Modelling the Masting Behaviour of Betula platyphylla var. japonica using the Resource Budget Model

A masting model of Betula platyphylla var. japonica, a majorwind-pollinated tree in Hokkaido, northern Japan, was constructedfrom the perspective of the resource budget model. An 11-yeardata series of pollen dispersal by birch showed marked annualfluctuations in flowering. Although flowering fluctuated widelyamong years, a reciprocal relationship was observed betweentwo consecutive years; very little flowering occurred aftera mast year. This suggests that there is a negative relationshipbetween current fruiting and flower bud induction. There wasa significant positive relationship in flowering between regions,which suggests that weather conditions regulate flowering inbirch. A model that included weather variables and resourceallocation systems among years explained 94·5% of theobserved annual fluctuations in flowering. In the model, warmspring conditions from bud burst to flower bud development andlittle flowering in the previous year (t-1) resulted in increasedflowering in the current year (t), whereas abundant floweringin year t-2 resulted in a decrease in flowering in the currentyear (t). The latter indicates that flowering in year t-2 affectsresource storage after overwintering; the balance is carriedforward to year t-1 and affects the initiation of flower primordiabefore bud burst. In the model, fluctuating weather conditionsin the previous spring strongly affected the masting behaviourof birch. Copyright 2001 Annals of Botany Company Betula platyphylla var. japonica, flowering, masting, modelling, pollen dispersal, resource allocation, resource budget model, weather conditions     

A Comparison of the Flowering and Branching Control Systems in Lathyrus odoratus L. and Pisum sativum L.

In the sweet pea (Lathyrus odoratus L.) the difference in floweringbehaviourbetween photoperiodic (long-day) and day-neutral cultivars appearsto be due to a difference in their ability to produce a graft-transmissiblefloral inhibitor. The flowering control systems in the sweetpea and the garden pea (Pisum sativum L.) appear to be verysimilar on the basis of inter-generic graft results. It is suggestedthat the major flowering genes Dn* in L. odoratus and Sn andDne in P. sativum control steps in a biochemical pathway commonto these two species (which are related at the tribal level)and that the product of this pathway inhibits flowering andpromotes outgrowth of basal laterals in both species.     

Mechanisms of Developmental Integration of Aster novae-angliae L. and Hieracium murorum L.

This paper is an inquiry into the regulatory features of developmentof Aster novae-angliae and Hieracium murorum. Computer-generatedplant models are compared with real plants to analyze branching,conver sion from vegetative to flowering development, stem elongation,and flowering.     

Stage Development and Flowering in Dactylis glomerata L.

The results of pilot experiments lead to the conclusion thatD. glomerata exhibits a number of developmental stages: firstly,a juvenile stage during which the plant is insensitive to environmentalconditions which later stimulate flowering; secondly, an inductivestage, when the plant responds to periodic exposure to darknessat the conclusion of which it is fully induced or ripe to flower,and finally, a post-inductive stage during which inflorescencesare initiated and undergo further development; these are long-dayprocesses. In four populations studied the juvenile stage lasts about fiveweeks. In north European material daily exposure to seven hoursof darkness is near the minimum for induction although thereis considerable within-population variation. Further, it appearsthat the daily dark requirement becomes less as the plant ages. Comparisons are made of the flowering behaviour of D. glomerataand Lolium perenne. The differences between these species resultfrom the presence of a juvenile stage in Dactylis and the possibilityof satisfying its inductive requirement by long days. Inductionin Lolium requires short days or low temperature. The significance of these results is discussed in the lightof previous work on the environmental control of flowering inherbage grasses. The existence of three developmental stagescan explain the wide differences in interpretation of the floweringrequirements of Dactylis previously held. The possible evolutionof flowering requirements is also discussed.     

Flowering responses of Lemna perpusilla and L. gibba in relation to nitrate concentration in the culture medium

Flowering responses of Lemna perpusilla strain 6746, a short-dayplant, and L. gibba strain G3, a long-day plant, to nitrateconcentration in Hoagland's type medium with or without EDTA,were compared. Maximum flowering of L. perpusilla under SD occurredat higher nitrate concentrations than did colony proliferation.Even under CL, L. perpusilla grown at sub-optimal nitrate concentrationsfor colony proliferation, flowered irrespective of the presenceof EDTA which reduces flowering. Unlike L. perpusilla, L. gibba failed to flower under SD atany nitrate concentration whether or not EDTA was added. UnderCL, however, L. gibba flowered at almost any nitrate concentrationwith or without EDTA. Double optima for nitrate concentrationwas exhibited in the presence of EDTA; optimal concentrationfor colony proliferation came between the two optima for flowering. We concluded that the nitrogen level of the medium is importantin regulating flowering of duckweeds, and that the effect ofEDTA, if any, may primarily be on colony proliferation and onlysecondarily or antagonistically on flowering. ¹ Present address: Institute for Agricultural Research, TohokuUniversity, Sendai 980, Japan. (Received September 25, 1971; )     

Experimental control of flowering in Pistia stratiotes L.

GA₃, salicylic acid and EDDHA induced flowering in Pistia stratiotesin vitro under short days and conditions of continuous light.It has been hypothesized that EDDHA and salicylic acid bringabout the same effect on flowering in Pistia and the duckweedspecies Lemma gibba G3 whereas the effect of GA₃ on the floweringmechanism of these species is basically different. (Received March 14, 1978; )     

Mutant dn Influences Dry Matter Distribution, Assimilate Partitioning and Flowering in Lathyrus odoratus L.

The flowering mutant dn in sweet pea was used as a tool to study¹⁴C-assimilate and dry matter partitioning with respect to nutrientdiversion theories on the control of flower initiation. Wildtype plants (Dn^h) are photoperiodic and exhibit late floweringand profuse basal branching in short days while mutant plants(dn) are day neutral, early flowering and devoid of basal laterals.In short days, dn plants exported a significantly greater proportionof assimilate acropetally than (Dn^h) plants and the upper portionof dn plants had a greater dry weight. These differences werereduced dramatically when basal laterals were excised regularlyfrom the (Dn^h) plants although the difference in flowering remained.However, the effect of dn on resource allocation within theapical region may be more important in regard to flowering thanthe effect on acropetal versus basipetal movement. In shortdays, the dn plants partitioned significantly more resourcesinto their internodes and petioles, and less into their leaflets,than Dn^h plants as shown by dry weight and ¹⁴C-assimilate measurements.These differences were apparent from as early as node 7 up tothe node of flower initiation in dn plants (node 30) and theywere not eliminated by removal of basal laterals from Dn^h plants.Differences between dn and Dn^h plants in partitioning and floweringwere largely eliminated under long days. The fact that in thisspecies a single gene influences both resource allocation andflower initiation lends further support to nutrient diversionhypotheses on the control of flowering. Key words: Assimilate partitioning, branching, flowering, mutant, sweet pea     

Growth and flowering of Lemna paucicostata I. General aspects and role of chelating agents in flowering

Lemna paucicostata HEGELM. is normally a short-day plant andflowers only in the presence of a chelating agent (EDTA or EDDHA)in the medium. The plant can be induced to flower even by asingle long night treatment; the flowering percentage, however,increases with further inductive cycles. The length of the criticaldark period depends upon the chelating agent employed in themedium. It is between 10 and 12 hr in the medium containingEDTA and about 8 hr in the EDDHA-supplemented medium. Red lightinterruption in the middle of the dark period—even fora minute—is inhibitory for flowering. Attempts to identify the metal ion(s) chelated reveal that thechelating agents affect flowering by facilitating iron uptake.This is also supported by the fact that the requirement of achelating agent for flowering can be overcome with an excessof iron in the medium. Interestingly, provision of EDDHA andexcess of ferric citrate, together, can bring about floweringeven under long days. ¹Originally HEGELMAIER (1) designated L. paucicostata as a separatespecies; however, THOMPSON (2) and DAUBS (3) have treated itsynonymous to L. perpusilla. More recently, based on physiologicaland chemotaxonomic studies, the distinctiveness of L. paucicostatafrom L. perpusilla has been favoured (4, 5). (Received September 8, 1969; )     

The Mechanism of Action of Vernalization in Lathyrus odoratus L.

In the sweet pea (Lathyrus odoratus L.) genes Dn^l andDr^h controlthe production of a graft-transmissible substance which delaysflowering and promotes outgrowth of basal laterals. Seed vernalizationpromotes flowering and reduces lateral outgrowth in intact plantsand grafted scions of genotype DnⁱDn^l, suggesting that vernalizationreduces output of the Dnⁱ system, possibly by disrupting therelationship between chronological and plastochronic age. Whenlateral outgrowth and floral abortion are used as indicatorsof inhibitor levels, it can be shown that vernalized Dnⁱ plantspossess more inhibitor but initiate flower buds at a lower nodethan unvernalized dn plants. This supports the suggestion thatin regard to floral initiation vernalization also alters thesensitivity of the shoot apex to the flowering hormone(s). InLathyrus odoratus an hormonally based vernalization responseof considerable magnitude can be shown for day-neutral (dndn)lines, supporting the suggestion that vernalization also influencesthe level of a flower promotor. Lathyrus odoratus L., sweet pea, vernalization, flowering, branching, genotype, grafting     

Effects of Interactions between Low-temperature Treatments, Gibberellin (GA3) and Photoperiod on Flowering and Stem Height of Spring Rape (Brassica napus var. annua)

Exogenous gibberellin A₃(GA₃) reduced the number of leaf nodesat flowering and time to flowering and increased the stem heightat flowering in three genotypes of spring rape (Brassica napusvar.annua L.). The responses to GA₃were similar to those forlong days (LD) and low-temperature treatments, suggesting thatthe effect of photoperiod and the vernalization response areprobably mediated through gibberellins. The response to exogenousGA₃was greatest in non-cold-treated plants in short days (SD)suggesting that endogenous GAs are limiting in these conditions.CCC, an inhibitor of gibberellin biosynthesis, caused a smallincrease in the number of leaf nodes at flowering and time toflowering and a small decrease in the stem height at flowering,but unexpectedly, its effect was hardly influenced by the applicationof exogenous GA₃. Genotypes that showed the clearest responsesto the treatments with regard to the number of leaf nodes atflowering and time to flowering did not show the clearest responseswith regard to the stem height at flowering; the pattern ofresponses of the number of leaf nodes at flowering and timeto flowering was distinct from that of stem height at flowering.This indicates that flower formation and stem elongation areseparable developmental processes which may be controlled bydifferent endogenous gibberellins, different levels of a specificendogenous gibberellin, or different responses to gibberellin.Copyright 1999 Annals of Botany Company Brassica napus var. annua, gibberellin, photoperiod, spring rape, vernalization.     

Developmental and photobiological factors affecting photoperiodic induction in Arabidopsis thaliana Heynh. Landsberg erecta

We have tested whether the promotion of flowering by long days(LD) in Arabidopsis thaliana is a consequence of photoperiodicinduction. To achieve this, the flowering responses of Arabidopsisthaliana (L.) Heynh. Landsberg erecta (Ler) and the long-hypocotylmutants hy2, hy3 and hy4 were determined with respect to age,daylength and light quality. Ler was capable of distinguishingbetween short days (SD) and long days (LD) from about 4 d aftersowing at 20 C, the time at which cotyledons were expandingand greening. At this stage, the critical daylength was between8 h and 10 h. At 7 d, seedlings required five LD for inductionand, as the seedlings aged, they became more sensitive so thatby day 20, one LD was fully inductive. The response to SD innewly germinated seedlings was to delay flowering without alteringleaf number, but after about 10 d, delay of flowering by SDwas accompanied by extra leaves. In light quality experiments,blue light (B) was inductive for 5-d-old plants and in all subsequenttreatments, far-red (FR) caused induction in treatments at 12d and 18 d and low pressure sodium, equivalent to red, was notinductive at 5 d and 12 d, but partially inductive at day 18.Hence, both a specific blue-light photoreceptor and phytochromeA in High Irradiance Response mode promote floral induction.In daylength transfer experiments all three hy mutants respondedto LD by earlier flowering. Both hy2 and hy3 produced substantiallyfewer leaves than Ler in SD and hy3 flowered slightly earlierthan Ler. The hy4 mutants flowered later than Ler in SD andhad a higher leaf number. A scheme is proposed in which photoperiodicinduction depends on the ability of the plant to sense photoperiod,the stage of development and the photobiological input. We alsopropose that phytochrome A and the blue photoreceptor promoteflowering whereas phytochrome B promotes vegetative development. Key words: Arabidopsis thaliana, blue-absorbing photoreceptor, flowering, photoperiodic induction, phytochrome     

A STUDY ON VARIETAL DIFFERENCE IN FLOWERING HABITS OF SOYBEAN PLANTS AS FOLLOWED BY GRAFTING EXPERIMENTS

The material basis of varietal differences in flowering habitwas investigated from the standpoint that flowering is determinedby the balance in amounts of flowering promotor and inhibitor.The grafting method was used throughout the experiments. Late variety of Glycine max L. seems to produce flowering inhibitor(or inhibitors) under the conditions under which midseason varietyproduces flower. Early variety seems to produce flowering hormonewhich overcomes the flower-inhibiting action in the late variety. The amounts of flowering hormone produced under short day conditionbymidseason and late varieties were compared. The results showthat, under the short day condition, the midseason variety producesequal or smaller amounts of flowering hormone as compared withthe late variety. On the basis of these results, the mechanismby which the flowering habits are determined in various varietiesof soybean plants was discussed. (Received June 18, 1962; )     

Developmental Responses to Temperature and Photoperiod in Ecotypes of Medicago polymorpha L. Collected Along an Environmental Gradient in Central Chile

The phenological development of nine Chilean accessions of Medicagopolymorpha, collected along a north–south aridity gradient,and of two commercial cultivars of the same species, were comparedin 12 sequential outdoor sowings at Cauquenes (35°58'S,72°17'W, elev. 177 m), in the sub-humid Mediterranean climatezone of Chile. A glasshouse experiment was also conducted toevaluate the effect of photoperiod on phenophase timing. Therewas a clear gradient in precocity among the Chilean accessionsin both experiments: accessions MPO-9-88 and MPO-7-88, fromthe arid zone, were the earliest-flowering accessions, whereasMPO-36-88 from the humid Mediterranean zone was the latest.Both experiments revealed significant variation among the Chileanaccessions in the response of flowering time to variation inphotoperiod regime. Differences in days to flowering betweenthe least- (8 h) and the most- (16 h) inductive photoperiodswere lower in precocious accessions from arid and semi-aridzones, than in late-flowering accessions from more humid zones.Rate of progress to flowering, defined as the inverse of timefrom emergence to first flower appearance (1/ f), was relatedto mean diurnal temperature, or to both mean diurnal temperatureand mean photoperiod. In two early-flowering accessions fromthe arid zone, and in the Australian cultivar ‘CircleValley’, 1/ f was affected significantly (P < 0.05)by both temperature and photoperiod. In the remaining accessions,no significant responses to temperatures were detected; 1/ fwas influenced significantly by photoperiod only. Copyright2000 Annals of Botany Company Annual medic, aridity gradient, Medicago polymorpha, flowering time, rate of development     

The Influence of Ringing on Bud Development and Flowering in Satsuma Mandarin

Ringing of Satsuma mandarin (Citrus unshiu Marc.) trees showedincreased flowering in the following spring when performed duringSeptember and October, but not during November. Most of theeffect on flowering was due to an enhancement of both bud sproutingand the number of flowering shoots formed per node. In addition,a direct effect of ringing on flower initiation was demonstrated,since the number of vegetative shoots was reduced. The response of the buds to ringing was rapid as demonstratedby changes in bud weight, protein content, and electrophoreticpattern and behaviour when cultured in vitro. Buds from ringedtrees readily flowered in vitro when forced during the winterrest period and flower formation was enhanced by the additionof cytokinin. Buds from control trees formed a smaller numberof flowers in vitro, and flowering was much less enhanced bythe addition of cytokinin. It is concluded that ringing acceleratesflower initiation in the buds and this effect takes place beforethe winter rest period. Key words: Bud sprouting, Citrus unshiu Marc., flower initiation, flowering, in vitro flowering, Satsuma mandarin, ringing     

The In Vitro Flowering of Kalanchoe blossfeldiana Poellniz: I. ROLE OF CULTURE CONDITIONS AND NUTRIENTS

Dickens, C. W. S. and Van Staden, J. 1988. The in vitro floweringof Kalanchoe blossfeldiana Poellniz. 1. Role of culture conditions.—J.exp. Bot. 39: 461—471. Nodal explants of Kalanchöe blossfeldiana Poellniz. werecultured in vitro on a low nutrient hormone-free medium. Floweringwas achieved in response to short-day inductive cycles. Thissystem was used to test the influence, on the flowering response,of a variety of culture conditions and media. Reduced vesseland medium volume both inhibited flowering, as did renderingthe vessel impervious to gasses. Nitrogen in the form of NH₄NO₃and KNO₃ promoted flowering and vegetative growth in differentways. Increasing sucrose content in the medium caused some increasein the flowering response and in leaf anthocyanin production,but inhibited most aspects of vegetative growth. All of theseaspects are discussed in relation to the induction and evocationof flowering. Key words: Kalanche, flowering, in vitro     

Relationships Between Climate and Flowering of Eight Herbs in a Swedish Deciduous Forest

Effects of annual variation in rainfall, temperature and humidityon flowering abundance of eight temperate woodland plants (Anemonenemorosa, Cardamine bulbifera, Lamiastrum galeobdolon,Oxalisacetosella , Ranunculus ficaria, Stellaria holostea, Viola reichenbachianaand Viola riviniana) were studied during 12 consecutive years(1989–2000) in a hornbeam (Carpinus betulus) forest insoutheast Sweden. Above-average rainfall/humidity in late summerto early autumn of the preceding year increased flowering abundancein L. galeobdolon, O. acetosella, V. reichenbachiana, V. rivinianaand, especially, in R. ficaria, but not in S. holostea and A.nemorosa. Moreover, flowering of R. ficaria and O. acetosellawas positively related to rainfall/humidity during several partsof, or the entire, preceding year. On the contrary, floweringof S. holostea and A. nemorosa was closely related to low valuesof rainfall/humidity in autumn and/or winter of the precedingyear and also to low humidity in the current year in A. nemorosa.Two long periods (3–4 years) of increasing rainfall deficitcoincided with decreasing flowering abundance in most of thespecies, but not with decreasing vegetative development. Temperaturevariability was less consistently related to flowering. A coolperiod during the preceding summer or autumn seemed importantfor flowering in L. galeobdolon, O. acetosella and the Violaspecies, although these relations were, at least partly, causedby interactions with rainfall/humidity. No significant (P <0.05) correlations were found between flowering and the conditionsprevailing in April to May—the main flowering season—ofthe current year. Copyright 2001 Annals of Botany Company Climate, flowering, rainfall, temperature, Anemone nemorosa, Cardamine bulbifera, Lamiastrum galeobdolon, Oxalis acetosella, Ranunculus ficaria, Stellaria holostea, Viola reichenbachiana, Viola riviniana     

Studies with Liatris spicata Willd. 2. Effects of Photoperiod on Stem Extension, Flowering and Gibberellin Content

Flower formation in Liatris spicata Willd. was not affectedby photoperiodic treatments, but long days (16 h) had a pronouncedeffect on elongation of the flowering stem. An illuminance of2 Ix was sufficient to produce near maximal elongation. Long days caused a decrease in endogenous gibberellins in thetips of rapidly elongating stems and decreased the number offlowering stems per corm. Liatris spicata, elongation, flowering, gibberellin, light, photoperiod     

Phloem Exudate of Perilla crispa and its Effects on Flowering of P. crispa Shoot Explants

The aim was to develop an assay for the flowering stimulus ofa photoperiodically-sensitive plant. Phloem exudate solutionswere obtained from photoperiodically induced and non-inducedleaves of Perilla crispa (Thunb.) Tanaka, following treatmentof excised leaves with solutions of EDTA or phytic acid. Theamounts of exudate obtained were estimated polarimetrically,and the conditions for obtaining maximum exudate yields weredetermined. Shoot explants from non-induced P. crispa plantswere grown on a nutrient medium. Under short days the explantsreached anthesis after c. 35 d. In continuous light a smallproportion of the explants showed signs of flowering after 100d. The effects of test substances and phloem exudate on theflowering of explants grown in continuous light was investigated.(?)-ABA (4.0 µM), sucrose (14.6 mM) and phloem exudatefrom both induced and non-induced leaves caused some promotionof flowering. In three experiments, phloem exudate from inducedleaves enhanced flowering to a greater extent than exudate fromnon-induced leaves; in other experiments the effects of thetwo types of exudate were similar. There was no evidence thatABA or sucrose in the phloem exudate caused flowering. Concentrationsof phloem exudate above 2.0 g I^–1 were phytotoxic to theexplants. Key words: Chelating agents, Flowering, Perilla crispa, Phloem exudate, Phytic acid, Shoot culture     

Changes in Dormancy and Sensitivity to Vernalization in Axillary Buds of Satsuma Mandarin Examined in vitro During the Annual Cycle

Effect of season and the presence of fruit on bud-endodormancyand the flowering response to low temperature treatments weredetermined using bud cultures of Owari satsuma mandarin (Citrusunshiu Marc). Bud dormancy was deeper in fruiting as comparedto defruited trees. In fruiting trees, the intensity of buddormancy was highest in spring, decreased to a low value byearly Jul. and then increased until early winter. This increasein dormancy during summer and early autumn did not occur innon-fruiting trees. No flowers formed in buds cultured betweenMay and Sep. Both in fruiting and defruited trees, buds becamecompetent to show a vernalization response to chilling by theend of Oct., at the time they also became capable of sproutingin vitro at low temperature (15/10 °C). There was a directeffect of fruit on the buds which persisted long after fruitremoval and resulted in a reduction of the flowering responseto chilling.Copyright 1995, 1999 Academic Press Citrus flowering, Citrus unshiu Marc., dormancy, flower induction, flowering, in vitro flowering, satsuma mandarin, vernalization