Soluble and insoluble invertase activity in elongating Tulipa gesneriana flower stalks

Previously 'frozen' Tulipa gesneriana L. bulbs cv. Apeldoorn, were planted and grown at higher temperatures to study the role of invertase (EC 3.2.1.26) in the cold-induced elongation of the flower stalk internodes. After planting, flower stalks were left intact, or, the leaves and flower bud were both removed to inhibit internode elongation. In intact flower stalks, elongation of the internodes was accompanied by an accumulation of glucose and an initial decrease in the sucrose content g,⁻¹ dry weight. Insoluble invertase activity g,⁻¹ dry weight hardly changed, but soluble invertase activity showed a peak pattern, that was related, at least for the greater part, to the changes in the sugar contents. Peak activities of soluble invertase were found during (lower- and uppermost internodes) or around the onset of the rapid phase of internode elongation (middle internodes). Internode elongation and glucose accumulation immediately ceased when the leaves and flower bud were removed. Insoluble invertase activity g,⁻¹ dry weight remained at its initial level (lowermost internode) or increased more towards the upper internodes. Soluble invertase activity did not further increase (uppermost internode) or decreased abruptly to a low level. It is concluded that soluble invertase may be one of the factors contributing to glucose accumulation and internode elongation in the tulip flower stalk.     

Effect of morphactin on stem growth in relation to auxin in precooled rooted tulip bulbs

Effect of morphactin IT 3456, an auxin transport inhibitor, on tulip stem elongation induced by indole-3-acetic acid (IAA) was investigated. Tulip stem growth induced by IAA 0.1 % in lanolin paste applied on the top internode after excision of flower bud and removal of all leaves was greatly inhibited by 0.2 % morphactin IT 3456 applied on the 4th, 3rd, 2nd and 1st internode. The inhibitory effect of the morphactin on tulips stem growth promoted by IAA was restored by additional application of IAA below the morphactin treatment place. Morphactin inhibited also the growth of all internodes induced by flower bud in the absence of leaves. These results suggest a crucial role of auxin in the control growth of all internodes in tulip stem.     

Changes in Endogenous Gibberellin and Auxin Activities during First Internode Elongation in Tulip Flower Stalk

Dark treatment during the most active period of tulip shootgrowth induced rapid elongation of the first internode. Endogenousfree-form gibberellin and diffusible auxin in the first internodeincreased while bound-form gibberellin decreased after the darktreatment. Alternating dark and light treatments at 24-h intervalscaused increases in elongation of the first internode and theamounts of free-form gibberellin and diffusible auxin in thedark but their decreases in the light. TIBA treatment at thefirst node inhibited both the elongation and the increase indiffusible auxin, but did not affect the gibberellin amount.Ancymidol application prior to the dark treatment inhibitedthe increase in both free-form gibberellin and diffusible auxin.Application of gibberellin A₃ increased both elongation of thefirst internode and the amount of diffusible auxin. It alsocaused recovery from ancymidol-mediated reduction in elongationand diffusible auxin content. Dark-induced elongation of thefirst internode was inhibited when all organs above the firstinternode were excised, but endogenous free-form gibberellinincreased and bound-form gibberellin decreased. After excision,elongation of the first internode occurred only when both GA₃and IAA were applied exogenously, or when IAA was applied withdark treatment. These results indicate that dark-induced elongationof the first internode of tulip is promoted by auxin, whichis transported from the upper organs into the first internodedue to stimulation from the dark-induced increase in free-formgibberellin. Free- and bound-form gibberellins changed complementarilywith the dark and light treatments. An interconversion systembetween the two forms in the first internode and its dependenceon light conditions are also discussed. (Received June 23, 1984; Accepted March 5, 1985)     

Effects of exogenous gibberellins and paclobutrazol on floral stalk growth of tulip sprouts isolated from cooled and non-cooled tulip bulbs

The involvement of gibberellins (GAs) in the regulation of floral stalk elongation and flower development has been studied in tulip. The biological activity of GA₄ and GA₉, both endogenous in tulip bulb sprouts, and GA₁, was tested in vitro on sprouts of cooled and non-cooled tulip bulbs ( Tulipa gesneriana L. cv. Apeldoorn), in the presence or absence of the GA biosynthesis inhibitor paclobutrazol. At early starting dates of incubation, floral stalks from both cooled and non-cooled bulbs hardly showed any elongation in the absence of exogenous GA. Paclobutrazol had no effect on floral stalk elongation, and the response to GAs of sprouts from cooled bulbs was greater than that of sprouts from non-cooled bulbs. At later starts of incubation, considerable floral stalk elongation occurred without GA application. Paclobutrazol inhibited this floral stalk elongation, and the growth of sprouts from both cooled and non-cooled bulbs was stimulated by GA application. The effect of paclobutrazol was reversed by simultaneous application of GA₄ or GA₉. Application of GA with and without paclobutrazol resulted in the same elongation of the floral stalk, indicating the absence of substantial side effects of the inhibitor. The isolated sprouts did not develop a full-grown flower without the addition of GA. GA₄ was more effective than GA₉ in stimulating this flower development. The results demonstrate that both sprouts from cooled and non-cooled bulbs are responsive to exogenous GAs in vitro, and may be a site of GA biosynthesis.     

Carbohydrate Status of Tulip Bulbs during Cold-Induced Flower Stalk Elongation and Flowering

The effect of a cold treatment on the carbohydrate status of the scales and flower stalk of Tulipa gesneriana L. cv Apeldoorn bulbs during growth after planting was studied and compared with bulbs not given cold treatment. Bulbs were stored dry for 12 weeks at 5[deg]C (precooled) or 17[deg]C (noncooled). Only the 5[deg]C treatment led to rapid flower stalk elongation and flowering following planting at higher temperatures. Precooling enhanced mobilization of starch, fructans, and sucrose in the scales. The cold-stimulated starch breakdown was initially accompanied by increased [alpha]-amylase activity per scale. In noncooled bulbs, [alpha]-amylase activity slightly decreased or remained more or less constant. Cold-induced flower stalk elongation was partially accompanied by a decrease in the sucrose content and an increase in the glucose content and invertase activity per g dry weight. The starch content in internodes initially decreased and subsequently increased; [alpha]-amylase activity per g dry weight of the lowermost internode showed a peak pattern during starch breakdown and increased thereafter. The internodes of noncooled bulbs, on the contrary, accumulated sucrose. Their glucose content and invertase activity per g dry weight remained low. Starch breakdown was not found and [alpha]-amylase activity per g dry weight of the lowermost internode remained at a low level. Precooling of tulip bulbs thus favors reserve mobilization in the scales and flower stalk and glucose accumulation in the elongating internodes.     

Changes in free polyamines in Tulipa gesneriana flower stalks during dry-storage and after planting of bulbs

Tulip bulbs cv. Apeldoorn are dry-stored at 5°C for 12 weeks to ensure sufficient elongation of the flower stalk, when subsequently planted at higher temperatures (17–20°C). To investigate whether free polyamines are involved in this process, flower stalk internodes were analyzed during dry-storage and after planting of the bulbs.During dry-storage for 12 weeks at 5°C (cooled) and 17°C (non-cooled), the free putrescine, spermidine and spermine amounts per flower stalk increased. The putrescine amount increased at 5°C significantly more than at 17°C, whereas the opposite was found for the spermine amount. These differences developed early during dry-storage and disappeared rapidly at subsequent higher temperatures.After planting, the lower- and uppermost flower stalk internodes of the pre-cooled bulbs elongated much faster than those of the non-cooled ones. In the pre-cooled bulbs, the free polyamine amounts per internode increased with time after planting, but the time course of these changes was different. In the non-cooled bulbs, the free polyamine amounts increased to a much lesser extent or remained more or less constant.It is argued that the observed changes in the free polyamine contents are probably not required for the cold-induced extension growth of tulips cv. Apeldoorn.Abbreviations PA polyamine - Put putrescine - Spd spermidine - Spm spermine     

Gibberellin levels and cold-induced floral stalk elongation in tulip

To investigate the role of gibberellins (GAs) in the cold requirement of tulip ( Tulipa gesneriana L. cv. Apeldoorn), bulbs were dry-stored at 5°C or at 17°C for 12 weeks prior to planting at 20°C. Only precooled bulbs showed rapid sprout growth and developed a full-grown flower. Endogenous GA levels were measured in sprouts and basal plates at the time of planting and in the second week after planting, by combined gas chromatography-mass spectrometry using deuterated internal standards. GA₄ was the major gibberellin. while GA₁, GA₉ and GA₃₄ were present in lower amounts. At the time of planting, sprouts from non-cooled bulbs contained significantly more GA₄ and GA₁, per sprout than those from precooled bulbs. Hence, there is no direct correlation between rapid sprout growth after planting and high GA levels at planting. In the second week after planting, floral stalks of precooled bulbs contained 2 to 3 times more GA₄ and its metabolite GA₃₄ per floral stalk and per g fresh weight than those of non-cooled bulbs. The results are discussed with regard to the role of gibberellins in the cold-induced floral stalk elongation of tulip.     

Growth and anthocyanin synthesis in excised Sorghum internodes

Summary Ligh-induced anthocyanin synthesis in excised dark-grown internodes of Sorghum was depressed by the addition of auxin to the incubating medium at physiological concentrations. Both IAA and the synthetic auxin, 2,4-D, reduced anthocyanin yield. Similar results were obtained with isolated internode segments and in internodes incubated with coleoptiles (the major source of endogenous auxins) attached. Auxin increased the duration of the lag phase before anthocyanin synthesis began and reduced the rate during the subsequent linear phase. Elongation continued longer with IAA than without it and anthocyanin formation did not begin until extension growth had ceased or was slowing down in both cases; the rate of anthocyanin synthesis in the IAA solution remained depressed compared with that in buffer even after extension growth had ceased in both.At low concentrations IAA stimulated elongation growth without reducing anthocyanin yield and it is unlikely that the effect of IAA on anthocyanin synthesis results from the increased utilisation in growth of substrates needed for anthocyanin formation. The results of reciprocal transfer experiments from dark to light, and vice versa, showed that the action of IAA was associated with its presence in the incubating medium during the irradiation period. If present only in darkness, before or after transfer to light, IAA did not reduce anthocyanin formation; in the former case total yield was increased by IAA as a result of the stimulation of elongation growth, the concentration of anthocyanin remaining unchanged.GA₃ also decreased anthocyanin content; the effect was greater in sections incubated with coleoptiles attached and it is possible that GA₃ acts by increasing the concentration of endogenous auxins. However, CCC, which has been reported to decrease endogenous auxin levels, also reduced anthocyanin yield.The effect of IAA was not influenced by the presence of ascorbate in the incubating medium, nor did added ascorbate result in the formation of any acylated cyanidin derivative in internodes maintained in darkness.Possible relationships between light-induced anthocyanin formation and the photo-inhibition of elongation are discussed.     

鹅掌楸属种间杂种优势与内源植物激素的关系

研究了鹅掌楸属( Liriodendron )种间F1杂种(杂种马褂木 L.chinense × L.tulipifera )及其亲本种(中国马褂木 L.chinense (Hemsl.) Sarg.和北美鹅掌楸 L.tulipifera L.)在生长性状和内源GA1/3、IAA和iPA含量上的差异性.结果表明:(1)杂种马褂木高生长性状杂种优势主要是由节间的相对伸长造成的,鹅掌楸属节间伸长区位于顶芽下第1～3节间,其中第1节间伸长量最大、是产生杂种优势的主要节间; (2)中国马褂木、北美鹅掌楸和杂种马褂木内源GA1/3、IAA和iPA含量差异很大,顶芽下第1节间GA1/3和iPA含量杂种家系分别为两个亲本种中含量相对较高的中国马褂木的133.58%～284.17%和396.64%～1 264.28%.杂种马褂木顶芽下第1节间中GA1/3和iPA含量的大量增加可能与高生长性状杂种优势有关; (3)杂种家系3年生时其苗高生长量排序与顶芽下第1节间中GA1/3和iPA含量排序并不一致,不能以第1节间GA1/3和iPA含量的高低作为预测杂种家系间杂种优势大小的依据.     

Hormonal control of floral abscission in zucchini squash (<Emphasis Type="Italic">Cucurbita pepo</Emphasis>)

In the zucchini squash, Cucurbita pepo, a well coordinated abscission of the female flower during fruit set is essential to obtain a fruit of commercial value. In Spain zucchini is mainly produced in greenhouses in Almería, where high temperatures during the spring-summer period provoke a cultivar-dependent defect in fruits known as the “sticky flower” syndrome. This disorder is characterised by an arrest in growth and maturation of floral organs, and a lack of female floral abscission, thus diminishing fruit shelf-life, commercial quality and value. The aim of the present work was to improve knowledge of the abscission process in C. pepo to better understand the fundamental causes of this disorder. The anatomical analysis of abscission shows a well defined male floral abscission zone (AZ), few hours after anthesis, which differs from the female zone which is not differentiated from the adjacent tissue until the abscission process has begun, and which occurs as a consequence of AZ cell enlargement and the dissolution of their cell walls. To evaluate the role of ethylene and auxins in the regulation of floral abscission in zucchini we performed several treatments, with: ethylene, added as 0.25% ethrel solution; AVG, the inhibitor of ethylene synthesis, at 100 μM; indol-3-acetic acid, 100 μM; and TIBA, the inhibitor of auxin polar transport, at 10 mM. These treatments show that ethylene is an accelerator of zucchini floral abscission, and also promotes abscission in isolated AZs of sticky flowers. On the other hand, IAA delays abscission of the female flowers, whilst the inhibitor of auxin polar transport promotes it. The activity of the cell wall hydrolytic enzymes, polygalacturonase and cellulase, sharply increased just before the shedding of zucchini floral organs (72 h after anthesis). Moreover, both enzyme activities were induced by ethylene, which partly explains the ethylene promoting effect.     

Opening of Iris flowers is regulated by endogenous auxins

Flower opening in Iris (Iris × hollandica) requires elongation of the pedicel and ovary. This moves the floral bud upwards, thereby allowing the tepals to move laterally. Flower opening is requires with elongation of the pedicel and ovary. In cv. Blue Magic, we investigated the possible role of hormones other than ethylene in pedicel and ovary elongation and flower opening. Exogenous salicylic acid (SA) and the cytokinins benzyladenine (N6-benzyladenine, BA) and zeatin did not affect opening. Jasmonic acid (JA) and abscisic acid (ABA) were slightly inhibitory, but an inhibitor of ABA synthesis (norflurazon) was without effect. Flower opening was promoted by gibberellic acid (GA₃), but two inhibitors of gibberellin synthesis (4-hydroxy-5-isopropyl-2-methylphenyltrimethyl ammonium chloride-1-piperidine carboxylate, AMO-1618; ancymidol) did not change opening. The auxins indoleacetic acid (IAA) and naphthaleneacetic acid (NAA) strongly promoted elongation and opening. An inhibitor of auxin transport (2,3,5-triodobenzoic acid, TIBA) and an inhibitor of auxin effects [α-(p-chlorophenoxy)-isobutyric acid; PCIB] inhibited elongation and opening. The data suggest that endogenous auxins are among the regulators of the pedicel and ovary elongation and thus of flower opening in Iris.     

穗花牡荆花芽分化过程中形态和生理指标变化

以穗花牡荆为研究材料,通过探究其花芽分化进程和生理特性,为花期调控技术提供成花机理。采用物候期观察和石蜡切片相结合的方法并测定花芽分化过程中相关生理指标,研究花发育过程中的形态和生理变化。结果表明,穗花牡荆花芽分化为一年多次分化型,其进程可划分为七个时期：未分化期、总轴花序原基分化期、初级分轴花序原基分化期、次级分轴花序原基分化期、小花原基分化期、花器官分化前期和花器官分化后期。同一植株不同位置花芽及同一花序中不同单花分化的进程不同,第一季花期后各阶段的花芽分化形态常存在重叠。花芽分化过程中不同时期叶片和花芽的可溶性糖和可溶性蛋白质含量均有上升下降的变化,总体上叶片中营养物质含量高于花芽保证营养供应。花芽分化过程中,IAA、ABA、CTK和GA3整体水平上先升后降有利于花芽分化进行。研究认为,花芽中大量的可溶性糖和蛋白质积累及较高的碳氮比,有利于穗花牡荆花芽形态分化顺利完成。低水平的GA3/ABA和IAA/CTK有利于花序的形成,ABA/CTK和ABA/IAA比值升高促进小花原基和小花萼片原基的分化, GA3/CTK、GA3/ABA和GA3/IAA比值升高促进花瓣原基、雄雌蕊原基发育。     

Gibberellins in Diffusates from Shoots of Apple Trees

Excised shoot apices, leaves and internodes from shoots of apple trees (Malus×domestica) give off gibberellins by diffusion on agar. A methanol extract of the agar was prepared, the extract separated on thin layer plates, and the gibberellin activity estimated by means of Rumex and lettuce hypocotyl bioassays. The largest amounts of gibberellin are found in diffusates from the shoot apex, the two upper leaves and the two upper internodes. Several promotive fractions are found on the chromatograms as well as growth inhibitors. Removal of young leaves retards elongation of the internodes. Probably gibberellins produced in young leaves exercise some control over this process. The growth regulators Alar and CCC also retard internode elongation. Diffusates from shoots treated with these substances were also examined. Preliminary results suggest that the amount of diffusible gibberellins from treated shoots is not reduced.     

GIBBERELLIN-INDUCED INHIBITION OF FLORAL INITIATION IN FUCHSIA

The ‘Lord Byron’ cultivar of Fuchsia hybrida is a long day plant for which GA acts as an inhibitor of flower initiation. At the dosages required to inhibit initiation (0.025 μg per plant) GA also promotes increased stem elongation but causes no other departures from normal development. Similar tests with auxins, antiauxins, kinins, and other substances showed no effect on flower initiation at dosages equivalent to that for GA. At 10- to 100-fold greater dosages, auxins, kinins, and anti-auxins inhibit not only flower initiation but also vegetative development. Thus the effect of GA on flower initiation appears to be unique, although other hormonal substances, such as abscisin, have not been tested. GA-induced inhibition is directly proportional to the dosage applied and inversely to the strength of long day induction (as measured by the number of long days). GA is most effective when applied to the terminal bud rather than to the mature leaves, suggesting that it is active at the site of flower initiation rather than in the leaves. If it is applied after translocation of the floral stimuli from the leaves, GA does not prevent flower initiation. Regardless of the dose applied, GA is less effective if applied later rather than earlier during LD induction. The inhibitory effect persists for several days. For example, an 0.85 μg dosage causes an 8–10-day delay in initiation; lower dosages have reduced effects. GA inhibits flower initiation but has no effect upon flower development. The rate of bud development is the same in GA-treated and control plants. Apparently no more than one to two axillary buds immediately below the apical meristem are receptive to long day-induced floral stimuli from the leaves. Regardless of the daylength conditions axillary buds more basal do not initiate flowers but develop into branch axes. The effect of a long day treatment persists for a very short time, perhaps no longer than the inhibition caused by minimal GA dosage. Thus flower initiation continues for a very short time following the end of long day induction. The significance of these findings is discussed in relation to the many reports of GA-induced inhibition as well as promotion of flower initiation. In particular, the discussion concerns the nation that flower initiation in fuchsia may be controlled by a gibberellin-like transmissible inhibitor.     

Evidence that the mature leaves contribute auxin to the immature tissues of pea (<Emphasis Type="Italic">Pisum sativum</Emphasis> L.)

In plants such as the garden pea (Pisum sativum L.), it is widely thought that the auxin indole-3-acetic acid (IAA) is synthesised mainly in the immature tissues of the apical bud and then transported basipetally to other parts of the plant. Consistent with this belief are results showing that removal of the apical bud markedly reduces the IAA content in the stem. However, it has also been suggested that the mature leaves may synthesise substantial amounts of IAA, which enters the basipetal transport stream after being transported to the shoot apex in the phloem (Cambridge and Morris in Planta 99:583–588, 1996). To examine this theory, we defoliated pea plants and measured the effect on IAA content in the remaining shoot tissues. IAA levels were reduced in the internodes, and to a lesser extent in the apical bud, after defoliation, suggesting that mature leaves are indeed an important source of auxin for the shoot. Consistent with this idea, we have demonstrated that mature, fully expanded leaves are capable of de novo IAA synthesis. Furthermore, we report evidence for the presence of IAA in the phloem sap of pea. Together these results support those of Cambridge and Morris, suggesting that mature leaves are a source of the IAA in the basipetal transport stream.     

Changes of Endogenous Hormone Contents During Floral Bud and Vegetative Bud Differentiation in Thin Cell Layer Culture of Cichorium intybus L. Explant

The sectioned thin cell layers (TCL) of flower stalk of Cichorium intybus L. were cultured in MS medium supplemented with NAA and BA or IAA and BA where floral and vegetative buds were developed from the explant. Endogenous IAA, DHZ+DHZR, iPA increased significantly during the floral bud formation, while Z+ZR remained changed. The levels of cytokinins, DHZ +DHZR, iPA, and Z-f-ZR all increased significantly during the vegetative bud formation, however IAA level was reduced during the first 7 days of culture and increased to two-thirds of initial values on the day when the bud primordia were formed. The results suggested that the initiation of floral buds was associated with a high IAA/CTK ratio, whereas the induction of vegetative bud differentiation was related to a low IAA/CTK ratio.     

Heterotopic expression of class B floral homeotic genes supports a modified ABC model for tulip (Tulipa gesneriana)

In higher eudicotyledonous angiosperms the floral organs are typically arranged in four different whorls, containing sepals, petals, stamens and carpels. According to the ABC model, the identity of these organs is specified by floral homeotic genes of class A, A+B, B+C and C, respectively. In contrast to the sepal and petal whorls of eudicots, the perianths of many plants from the Liliaceae family have two outer whorls of almost identical petaloid organs, called tepals. To explain the Liliaceae flower morphology, van Tunen et al. (1993) proposed a modified ABC model, exemplified with tulip. According to this model, class B genes are not only expressed in whorls 2 and 3, but also in whorl 1. Thus the organs of both whorls 1 and 2 express class A plus class B genes and, therefore, get the same petaloid identity. To test this modified ABC model we have cloned and characterized putative class B genes from tulip. Two DEF- and one GLO-like gene were identified, named TGDEFA, TGDEFB and TGGLO. Northern hybridization analysis showed that all of these genes are expressed in whorls 1, 2 and 3 (outer and inner tepals and stamens), thus corroborating the modified ABC model. In addition, these experiments demonstrated that TGGLO is also weakly expressed in carpels, leaves, stems and bracts. Gel retardation assays revealed that TGGLO alone binds to DNA as a homodimer. In contrast, TGDEFA and TGDEFB cannot homodimerize, but make heterodimers with PI. Homodimerization of GLO-like protein has also been reported for lily, suggesting that this phenomenon is conserved within Liliaceae plants or even monocot species.these authors contributed equally to this work     

菊苣薄层培养花芽,营养芽分化中内源激素的动态变化

菊苣（Ｃｉｃｈｏｒｉｕｍ ｉｎｔｙｂｕｓＬ．）花梗薄层细胞培养于ＭＳ附加ＮＡＡ 和ＢＡ 或ＩＡＡ 和ＢＡ 的ＭＳ培养基上有花芽或营养芽分化． 花芽分化中内源ＩＡＡ、ＤＨＺ＋ ＤＨＺＲ、ｉＰＡ 含量明显增加,而Ｚ＋ ＺＲ变化不明显．营养芽分化中内源细胞分裂素含量增加明显,而ＩＡＡ 在培养前７ ｄ 含量下降,随后有所增加,在原基形成时含量达原初水平的２／３． 可见,花芽分化比营养芽分化所需内源ＩＡＡ／ＣＴＫ 比值要高     

Temperature alternations and the influence of gibberellins and indoleacetic acid on elongation growth and flowering of Begonia x hiemalis Fotsch

The aim of this study was to investigate the role of plant hormones, particularly the gibberellins (GAs), in the thermoperiodic regulation of stem elongation in the short day plant (SDP) Begonia x hiemalis. Effects of GAs and some GA precursors were tested on plants grown under alternating day/night temperatures (DT/NT; 12/12 h), and the effects of these temperature regimes on endogenous plant hormones were analyzed using combined gas chromatography and mass spectrometry (GC-MS).Compared with constant temperatures (19/19 °C; 21/21 °C), stem elongation was significantly inhibited by low DT/high NT (14/24 °C; 18/24 °C) and enhanced by the opposite treatments (24/14 °C; 26/17 °C). GA1 stimulated elongation of internodes and petioles while ent-kaurene, kaurenoic acid, GA12, GA19, GA20 had no significant effect. The effect of GA1 was enhanced by a simultaneous application of calcium 3,5-dioxo-4-propionylcyclohexanecarboxylate (BX-112). BX-112 inhibited internode elongation at high DT/low NT (24/14 °C) but not at the reverse temperature regime.Gibberellins A53, A19, A20, A1, A4, A9, and indoleacetic acid (IAA), were identified by GC-MS from both leaves, including the petioles, and stems of B. x hiemalis. There were no apparent relationships between elongation of internodes and petioles and endogenous contents of gibberellins A53, A19, A20, and A1. Recoveries of deuterated GA4 and GA9 were generally too low for estimation of endogenous levels of these GAs.Constant temperature resulted in more open flowers and flower buds compared to alternating DT and NT. BX-112 decreased the time to anthesis.     

Petal: a reliable explant for direct bulblet regeneration of endangered wild populations of <Emphasis Type="Italic">Fritillaria imperialis</Emphasis> L.

Wild populations of Fritillaria imperialis L. are facing extinction and need urgent conservation. This paper presents an efficient system for in vitro direct bulblet regeneration of these populations by petal culturing of flower buds. Petals at different developmental stages, green-closed flower bud (before nectar secretion) and red-closed flower bud (beginning of nectar secretion), were used as explants, and the effects of various proportions of cytokinin to auxin on direct bulblet regeneration pathway were evaluated. More explants switched on direct regeneration pathway in combination of auxins (0.6 mg l⁻¹ NAA + 0.4 mg l⁻¹ IAA) with higher level of cytokinin (1 mg l⁻¹ BAP). In contrast, auxins (0.6 mg l⁻¹ NAA + 0.4 mg l⁻¹ IAA) with lower level of cytokinin (0.1 mg l⁻¹ BAP) produced more bulblets per regenerated explant. In green-closed flower bud stage, direct bulblets regenerated from the end of petal where it was connected to the receptacle, while nectar secretion site was the place of bulblet formation in red-closed flower bud stage. In addition, genotype-dependency of direct bulblet regeneration pathway was investigated by using two different wild populations of Fritillaria imperialis. This plant regeneration procedure was applicable to different Fritillaria genotypes and regenerated bulblets were normal.