IAA, ABA, polyamines and free amino acids associated with zygotic embryo development of Ocotea catharinensis

The aim of this work was to study morphological and biochemical aspects during zygotic embryogenesis in O. catharinensis, by measuring changes in the endogenous concentrations of proteins, amino acids, polyamines (PAs), indole-3-acetic acid (IAA) and abscisic acid (ABA). Buffer-soluble and insoluble protein contents were determined by spectrometry, and amino acids, PAs, IAA and ABA concentrations were determined by high performance liquid chromatography. Total amino acid accumulation, predominantly asparagine, occurred when the embryo showed completely developed cotyledons, with posterior reduction in the mature embryo. This decrease in total amino acid concentration in the mature embryo may result from their use in storage␣as well as for LEA protein synthesis. Free putrescine (Put) concentration decreased, while free spermine (Spm) increased during embryo development. This suggest a role for Put in the initial phases of embryogenesis when high rates of cell division occur, while elevated concentration of Spm are essential from the middle to the end of embryo development, when growth is mainly due to cell elongation. An IAA peak in zygotic embryos occurred during initial development, suggesting a link between growth and cellular division as well as with the establishment of bilateral symmetry. ABA concentration declined during initial stages of development then increased at the mature embryo stage, suggesting a possible relationship with dormancy and recalcitrance characteristics. Our results show that changes in the phytohormones (IAA, ABA and PAs) concentrations in combination with amino acids are likely important factors determining the developmental stages of O.␣catharinensis zygotic embryos.     

The effect of plant growth regulator treatments on the levels of ethylene emanating from excised turgid and wilted wheat leaves

Abscisic acid (ABA) inhibits the production of ethylene induced by water stress in excised wheat leaves and counteracts the stimulatory effect of 6-benzyladenine (BA) on this process. The stimulatory effect of BA and the inhibitory effect of ABA were equally pronounced whether external or endogenous ethylene levels were determined. When leaves were sprayed or floated on solutions of BA, indole-3-acetic acid (IAA), gibberellic acid (GA₃), or ABA, the relative activities of these growth regulators on stress-induced ethylene at 10^-4 mol l^-1 were BA>IAA >GA₃>controls>ABA. In non-stressed leaves, however, where the levels of ethylene produced were 2–20 times smaller, the relative activities were IAA >BA>GA₃>controls>ABA. The effects of BA and ABA spray treatment on water stress induced ethylene were closely similar whether the solutions were applied 2 or 18 h prior to the initiation of water stress. The relationships between the levels of endogenous growth regulators in the plant and ethylene release induced by water stress are discussed.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic acid - GA₃ gibberellic acid - ABA abscisic acid - GLC gas-liquid chromatography - _leaf leaf water potential     

中国沙棘克隆生长对灌水强度的响应规律及其激素调控机制

关于中国沙棘克隆生长调节研究目前局限于外在机制,旨在探讨其克隆生长对灌水强度的响应规律及其激素调控的内在机制。结果表明:随着灌水强度的增大,分株生长、克隆繁殖、克隆扩散能力先升后降,IAA(吲哚-3-乙酸)、ZR(玉米素核苷)、GA_3(赤霉酸)含量及其与ABA(脱落酸)的比值先升后降而ABA含量先降后升。同时,分株生长、克隆繁殖、克隆扩散能力与IAA、ZR、GA_3含量以及IAA/ABA、ZR/ABA、GA_3/ABA呈极显著或显著正相关,与ABA含量呈极显著负相关。灌水强度过小或过大,IAA、ZR、GA_3含量以及IAA/ABA、ZR/ABA、GA_3/ABA低而ABA含量高,克隆生长潜力受到抑制,种群以分株小、数量少(分布稀疏)、扩散(水平根延伸和分枝)能力弱为特征,克隆生长格局倾向于"游击型"、种群早衰概率高;灌水强度适宜,IAA、ZR、GA_3含量以及IAA/ABA、ZR/ABA、GA_3/ABA高而ABA含量低,克隆生长潜力得以充分发挥,种群以分株大、数量多(分布密集)、扩散能力强为特征,克隆生长格局倾向于"聚集型"、种群稳定性高。随着灌水强度过小-适宜-过大的连续变化,中国沙棘通过改变激素状况调控克隆生长,从而形成与灌水强度相适应的克隆生长格局连续体"游击型-聚集型-游击型",种群稳定性呈"低-高-低"的连续变化过程。由此可见:灌水强度诱导内源激素发生改变,激素特征调控克隆生长格局,克隆生长格局决定种群稳定性。     

Endogenous phytohormone profile during oat (Avena sativa L.) haploid embryo development

The development of embryos requires interaction of many endogenous hormones. The aim of the study was to determine which endogenous phytohormones are involved in the process of oat (Avena sativa L.) haploidization. Oat haploids were obtained by wide crossing with Zea mays L. The hormonal profiles of the ovaries with (OE) and without developed embryo (OWE) were compared. Phytohormone contents were measured by UHPLC coupled with mass spectrometer. The total content of indole-3-acetic acid (IAA), trans-zeatin (tZ), and kinetin (KN) in OE was significantly higher than in OWE. 4-Chloroindole-3-acetic acid was detected only in OWE. There were no differences between OE and OWE in the content of gibberellins (GA₁, GA₃, GA₄, GA₆, GA₇) and stress hormones (abscisic, salicylic, jasmonic acids). Content of endogenous KN was highly negatively correlated with the percentage of haploid embryos, germinated haploid embryos, haploid plants on MS (in vitro), haploid plants in soil (ex vitro), and doubled haploid lines. The tZ content negatively correlated with the frequency of haploid embryo formation, germination, and haploid plants obtained in vitro, as opposed to GA₁, which correlated positively. A positive correlation was found between IAA and tZ in OE, whereas in OWE it was a negative correlation. The profiles of phytohormones in OE and OWE were determined; however, their mode of action needs to be clarified.

     

Induced parthenocarpy—a way of changing the levels of endogenous hormones in tomato fruits (Lycopersicon esculentum Mill.) 1. Extractable hormones

Ethylene, indol-3-acetic acid (IAA), gibberellin-like substances (GAs) and abscisic acid (ABA) were analysed in extracts from normal, seed-containing and parthenocarpic tomato fruits throughout fruit development. Parthenocarpic fruit growth was induced with an auxin (4-CPA), morphactin (CME) or gibberellic acid (GA₃) and compared with that of pollinated control fruits. Fruit growth was only affected by the treatment with GA₃, decreasing size and fresh weight by 60%. The peak sequence of hormones during fruit development was ethylene-GAs-IAA-ABA. Seeded fruits contained the highest levels of IAA and ABA but the lowest levels of GAs. Also, in seeded fruits, a high proportion of IAA and ABA was found in the seeds whereas this was not the case for GAs.Hormone levels of tomato fruits may be successfully, easily and reproducibly altered by inducing parthenocarpic fruit growth and thus eliminating development of seeds which are a major source of hormone synthesis. In spite of markedly changed hormone levels, there was no obvious relationship between fruit growth and extractable hormones per se. However, the results indicate that a high ratio of GAs: auxins is unfavourable for growth of tomato fruits.     

Estimation of endogenous contents of phytohormones during internode development in <Emphasis Type="Italic">Merremia emarginata</Emphasis>

During the entire period of internode growth of Merremia emarginata contents of gibberellic acid (GA₃), phenyl-acetic acid (PAA), indole-3-acetic acid (IAA, free and conjugated) and abscisic acid (ABA, free and conjugated) were estimated by ELISA using polyclonal antibodies raised against each hormones. At the time of internode elongation free auxin content was low and increased with the decrease in the rate of elongation. In contrast, conjugated IAA showed declining trend where free IAA content was remarkably high, suggesting thereby that conjugated IAA might have mobilized during the later phase of internode development. The endogenous GA₃ contents were high as compared to other hormones; however, no significant role of GA₃ was discernible in elongation growth. Conjugated ABA contents remained very low during the elongation growth and increased thereafter.     

A hormonal misunderstanding in Acca sellowiana embryogenesis: levels of zygotic embryogenesis do not match those of somatic embryogenesis

Endogenous levels of IAA, ABA and four types of CKs were analyzed in zygotic and indirect (ISE) and direct somatic embryogenesis of Acca sellowiana. Zygotic and somatic embryos at different developmental stages were sampled for morphological and hormonal analysis. Both embryo types showed substantial asymmetry in hormone levels. Zygotic embryos displayed a conspicuous peak of IAA in early developmental stages. The results outlined the hormonal variations occurring during zygotic and somatic embryogenesis regarding the timing, nature and hormonal status involved in both processes. The short transient pulse of IAA observed on the 3rd day in culture was suggested to be involved with the signaling for the induction of somatic embryogenesis. Fertilized ovule development was associated with increased IAA levels 21?C24?days after pollination, followed by a sharp decrease in the cotyledonary stage, both in zygotic and somatic embryos. There was a prominent increase in ABA levels in cultures which generated ISE 24?C30?days after pollination, a period that corresponds to the heart and torpedo stages. The levels of total CKs (Z, [9R]Z, iP and [9R]iP) were also always higher in zygotic than in somatic embryogenesis. While zygotic embryogenesis was dominated by the presence of zeatin, the somatic process, contrarily, was characterized by a large variation of the other cytokinin forms and amounts studied. The above results, when taken together, could be related to the previously observed high frequency formation of anomalous somatic embryos formed in A. sellowiana, as well as to their low germination ability.     

Pollen tube growth is affected by exogenous hormones and correlated with hormone changes in styles in <Emphasis Type="Italic">Torenia fournieri</Emphasis> L.

In the present report, we described the effects of indole-3-acetic acid (IAA), zeatin (ZT), gibberellin (GA₃), and abscisic acid (ABA) on in vitro pollen germination and pollen tube growth in Torenia fournieri L. The results showed that IAA and GA₃ stimulated in vitro pollen tube growth, ABA inhibited pollen tube growth, and ZT had no significant effect on the process. The stimulating effect of exogenous IAA was particularly distinct, and led to synchronous growth of straighter and more slender pollen tubes compared with the controls. However, no significant changes were found in the germination of the treated pollen. The auxin efflux inhibitor, 10 μM 1-N-naphthylphthalamic acid (NPA), was also found to stimulate pollen tube growth. We measured the content of hormones (free IAA, ZT, GA₃, and ABA) in the stigmas and styles before and after pollination. The hormone contents of stigmas measured 0.5 h after pollination (0.5 HAP) showed that ABA content decreased, whereas the content of IAA, ZT, or GA₃ did not change significantly. The hormone level in pollinated styles (4 HAP) when pollen tubes had grown into the middle part of style was characterized by an increase in free IAA and GA₃ and a decrease in ABA, which was in agreement with the results that IAA and GA₃ promoted but ABA inhibited pollen tube growth in vitro. Furthermore, the change of IAA level in styles was most notable, which was accordant to the fact that auxin stimulated significantly pollen tube growth in vitro. Using immunoenzyme and immunogold labeling techniques and an anti-IAA monoclonal antibody, we confirmed that free IAA was present throughout style tissues, and distributed in the nucleus and cytoplasm of style cells. All these results suggested that hormones, especially IAA, play important roles in pollen tube growth of T. fournieri. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fluctuation in levels of endogenous plant hormones in ovules of normal and mutant cotton during flowering and their relation to fiber development

The contents of indole-3-acetic acid (IAA), gibberellins (GAs), abscisic acid (ABA), and cytokinins were determined in ovules of normal cotton (Tm-1) and a kind of fiber differentiation mutant (Xin) before and after flowering by enzyme-linked immunosorbent assays. It was found that 24 h before flowering, a peak of IAA content was observed in ovules of Tm-1, whereas in ovules of Xin, a low level of IAA was determined. From –1 day (1 day before flowering) to +3 days (3 days after flowering), GA₁₊₃ levels in ovules of Xin were 40–70% lower than those of Tm-1; GA₄₊₇ levels were very low, and there was no visible difference in GA₄₊₇ content between normal and mutant cotton. The ABA content in ovule of Tm-1 decreased by 70% 3 days after flowering, whereas that of Xin only decreased by 20%. The levels of cytokinins in ovules of Tm-1 decreased after flowering, and those of Xin kept up a steady increase.Abbreviations IAA indole-3-acetic acid - GA gibberellin - ABA abscisic acid - ELISA enzyme-linked immunosorbent assay - FW fresh weight - PBS phosphate-buffered saline - iPA isopentenyladenosine - ZR zeatin riboside - DHZR dihydrozeatin riboside - CTK cytokinin     

Induced parthenocarpy-a way of manipulating levels of endogenous hormones in tomato fruits (Lycopersicon esculentum Mill.) 2. Diffusible hormones

Indol-3-acetic acid (IAA), gibberellin-like substances (GAs), and abscisic acid (ABA) were measured throughout the first 35 days of fruit development in agar diffusates from seeded and parthenocarpic tomato fruits. Parthenocarpic fruit growth was induced with either an auxin (4-CPA), morphactin (CME) or gibberellic acid (GA₃). IAA and GAs were at their highest levels in diffusates during the early stages of fruit growth, whereas diffusible ABA increased later. Most IAA was found in diffusates from auxin-induced and seeded fruits, whereas GAs were at their lowest levels in seeded fruits. There were only minor differences in ABA concentrations regardlesss of the treatments.Levels of diffusible hormones of tomato fruits may be easily manipulated by inducing parthenocarpic fruit growth. In spite of no obvious relationship between fruit growth and hormone levels in this study, induced parthenocarpy is considered a useful tool to further elucidate the role of hormones in fruit development and sink-source interactions.     

Effect of exogenous ABA on embryo maturation and quantification of endogenous levels of ABA and IAA in <Emphasis Type="Italic">Quercus suber</Emphasis> somatic embryos

Knowledge of the relationship between indole-3-acetic acid (IAA) and abscisic acid (ABA) is relevant to control the development and the maturation of cork oak (Quercus suber L.) somatic embryos. The addition of 1 M ABA to the culture medium significantly promoted somatic embryo maturation and increased both fresh and dry matter without affecting the relative water content. This effect was parallel to the pattern of variation observed in the endogenous ABA level, which increased from the immature to the mature stage. Endogenous ABA content during the occurrence of secondary embryogenesis was similar to that of the immature stage, showing that embryos with lower ABA levels produced secondary embryos. In contrast, IAA showed the highest concentration during early embryo development and decreased afterwards. Only in somatic embryos subjected to 1-week desiccation followed by stratification at 4 °C for 2 weeks, was a moderate increment of endogenous IAA content observed. IAA and ABA showed opposite levels during the development and maturation of cork oak somatic embryos and characterised specific stages of the embryonic development.     

Changes in indole-3-acetic acid levels during tomato (Lycopersicon esculentum Mill.) seed development

Summary The changes in the level of indole-3-acetic acid (IAA) were investigated in seeds and fruit tissues-placenta and mesocarp-during tomato (Lycopersicon esculentum Mill.) zygotic embryogenesis, which was characterized through eight morphological embryo stages [from globular (stage 1) to mature embryo (stage 8)]. In whole seeds, IAA levels increased mainly at stage 3 (young torpedo) and at stage 5 (late torpedo stage). As the seed matured and dehydrated, IAA levels decreased and showed a new distribution pattern within seed structures, preferentially in endosperm tissue. IAA contents in fruit tissues were lower but followed the same pattern as those of seeds. These data support the hypothesis of IAA biosynthesis in seeds with a transient role of the endosperm at the end of embryo development and suggest a role of IAA in fruit and seed growth. Moreover a comparison of IAA and ABA changes suggests that IAA could be especially necessary for the beginning of embryo growth, whereas ABA could act mainly at the end of the growth phase.Abbreviations ABA abscisic acid - ABTS 2,2-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) - BHT butylhydroxytoluene - DW dry weight - ELISA enzyme linked immunosorbent assay - HPLC high performance liquid chromatography - IAA indole-3-acetic acid. PGRs: plant growth regulators     

Control of macaw palm seed germination by the gibberellin/abscisic acid balance

The hormonal mechanisms involved in palm seed germination are not fully understood. To better understand how germination is regulated in Arecaceae, we used macaw palm (Acrocomia aculeata (Jacq.) Lodd. Ex Mart.) seed as a model. Endogenous hormone concentrations, tocopherol and tocotrienol and lipid peroxidation during germination were studied separately in the embryo and endosperm. Evaluations were performed in dry (D), imbibed (I), germinated (G) and non‐germinated (NG) seeds treated (+GA₃) or not treated (control) with gibberellins (GA). With GA₃ treatment, seeds germinated faster and to a higher percentage than control seeds. The +GA₃ treatment increased total bioactive GA in the embryo during germination relative to the control. Abscisic acid (ABA) concentrations decreased gradually from D to G in both tissues. Embryos of G seeds had a lower ABA content than NG seeds in both treatments. The GA/ABA ratio in the embryo was significantly higher in G than NG seeds. The +GA₃ treatment did not significantly affect the GA/ABA ratio in either treatment. Cytokinin content increased from dry to germinated seeds. Jasmonic acid (JA) increased and 1‐aminocyclopropane‐1‐carboylic acid (ACC) decreased after imbibition. In addition, α‐tocopherol and α‐tocotrienol decreased, while lipid peroxidation increased in the embryo during germination. We conclude that germination in macaw palm seed involves reductions in ABA content and, consequently, increased GA/ABA in the embryo. Furthermore, the imbibition process generates oxidative stress (as observed by changes in vitamin E and MDA).     

Physiological and morphological characteristics during development of pedunculate oak (Quercus robur L.) zygotic embryos

The developmental stages of oak zygotic embryos (ZEs) are characterized here according to morphological and physiological features. Seeds were harvested from June to September in 1-week intervals. Excised embryos were classified into four stages of development by using growth parameters. For physiological characterization, endogenous levels of abscisic acid (ABA), indole-3-acetic acid (IAA), l-proline, starch content and water status were determined. The expression of the oak legumin storage protein gene was tested in immature cotyledonary ZEs before and after ABA treatment. The ABA levels of the embryos showed a significant peak during the intermediate stage of maturation (stage III) and then decreased again at the end of the late maturation phase (stage IV). Concomitant with ABA, the moisture content declined with the maximum embryo size. High IAA levels were found at the beginning of embryo enlargement as exponential growth occurred (stage II) but decreased during further development. Starch accumulated gradually in the course of maturation, whereas significant values were found in stage IV ZEs near shedding. Proline, on fresh weight basis, was high during stages I and II. Osmotic potential increased when, by rapid dry matter accumulation, stage II ZEs reached their maximum size during early intermediate development. Expression of precocious germination was higher on hormone-free medium, in particular, among stage II and stage III ZEs. Variations in phytohormone levels in combination with changes in tissue water status seem to be important factors for oak ZE development.     

Hormonal changes associated with fruit set and development in mandarins differing in their parthenocarpic ability

Satsuma [Citrus unshiu (Mak) Marc.] and Clementine [Citrus reticulata (Hort.) Ex. Tanaka, cv. Oroval] are two related species of seedless mandarins which differ in their tendency to set parthenocarpic fruits. Satsuma fruits naturally set parthenocarpically whereas Clementine mandarins show very low ability to set fruit in the absence of cross-pollination. The endogenous levels of gibberellins (GAs) and free and conjugated indole-acetic acid (IAA) and abscisic acid (ABA) throughout early stages of fruit development were investigated in seedless cultivars of both species. Analyses performed by full-scan combined gas chromatography-mass spectrometry (GC-MS) of extracts from ovaries at anthesis demonstrated the presence of GA₁₉, GA₂₀, GA₂₉, GA₁, GA₈, GA₃ and iso-GA₃ in Satsuma mandarin, whereas only GA₂₉, GA₃ and trace levels of GA₈ were detected in Clementine. At this developmental stage GA-like substances, as estimated by bioassay, reached their highest levels in Satsuma, while Clementine mandarins contained relatively lower levels. In both species the highest levels of free IAA were found at petal-fall stage at which time free ABA levels also peaked. Developing fruits of Clementine had higher amounts of both free IAA and ABA. In Satsuma, levels of conjugated IAA remained low throughout reproductive development whereas in Clementine they increased as the free form declined. In contrast, conjugated ABA was at low levels in Clementine but reached higher concentrations in Satsuma. These results suggest that in these mandarins the potential for setting parthenocarpic fruits is mainly influenced by the hormonal status of the fruit during the later stages of cell division and early stages of cell enlargement. Thus, the condition of low ability to set parthenocarpic fruits appears to be associated with lower levels of active GAs, lower capability to catabolize ABA to conjugated ABA and higher ability to conjugate IAA during this period.     

Endogenous hormone concentrations and embryogenic callus development in wheat

Immature zygotic embryos of two wheat (Triticum aestivum L.) genotypes, known for their different ability to generate embryogenic callus, were used as initial explants to establish callus cultures. Embryogenic and non-embryogenic calluses were obtained from the competent genotype (`Combi'), while only non-embryogenic callus was produced by the incompetent one (`Devon'). The morphogenetic competence of each callus type was evaluated by transferring some segments to regeneration conditions. The endogenous hormone concentrations (free indole-3-acetic acid [IAA], abscisic acid [ABA], gibberellins ₁, ₃ and ₂₀ [GAs], zeatin/zeatin riboside [Z/ZR] and N ⁶[²-isopentenyl] adenine/ N ⁶[²-isopentenyl] adenosine; [iP/iPA]) of the initial explants were determined by means of radio-immunoassay and showed that the only difference was the higher concentration of ABA found in the embryos of the most competent genotype; whose embryos showed a reduced rate of precocious germination. When analysing the endogenous hormone concentrations in the various callus types generated in each genotype, it was found that only differences in the free IAA concentrations were associated with variations in the morphogenic properties of the calluses. Higher concentrations of endogenous free IAA were typical of embryogenic callus cultures. It was also observed that a loss in the embryogenic competence of the calluses, due to a prolonged time of culture, occurred concomitantly with a reduction in free IAA concentrations, practically to the concentrations found in the non-embryogenic calluses.     

薇甘菊花芽分化前后内源激素及相关基因表达的研究

以云南省瑞丽市勐秀林场扦插种植的薇甘菊为试材,采用液相色谱串联质谱(LC-MS/MS)技术对花芽未分化期和花序原基分化期花芽中的生长素(IAA)、赤霉素(GA)、脱落酸(ABA)、反式玉米素(tZ)、异戊烯腺嘌呤(IP)、1-氨基环丙烷羧酸(ACC)、茉莉酸(JA)和水杨酸(SA)含量进行定量分析,同时基于转录组基因功能注释数据对内源激素合成、代谢及信号转导途径相关基因进行表达分析,以探讨不同内源激素对薇甘菊花芽形成的调控作用,以及内源激素合成和信号转导途径相关基因调控薇甘菊花芽分化的机制,为后期通过外源激素调控薇甘菊内源激素水平的方式来控制薇甘菊的有性繁殖提供理论和技术支持。结果表明：(1)薇甘菊未分化期花芽中GA₁₅、GA₁₉、GA₂₀、GA₂₄、IAA、ABA和ETH含量低于花序原基分化期,而未分化期花芽中两种细胞分裂素tZ和IP含量显著高于花序原基分化期。(2)基于RNA-seq测序结果,在薇甘菊两个花芽分化时期共获得7 116个差异表达基因(DEGs),其中上调3 907个,下调3 209个。(3)在内源激素合成方面,参与GA₁₅、GA₁₉、GA₂₀、GA₂₄、IAA、ABA和ACC合成的大量DEGs在花序原基分化期上调表达,这与它们在薇甘菊花序原基分化期的高含量趋势相一致;参与IAA合成的YUCCA基因家族和ACC合成的ACS基因在花序原基分化期的高表达也可能参与促进薇甘菊花芽分化。(4)在植物激素转导途径中,在花序原基分化期,生长素信号转导途径通过AUX/IAA(gene-E3N88_07743)的下调表达和ARF(gene-E3N88_41119)的上调表达,乙烯信号转导途径通过ERF(gene-E3N88_41547)的上调表达,赤霉素信号转导途径通过GID1(gene-E3N88_19448)基因的上调表达,细胞分裂素信号转导途径通过B-ARR(gene-E3N88_28086)和A-RRR(gene-E3N88_40764)基因的下调表达,脱落酸途径通过AREB(gene-E3N88_18558)基因的上调表达,茉莉酸信号转导途径通过JAZ(gene-E3N88_05628)的上调表达和MYC2(gene-E3N88_32405)的下调表达来调控薇甘菊花芽分化。研究发现,高水平的GA₁₅、GA₁₉、GA₂₀、GA₂₄、IAA、ABA和ACC有利于薇甘菊的花芽分化;薇甘菊在花芽分化过程中通过改变不同种类内源激素合成、代谢基因的表达来调控激素浓度,而激素又通过信号转导途径引起下游基因的表达,进而调控薇甘菊的花芽分化。     

In vitro induction of pollen embryos and plantlets in Aesculus carnea Hayne through anther culture

Uninuclear microspores in red horse chestnut anther cultures formed pollen embryos and plantlents in MS agar medium supplemented with varying 2,4-D concentrations (1.0, 1.5 or 2.0 mg l^-1) and 1.0 mg l^-1 Kin. The highest number of embryogenic anthers (38%) was obtained in MS medium containing 1.0 mg l^-1 of each 2,4-D and Kin. The ability of pollen embryos to germinate was closely correlated with normal embryo morphology and was influenced by hormone content in the medium (MS+;1.0 mg l^-1 IAA+1.0 mg l^-1 GA₃+0.1 mg l^-1 Kin+400 mg l^-1 glutamine). Pollen embryos and plantlets had the haploid chromosome number (x=n=40). Cytological examinations demonstrated pollen dimorphism of this Aesculus species.Abbreviations AC activated charcoal - 2,4-D 2,4-dichlorophenoxyacetic acid - IAA indole-3-acetic acid - Kin 6-furfurylaminopurine - GA₃ gibberellic acid - MS Murashige and Skoog     

Endogenous hormonal content and somatic embryogenic capacity of Corylus avellana L. cotyledons

Endogenous indole-3-acetic acid (IAA), abscisic acid (ABA) and cytokinins [zeatin (Z) zeatin riboside, dihydrozeatin, dihydrozeatin riboside, N⁶-isopentenyl adenine (iP) and N⁶-isopentenyladenine riboside] were evaluated in hazelnut (Corylus avellana L.) cotyledons of different developmental stage and genetic source for their somatic embryogenic capacity. There was an inverse correlation between the embryogenic potential of cotyledons and the degree of maturity of zygotic embryos, the first characteristic being associated with iP-type cytokinins and the second with Z-type cytokinins. Although the differences in total cytokinin, ABA and IAA contents between the cotyledons were small, the IAA/ABA and, mainly, the iP-type/Z-type cytokinin ratios were found to be two good indexes of the embryogenic competence of explants, suggesting that the endogenous hormonal balance is a very important factor defining the in vitro potential of hazelnut cotyledons. Received: 6 January 1997 / Revision received: 3 March 1997 / Accepted 1 April 1997