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     

Correlative Inhibition of Lateral Bud Growth in Pisum sativum L. and Phaseolus vulgaris L.: Studies of the Role of Abscisic Acid

The possibility has been investigated that abscisic acid (ABA)might act as a correlative inhibitor of lateral bud growth inPisum sativum and Phaseolus vulgaris. Application of ABA insmall quantities (2µg) to axillary buds on decapitatedplants of P. sativum caused appreciable inhibition of theirgrowth, and induced a compensatory growth of the bud on an adjacentnode. Application of this same quantity of ABA to axillary budson decapitated plants of Phaseolus vulgaris was without effect,but a high concentration in lanolin (1 mg g^–1) did substantiallyreduce bud outgrowth. Endogenous ABA-like substances in Phaseolusvulgaris, detected by bioassay and electron capture g.l.c.,were present in similar concentrations in shoot tips, lateralbuds on intact plants and lateral buds on plants decapitated24 h earlier. The effects of applied ABA suggested that it might be involvedin the mechanism of correlative inhibition in Pisum sativum,but it was not possible to test this hypothesis by determiningendogenous ABA levels in axillary buds because of their smallsize. The evidence presented here suggests that ABA is not acorrelative inhibitor in Phaseolus vulgaris even though at highconcentration it can inhibit the growth of axillary buds.     

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     

Some Effects of Indol-3-ylacetic Acid on the Rates of Initiation and Development of Flower Buds of Chrysanthemum morifolium

Frequent applications of a solution containing 50 p.p.m. IAAto the upper leaves of Chrysanthemum plants reduced the numbersof open and opening flowers and delayed harvesting. The ratesof initiation and development of flower buds were studied bydissection in relation to the concentrations of indol-3-yl-aceticacid (IAA) (20–200 p.p.m.) applied to the tops of theplants. Inereasing the concentrations of IAA resulted in a progressivedelay in bud initiation (P<0•001), but had little effecton their subsequent rates of development. The results differedfrom those previously obtained with copper deficient plantsin that the latter deficiency affected both initiation and developmentof the buds.     

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.     

Factors Influencing the Distribution of Growth Between Stem and Axillary Buds in Decapitated Bean Plants

Phaseolus multiflorus plants at three stages of developmentwere decapitated either immediately below the apical bud orlower down at a point 1 cm above the insertion of the primaryleaves. Growth regulators in lanolin were applied to the cutstem surface. IAA always inhibited axillary bud elongation anddry-matter accumulation, and enhanced internode dry weight butnot elongation. GA₃ applied below the apical bud greatly increasedinternode elongation and dry weight, but simultaneously reducedbud elongation and dry-weight increase. Application of GA₃ 1cm above the buds had no effect on bud elongation in the youngestplants, but enhanced their elongation in the two older groups.IAA always antagonized GA₃-enhancement of internode extensiongrowth, whereas its effects on GA₃-enhanced dry-matter accumulationdepended on the stage of internode development. Bud elongationwas greater in plants treated with GA₃+IAA than in plants treatedonly with IAA, except in the youngest plants decapitated immediatelybelow the apical bud, where GA₃ caused a slight increase inIAA-induced bud inhibition. GA₃ increased inhibition of buddry weight by IAA in the two youngest groups of plants, butslightly reduced it in the oldest plants. No simple compensatorygrowth relationship existed between internode and buds. It wasconcluded that, (1) auxin appears to be the principal growthhormone concerned in correlative inhibition, and (2) availabilityof gibberellin to internode and buds is of importance as a modifyingfactor in auxin-regulated apical dominance by virtue of itslocal effects on growth in the internode and in the buds.     

Development of Oilseed Rape Buds, Flowers, and Pods In Vitro

A technique for growing buds, flowers, and pods of oilseed rape(Brassica napus L. cv. Haplona) on stem explants in vitro hasbeen developed. Open flowers and young pods underwent normaldevelopment on a basal medium of minerals, vitamins, and sucrosebut the development of buds was less successful. Young buds(3 mm long) did not develop and only limited development ofthe older buds (5 mm long) took place. Some 3 mm-long buds wereinduced to develop to open flowers by adding naphthyl aceticacid or gibberellic acid. Pod and seed set in open flowers werenot affected by adding plant growth substances to the medium,but pod elongation and pod dry weight were promoted by gibberellicacid, 105 M, and benzyl amino purine, 10⁷ M, respectively. Reducingthe supply of sucrose or minerals to open flowers reduced seedset, pod elongation and pod weight but did not affect pod set.The physiological significance of the results is discussed. Key words: In vitro cultures, oilseed rape, pod development, flower development     

Initial Anatomical Changes Associated with Tuber Formation on Single-node Potato (Solanum tuberosum L.) Cuttings: A Re-evaluation

Cell division and cell expansion during early stages of tuberdevelopment were studied using developing axillary buds on single-leafcuttings from potato (Solanum tuberosum L.). Cuttings takenfrom plants induced to form tubers, by short day (SD) treatment,were compared with cuttings from non-induced (long day, LD)plants. In the apical zone of the buds, cell division occurredfrom the first day after cutting, in both LD and SD cuttings.The planes of these divisions were transverse, associated withelongation of the buds. At day 5, a new orientation of celldivision was observed in the subapical zone of SD cuttings only.These divisions were longitudinal, associated with radial growth.Cell expansion occurred in both SD and LD cuttings, and wasnot uniquely related to the onset of tuber formation. Copyright1999 Annals of Botany Company Solanum tuberosum L., potato, tuber formation, cell division, cell expansion.     

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     

Effect of Severity of Defoliation on the Viability of Reproductive and Vegetative Axillary Buds of Trifolium repens L.

This glasshouse experiment was performed to assess the effectsof a range of constant defoliation regimes applied to cuttingsof a single large-leaved genotype ofTrifolium repens L. on theviability of its axillary buds. Plants were established to comprisea single main stolon (axillary branches were removed) and defoliationtreatments were applied by removing the older (basal) leavesuntil leaf complements of 1·0, 1·5, 2·0,2·5, 3·0 or all leaves (control) remained. Basalleaves were subsequently removed as necessary to maintain thetarget leaf complements. Only severe defoliation (leaf complements of 1·0 and1·5) induced a loss of viability in axillary buds. Lossof viability was greatest in reproductive buds present withinthe apical bud when the treatments were first imposed. Althoughthe most severe treatment (leaf complement 1·0) resultedin death of half the plants, in plants surviving that treatment,death of vegetative axillary buds was restricted to 21% of thevegetative buds at the three youngest node positions withinthe apical bud at the time of treatment application. No othertreatment induced any loss of viability of vegetative buds.There was no loss of viability of axillary buds at nodes formedafter the treatments were imposed. The frequency of initiationof inflorescences at nodes formed after treatments were imposeddecreased as defoliation severity increased. Severe defoliation resulted in marked changes in plant morphologyindicative of a sharp decrease in availability of intraplantresources. It was concluded that under severe defoliation: (1)the potential for vegetative growth (as represented by viablevegetative axillary buds) was maintained at the expense of reproductivegrowth; and (2) that the loss of viability of axillary budswas associated with the sudden changes in physiological processesinduced by defoliation as there was no loss of viability inbuds formed after plants had adjusted their phenotype to oneof smaller size. Trifolium repens L.; white clover; defoliation; axillary buds; viability; inflorescences     

The Rest Period of Rhododendron Flower Buds: II. STUDIES ON THE REST PERIOD IN TISSUE 3IN SITU

Shortly after the onset of rest in Rhododendron flower buds,the buds were transferred to a tissue-culture medium. The resultsreported here show that the rest period in culture was identicalto the rest period of buds in situ. In both environments theduration of rest and the frequnency distribution of elongationof the buds were the same. Histograms of bud development againsttime were bimodal, with about 20 per cent of the buds elongatingduring the second peak. In culture, the rest period was notaffected by changes in pH, temperature, or the addition of nutrientsalts. The results further show that the duration of the rest periodof each bud was independent of the time of the onset of rest.Buds that were supplied with either indol-3yl-acetic acid orgibberellic acid in culture or in situ remained in rest. Onlya low temperature treatment had a rest-breaking influence.     

Effect of Cutting During Reproductive Development on the Regrowth and Regenerative Capacity of the Perennial Grass, Phalaris aquatica L., in a Controlled Environment

Two cultivars of phalaris (Phalaris aquatica L.), Australianand Sirolan, were cut at four stages of development in a controlledenvironment to study factors involved in the sensitivity ofphalaris to grazing during spring. Effects on tillering, regrowthafter cutting and regenerative capacity after an artificiallyimposed summer dormant period were observed. Compared with Australian,Sirolan cut after the commencement of stem elongation was characterizedby a higher degree of decapitation due to more synchronous elevationof its apices, and displayed a more severe reduction in regrowth,size of tiller bases and dormant buds and levels of carbohydratereserves in summer relative to plants cut before stem elongation.Suppressed bud activity in tillers of Sirolan decapitated atearly stem elongation, and the potential for profuse tilleringassociated with low bud dormancy after cutting at the earlyboot stage, could reduce persistence under field conditions. Relative to plants cut before stem elongation, regenerationgrowth after 'summer' by plants cut during reproductive developmentwas depressed more severely for Sirolan (56-70%; P 0·05)than Australian (28%; n.s), a result more closely related toregenerating tiller size than number. Regeneration growth didnot differ significantly with stage reproductive developmentat cutting in either cultivar. Regenerative capacity of phalariscut during reproductive development can be considered to dependon an increasing contribution from buds on bases of tillersdecapitated when cut and a contribution from buds on intacttiller bases which declines as the stage of cutting becomeslater. The balance between these source will depend on the environment.Copyright1993, 1999 Academic Press Phalaris aquatica L., phalaris, regrowth, persistence, defoliation, cutting, perennial grass, tillering     

Floral initiation of Pharbitis nil, a short-day plant, under continuous high-intensity light

Pharbitis nil, a short-day plant, initiated floral buds undercontinuous illumination at 23°C, provided that the lightintensity was kept at 16,000 lux or above. Stem elongation ofthe plants was strongly inhibited but leaves developed normallyunder this condition. (Received November 26, 1971; )     

Inhibition of Flower Induction by Some Inhibitors of Protease in the Short-day Plant Lemna paucicostata 6746 and the Long-day Plant Lemna gibba G3

Four inhibitors of proteases, namely, bestatin, diisopropylfluorophosphate, elastatinal and p-toluenesulfonyl-L-lysinechloromethyl ketone hydrochloride, were examined for their effectson flowering of a short-day plant Lemna paucicostata 6746 anda long-day plant Lemna gibba G3. Each of the inhibitors greatlyinhibited the flowering of Lemna paucicostata 6746 that is normallyinduced by nitrogen deficiency. Bestatin or elastatinal givenonly during the first half of the culture period inhibited theflowering more clearly than when each was given during the latterhalf, suggesting that they inhibited the inductive process(es)involved in flowering rather than development of flower buds.Bestatin or elastatinal greatly inhibited the flowering of Lemnapaucicostata 6746 induced by photoperiodic stimulus, ferricyanideand continuous far-red light. Simultaneous application of thesetwo inhibitors was more effective in the inhibition of photoperiodicallyinduced and ferricyanide-induced flowering than was each inhibitoralone. They also completely inhibited the photoperiodic floweringof Lemna gibba G3. These results suggest that the inductionor activation of some proteases, probably followed by the degradationof some protein(s), is necessary for the induction of floweringin both these plants. (Received November 21, 1989; Accepted February 19, 1990)     

Flowering in Pisum: A Fifth Locus, Veg

In addition to the known loci, If, e, sn and hr, a fifth locus,veg, is shown to control flowering in peas. Regardless of thegenotype for the other flowering genes, plants homozygous forthe gene veg did not initiate flower buds under a wide rangeof photoperiod and temperature regimes, including those normallyhighly promotory in peas. Treatment with various plant growthsubstances and grafting to stocks known to promote floweringalso failed to cause initiation. Gene veg prevented expressionof allelic differences at the If locus but segregation for allelesat the sn and hr loci was clearly visible by examination ofseveral vegetative characteristics. For example, sn hr veg andSn hr veg plants showed an opening of the apical bud, productionof lateral branches, and a reduction in growth rate, leafletsize, internode length and stem thickness at approx the sametime as sn hr Veg and Sn hr Veg plants carrying the Lf allelecommenced fruit production, respectively. The graft-transmissibleinhibitor controlled by gene Sn is therefore not specific forthe transition from vegetative to reproductive growth. Geneveg allows the processes leading to apical and foliar senescenceto be examined independently of any effect of flowering andfruiting. We found that gene Sn influenced the total numberof leaves expanded in veg plants but not the time of shoot senescence,which, in plants without flowers and fruits appeared to resultfrom failure of the root system. Pisum sativum L., garden pea, flowering, senescence, genetics     

Histoautoradiographic analysis of the thermoinductive processes in the shoot apex of Arabidopsis thaliana L. Heynh, vernalized at different stages of development

The cytochemical reactions of various zones of the shoot apexof an annual winter plant (Arabidopsis thaliana), vernalizedat two different ages (26 and 85 days), were analyzed usinghistoautoradiography after incorporation of tritiated thymidine.The following sequence of events was observed during a coldtreatment of 40 days: subapical activation (in DNA synthesis)of the rib meristem (this took place regardless of the age ofthe plants; dedifferentiation of axial cells (the beginningof which was earlier in the older plants). After cold treatment, the plants were resubmitted to warm temperaturesunder long day conditions. A re-establishment of the zonationin the meristem was seen during the first week for plants inthe "intermediate stage". The activation of axial cells increasedduring the next two weeks and a few days later both groups ofplants entered the prefloral stage followed by the formationof their first floral buds. These apical reactions were comparedto those of a French variety of A. thaliana, a quantitativelong-day plant, submitted to different photoperiods and to gibberellicacid (GA₃). (Received January 17, 1977; )     

Flavan-3-ols in Trichomes, Pistils and Phelloderm of Some Tree Species

Tissues from nine tree species were examined histochemicallyfor the presence of flavan-3-ols including the catechins. Itwas possible to stain these phenolics selectively with p-dimethylaminocinnamaldehyde(DMACA) and to show that they were located in trichomes, pistilsand shoot phelloderm. The staining intensity of the tissueswas categorized into four groups. The flavan-3-ols were extractedfrom three tree species and the diverse components were distinguishedusing a combination of HPLC and chemical reaction detection(CRD). Twelve flavan-3-ols were isolated from pistils of Tiliagrandifolia and 32 from leaves of Acer platanoides. The hairsof the leaves of dormant buds from Aesculus hippocastanum yielded13 components. Epicatechin and ( + )-catechin were present inall three species. Trees, trichomes, pistils, phelloderm, histochemistry, HPLC, CRD     

Studies on the Growth, Flowering, and Production of Female Sterile Flowers as Affected by Different Levels of Foliar Potassium in Solanum sisymbrifolium Lam.: I. EFFECT OF POTASSIUM CONTENT OF THE PLANT ON VEGETATIVE GROWTH AND FLOWERING

As compared to a high level of foliar potassium, a low but nota deficient level promotes shoot elongation and flowering inS.sisymbrifolium.This is accompanied by formation of flowers with rudimentaryovaries in which the megagametophyte in the ovules aborts atthe two- or the four-nucleate stage. Plants having a higherK content do not bear the female sterile flowers. Inflorescencesof the high-K plants with 20 per cent fewer buds have 23 percent higher dry weight than inflorescences of low-K plants.The ratio of organic nitrogen to dry weight is not affected,indicating that the inflorescences of the high-K plants arebetter supplied with metabolites in general.     

Abscisic Acid and Apical Dominance in Phaseolus coccineus L. The Role of Tissue Age

Abscisic acid (ABA) applied to the decapitated second internodeof runner bean plants enhanced outgrowth of lateral buds onlywhen internode stumps were no longer elongating. Applied toelongating internodes of slightly younger plants, ABA causesinhibition of bud outgrowth. Together with 10^–4 M indol-3-ylacetic acid (IAA), ABA stimulated internode elongation and interactedadditively in the inhibition of bud outgrowth. A mixture of10^–5 M ABA and 10^–6 M gibberellic acid (GA₃ ) causedsimilar effects on internode growth as IAA + ABA, but was mutuallyantagonistic in effect on growth of the lateral buds. Abscisic acid, apical dominance, gibberellic acid, indol-3yl acetic acid, Phaseolus coccineus, bean