Control of Morphogenesis in Sorghum by 2,4-Dichlorophenoxyacetic Acid and Cytokinins

2, 4-Dichlorophenoxyacetic acid caused a shortening of rootsand shoots when mature seeds of Sorghum bicolor (L.) Moenchcv. BT3197 were germinated on Murashige and Skoog (MS) mediumthat contained 2,4-D. Shoot growth was restored with cytokinins.A callus formed at the nodal region, the further differentiationof which was determined by the ratio of 2,4-D and cytokininsin the initial culture medium. A high auxin to cytokinin ratiopromoted primarily root differentiation while a high cytokininto auxin ratio promoted multiple bud development. Isolated shootapical meristem with the subtending node produced embryogeniccallus at low cytokinin levels and green buds on high cytokininlevels when cultured in the presence of 2,4-D. It is concludedthat cells potentially capable of differentiation into roots,somatic embryos or axillary buds are present in the first nodalregion. Sorghum bicolor, organogenesis, embryogenesis, 2, 4-D: cytokinin ratios, tissue culture     

Explant Orientation and Polarity Determine the Morphogenic Response of Epicotyl Segments of Troyer Citrange

The morphogenic pathway of adventitious bud and shoot regenerationat the ends of Troyer citrange epicotyl cuttings is determinedby polarity and explant orientation. In explants planted verticallywith the basal end inserted in the medium, bud formation atthe apical end occurs by direct organogenesis. Bud growth andsubsequent shoot formation is markedly increased by the additionof 6-benzyladenine (BA) to the medium. This growth regulatoralso increases the number of buds formed. When they come intocontact with the culture medium, both the apical end and thebasal end of the cuttings form a vigorous callus with many xyllaryelements, more numerous in the calli from the basal end. Inthese calli, buds differentiate by a process of indirect organogenesis.This indirect regeneration pathway requires the addition of6-benzyladenine to the medium, and the number of buds formedis higher at the apical end than at the basal end of the cuttings.This pathway of regeneration is reduced as the position of thecuttings during incubation deviates from the normal uprightvertical position. Thus, for the basal end of the cuttings,the number of buds and shoots formed is higher when the explantsare placed vertically than when they lie on the surface of themedium. For the apical end, this number is higher in explantsplaced horizontally than when inserted vertically in the mediumin an inverted position. Copyright 1999 Annals of Botany Company Troyer citrange, Citrus sinensis x Poncirus trifoliata, explant orientation, histology, hormone dependence, morphogenesis, organogenesis, polarity, xylogenesis.     

Development of Chrysanthemum Cuttings: The Influence of Age and Position of the Axillary Buds

In three experiments (twoin-vivo, onein-vitro), an attempt wasmade to separate the possible effects of age and position ofaxillary buds of chrysanthemum on bud outgrowth and the subsequentquality of cuttings. In thein-vivoexperiments, bud age and bud position were notsignificant factors in bud outgrowth and subsequent qualityof cuttings. Nevertheless, most outgrowth parameters showedslightly higher values for the lower positioned buds and thetime needed to produce a cutting tended to decrease with theage of the axillary bud. In thein-vitroexperiment, the relationship between age and thevarious parameters showed an optimum. axillary bud; Chrysanthemum morifolium; Dendranthema grandiflora; Age; cutting; chrysanthemum; position     

东北草地异质生境芦苇种群根茎芽年龄结构及输出规律

为明确异质生境条件下芦苇种群根茎芽年龄结构及输出规律,揭示芦苇种群的营养繁殖特性,采用单位土体挖掘取样,分别计数各龄级根茎芽的调查与统计方法,对东北草甸草原草甸土和盐碱土两个生境单优群落芦苇种群根茎芽动态进行比较分析。结果表明,两个生境芦苇种群根茎芽库主要均由6个龄级组成;草甸土生境在6—10月均为增长型年龄结构;盐碱土生境6—7月份为衰退型年龄结构,8月份为稳定型年龄结构,9—10月份为增长型年龄结构。根茎芽数量1—4a普遍以草甸土生境高于盐碱土生境,5—6a普遍以盐碱土生境高于草甸土生境,各龄级根茎芽数量与月份之间均符合y=a+bx直线关系(P0.05)。随着龄级的增加,休眠芽比率呈逐渐下降趋势,而萌发芽比率则呈逐渐上升趋势,5个生育期的休眠芽比率和萌发芽比率与龄级之间均符合y=a+bx直线关系(P0.01)。各龄级根茎的休眠芽具有一个相对稳定的萌发输出过程,草甸土生境根茎休眠芽按每年11%的比率萌发输出,而盐碱土生境根茎休眠芽按每年7%的比率萌发输出。虽然芦苇种群根茎芽年龄结构及年龄谱在异质生境中存在显著差异,但却有着相同的季节变化规律,均以不断形成新根茎的芽来维持着种群的营养繁殖更新。     

In Vitro Plantlet Formation in Mangosteen (Garcinia mangostana L.)

Optimum conditions were determined for in vivo growth and multiplicationof Garcinia mangostana L. using explants from aseptically germinatedseedlings and field-grown plants. Proliferating shoots wereobtained from cotyledon segments cultured on modified Murashigeand Skoog's (1962) medium with 6-benzylaminopurine. Juvenileleaf segments produced adventitious buds on Woody Plant Medium(Lloyd and McCown, 1981). Root segments gave few buds. Shoottip, nodal, and internodal explants gave multiple axillary andadventitious buds. Shoots were multiplied by enhanced axillaryand adventitious bud formation. The shoots were rooted withindolebutyric acid treatment. Rooted shoots were readily establishedin vermiculite: sand (1:1) mixture. Garcinia mangostana L., Mangosteen, tissue culture, shoot regeneration, bud development     

Influence of Bud Position and Plant Ontogeny on the Morphology of Branch Shoots in Pea (Pisum sativum L. cv. Alaska)

The morphology of axillary shoots of pea plants (Pisum sativumL. cv. Alaska) was analysed as a function of the position ofthe bud on the plant axis and the stage of plant developmentwhen the buds began to grow. Buds from the three most basalnodes were stimulated to develop by decapitating the main shootwhen buds were still growing (4 d plants), shortly after budsbecame dormant (7 d plants) or after the initiation of floweringon the main shoot (post-flowering plants, about 21 d after sowing).Branch shoots were scored for node of floral initiation (NFI),shoot length, and node of multiple leaflets (NML), a measureof leaf complexity. Shoots that developed spontaneously fromupper nodes (nodes 5-9) on intact post-flowering plants werescored for NFI. NFI for basal buds on 4 and 7 d plants variedas a function of nodal position and ranged from 5 to 6·7nodes. NFI on these plants was not influenced by bud size orwhether a bud was growing or dormant when the plant was decapitated.NFI for shoots derived from basal buds on decapitated post-floweringplants and upper nodes on intact post-flowering plants was about4. Reduced NFI on post-flowering plants may be due to depletionof a cotyledon-derived floral inhibitor. Basal axillary shootson 4 d plants were about 20% longer than those on 7 d plantsand about five times longer than those on post-flowering plants.These differences may be due to depletion of gibberellic acidsfrom the cotyledons. NFI and NML for the main shoot and forbasal axillary shoots were similar under some experimental conditionsbut different under other conditions, so it is likely that eachdevelopmental transition is regulated independently.Copyright1995, 1999 Academic Press Apical dominance, bud development, garden pea, initiation of flowering, Pisum sativum L., shoot morphology     

Basipetal Gradient of Axillary Bud Inhibition Along a Rose (Rosa hybridaL.) Stem: Growth Potential of Primary Buds and their Two Most Basal Secondary Buds as Affected by Position and Age

InRosa hybridaL. cv. Ruidriko ‘Vivaldi’®, theeffect of position on growth and development potentials of axillarybuds was investigated by single internode cuttings excised alongthe floral stem and its bearing shoot. The experiments werecarried out in both glasshouses and in a phytotron. The studyfirstly concerned the development of the primary shoot fromthe onset of bud growth until anthesis. The primary shoot wasthen bent horizontally to promote the growth of the two mostproximal secondary buds, the collateral buds, already differentiatedinside the primary bud. They gave rise to basal shoots. In thebasipetal direction, the axillary buds along the floral stemexhibited both an increase in the lag time before bud growthand a decrease in bud growth percentage, demonstrating the existenceof a physiological basipetal gradient of inhibition intrinsicto the buds or due to short range correlations. The same basipetalgradient of inhibition was observed along the floral stem andits bearing shoot, demonstrating that the age of the bud wasnot a major factor in determining the rate of bud growth. Afterbending the primary shoot, the percentage of collateral budgrowth was also affected by the cutting position. The more proximalthe cutting, the lower the sprouting ability of collateral buds.The growth potential of these buds appeared to be already determinedinside the main bud before cutting excision.Copyright 1998 Annalsof Botany Company Axillary bud; basal shoot; cutting; development; endodormancy; growth; paradormancy; position; primary shoot;Rosa hybridaL.; rose; secondary bud; topophysis.     

Bud Structure in Relation to Shoot Morphology and Position on the Vegetative Annual Shoots of Juglans regia L. (Juglandaceae)

The length and basal diameter of all lateral and terminal budsof vegetative annual shoots of 7-year-oldJuglans regia treeswere measured. All buds were dissected and numbers of cataphylls,embryonic leaves and leaf primordia were recorded. Each axillarybud was ranked according to the position of its associated leaffrom the apex to the base of its parent shoot. Bud size andcontent were analysed in relation to bud position and were comparedwith the size and number of leaves of shoots in equivalent positionswhich extended during the following growing season. Length andbasal diameter of axillary buds varied according to their positionon the parent shoot. Terminal buds contained more embryonicleaves than any axillary bud. The number of leaves was smallerfor apical and basal axillary buds than for buds in intermediatepositions on the parent shoot only. All new extended shootswere entirely preformed in the buds that gave rise to them.Lateral shoots were formed in the median part of the parentshoot. These lateral shoots derived from buds which were largerthan both apical and basal ones. Copyright 2001 Annals of BotanyCompany Juglans regia L., Persian walnut tree, branching pattern, preformation, bud content, shoot morphology     

Polarity in Adventitious Bud Formation on Excised Leaves of Heloniopsis orientalis (Liliaceae)

The position of adventitious bud formation on isolated leavesfrom young, green and etiolated plants of Heloniopsis orientaliswas considerably influenced by their orientation on the medium.Homogeneous distribution of buds over the whole surface of theleaves was observed in darkness, however, irrespective of theirorientation. The polarity of the bud regeneration was influencedby the application of various growth regulators, such as fusicoccin,cytokinins or abscisic acid. All attempts to induce the formationof adventitious buds on the abaxial side of the leaves wereunsuccessful. From the present and previous results, three polarityaxes (longitudinal, transverse and dorsiventral axes) in thesiting of bud formation on leaves are described. The gradientin the quantity and relative position of vascular bundles andchanges in the stomatal density of a leaf are discussed in termsof their possible roles in the determination of the sites ofbudding on isolated leaves. (Received March 9, 1981; Accepted August 28, 1981)     

ORIGIN AND EARLY MORPHOGENESIS OF LATERAL BUDS IN THE FERN DAVALLIA

The general organography, vascular organization, and leaf and bud development in Davallia solida and D. trichomanoides are described. These epiphytic species have creeping shoots with dorsally-borne leaves in a distichous phyllotaxis and the buds occur near each leaf base. Roots are borne on the ventral and flanking surfaces of the rhizome, but only at bud positions. The vascular pattern of these species is a perforated solenostele. Leaf and bud traces have distinctly different origins. While the proximity of buds to leaves has suggested that bud origin is axillary, observations show that the origin of buds is cauline and that their position is extra-axillary from inception. The stages of structural morphogenesis in Davallia buds differ significantly from the scheme proposed by Wardlaw. The principal difference is the absence of a resting period occurring between the origin and continued development of buds in Davallia. The elongated internodes which separate leaf-bud pairs from one another, the topographically distinct and predictable positions of leaves and buds, the structural equivalence of unexpanded buds, and vascular differences in leaves and buds make Davallia an useful species for physiological studies of differential bud expansion.     

CONTROL OF SHOOT-RHIZOME DIMORPHISM IN THE WOODY MONOCOTYLEDON,CORDYLINE (AGAVACEAE)

In Cordyline terminalis negatively geotropic leafy shoots and positively geotropic rhizomes develop from single axillary buds on either shoots or rhizomes. All axillary buds have similar morphogenetic potential when released from apical dominance. Experiments in which the orientation of the apex is changed, organs removed, or growth regulators applied indicate that after a rhizome is initiated, it is maintained as a rhizome by auxin originating in the leafy shoot. When auxin levels are lowered by changes in the orientation of the axis or shoot removal, the rhizome apex becomes a shoot apex, which appears to be the stable state of the actively growing apex. Benzyl adenine when applied exogenously to the apex or lateral buds has the same effect as lowering the auxin level. Gibberellic acid has no effect on the apex or lateral buds. High levels of exogenous naphthaleneacetic acid cause bud release and development of rhizomes from previously inhibited axillary buds of the shoot. However, it was not possible to convert a shoot apex into a rhizome apex by auxin treatment. It is suggested that the release of buds on the lower side of horizontal branches and of buds directly above a stem girdle is caused by high auxin levels on the lower side or distal to the girdle. The experimental results are discussed in relation to naturally occurring shoot-rhizome dimorphism.     

The Dormancy of Buds of Citrus sinensis (L.) Osbeck Inserted into Rootstock Stems: Factors Intrinsic to the Inserted Bud

Buds of sweet orange, harvested from shoots of different timeof flushing and from different positions along the shoot, wereused to examine whether lack of burst of inserted buds was acharacteristic of the bud. Bursting of inserted buds was significantlyslower in buds taken from (a) older branches (b) shoots producedunder winter conditions, and (c) basal rather than apical budson the same shoot. The slowness to burst when transferred matched a tendency todormancy in buds on shoot segments grown in vitro, suggestingthat the variation in budburst was intrinsic to the bud. Budburstwas correlated with the extent of secondary bud development;the majority of buds from apical regions of the shoot had developeda secondary bud by the time of implantation, but basal budshad not. Adequate vascular connections with the host tissueswere found in both burst and unburst buds. Citrus sinensis (L.) Osbeck, sweet orange, buds, endodormancy, budding     

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     

Regulation of Branching in Decussate Species with Unequal Lateral Buds

In the decussate plants Alternanthera philoxeroides and Hygrophilasp. the opposite axillary bud primordia are of unequal sizefrom the time of their inception; the larger or + buds lie alongone helix and the smaller or – buds along another (helicoidalsystem). In decapitated plants of Alternanthera both buds grewout, but unequally; if the node was vertically split growthof the two shoots was more equal, and if the + buds were excisedgrowth of the – shoots approximately equalled that ofcontrol + shoots. In decapitated shoots of Hygrophila grownin sterile culture only one bud, the + or larger one, grew outat each of the upper nodes. In excised cultured nodes, also,only the + bud grew out; but if the nodes were split longitudinallyboth buds grew out, initially rather unequally. These experimentssupport the view that the regulation of branching in these specieshas two components, apical dominance and the dominance of thelarger (+) bud over the smaller (–) bud at the same node.The restriction of growth potentiality imposed on the –bud is not permanent but can be modified. Further correlativeeffects on bud outgrowth include those of the subtending leavesand of buds at other nodes.     

Development of Axillary and Leaf-opposed Buds in Rattan Palms

Axillary vegetative buds are present in Calamus, Ceratolobus,and Plectocomiopsis. Two species of Daemonorops Sect. Piptospathaalso have axillary vegetative buds. All species of Daemonoropshave only displaced adnate axillary inflorescence buds. A singlebud is initiated in the axil of the first or second leaf primordiumin a way similar to that for axillary inflorescence buds. Themeristem is displaced during development on to the internodeabove and sometimes on to the base of the leaf above. Leaf-opposedvegetative buds occur in five species of Daemonorops Sect. Cymbospathaand in one species of Daemonorops Sect. Piptospatha. This typeof bud is initiated 180° away from the axil of the firstor second leaf primordium. It is not a displaced axillary bud,but does become adnate to the internode above like the axillarybuds. One or more leaves, transitional between juvenile andadult, on a shoot often subtend both types of buds. Myrialepishas leaf-opposed vegetative buds, but their development wasnot observed. Korthalsia has buds that are displaced about 130°from the leaf axil and are intermediate between the axillaryand the leaf-opposed condition. Other forms of vegetative budsare described: multiple buds in Plectocomia, aerial forkingin Korthalsia, and suckering from inflorescences and from aerialstems in Calamus. bud development, rattan palms, palm taxonomy, branching     

Effect of Assimilate Supply on Development and Growth Potential of Axillary Buds in Roses

The effect of assimilate supply on axillary bud developmentand subsequent shoot growth was investigated in roses. Differencesin assimilate supply were imposed by differential defoliation.Fresh and dry mass of axillary buds increased with increasedassimilate supply. The growth potential of buds was studiedeither by pruning the parent shoot above the bud, by graftingthe bud or by culturing the bud in vitro. Time until bud breakwas not clearly affected by assimilate supply during bud development,Increase in assimilate supply slightly increased the numberof leaves and leaf primordia in the bud; the number of leavespreceding the flower on the shoot grown from the axillary budsubstantially increased. No difference was found in the numberof leaves preceding the flower on shoots grown from buds attachedto the parent shoot and those from buds grafted on a cutting,indicating that at the moment of release from inhibition thebud meristem became determined to produce a specific numberof leaves and to develop into a flower. Assimilate supply duringaxillary bud development increased the number of pith cells,but the final size of the pith in the subsequent shoot was largelydetermined by cell enlargement, which was dependent on assimilatesupply during shoot growth. Shoot growth after release frominhibition was affected by assimilate supply during axillarybud development only when buds sprouted attached to the parentshoot, indicating that shoot growth is, to a major extent, dependenton the assimilate supply available while growth is taking place.Copyright1994, 1999 Academic Press Assimilate supply, axillary bud, cell number, cell size, defoliation, development, growth potential, meristem programming, pith, Rosa hybrida, rose, shoot growth     

Grafting Experiments on Correlative Effects between Lateral Buds

Shoots of Hygrophila sp., which are decussate and have budsof unequal size at a node, were grown in liquid culture. Inexcised nodes it is known that the larger (+) bud inhibits thesmaller (–) bud in the axil of the opposite leaf, andonly one shoot grows out; in nodes split longitudinally bothbuds grow out. When nodes were split and grafted together again(+/– grafts), in general only one bud grew out; if aluminiumfoil was introduced at the nodal region both buds grew out.Thus the inhibitory effect of a + on a – bud is laterallytransmissible across a graft union. In +/– grafts of half-nodesdiffering in age by two plastochrones, a higher proportion yieldedtwo shoots, suggesting that the age differential had some importance.This view is supported by observations on sectioned material.Grafts having two + or two – buds (+/+ grafts) were madebetween half-nodes differing in age by two plastochrones; inthe majority both buds grew out. Thus a + bud inhibits a –bud but usually not another + bud; in either case a considerabledifference in stage of development of the half-nodes may affectthe results. It is concluded that bud dominance resembles apicaldominance, and is probably mediated by hormonal means.     

Bud Content and its Relation to Shoot Size and Structure in Nothofagus pumilio(Poepp. et Endl.) Krasser (Nothofagaceae)

Buds of shoots from the trunk, main branches, secondary branchesand short branches of 10–21 year-old Nothofagus pumiliotrees were dissected and their contents recorded. The numberof differentiated nodes in buds was compared with the numberof nodes of sibling shoots developed at equivalent positionsduring the following growing season. Axillary buds generallyhad four cataphylls, irrespective of bud position in the tree,whereas terminal buds had up to two cataphylls. There were morenodes in terminal buds, and the most distal axillary buds, oftrunk shoots than in more proximal buds of trunk shoots, andin all buds of shoots at all other positions. The highest numberof nodes in the embryonic shoot of a bud varied between 15 and20. All shoots had proximal lateral buds containing an embryonicshoot with seven nodes, four with cataphylls and three withgreen leaf primordia. The largest trunk, and main branch, shootswere made up of a preformed portion and a neoformed portion;all other shoots were entirely preformed. In N. pumilio, theacropetally-increasing size of the sibling shoots derived froma particular parent shoot resulted from differences in: (1)the number of differentiated organs in the buds; (2) the probabilityof differentiation of additional organs during sibling shootextension; (3) sibling shoot length; (4) sibling shoot diameter;and (5) the death of the apex and the most distal leaves ofeach sibling shoot. Copyright 2000 Annals of Botany Company Axis differentiation, branching, bud structure, leaf primordia, neoformation, Nothofagus pumilio, preformation, size gradient     

Dwarfism Caused by Floral-Bud Removal in Petunia and its Reversal by Gibberellin

The effect of floral-bud removal at different stages of developmenton the plant height and on the total number of buds of Petuniawas studied. Continuous removal of all the floral buds 2 d beforeanthesis caused a marked decrease in plant height and also increasedthe total number of floral buds formed thereafter. At otherstages of floral bud development, bud removal had a lesser effecton both phenomena. Moreover, the plants did not respond to budremoval at anthesis. GA₃ at 25 ppm applied to plants from which the buds had beenremoved, promoted stem elongation. The most pronounced effectwas on plants from which the buds were removed 2 d before anthesis,but it had no effect on plants from which the buds were removedat anthesis stage. The possible involvement of endogenous growth hormones in theresponse of Petunia plants to floral-bud removal and to applicationof GA₃ is discussed. Bud removal, bud number, dwarfness, GA₃, Petunia, plant height     

Assessment of consumption,utilisation and growth of Oedaleus abruptus (Thunberg) and Spathosternum prasiniferum prasiniferum (Walker) (Orthoptera: Acrididae) fed with various food plants in laboratory conditions

Summary. Grasshoppers are serious pests of crops worldwide. In the present era of changing agricultural practices and uncertainty regarding the impacts of global climate change, the need to understand the nutritional ecology of grasshoppers is urgent. In the present study newly hatched nymphs of two multivoltine acridids, Spathosternum prasiniferum prasiniferum and Oedaleus abruptus, were fed with four food plants of the family Poaceae: Cynodon dactylon, Triticum aestivum, Sorghum halepense and Oryza sativa. Then their growth, adult life span, food consumption and utilisation were recorded. Sorghum halepense was found to be the most suitable food plant for S. pr. prasiniferum whereas for O. abruptus it was Triticum aestivum followed by Sorghum halepense in most cases. The results from the present study may help forecasting modellers to simulate a predictive model that may speculate future outbreaks, forage loss and its possible effects on the economy more efficiently.