Kinetin Transport to Axillary Buds of Dwarf Pea (Pisum sativum L.)

Decapitation resulted in the transport of significant amountsof ¹⁴C to the axillary buds from either point of application,but pretreatment of the cut internode surface of decapitatedplants with IAA (alone or in combination with unlabelled kinetin)inhibited the transport of label to the axillary buds and resultedin its accumulation in the IAA-treated region of the stem. Inintact plants to which labelled kinetin was applied to the apicalbud there was little movement of ¹⁴C beyond the internode subtendingthis bud; when labelled kinetin was applied to the roots ofintact plants, ¹⁴C accumulated in the stem and apical bud butwas not transported to the axillary buds. A considerable proportionof the applied radioactivity became incorporated into ethanol-insoluble/NaOH-solublecompounds in the apical bud of intact plants, in internodestreated with IAA, and in axillary buds released from dominanceby removal of the apical bud. The results are discussed in relation to the possible role ofhormone-directed transport of cytokinins m the regulation ofaxillary bud growth.     

Factors affecting variability in anther culture and in conversion of androgenic embryos ofSolanum phureja

The variation for embryo production in anther ofSolanum phureja was examined as a function of maximum greenhouse temperature prior to bud harvest and innate responsiveness among anthers within a bud. Four clones ofS. phuyreja were grown in a greenhouse under a 16-h photoperiod. The temperature was monitored continuously. Buds (60 per day on 10 days) were collected and the anthers cultured in two groups of five flasks (30 anthers per flask). In the first group, each flask contained the 30 anthers from six buds; in the second group, each flask contained one anther from each of 30 buds. Significantly smaller coefficients of variation were observed for the second group, suggesting that variation for embryogenic capcity among buds was greater than that among anthers within a bud. Variation in embryo yield as a function of greenhouse temperature was examined by stepwise regression analysis. Embryogenic capacity of one clone was adversely affected by high temperatures (31–37°C) that occurred two and seven days before bud harvest. However, similarly high temperatures appeared to enhance the androgenic response of another clone. Conversion of anther-derived embryos over three subcultures to fresh regeneration medium was examined as a function of anther donor or clone, cold pretreatment of embryos, and morphological classification of embryos. Only clonal origin significantly affected conversion rate which ranged from 12.5% to 46.0%. Conversion rate declined on each serial subculture.Abbreviations BA N⁶-benzyladenine - GA₃ gibberellic acid, IAA-indole-3-acetic acid     

Determination for inflorescence development is a stable state,separable from determination for flower development in Pisum sativum L. buds

Terminal meristems of Pisum sativum (garden pea) transit from vegetative to inflorescence development, and begin producing floral axillary meristems. Determination for inflorescence development was assessed by culturing excised buds and meristems. The first node of floral initiation (NFI) for bud expiants developing in culture and for adventitious shoots forming on cultured meristems was compared with the NFI of intact control buds. When terminal buds having eight leaf primordia were excised from plants of different ages (i.e., number of unfolded leaves) and cultured on 6-benzylaminopurine and kinetin-supplemented medium, the NFI was a function of the age of the source plant. By age 3, all terminal buds were determined for inflorescence development. Determination occurred at least eight nodes before the first axillary flower was initiated. Thus, the axillary meristems contributing to the inflorescence had not formed at the time the bud was explanted. Similar results were obtained for cultured axillary buds. In addition, meristems excised without leaf primordia from axillary buds three nodes above the cotyledons of age-3 plants gave rise to adventitious buds with an NFI of 8.3 ±0.3 nodes. In contrast seed-derived plants had an NFI of 16.5 ±0.2. Thus cells within the meristem were determined for inflorescence development. These findings indicate that determination for inflorescence development in P. sativum is a stable developmental state, separable from determination for flower development, and occurring prior to initiation of the inflorescence at the level of meristems.     

Pro-embryos induction from <Emphasis Type="Italic">Olea europaea</Emphasis> L. isolated microspore culture

Studies were undertaken with one olive (Olea europaea L.) cultivar to identify buds with microspores competent to embryogenesis in vitro. Isolated microspore cultures were performed for the induction of gametic embryogenesis. Different pollen development stages and stress conditions (heat or cold shock) were evaluated. The correlation of inflorescence, anther morphology and the suitable stage of microspore development were analysed. The morphology of responsive buds was identified which corresponded with microspores from the late uni-nucleate to early bi-nucleate pollen stages. Symmetrical divisions of microspores as well as resulting multinucleate structures and pro-embryos were observed. In this paper, a new method of isolated microspore culture that leads to cell division and pro-embryos in olive, is reported.     

Density and the commitment of apical meristems to clonal growth and reproduction in Hieracium pilosella

Summary We examined responses to population density in the commitment of apical meristems to reproduction and clonal growth in a rosette-forming, stoloniferous herb (Hieracium pilosella). Despite close physiological coupling between the evocation of the terminal inflorescence bud and the development of one or more axillary buds into stolons, the allocation of meristems was extremely plastic.Genets at the higher sowing densities showed density-dependent mortality consistent with self-thinning along a-3/2 trajectory. The probability of inflorescence evocation and associated stolon development was negatively dependent on surviving density. The proportinal distribution of primary stolons amongst genets became strikingly more unequal (expressed as the Gini coefficient) with increasing density. Clonal growth was resolved into the number of primary stolons per stoloniferous genet and the extent of stolon branching (i.e. number of apices per primary stolon); both showed strongly negative density-dependence. Reproduction, expressed as the mean number of flowering capitula per stoloniferous genet, declined 15-fold with increasing density; although theoretically expected to be unity, greater values resulted from capitulum production by attached secondary rosettes and lower values reflected the increasing abortion rate of inflorescence buds with increasing density.Both the total number of apices produced per unit area and the corresponding number of reproductive apices were maximal at intermediate surviving densities (700–1,000 m^-2). The balance between reproductive and clonal growth may be expressed as the probability of an apical meristem producing a capitulum, that also peaked sharply at intermediate density. This finding does not conform with linear models that predict a shift from vegetative growth to sexual reproduction with increasing population density.     

A COMPARATIVE DEVELOPMENTAL STUDY OF THE MUTANT SIDESHOOTLESS AND NORMAL TOMATO PLANTS

'Sideshootless,’ a mutant strain of tomato which does not produce axillary buds during vegetative growth, was compared with normally branching plants in order to study the nature of development particularly with regard to axillary buds. Sectioned material revealed no indication of axillary bud initiation in the sideshootless plant at any time during the vegetative phase of growth. In the normal plants, buds were noted to arise in the axil of the fifth youngest leaf. The buds take their origin in tissue which is in direct continuity with the apical meristem. The bud primordia later become set apart from the apex as vacuolation takes place in the surrounding tissue. At the time of floral initiation, the mutant and normal strains behave similarly. Axillary buds appear in the axils of the 2 leaves immediately below the floral apex. One of the buds elongates to overtop the existing plant axis; the other develops as a typical sidebranch. The inflorescence is pushed aside in the process. This pattern is repeated with each inflorescence; thus an axis composed of several superimposed laterals results.     

A Developmental Pattern of Flowering in Colored <Emphasis Type="Italic">Zantedeschia</Emphasis> spp.: Effects of Bud Position and Gibberellin

The restricted flowering of colored cultivars ofZantedeschia is a consequence of developmental constraints imposed by apical dominance of the primary bud on secondary buds in the tuber, and by the sympodial growth of individual shoots. GA₃ enhances flowering inZantedeschia by increasing the number of flowering shoots per tuber and inflorescences per shoot. The effects of gibberellin on the pattern of flowering and on the developmental fate of differentiated inflorescences along the tuber axis and individual shoot axes were studied in GA₃ and Uniconazole-treated tubers. Inflorescence primordia and fully developed (emerged) floral stems produced during tuber storage and the plant growth period were recorded. Days to flowering, percent of flowering shoots and floral stem length decreased basipetally along the shoot and tuber axes. GA₃ prolonged the flowering period and increased both the number of flowering shoots per tuber and the differentiated inflorescences per shoot. Activated buds were GA₃ responsive regardless of meristem size or age. Uniconazole did not inhibit inflorescence differentiation but inhibited floral stem elongation. The results suggest that GA₃ has a dual action in the flowering process: induction of inflorescence differentiation and promotion of floral stem elongation. The flowering pattern could be a result of a gradient in the distribution of endogenous factors involved in inflorescence differentialtion (possibly GAs) and in floral stem growth. This gradient along the tuber and shoot axes is probably controlled by apical dominance of the primary bud. Online publication: 7 April 2005     

Enhanced post-germinative growth of encapsulated somatic embryos of Siberian ginseng by carbohydrate addition to the encapsulation matrix

Based on a protocol for microspore culture in apple (Malus domestica Borkh.), the embryo induction phase has been improved with regard to pretreatment of microspores for initiation of microspore embryogenesis, the concentration of carbon source in the induction medium and the microspore density in the suspension. Furthermore, the effect of the genotype was studied. To determine the efficiency of in vitro androgenesis, both methods, via anther and microspore culture, were investigated using the same bud material. A comparison of the efficiency of embryo induction in anther and microspore cultures showed that microspore culture resulted in an increase up to 10 times, depending on the genotype. The regeneration route in microspore culture is similar to that of androgenic embryos via anther culture and showed adventitious shoot formation in most cases after a long period of secondary embryogenesis.Communicated by H. Lörz     

NODE COUNTING IN AXILLARY BUDS OF NICOTIANA TABACUM CV. WISCONSIN 38, A DAY-NEUTRAL PLANT

A mature, quiescent, primary axillary bud on the main axis of a flowering Nicotiana tabacum cv. Wisconsin 38 plant, when released from apical dominance and before forming its terminal flower, produced a number of nodes which was dependent upon its position on the main axis. Each bud produced about one more node than the next bud above it. The total number of nodes produced by an axillary bud was about 6 to 8 greater than the number of nodes present above this bud on the main axis. At anthesis of the terminal flower on the main axis, mature, quiescent, primary axillary buds had initiated 7 to 9 leaf primordia while secondary axillary buds, sometimes present in addition to the primary ones, had initiated 4 to 5 leaf primordia. When permitted to grow out independently, primary and secondary axillary buds located at the same node on the main axis produced the same number of nodes before forming their terminal flowers. In contrast, immature primary axillary buds which had produced only 5 leaf primordia and which were released from apical dominance prior to the formation of flowers on the main axis produced only as many nodes as would be produced above them on the main axis by the terminal meristem, i.e., “extra” nodes were not produced. Therefore, it is the physiological status of the plant and not the number of nodes on the bud at the time of release from apical dominance that influenced the node-counting process of a bud. When two axillary buds were permitted to develop on the same main axis, each produced the same number of nodes as single axillary buds developing at these nodes. Thus, the counting process in an axillary bud of tobacco is independent of other buds. Axillary buds on main axes of plants that had been placed horizontally produced the same number of nodes as identically-positioned axillary buds on vertical plants, indicating that gravity does not play a major role in the counting, by an axillary bud, of the nodes on the main axis.     

Adventitious Bud Formation from Mature Embryos of Picea chihuahuana Martinez, an Endangered Mexican Spruce Tree

Zygotic embryos of Picea chihuahuana Martínez were cultivatedin vitro to determine the time of organogenic competence andto maximize adventitious bud induction. The induction mediumconsisted of modified B5 substrate supplemented with N⁶-benzyladenine(with or without naphthalene acetic acid) or kinetin (with orwithout 2-4, dichlorophenoxyacetic acid) at different concentrationsand induction times. The minimum induction time required forbud formation was 14 d with kinetin and 17 d with N⁶-benzyladenine.After induction embryos were transferred to the proliferationmedium (modified B5 substrate with 50% of its components andwithout growth regulators) for 30 d. The subsequent buds weretransferred every 15 d to Schenk and Hildebrandt medium at halfits concentration without growth regulators. The most effectivetreatments were 3 and 5 mg l^-1kinetin or N⁶-benzyladenine whichproduced five to seven buds per embryo. The largest shoots weresubjected to rooting trials with pulses of different concentrationsof indole butyric acid resulting in only one bud developinga root. Histological analysis revealed clusters of three tofour cells that became more evident as induction time increased.Kinetin promoted the development of an organized structure priorto adventitious buds formation sooner than N⁶-benzyladenine.Copyright 2000 Annals of Botany Company Competence, plant tissue culture, micropropagation, Picea chihuahuana, endangered species, spruce     

Lateral Bud Growth in Phaseolus vulgaris L. and the Levels of Ethylene in the Bud and Adjacent Tissue

Ethephon and the ethylene inhibitors Ag⁺ and aminoethoxyvinylglycine (AVG) inhibited outgrowth of the axillary bud of thefirst trifoliate leaf in decapitated plants of Phaseolus vulgaris.Endogenous ethylene levels decreased in the stem upon decapitationalthough it is not conclusive that a causal relationship existsbetween this decrease and the release of axillary buds frominhibition. The proposition that auxin-induced ethylene is responsiblefor the suppression of axillary bud growth in the decapitatedplant when the apical shoot is replaced by auxin is not borneout in this study. Application of IAA directly to the axillarybud of intact plants gave rise to a transient increase in budgrowth. This growth increment was annulled when AVG was suppliedwith IAA to the bud despite the fact that the dosage of AVGused did not affect the normal slow growth rate of the bud ofthe intact plant or bud outgrowth resulting from shoot decapitation.     

Endorhythmic development in Choisya ternata Kunth (Rutaceae), with a further elucidation of lammas shoots, as well as sylleptic and proleptic shoots

Most apical resting buds of Choisya tenata include inflorescence buds in the axils of their lower consecutive paired scales. These inflorescences develop as apical buds which burst in spring. The whole of the lateral inflorescence system on a shoot originating from an apical bud may be viewed as a single, proliferous inflorescence. After the spring flush there are usually two other flushes of the same shoot within the same season, each of which may be accompanied by the development of lateral inflorescences as in the spring flush. Each further flush produces an apical 'lammas shoot'. As an apical lammas shoot elongates, lateral lammas shoots may also develop from upper, previously resting, axillary buds on the underlying stem segment of the preceding flush. Lateral inflorescences on apical lammas shoots arise from axillary buds preformed within the briefly-dormant apical buds terminating the preceding flush. These inflorescences, as well as the spring ones, represent proleptic shoots. The production of resting apical buds between two intra-season flushes of a shoot may be fugacous, without the differentiation of perfect bud-scales, and with curtailmenl ol internode elongation. As no environmental influence seems to be responsible for intra-season rhythmicity in development, this is said to be endorhythmic. The interrelations of proleptic to sylleptic shoots are discussed.     

Tiller Bud Suppression in Reproductive Plants of Lolium multiflorum Lam. Cv. Westerwoldicum

The control of tiller bud growth during reproductive developmentwas investigated in experimental plants ofLolium multiflorumLam. cv. Westerwoldicum that were reduced to a main axis havinga developing but unemerged ear, elongating stem internodes,a series of expanded leaves, slow-growing tiller buds and aroot system. Isolation of the ear by excision of its base, ordecapitation so as to remove the ear together with the upperleaves, promoted the movement of ¹⁴C-assimilates to tiller buds,decapitation being the more effective treatment. Applicationof 0.1 per cent indol–3yl-acetic acid (IAA) to cut tissuesof decapitated plants diverted ¹⁴C-assimilates to upper internodesbut did not reduce import by buds, whereas application of 1.0per cent IAA both diverted labelled assimilates to upper internodesand reduced bud import. Radioactivity from [¹⁴C] IAA appliedto the upper leaves or to the ear base was recovered from budsin very small amounts; larger amounts were recovered from budsfollowing the application of labelled IAA to an elongating internode,especially from the bud at the base of the treated internode.It is suggested that tiller bud suppression may be influencedby the movement of inhibitory levels of auxin into buds fromnearby elongating stem internodes, whose activity in turn maybe controlled by the developing inflorescence and upper leaves.     

Effect of plant growth substances on the growth of axillary buds in cultured stem segments of Phaseolus vulgaris L.

The hormonal control of axillary bud growth was investigated in cultured stem segments of Phaseolus vulgaris L. When the stem explants were excised and implanted with their apical end in a solid nutrient medium, outgrowth of the axillary buds-located at the midline of the segment-was induced. However, if indoleacetic acid (IAA) or naphthaleneacetic acid (NAA) was included in the medium, bud growth was inhibited. The exposure of the apical end to IAA also caused bud abscission and prevented the appearance of new lateral buds.In contrast to apically inserted segments, those implanted in the control medium with their basal end showed much less bud growth. In these segments, the auxin added to the medium either had no effect or caused a slight stimulation of bud growth.The IAA transport inhibitor N-1-naphthylphthalamic acid (NPA) relieved bud growth inhibition by IAA. This suggests that the effect of IAA applied at the apical end requires the transport of IAA itself rather than a second factor. With the apical end of the segment inserted into the IAA-containing medium, simultaneous basal application of IAA relieved to some extent the inhibitory effect of the apical IAA treatment. These results, together with data presented in a related article [Lim R and Tamas I (1989) Plant Growth Regul 8: 151–164], show that the polarity of IAA transport is a critical factor in the control of axillary bud growth.Of the IAA conjugates tested for their effect on axillary bud growth, indoleacetyl alanine, indoleacetic acid ethyl ester, indoleacetyl-myo-inositol and indoleacetyl glucopyranose were strongly inhibitory when they were applied to the apical end of the stem explants. There was a modest reduction of growth by indoleacetyl glycine and indoleacetyl phenylalanine. Indoleacetyl aspartic acid and indoleglyoxylic acid had no effect.In addition to IAA and its conjugates, a number of other plant growth substances also affected axillary bud growth when applied to the apical end of stem segments. Myo-inositol caused some increase in the rate of growth, but it slightly enhanced the inhibitory effect of IAA when the two substances were added together. Gibberellic acid (GA₃) caused some stimulation of bud growth when the explants were from younger, rather than older plants. The presence of abscisic acid (ABA) in the medium had no effect on axillary bud growth. Both kinetin and zeatin caused some inhibition of axillary buds from younger plants but had the opposite effect on buds from older ones. Kinetin also enhanced the inhibitory effect of IAA when the two were applied together.In conclusion, axillary buds of cultured stem segments showed great sensitivity to auxins and certain other substances. Their growth responded to polarity effects and the interaction among different substances. Therefore, the use of cultured stem segments seems to offer a convenient, sensitive and versatile test system for the study of axillary bud growth regulation.     

花楸腋芽增殖途径快繁技术研究

选用花楸茎节为外植体进行组培腋芽增殖途径研究,结果表明：利于花楸生长的最适宜基本培养基为MS培养基;芽诱导培养基为1/2MS+6-BA 2.5 mg·L^-1+2.4-D 0.5 mg·L^-1;增殖培养基为MS+6-BA（1.600~2.100）mg·L^-1+NAA（0.140~0.230） mg·L^-1,平均繁殖系数达到13倍以上;继代壮苗培养的最佳培养基为MS+6-BA 0.2 mg·L^-1+IBA 0.2 mg·L^-1;在1/2MS+IBA 0.3 mg·L^-1培养基上,平均生根数为5.96,生根率达90.20%。将生根后的组培苗移栽至腐殖土：泥炭土：河沙（比例为3：2：1）的基质中,成活率达95.55%。     

Development of shoot inHydrangea macrophylla I. Terminal and axillary buds

The structure of shoots, in particular of winter buds, ofHydrangea macrophylla was examined. The non-flower-bearing shoot is usually composed of a lower and an upper part, between which a boundary is discernible by means of a distinctly short internode. This internode is the lowermost of the upper part, and it is usually shorter than the internodes immediately above and below, although the internodes tend to shorten successively from the proximal to the distal part of the shoot. Variations exist in the following characters among the terminal bud, the axillary bud on the lower part of the shoot and the axillary bud on the upper part: (1) length of bud; (2) character of the outermost pair of leaf primordia; (3) degree of development of secondary buds in the winter bud; and (4) the number of leaf primordia. Usually, the terminal bud contains several pairs of foliage leaf primordia with a primordial inflorescence at the terminal of the bud, but the axiallary bud contains only the primordia of foliage leaves in addition to a pair of bud scales.     

Development and Growth Potential of Axillary Buds in Roses as Affected by Bud Age

The effect of axillary bud age on the development and potentialfor growth of the bud into a shoot was studied in roses. Ageof the buds occupying a similar position on the plant variedfrom 'subtending leaf just unfolded' up to 1 year later. Withincreasing age of the axillary bud its dry mass, dry-matterpercentage and number of leaves, including leaf primordia, increased.The apical meristem of the axillary bud remained vegetativeas long as subjected to apical dominance, even for 1 year. The potential for growth of buds was studied either by pruningthe parent shoot above the bud, by grafting the bud or by culturingthe bud in vitro. When the correlative inhibition (i.e. dominationof the apical region over the axillary buds) was released, additionalleaves and eventually a flower formed. The number of additionalleaves decreased with increasing bud age and became more orless constant for axillary buds of shoots beyond the harvestablestage, while the total number of leaves preceding the flowerincreased. An increase in bud age was reflected in a greaternumber of scales, including transitional leaves, and in a greaternumber of non-elongated internodes of the subsequent shoot.Time until bud break slightly decreased with increasing budage; it was long, relatively, for 1 year old buds, when theysprouted attached to the parent shoot. Shoot length, mass andleaf area were not clearly affected by the age of the bud thatdeveloped into the shoot. With increasing bud age the numberof pith cells in the subsequent shoot increased, indicatinga greater potential diameter of the shoot. However, final diameterwas dependent on the assimilate supply after bud break. Axillarybuds obviously need a certain developmental stage to be ableto break. When released from correlative inhibition at an earlierstage, increased leaf initiation occurs before bud break.Copyright1994, 1999 Academic Press Age, axillary bud, cell number, cell size, pith, shoot growth, Rosa hybrida, rose     

Isolated microspore culture of Chinese flowering cabbage (Brassica campestris ssp. parachinensis)

Microspores of several genotypes of Brassica campestris ssp. parachinensis have been cultured in vitro and induced to undergo embryogenesis and plant formation. Conditions favourable for embryogenesis in this species include a bud size of 2–2.9 mm, NLN-13 culture medium (Nitsch and Nitsch 1967; Lichter 1981, 1982; Swanson 1990), and an induction through exposure to 32°C for a period of 48 h. Longer periods of an elevated temperature for induction of embryogenesis resulted in embryo abortion at early developmental stages. With the protocol developed here, microspores of 60–80% of donor plants could be induced to produce embryos, although embryo yields were low, i.e. 2–5 embryos per 10 buds. Some genotypes responded to culture conditions with high numbers of embryo formation (100–150 embryos per 10 buds) but most of these subsequently failed to mature. The pattern of cell division and morphological changes of the microspores in culture were studied using various microscopic techniques.     

Micropropagation of chinese redbud (<Emphasis Type="Italic">Cercis yunnanensis</Emphasis>) through axillary bud breaking and induction of adventitious shoots from leaf pieces

Summary Factors affecting in vitro shoot production and regeneration of Cercis yunnanensis Hu et Cheng were investigated by comparing various growth regulators and explant types. For optimum shoot production from axillary buds, Murashige and Skoog (MS) media containing 6-benzyladenine, either alone or in combination with a low concentration of thidiazuron, resulted in the greatest number of shoots formed per explant (>3). Explants (2 mm long) containing one axillary bud placed in directcontact with the medium yielded the most shoots per bud (1.6) when grown on growth regulator-free medium. Root formation on 70–80% of shoot explants was accomplished using either indole-3-butyric acid or α-naphthaleneacetic acid in the medium, with significantly more roots formed on explants possessing and apical bud than those without the bud. Direct shoot organogenesis from leaf explants occurred on MS medium containing 10–30 μM thidiazuron, with up to 42% of leaf explants producing shoots.