Hormone Levels and Apical Dominance in the Aquatic Fern Marsilea drummondii A. Br

Terminal buds and successively subjacent lateral buds of the water fern, Marsilea drummondii, were examined to determine the pattern of hormone distribution in relation to apical dominance. Quantitative levels of indole-3-acetic acid (IAA), abscisic acid (ABA), zeatin and zeatin riboside (Z and ZR), and isopentenyladenosine (iPA) were determined by a solid-phase immunoassay using polycional antihormone antibodies. Enzyme-linked immunosorbent assay was used following a one-step HPLC purification procedure to obtain the free hormones. Active shoot apices contained the most IAA and Z-type cytokinins and inhibited buds the least. No significant differences in ABA levels were found leading to the conclusion that ABA did not play any role in apical dominance. The normal precedence of the most rapid outgrowth of the youngest inhibited bud as observed previously in decapitated plants was well correlated with its very high level of iPA observed in this study. The same phenomenon was observed in the median buds but with a weaker amplitude. The presence of this storage form could indicate that a bud at its entry into quiescence eventually looses the ability to hydroxylate iPA to Z-type cytokinins when it is fully inhibited. IAA and Z + ZR are concluded to be essential for lateral bud growth.     

罗汉果花芽分化过程中形态及其激素水平变化特征

采用石蜡切片和酶联免疫法(ELISA)对罗汉果雄性、雌性、两性花芽分化过程的形态和激素水平变化进行观测,为罗汉果开花调控和品种选育提供科学依据。结果表明:(1)罗汉果雄性、雌性、两性花的花芽分化过程均可分为花芽未分化期、花芽分化初期、花序分化期、萼片原基分化期、花瓣原基分化期、雄蕊原基分化期和雌蕊原基分化期7个阶段。雄蕊原基分化期前,3种花芽分化过程无明显差异,各时期形态特征均依次为:茎端呈圆锥状(花芽未分化期)→茎端经半球形变成扁平状(花芽分化初期)→距茎端5~7节位处分化出穗状花序(花序分化期)→小花原基周围形成5个萼片原基(萼片原基分化期)→萼片原基内侧形成5个花瓣原基(花瓣原基分化期)。雄蕊和雌蕊原基分化期,3种花芽分化过程存在明显差异,雄蕊原基内侧出现雌蕊原基后,雄花芽雄蕊原基继续发育成雄蕊,雌蕊原基停滞生长,退为一个小突起;雌花芽雌蕊原基继续发育成雌蕊,雄蕊原基生长缓慢,退化为小花丝;两性花芽雌蕊和雄蕊原基均继续发育,形成外观正常的雌蕊和雄蕊。(2)内源激素脱落酸(ABA)、赤霉素(GAs)和玉米素核苷(ZR)含量在3种花芽分化过程中变化规律相似,即ABA含量在花芽生理分化期降低,花芽形态分化期升高,而GAs和ZR含量则基本保持不变;吲哚乙酸(IAA)含量在3种花芽分化过程中变化存在明显差异,雌花芽IAA含量在花芽生理分化期升高,花芽形态分化期逐渐降低,而雄性和两性花芽的IAA含量则基本保持不变。ABA/GAs、ABA/IAA、ZR/IAA和ZR/GAs激素含量比值在3种花芽分化过程中变化规律相似,ABA/GAs在花芽生理分化期降低,花芽形态分化期升高,而BA/IAA、ZR/IAA和ZR/GAs则基本保持不变。研究认为,罗汉果花芽分化过程经历一个"两性期",高ABA含量和ABA/GAs比值有利于罗汉果花芽分化,IAA可能对罗汉果花性分化具有重要作用。     

In vitro flowering and pod formation from cotyledons of groundnut (Arachis hypogaea L.)

Summary The response of groundnut cotyledons to the presence of various growth regulators in concentrations from 0.1 to 5 mg/l has been studied in detail using several genotypes of groundnut on two different media. Cotyledons with embryo axis, cultured on Blaydes' medium with cytokinins, produced shoots, in the axils of which 2–7 flower buds could be seen. The frequency of flower bud induction in general increased with increasing concentrations of cytokinins, the optimal levels being 3 mg/l of KN or 4 mg/l of BAP. Cotyledons without embryo axis, cultured on Blaydes' medium with BAP (0.5 mg/l), produced a cluster of flower buds directly, ranging in number from 8–28, without any vegetative growth. Excised embryo axes cultured on the same medium gave plantlets without flower buds. The growth regulators IAA, NAA, GA₃ and ABA failed to induce flower buds in independent treatments. However, lower concentrations of IAA and NAA in combination with cytokinins exerted a positive influence on flowering. The blooming of the flower buds was facilitated on media supplemented with low concentrations of cytokinins. Six percent of the induced flowers resulted in gynophore development and ultimately formed pods when cultured under complete dark conditions in modified MS medium supplemented with kinetin.     

低温处理对牡丹春节催花及营养类物质变化的影响

连续观察、测定了牡丹春节催花进程中不同低温天数处理对温室外自然低温解除休眠及温室内培养过程中形态及某些生理生化变化的影响,结果显示：低温处理34d后的11月28日温室外牡丹花芽形态及可溶性糖、淀粉、可溶性蛋白、游离氨基酸含量变化显著,11月28日左右是低温处理期间牡丹花芽代谢变化剧烈的时期;处理41d后的12月5口及以后移入温室的植株能够正常开花。以上结果从形态与营养物质变化的角度说明了11月28日左右牡丹花芽开始逐步解除休眠,12月5日花芽已彻底解除休眠,不同低温对牡丹春节催花过程中花芽的发育有着质的作用。     

Bud abortion in tulip bulbs studied by magnetic resonance imaging

After storage and subsequent planting of flower bulbs, the flower bud frequently appears to be aborted. This physiological aberration is probably caused by a change in the water status of the bulb and may be initiated during storage. The development of bud abortion in tulip bulbs was studied during long-term dry storage of the bulbs at 5 degrees C. The anatomy of individual tulip bulbs was followed non-invasively with T2-weighted NMR imaging, which allowed the monitoring of the growth of the shoot and daughter bulbs. Quantitative maps of T1 and T2 relaxation times of individual bulbs were used to assess regional changes in the water status of different tissues. Parallel to the NMR measurements, bulbs were planted to assess the ultimate flower quality. Moreover, water content, osmolality of tissue sap and ion leakage of excised shoot and scale tissues were determined to obtain information about the water status and viability of the bulbs. Significant decreases during long-term storage were found in T1 and T2 relaxation times in the shoot and particularly in the stamens. An increase in the osmolality of tissue sap and the decrease in relaxation times in the shoot below a certain threshold value attained after 24 weeks of storage, could be indicative for the emergence of bud abortion in tulips.     

香荚兰花芽分化至萌发期内源激素的变化

以香荚兰 (Vanillafragrans)为材料 ,研究不同栽培条件下花芽分化和萌发期内源激素变化 ,分析和探讨内源激素在花芽分化和萌发中的作用 ,香荚兰花芽分化时期茎里的激素含量降低 ,芽里激素含量升高 ,其中相对高的ZR和ZR ABA有利于分化 ,IAA和IAA ABA的一定增加也利于分化 ,过高或没有IAA的增加则不利于花芽分化。大多数花芽形成于倒垂茎蔓上 ,花芽分化期 (11～ 12月 ) ,倒垂茎蔓的茎里生长类激素含量降低大于竖立茎蔓 ,芽的激素含量增高则多于竖立茎蔓 ,倒垂茎蔓的这种变化可能是有利于花芽分化。香荚兰生长中顶端优势明显 ,去顶后侧芽里ZR、GA、IAA增高 ,这与 11～ 12月去顶促进倒垂茎蔓开花可能有关。     

喷施烯效唑对苹果顶芽激素水平和花芽分化的影响

用烯效唑(uniconazol,S3307)1 g/L喷洒“红富士“苹果树降低了顶芽IAA、GA1,3,4,7含量,提高了ZR、ABA含量,从而提高了ZR/IAA、ZR/GA1,3,4,7、ABA/IAA和ABA/GA1,3,4,7比值.烯效唑处理增加了花芽形成百分率,加速了花芽分化的进程,缩短了花芽形成的延续时期,但对花芽生理孕育临界时期长短没有影响.烯效唑处理对花芽的节位数没有影响,但使叶芽节位数增加了1节.     

Changes in Cytokinins before and during Early Flower Bud Differentiation in Lychee (Litchi chinensis Sonn.)

Lychee (Litchi chinensis) has been analyzed for cytokinins in buds before and after flower bud differentiation, using reversephase high performance liquid chromatography in combination with Amaranthus bioassay and gas chromatography-mass spectrometry-selected ion monitoring. Four cytokinins, zeatin, zeatin riboside, N⁶-(δ²-isopentenyl)adenine, and N⁶-(δ⁶-isopentenyl) adenine riboside, were detected in buds. There was an increase of cytokinin activity in the buds during flower bud differentiation. In dormant buds, the endogenous cytokinin content was low, and the buds did not respond to exogenous cytokinin application. Application of kinetin promotes flower bud differentiation significantly after bud dormancy. These results are interpreted as an indication that the increase in endogenous cytokinin levels during flower bud differentiation may be correlative rather than the cause of flower bud initiation.     

“Lateral Control”: Phytohormone Relations in the Conifer Treetop and the Short- and Long-Term Effects of Bud Excision in Abies nordmanniana

In a conifer tree, such as Nordmann fir, Abies nordmanniana Spach, the leader bud and its immediate surroundings play a decisive role in crown architecture. As subapical branch buds are segregated from the leader meristem, resource allocation between ortho- and plagiotropic growth is determined. The relationship between treetop buds in young trees was studied in the natural state and after surgical removal in early July of either the leader bud (decapitation) or the subapical whorl branch buds (destipitation). The two bud types showed consistent cytokinin profile differences but similar seasonal dynamics in cytokinins and auxin (IAA). After bud excision, ZRP increased dramatically in the subapical stem within 1 h, followed by ZR within 1 week. Supernormal levels of ZR were maintained through autumn and persisted in spring in the destipitated trees, but had returned to normal in the decapitated trees. The treetop buds remaining after bud excision experienced an immediate decrease in most cytokinins, followed, however, by a large surplus later in the season. The following spring this high level persisted in the leader bud of destipitated trees, but not in whorl buds of decapitated trees. Conspicuous growth pattern changes followed from destipitation, but few from decapitation. Growth reactions suggest that resource allocation to main branch buds inhibits leader growth in normal trees, a kind of “lateral control.” Auxin and ABA content in buds and stems was largely unaffected by treatments. Data suggest that subapical leader tissues beneath the apical bud group are a primary source of cytokinin regulation.     

麝香石竹花芽离体发育的阶段控制

在离体条件下,利用不同的培养基对麝香石竹顶芽外植体的花芽发育进行了阶段控制的研究.结果表明,麝香石竹的顶芽外植体在MS+KT1.0mg/L+IAA1.0mg/L+蔗糖3.0%+琼脂0.8%的Ⅰ级培养基上能被诱导花芽发育的启动;然后,将已诱导花芽发育启动的顶芽外植体,转接到MS+KT1.0mg/L+IAA0.5mg/L+蔗糖1.5%+葡萄糖1.5%+琼脂0.8%的Ⅱ级培养基上能进行花芽的进一步发育形成花蕾,且能从一个花蕾继续分化发育重新产生2—3个花蕾;把花蕾再转接到改良的MS+BA2.0mg/L+NAA0.2mg/L+蔗糖1.5%+葡萄糖1.5%+琼脂0.8%的Ⅲ级培养基上,培养一周后花蕾的花瓣张开,花朵全部开放.不同麝香石竹品种,诱导花芽发育启动的效果不同,Scania品种诱导效果最好.花芽发育初期可溶性蛋白含量较高,但随着花芽发育的进程而迅速下降,不同花芽发育时期的过氧化物酶活性均强于营养器官.本文为花芽分化发育机理的研究创造了条件,也为鲜花生产探索了新路子.     

Distribution of free and bound forms of cis-trans and trans-trans abscisic acid in broad-bean plants in relation to apical dominance

Levels of endogenous abscisic acid (ABA; free and bound forms) have been determined by gas chromatography in stems and buds of broad-bean plants ( Vicia faba L. cv. Aguadulce) in relation to apical dominance. A downward gradient of free cis-trans ABA occurred along the stem, from the apical bud to the roots. Except for the actively growing apical bud the levels of free cis-trans ABA were higher in the buds than in the corresponding nodes. An inverse correlation can be set up between levels of free cis-trans ABA and growth of buds, except for the cotyledonary ones. High levels of bound ABA ( cis-trans form) are correlated with the growth of the apical bud and that of the axillary bud ax1. The hormonal regulation of the growth of the cotyledonary buds, which contained high levels of trans-trans ABA in bound forms, is apparently different from that of the other buds.     

Changes of endogenous hormones in lateral buds of chrysanthemum during their outgrowth

The character of branching for two chrysanthemum (Chrysanthemum × morifolium) cvs. Jinghai and Jingyun was observed, and the changes of endogenous hormones in apical and lateral buds were investigated to determine the relationship between the pattern of hormone distribution, apical dominance, and lateral bud outgrowth. The growth rate of Jinghai lateral buds was higher than that of Jingyun. In vegetative growth stage, IAA level in apical buds of Jingyun was significantly higher than in Jinghai. After flower induction, IAA level in apical buds of two cultivars decreased remarkably, but the IAA level decreased in Jingyun faster than in Jinghai. These results showed that the higher was the IAA level in apical buds the stronger was inhibition of lateral bud outgrowth. An increase in IAA and iP/iPA and a decrease in ABA concentrations were closely associated with lateral bud growth alterations in chrysanthemum.     

补光对大棚火龙果冬季促花的影响

为探讨夜间补充光照对大棚火龙果冬季植株促花的效应,以2年生‘短芯’红肉(心)火龙果植株为试材,每天夜间补光6 h,以不补光为对照,观测火龙果枝条抽蕾状况。结果显示,在平均光强500 lx、每天补充光照6 h、连续补光45 d条件下,第一批次植株抽生花蕾率达83.3%,老枝(枝龄≥12个月)抽生花蕾率为15.2%,青枝(枝龄＜12个月)抽生花蕾率为28.0%,抽生花蕾枝条占植株总枝条数的21.4%;枝条花蕾数占枝条上芽点数的比率,老枝为2.7%、青枝为2.9%。而对照植株没有抽生花蕾,抽蕾率为0。表明夜间补充光照可有效地促进大棚火龙果冬季植株抽花。     

The effect of decapitation on the levels of IAA and ABA in the lateral buds of Betula pendula roth

The level of IAA and ABA in lateral buds of birch shoots 24 h and 5 days after the decapitation of the apical bud was determined. Twenty four hours after decapitation, when visible signs of outgrowth of lateral buds were not observed yet, an increase in the level of IAA and a decrease of ABA, as compared with the buds of non-decapitated shoots, was found. Five days later, when lateral buds were in the period of intensive outgrowth, a decrease in the levels of IAA and ABA was observed. It has been suggested that removing the source of auxin, by the decapitation of the apical bud makes possible the lateral buds to undertake the synthesis of their own auxin. It could lead to the decrease in the content of ABA. These all events could create suitable conditions for the outgrowth of lateral shoots.     

Seasonal Changes in the Levels of Free and Bound Abscisic Acid in Blackcurrant (Ribes nigrum) Buds and Beech (Fagus sylvatica) Buds

Free and bound abscisic acid (ABA) levels in blackcurrant andbeech buds have been determined by an extraction procedure involvingseveral thin-layer chromatography purification stages and finalbioassay in the wheat coleoptile straight-growth test. In bothspecies the highest level of free ABA occurs in the autumn atabout the time of onset of winter dormancy. The free ABA contentthen declines throughout the winter months reaching its lowestvalue just before bud burst. These results strengthen the viewthat free ABA plays an important role in the induction and maintenanceof winter dormancy. The bound ABA level increases in both species throughout theautumn and winter until halfway through the bud swelling phaseand then declines. It is proposed that the bound ABA accumulatesin the buds because it cannot be translocated or further metabolizedduring the winter months. The ratios of free to bound ABA were plotted and the resultingcurves show a distinctive annual cycle with the highest freeABA/ bound ABA ratio (F/B) occurring in the autumn and the highestbound ABA/ free ABA ratio (B/F) coinciding with bud burst. Agradual increase in the B/F ratio during bud swelling may indicatea feed-back reaction between free and bound ABA which maintainsthe free ABA at a sufficiently high level to put a gentle brakeon growth. At bud burst the B/F ratio falls very sharply anda period of very rapid growth ensues.     

The effect of LAB 173711 and ethephon on time of flowering and cold hardiness of peach flower buds

Peach flowers are often killed during bloom by spring frosts. LAB 173711, a compound with abscisic (ABA)-like activity, and ethephon delayed flowering in peach trees. In greenhouse experiments, LAB 173711, at concentrations of 10^?3–10^?2 M, was most effective in delaying bloom when applied after a 5°C cold storage period, rather than before the dormancy breaking treatment. In contrast, ethephon delayed bloom most effectively when applied before 5°C cold storage; ethephon caused flower bud abscission when treatments were made after the chilling requirement had been satisfied. In field experiments, ethephon delayed flowering by 6–7 days, which reduced bud injury after a spring frost during bloom. No flower bud injury was found on ethephon-treated trees after temperatures of ?4.3°C; whereas without ethephon 25% of the flower buds were frost damaged. LAB 173711 delayed the time to 50% bloom by 2–3 days. However, this was not long enough to avoid low-temperature injury to the flower buds.     

Cytokinins from terminal buds of Euphoria longana during different growth stages

The presence of endogenous cytokinins were detected in the terminal buds of longan ( Euphoria longana Lam.) after purification by ion exchange and Sephadex LH-20 chromatography, and bioassay, enzymic degradation, high-performance liquid chromatography and gas chromatography-mass spectrometry. Permethylated derivatives of two highly active cytokinin glucoside compounds from dormant buds were: 6-(4-O-β-D-glucosyl-3-methyl-but-2-enylamino) purine (zeatin-O-glucoside) and 9-β-D-ribofuranosyl-6-(4-hydroxy-3-methyl-but-2-enylamino) purine (zeatin riboside-O-glucoside). Simultaneously, four active cytokinins from buds at the stages of leaf flush and flower bud initiation were identified as 6-(4-hydroxy-3-methyl-but- trans -2-enylamino) purine (zeatin), zeatin-9-β-D-ribofuranosylpurine (zeatin riboside), 6-(3-methyl-2-butenyl) aminopurine (isopentenyladenosine, 2iPA) and N-(3-methyl-2-butenyl) adenine (isopentenyladenine, 2iP). The total cytokinin levels were low at leaf flush, with the zeatin and zeatin riboside in the buds about 70% of the total. In the transition of the terminal bud from leaf flush to dormancy, the principal cytokinins were zeatin-O-glucoside and zeatin riboside-O-glucoside. However, significant decreases in the levels of zeatin-O-glucoside and zeatin riboside-O-glucoside and increases in those of zeatin, zeatin riboside, 2iPA and 2iP were observed at flower bud initiation. It is suggested that in longan, the cytokinins that are translocated to the shoots are accumulated in the buds at the dormant stage, and that later there is a considerable increase in free cytokinins during flower bud initiation, leading to the promotion of flower bud development.     

棉花花芽分化及部分内源激素变化规律的研究

棉花（Ｇｏｓｓｙｐｉｕｍ ｈｉｒｓｕｔｕｍ）的腋芽原基,有的将来发育成叶枝;有的将来发育成果枝。这２种不同命运的腋芽,在其刚分化的初期就表现出了不同的解剖学特征。将来发育为叶枝的腋芽,其生长锥呈圆锥形或扁圆球形,体积较小,原套层数为１－２层;而将来发育为果枝的腋芽,其生长锥为圆柱形,顶端表面平坦,体积较大,原套层数为２－３层。从子叶展平后到肉眼可见花芽（现蕾）,连续测茎尖的内源ＡＢＡ及ＩＡＡ的含量     

Spatial and temporal changes in multiple hormone groups during lateral bud release shortly following apex decapitation of chickpea (Cicer arietinum) seedlings

Although the co-ordination of promotive root-sourced cytokinin (CK) and inhibitory shoot apex-sourced auxin (IAA) is central to all current models on lateral bud dormancy release, control by those hormones alone has appeared inadequate in many studies. Thus it was hypothesized that the IAA : CK model is the central control but that it must be considered within the relevant timeframe leading to lateral bud release and against a backdrop of interactions with other hormone groups. Therefore, IAA and a wide survey of cytokinins (CKs), were examined along with abscisic acid (ABA) and polyamines (PAs) in released buds, tissue surrounding buds and xylem sap at 1 and 4 h after apex removal, when lateral buds of chickpea are known to break dormancy. Three potential lateral bud growth inhibitors, IAA, ABA and cis -zeatin 9-riboside (ZR), declined sharply in the released buds and xylem following decapitation. This is in contrast to potential dormancy breaking CKs like trans -ZR and trans -zeantin 9-riboside 5'phosphate (ZRMP), which represented the strongest correlative changes by increasing 3.5-fold in xylem sap and 22-fold in buds. PAs had not changed significantly in buds or other tissues after 4 h, so they were not directly involved in the breaking of bud dormancy. Results from the xylem and surrounding tissues indicated that bud CK increases resulted from a combination synthesis in the bud and selective loading of CK nucleotides into the xylem from the root.