germination. Exposure of seeds to naturally prevailing conditions on the soil surface followed by testing under the 25/10°C regime produced the highest percent germination. No seeds germinated in the dark. In summary, seeds of S. marilandica exhibit physiological dormancy, which can be alleviated by exposure to light, after-ripening and/or cold stratification. It is probable that the differences in germination response among sites can be attributed to differences in environmental conditions during seed production. These experiments indicate that the seeds of S. marilandica must be buried shortly after dispersal in order to form a persistent seed bank.     

Hormonal Control of Germination under Saline Conditions of Three Halophytic Taxa in the Genus Suaeda

The interaction between hormones and salinity on seed germination of three halophytic taxa in the genus Suaeda: S. maritima (L.) Dum. var. flexilis Focke and var. macrocarpa Moq., and S. depressa (Pursh) Wats, was studied. Exogenous applications of kinetin and gibberellic acid (GA3) were applied in order to determine if either of these growth-promoting hormones would promote germination in the two dormant taxa, Suaeda depressa and S. maritima var. flexilis and to see if osmotically induced dormancy by NaCl could be alleviated. Our results indicate that gibberellic acid is capable of breaking dormancy in these species with dormant seeds, but kinetin proved to be ineffective. A seed dormancy that was induced by osmotic stress could also be alleviated by treatments with gibberellic acid. Endogenous concentrations of both cytokinins and gibberellins were measured in seeds exposed to osmotic stress (0.85 M NaCl), and we found a reduction in cytokinin activity in these three taxa. Gibberellin-like activity was reduced in S. depressa when seeds were soaked in 0.85 M NaCl.     

Evaluation of the effect of three growth regulators in the germination of <Emphasis Type="Italic">comparettia falcata</Emphasis> seeds under <Emphasis Type="Italic">in vitro</Emphasis> conditions

Summary The effect of 3-indoleacetic acid (IAA), 6-furfurylaminopurine (kinetin), and gibberellic acid (GA₃) on germination of the orchid Comparettia falcata was evaluated in a factorial experiment (4×4×4) with Murashige and Skoog (1962) basal medium. It was established that seeds of this orchid could be maintained under aseptic conditions as long as the necessary nutrients and appropriate concentrations of growth regulators were provided. Of the three growth regulators used, IAA significantly decreased seed germination of Comparettia falcata. There was a synergistic effect in the kinetin:GA₃ combination that produced a positive response in both percentage seed germination and development of seedlings. This study describes a single medium-based protocol able to achieve more than 160000 seedlings within 21 wk, starting from a single capsule, sufficient for both large-scale propagation and in vitro conservation of this threatened orchid.     

Seed Dormancy,Germination and Storage Behavior of Magnolia wilsonii (Magnoliaceae), an Endangered Plant in China

In this paper, we measured the embryo morphology and size of Magnolia wilsonii seeds. And the effects of temperature, stratification, KNO3 and soaking on seed dormancy and germination were studied. Seeds were desiccated to different moisture content, and then stored at 4℃ and -20℃ for 100 d. The effects of desiccation and storage temperature on seed viability of M. wilsonii were analyzed. The results showed that the underdeveloped embryos of Mwilsonii seeds needed cold stratification to achieve physiological afterripening. The favorable temperature for germination of Mwilsonii seeds was 25/20℃. Cold stratification and GA3 could effectively overcome dormancy of Mwilsonii seeds. Therefore, Mwilsonii seeds have morphophysiological dormancy. About 5350% of seeds could survive in the moisture content of 539%. After 100 d storage at -20℃, all seeds in different moisture contents died. However, after 100 d storage at 4℃, 76% of seeds survived. Thus, Mwilsonii seeds exhibited intermediate seed storage behavior. The optimum storage environments was dry or moist storage at 4℃.     

The Effects of Gibberellic Acid and Scarification on the Seed Dormancy and Germination in Luzula spicata

Luzula spicata L. seeds are completely dormant at maturity. A germination inhibitor is present at the micropylar end. Normally, the only effective means of eliciting germination is a precise scarification of the micropylar end which inactivates the inhibitor. Exogenous application of gibberellic acid, kinetin, KNO₃, and thiourea have no affect on the dormancy of unscarified seeds. Scarification of the hilar end of the seed does not elicit germination, but when gibberellic acid is applied to the hilar scarified seeds moderate germination results. Presumably, these seeds are dormant due to a deficit of endogenous gibberellin; a condition which can be overcome by the application of gibberellic acid to seeds scarified at a site in itself ineffective in producing germination. Apparently the gibberellic acid serves to initiate amylase activity in the endosperm, overcoming the inhibitor block. Luzula spicata seed dormancy is apparently unique in that a germination inhibitor is operative in conjunction with the commonly recognized gibberellin-amylase mechanism.     

濒危植物西康玉兰种子休眠、萌发及贮藏特性

研究了西康玉兰(Magnolia wilsonii)种胚的形态大小,温度、层积、硝酸钾、浸种处理和GA_3对种子休眠及萌发的影响.通过将种子脱水至不同含水量和在两种温度(4℃和一20℃)下贮藏100 d后测其生活力,分析各处理对西康玉兰种子活力的影响.结果表明:西康玉兰种子胚尚未分化完全,需经过低温层积完成生理后熟;低温层积和GA3可打破种子休眠.种子最适萌发温度为25/20℃.由此推测,西康玉兰种子具有形态生理休眠特性.西康玉兰种子当含水量降至5.39%,存活率为53.50%.不同含水量的种子贮藏在-20℃条件下,100 d后种子全部死亡;但在4℃下含水量为10.31%的种子存活力高达76%.因此,西康玉兰种子极可能属于中间性种子,其适宜贮藏环境为4℃下的干藏或湿藏.     

<Emphasis Type="Italic">In vitro</Emphasis> germination and micropropagation of <Emphasis Type="Italic">Givotia rottleriformis</Emphasis> Griff.

The propagation of Givotia rottleriformis Griff. is difficult as a result of long seed dormancy associated with poor seed germination. The present study was undertaken to develop a protocol to overcome seed dormancy by culture of zygotic embryo axes and then develop an efficient method for micropropagation of Givotia. Best germination frequency (78.3%) was achieved from mature zygotic embryo axes isolated from acid-scarified fresh seeds when cultured on Murashige and Skoog (MS) medium (half-strength major salts) with 28.9 μM gibberellic acid (GA₃). Efficient plant conversion was achieved by transfer of 10-d-old germinated embryos to MS medium (half-strength major salts) supplemented with 1.2 μM kinetin (KN) and 0.5 μM indole-3-butyric acid (IBA). However, acid scarification of 1-yr-old seeds decreased the germination frequency of zygotic embryo axes in comparison to those obtained from non-acid-scarified seeds which germinated (96.2%) and converted into plants (80.3%) on MS basal (half-strength major salts) medium. Multiple shoot bud induction was achieved by culture of shoot tips derived from in vitro germinated seedlings on MS medium with 0.5 μM thidiazuron for 4 wk, and the shoots elongated after transfer to a secondary medium with 1.2 μM KN. A maximum number of 7.8 shoots per explant with an average shoot length of 3.2 cm was achieved after two subcultures on this medium. The in vitro regenerated shoots rooted (41.5%) on half-strength MS medium with 0.5 μM IBA. The in vitro generated seedlings and micropropagated plants were established in soil with a survival frequency of 70% and 60%, respectively.     

Seed Dormancy and Germination in Cimicifuga nanchuanensis

Seed anatomy, dormancy breakage, the temperature effect to seed germination and seed life-span of Cimicifuga nanchuanensis Hsiao were studied and the endangerment of this plant in association to these biological characteristics was explored. The embryos were at the globular stage at the time of seed shedding in late November. Low temperature and humid conditions or treatment with exogenous GA3 stimulated the development of embryos and sped up the process of seed germination. The optimum temperature of germination was 20 ℃, but the seeds almost lost their viability after 9 months of storage. Nevertheless, in its natural habitation, the seeds could not acquire enough environmental humidity to accomplish their after-ripening during the dry and cold winter from late November to the following March; after then the temperature in the spring (averaged 10.1 ℃ in April and May) was much lower than 20 ℃ or so which is favorable for seed germination. Moreover, the testa could not provide adequate protection for the embryos and the short life-span of the seeds prevents their survival until the next germination. Therefore it seems reasonable to infer that the unfavorable environmental condition during the process of after-ripening until seed maturation is involved in the cause of endangerment of this plant species.