Main Inflorescence Research Articles

Modulation of eIF5A1 expression alters xylem abundance in Arabidopsis thaliana

Eukaryotic translation initiation factor 5A (eIF5A) is thought to facilitate protein synthesis by participating in the nuclear export of specific mRNAs. In Arabidopsis, there are three isoforms of eIF5A. One of them, AteIF5A1, has been shown to be expressed in vascular tissue, specifically developing vessel members, using GUS as a reporter. In order to determine whether AteIF5A1 plays a role in xylem formation, its full-length cDNA was constitutively over-expressed in transgenic Arabidopsis plants. Microscopic analysis revealed that the cross-sectional area of the xylem in the main inflorescence stems of transgenic plants was 1.9-fold higher than those of corresponding inflorescence stems of wild-type plants. In wild-type stems, the primary xylem typically comprised six cell layers and was approximately 105 mum thick, but increased to 9-11 cell layers, 140-155 mum thick, in transgenic stems. Similarly, the secondary xylem increased from six cell layers, approximately 70 mum thick, in control stems to approximately 9 cell layers, 95-105 mum thick, in transgenic stems. Moreover, constitutive down-regulation of AteIF5A1 using antisense technology resulted in the major suppression of xylem formation compared with control plants, and the antisense transgenic plants were also stunted. These data collectively indicate that eIF5A1 plays a role in xylogenesis.

Detection of QTL for six yield-related traits in oilseed rape (Brassica napus) using DH and immortalized F2 populations

The inheritance of yield-related traits in rapeseed (Brassica napus) is poorly understood, and the investigations on mapping of quantitative trait loci (QTL) for such traits are only few. QTL related to six traits were mapped which include plant height (PH), height of lowest primary effective branch (HPB), length of main inflorescence (LMI), silique length (SL), number of primary branches (FB) and silique density (SD). A set of 258 doubled haploid (DH) lines derivatives of a cross between a canola variety Quantum and a resynthesized B. napus line No.2127-17, and a fixed immortalized F(2) (designated as IF(2)) population generated by randomly permutated intermating of these DHs were investigated. A genetic linkage map was constructed using 208 SSR and 189 SRAP markers for the DH population. Phenotypic data were collected from three environments for the two populations. Using composite interval mapping analyses, 30 and 22 significant QTL were repeatedly detected across environments for the six traits in the DH and IF(2) populations, respectively. Twenty-nine QTL were common between the two populations. The directions of parental contribution for all common QTL were the same, showing a great potential for marker-assisted selection in improving these traits. Some chromosomal regions harbor QTL for multiple traits, which were consistent with significant phenotypic correlations observed among traits. The results provided a better understanding of the genetic factors controlling yield-related traits in rapeseed.

Growth and Flowering Responses of Lupinus varius L. to Paclobutrazol

The effects of method of application and dose of paclobutrazol on the growth and flowering characteristics of Lupinus varius L. were studied. On 17 Dec., seeds were sown into 18-cm pots (three seeds per pot) filled with a mixture consisting of 2 peat: 1 river sand (by volume). On 25 Mar., when 5% of the plants had elongated first internodes, doses of paclobutrazol at 0 (control), 0.625, 1.250, and 2.500 mg a.i./plant were applied to plants as a foliar spray or media drench. The application of paclobutrazol led to a slight shortening of the time to flowering, especially when applied as a foliar spray. Plant height and internode length, length, and internode length of the main inflorescence significantly decreased with increased doses of paclobutrazol and this also happened with the number of branches per plant, branch length, and length and internode length of branch inflorescence. On the contrary, stem, main, and branch inflorescence diameters significantly increased with increased doses of paclobutrazol, whether applied as a foliar spray or media drench. However, drench applications of paclobutrazol were consistently more effective than foliar spray treatments on most of the growth characteristics investigated. Paclobutrazol, in particular when applied as a foliar spray, also increased the number of flowers on main and branch inflorescences relative to the control, but media drenched applications of paclobutrazol at doses of 1.250 and 2.500 mg a.i./plant resulted in consistent significant reductions in the number of flowers on branch inflorescences. Chemical name used: (±)-(R*,R*)-β[(4-chlorophenyl)methyl]-α-(1,1-dimethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).

Responses of native Lupinus varius (L.) to culture conditions: effects of photoperiod and sowing time on growth and flowering characteristics

The effects of photoperiod and sowing time on growth and flowering characteristics of Lupinus varius were investigated during two growing periods to determine its responses to culture conditions as a potential native cut-flower crop. The seeds were sown in an unheated plastic greenhouse on 28 September, 28 October and 28 November under natural, 14- and 16-h day-length treatments. 14- and 16-h day-lengths were established by lengthening the natural day-lengths to 14 and 16 h with the use of night break photoperiodic lighting at 1.8–1.9 μmol m −2 s −1 in 400–700 nm. Photoperiodic lighting, in particular the 16-h day-length treatments, slightly (maximally 15 days) shortened days to flowering and increased plant height in all sowing times relative to natural photoperiods. There were no significant differences in stem and branch inflorescence diameters, in lengths of branch, in main and branch inflorescences in plants grown under natural photoperiod, and 16-h day-length treatments. The highest main inflorescence diameter, the number of branches per plant, and flower numbers on main and branch inflorescences were recorded in plants grown under natural photoperiods, whereas 14-h day-length treatments did not provide sufficient specimens to allow for the measurement of most of the characteristics studied. These findings were interpreted to indicate that L. varius behaves as a facultative long day plant. Additionally, there was a particular shortening of days to flower and growth, and flowering quality decreased linearly with delayed sowing dates under all photoperiodic treatments. The earliest and latest flowering dates were recorded for plants sown in September under 16-h day-length, and plants sown in November under natural photoperiods, respectively. Therefore, sowing in September under natural photoperiods or 16-h artificial day-length resulted in earlier flowering dates and a longer time from sowing to flowering and was consequently the best sowing time with respect to all of the characteristics considered in this study.

Inheritance and agronomic performance of an apetalous flower mutant in Brassica napus L

A spontaneous mutant with apetalous flowers was obtained from a hybrid progeny in Brassica napus. The result of genetic analysis showed that the apetalous character was controlled by only one gene locus, petalous flower exhibited incomplete dominance over apetalous flower and that its expression was not affected by cytoplasmic factors. Sixteen agronomically important characteristics of the apetalous line Apet33-10 were compared with those of its petalled near-isogenic line Pet33-10. Results from 4 years of tests indicated that there was no difference between Apet33-10 and Pet33-10 in all tested agronomic characteristics, except for the pod number of main inflorescence and second-order branches at low sclerotinia disease incidence. The Sclerotinia sclerotiorum disease severity index of Apet33-10 was significantly lower than that of Pet33-10, and correspondingly, the plot yield of Apet33-10 was increased obviously in comparison to that of Pet33-10 if sclerotinia disease was serious. The pod number of main inflorescence of Apet33-10 was significantly lower than that of Pet33-10. On the other hand, the pod number of second-order branches of Apet33-10 was significantly higher than that of Pet33-10, hence no overage difference of the pod number per plant was observed between the two lines.

Differences in flight activity of pests on winter and spring oilseed rape

For 6 years the flight activity of pests on winter and spring oilseed rape was studied from spring till harvest, using yellow traps. In all years the flight intensity was higher in winter rape than in spring rape. The dominant insect pests of winter oilseed rape were Ceutorhynchus obstrictus, C. napi, C. pallidactylus, Dasineura brassicae, Meligethes aeneus, Phyllotreta atra and Ph. nigripes; subdominant were Athalia rosae, Brevicoryne brassicae and Psylliodes chrysocephala. In spring rape the dominant species were Brevicoryne brassicae, Ceutorhynchus obstrictus, Dasineura brassicae, Meligethes aeneus, Phyllotreta atra and Ph. nigripes; subdominant were Athalia rosae, Ceutorhynchus napi, C. pallidactylus and Psylliodes chrysocephala. Dasineura brassicae was not evaluated from trap catches. The damage by D. brassicae is higher to pods on axillary branches than on the main inflorescence. The occurrence of pests on spring rape was tied to a unsuitable phenophase of the plants at the time of flight activity and to the suitability of food. Winter rape requires a higher intensity of chemical treatment against pests than spring rape.

Veronica spicata L. ssp. spicata and ssp. hybrida (L.) Gaudin (Pseudolysimachium spicatum (L.) Opiz)

Subgenus Pseuidolysihnachiiunm. Pubescent perennial herb. Shallow roots, white, fine and fibrous. Taproots 1.5 mm diameter, light brown, sparsely branched, but roots mostly adventitious, often into cracks and crevices of fragmented rocks. Rhizomes/ stolons somewhat woody, shortly creeping and rooted or long and thick, less than 10cm deep, arising above or below ground level. Stock shortly creeping, hard, almost woody. Stems erect, woody near base, ascending or spreading, e.g. near scrub edge or at cliff edges hanging down before ascending at or in the spike. Stems to 30 cm in ssp. spicata [in ssp. hybrida 60-85(-100) cm], stout, more or less densely hairy and glandular, rarely glabrous. Leaves decussate, 15-80 x 2-30 mm, lower ovate or oval crenate, sometimes doubly crenate, becoming linearlanceolate, crenate-serrate or upper leaves sometimes entire or sessile. Petioles 0-30 mm. Lowest leaves of ssp. spicata 15-30 x 8-12 mm, crenate-serrate only at widest part (nearly middle), gradually narrowed into petiole; in ssp. hybrida lowest leaves 20-40 x 10-20 mm, usually crenate-serrate along most of the margin, widest below the middle and abruptly narrowed into the petiole. Inflorescence a many-flowered terminal spike-like raceme. Mostly single, occasionally with up to 10 or more lateral inflorescences in ssp. hybriidac, usually smaller than main inflorescence, arising from axils of stem leaves; rarely the spike itself splits. Pedicels very short, 0.5 mm. Bracts 1-3 x 1-1.5 mm, broadly lanceolate, one per flower. Sepals 4, occasionally 5, 1-2.5 x 2-6 mm, lanceolate to triangular acute, glandular hairy, plus long glandless cilia (Fischer 1974); lower third of sepals joined. Corolla violet-blue, occasionally deep blue-purple, rarely white, pink or lilac, tube joined at lower third, 3mm. Petals 4, 4-6 x 1.5-3 mm, ovate-lanceolate; flat lower lobes of upper petal tend to be wider than the other three. Stamens 2; pollen 12 x 29 rim, yellow. Carpels two, stigma discoid. Capsule 2-4 x 2-4 mm, heart-shaped, retuse, emarginate, about as long as the calyx lobes, 2-chambered, style 4-10mm. Seed 0.8 x 0.5mm, ovoid, air-dry mass 0.082 ? 0.0001 mg, dark brown, with narrow deep vertical groove; radicle prominent. Stace (1997) maintains the division of British populations of V. spicata into two subspecies, ssp. spicata and ssp. hybrida, whereas the species in continental Europe is not divided. Stace (1997) distinguishes ssp. hybrida as 'usually ... taller and having larger, more extensively crenate-serrate leaves that are widest below (not at) the middle and are more abruptly narrowed into the petiole, but the differences are not constant and these races are only two of a large number in Europe'. Veroniica spicata is a plant of limestone rocks and of dry grassland on basic soils. It is of particular interest because of its wide distribution in Europe, its disjunct distribution in Britain where it is listed on Schedule 8 of the Wildlife & Countryside Act 1981 and the potential threat to ssp. spicata in eastern Britain. The latter was recorded in four 10-km squares of the National Grid in the period 1987-97 and is classified as vulnerable (VU) in the Red Data Book (Wigginton 1999).

Classificação de genótipos de amendoim baseada nos descritores agromorfológicos e isoenzimáticos

Procedeu-se à classificação de genótipos intraespecíficos de amendoim quanto aos descritores agromorfológicos e isoenzimáticos com auxílio da análise dos componentes principais. Vinte e três descritores foram analisados, dentre esses, onze foram morfológicos, nove agronômicos e três protéico- enzimáticos. Baseado nas evidências da análise dos componentes principais, verificou-se que os principais descritores morfológicos foram o tipo botânico, pigmentação da haste principal, padrão de inflorescência, ponto de maturação da vagem, cor dos folíolos, tamanho da vagem, hábito de crescimento, cor da semente e pilosidade da planta. Nos agronômicos, as maiores cargas foram para o início da floração, peso de 100 sementes, número de vagens/planta, porcentagem de vagens chochas e rendimento em amêndoas. Na combinação desses caracteres, as maiores cargas foram observadas para os descritores porcentagem de vagens chochas, número de semente/vagem, número de vagens/planta, rendimento em amêndoas, tamanho da vagem e o tipo botânico. Na análise dos sistemas enzimáticos, verificou-se que nenhum dos sistemas apresentou qualquer relação entre os padrões de banda e os tipos botânicos; contudo, constatou-se que a similaridade baseada nos tipos agromorfológicos dos genótipos do tipo Valência deve corresponder com a encontrada na base dos sistemas protéico-enzimáticos.

Investigation of flowering dynamics of the basil (Ocimum basilicum L.) and its consequences in production

The flowering dynamics of Ocimum basilicum L., (a common population maintained at the UHFI) was studied with the aim to create an exact and practically applicable method for definition of phenological phases.
 According to our observation the development of individual flowers of the basil can be characterized by 8 distinguishable phases, which must be considered for description of the actual phenological stage of a spike.
 An accurate model was created for the unambiguous description of flowering process of different flowers within the spike and for the individual plant as a whole. The new flowering index formula is calculated from the number of flowers weighed by their phenological phases.
 The time dependence of flowering is presented by functions fitted to values of the flowering index. The results reflected different patterns of the main inflorescence, the inflorescences formed on the side shoots in the first or in the second half of the flowering period. However, for description of the flowering process of the whole plant, a sigmoid function proved to be the appropriate model.
 The accumulation process of the essential oil could be characterized by the flowering index values. They showed close correlation (r=0.964) at high probability.
 The new method assures an exact definition of phenological phases in basil. Its application seems to be optimal during breeding procedures, seed production and even in production of high quality drugs, according to the requirements of the Good Agricultural Practice (Guidelines for GAP, 1998).

A critical revision of inflorescence structure in Crocus L. of the subgenus Nudiflori Maw (lridaceae)

Summary Some Crocus L. species of the subgenus Nudiflori M aw , which were assumed to produce a terminal flower, were selected for analysis of their inflorescence structure. The preliminary study of the bract and bracteole shapes during development revealed bidentate structure of both organs. The angles ofleaf divergence were measured in main florescence and paracladia. The obtained diagrams were transformed into axial schemata by a formal method. The investigation revealed, that the bract and bracteole are prophylls, thus the previously used terminology for Iridaceae inflorescene (bract, bracteole and prophyll) appeared to be an inadequate description for the correct organ homologization. In all analysed species, the flower was positioned on the axis of the third (in the main inflorescence) or fourth (in the paracladia) order, but it was never terminal as proposed earlier.

低温処理温度の違いがフリージアの開花に及ぼす影響

In Japan, freesia corms after root emergence are precooled at 8 to 10°C under moist condition for 5 to 7 weeks to advance flowering. Because flower initiation and differentiation occur under these conditions, low temperatures enhance it directly. In these experiments, we tested the effects of chilling temperatures on flowering were direct or an indirect ones on freesia corms of 'Elegance' and 'Blue Heaven' by keeping the corms at 5, 8, 10, 12, or 15°C under moist condition. They were then moved to 24/18°C (day/night) at the same stage of floral development. Corms chilled at 5°C for 13 weeks did not initiate flower buds, and were excluded from the experiments. Within a range of 8 to 15°C, not only a direct effect but also some after-effects on flowering were noticed. The number of florets per main inflorescence was determined as a direct effect of chilling temperature ; it decreased as corms were chilled at lower temperatures. Corms, chilled at lower temperatures, also had a higher flowering percentage and longer flower stem, and required fewer days from the end of chilling to flowering ; an after-effect of the chilling temperature.

Structural patterns of tomato plants grown in greenhouse

We characterize the growth form of the two types of commercial tomato cultivars. In both types of tomato the branching is sympodial. The difference between cultivars of the indeterminate and the determined type is given by variations in the intensity in which the spatial and temporal pattern of the sympodial growth is expressed. Variations that manifests itself in the relative rate of development of each sympodial unit and in the amount of sympodial shoots that are produced during the plant's lifetime. The inflorescences of tomato plants grown in greenhouse are studied. The main inflorescences variations that have been observed are: the appearance of either dichasial inflorescences or pleiochasial inflorescences; the bracts development at the level of either the branches of the inflorescence or individual flowers; and the proliferation of the apex of the inflorescence.

The Effects of Gender and Plant Architecture on Allocation to Flowers in Dioecious Silene latifolia (Caryophyllaceae)

In dioecious species, reproductive allocation in females and males may differ as a result of the different reproductive functions and needs of the two sexes. In Silene latifolia (Caryophyllaceae), males invested a total of 11% more biomass in flowers than females. However, individual female flowers were 2.6 times heavier than individual male flowers (on a dry mass basis), had significantly heavier sepals and pedicels, but not petals, and exceeded male flowers for five linear measures. Individual female flowers also contained 2.7 times more N and 2.9 times more P than individual male flowers. In females, N (on a mg/mg basis) was concentrated in ovules, nectary, petals, and styles and P was concentrated in ovules, nectary, styles, and petals. In males, N and P were concentrated in anthers, anthophor, and petals. Within flowers, the three currencies did not always predict each other, as anthers in males and ovules and styles in females contained higher, while sepals in both sexes contained lower, proportions of both nutrients than of biomass. Flower number was highly influenced by gender, pollination, and architecture. Males produced 2.9 times more flowers than unpollinated females and 14.3 times more flowers than pollinated females. In females, pollination of flowers on one of the two main inflorescence branches significantly reduced the number of flowers produced on that branch, both in comparison to the other inflorescence branch on the same plant and in comparison to the corresponding branch on control plants. Flower number also differed between the two inflorescence branches on control plants, indicating the importance of plant architecture on flower production. It is clear that selection can lead to different reproductive allocation patterns in females and males and that these patterns may vary depending on currency and in response to pollination and architecture in females.

Pleiotropic effects of flowering time genes in the annual crucifer Arabidopsis thaliana (Brassicaceae)

Variation in flowering time of Arabidopsis thaliana was studied in an experiment with mutant lines. The pleiotropic effects of flowering time genes on morphology and reproductive yield were assessed under three levels of nutrient supply. At all nutrient levels flowering time and number of rosette leaves at flowering varied among mutant lines. The relationship between these two traits depended strongly on nutrient supply. A lower nutrient supply first led to an extension of the vegetative phase, while the mean number of leaves at flowering was hardly affected. A further reduction resulted in no further extension of the vegetative phase and, on average, plants started flowering with a lower leaf number. At low nutrients, early flowering affected the timing of production of siliques rather than the total output, whereas late flowering was favorable at high nutrients. This may explain the fact that many plant species flower at a relatively small size under poor conditions. Flowering time genes had pleiotropic effects on the leaf length, number of rosette and cauline leaves, and number of axillary flowering shoots of the main inflorescence. Silique production was positively correlated with the number of axillary shoots of the main inflorescence; the number of axillary primordia appeared to have a large impact on reproductive yield.

Flowering in celeriac ( Apium graveolens L. var. rapaceum (Mill.) DC.): effects of photoperiod

The role of photoperiod in time of flowering in celeriac ( Apium graveolens L. var. rapaceum (Mill.) DC.) was analysed for three different phases, namely thermoinduction, evocation and inflorescence development. The effect of photoperiod during thermoinduction on the relationship between duration of exposure to a low temperature and the progress of thermoinduction was studied by transferring plants at different times from 12°C with a photoperiod of 8 or 16 h, to 20°C. The degree of thermoinduction at the time of the transfer was determined by later counting the final number of leaves. The degree of thermoinduction at 8 and 16 h did not increase during the first 21 days of the low temperature treatment, but it increased linearly after 21 days until thermoinduction was completed after 39 (8 h) and 34 (16 h) days. Rate of initiation of leaf primordia on the apex decreased with increasing photoperiod from 0.65 leaves per day at 8 h to 0.47 leaves per day at 16 h. At a photoperiod of 8 h completion of thermoinduction was followed immediately by initiation of the primordia of the main umbel on the apex. However, if plants remained at 16 h after the completion of the thermoinduction, leaf primordium initiation on the apex was strongly retarded, and initiation of the final leaf was delayed. If the photoperiod was varied after initiation of the main umbel on the apex, time of flowering of the main umbel at a photoperiod of 24 h was approximately 8 days earlier than at a photoperiod of 10 h. The main inflorescence stalk developed only at a 24 h photoperiod; at 10 h the main umbel was directly implanted on the tuber.

Application of cytokinins to flowers to increase pod set in Lupinus angustifolius L

Exogenous application of a 2 mol m-3 buffered solution of N6 benzylaminopurine (BAP) to flowers on the main stem inflorescence of Lupinus angustifolius L, cv. Danja profoundly altered reproductive development by reducing post-anthesis abscission of flowers and small pods. The same effect of BAP was recorded for a mutant (abs-) of cv. Danja, in which organ abscission was completely absent, indicating that localized application of cytokinin enhanced reproductive development rather than reduced pedicel abscission per se in the parent line. Application to pedicel and sepals at the open flower stage completely eliminated flower abortion on the main inflorescence, compared with less than 50% pod initiation on untreated inflorescences, more than doubled final pod yield on the main inflorescence and increased the number of mature pods on the whole plant by 33%. A single dose of BAP, to an inflorescence which bore flowers ranging in their stage of development from post-anthesis to immature flower buds, significantly increased the number of pods initiated and at final harvest, measured on a per plant basis. A number of synthetic and naturally occurring cytokinins, including zeatin riboside and dihydrozeatin riboside, were also effective. BAP application induced a longer period of flowering and resulted in a considerably thickened raceme. This was most marked at the distal end which showed enhanced cambial development and secondary vascularization compared with untreated controls. The positive effects of BAP application on pod initiation were not restricted to cv. Danja but were found also for cv. Warrah and cv. Gungurru, both of which have enhanced pod set compared with Danja. Enhanced pod initiation on the main inflorescence generally reduced the number of pods developing on branch inflorescences. Additional application of BAP to flowers on branches, even at the most opportune time and at the most effective site, did not enhance pod initiation and, in some cases, significantly reduced pod set on these branches. The data indicate that it would be very difficult to exploit the positive effect of exogenous cytokinin application on pod set in field crops of lupin. However, selection or genetic engineering of plants with higher levels of endogenous cytokinins in flowers or flower parts at anthesis may provide a means by which to assess the importance of this factor in determining yield stability.

Partitioning of dry matter into primary branches and pod initiation on the main inflorescence of Lupinus angustifolius

The hypothesis that pod load on the main inflorescence of Lupins angustifolius (L.) is negatively coupled to the amount of dry matter partitioned into primary branches was tested. Growth rates of main stem and primary branches during the period of pod initiation were measured in a series of field experiments at two different sites. Variation in pod set was generated experimentally by varying sowing date or density and by using four cultivars (Yandee, Danja, Gungurru and Warrah). The cultivars differed in their total growth rate, but not in the way dry matter was partitioned into main stem and primary branches. In contrast, significant variation in dry matter partitioning was observed for cv. Danja tested across site and sowing date. With increased plant density, at the same sowing date, the proportion of dry matter allocated to branches increased consistently, even though it decreased in absolute terms, and the number of pods initiated on the main infloresence also decreased consistently. Thus a negative relationship between pod load and the proportion of dry matter allocated into branches was observed as a result of variation in density. However, there was no consistent relationship when variations in pod load were induced by site, date of sowing or cultivar. These data are interpreted to indicate that increased pod initiation on the main inflorescence is not necessarily coupled with decreased partitioning of dry matter into primary branches.

Predominance of flowers and newly formed pods in reproductive abscission of Lupinus angustifolius L

The stage of development at which reproductive organs abscised on the main inflorescence of Lupinus angustifolius L. plants was studied in field plot trials which incorporated site, sowing date, density and cultivar treatments. The average number of pods on the main inflorescence at final harvest ranged over 1.8 to 8.4, the Reproductive Index (number of seeds per gram total above-ground dry weight, excluding seeds) varied from 3.1 to 7.6, and the Harvest Index from 0.17 to 0.50. Four stages at which abscission occurred were identified (flower [ovaries 7-8 mm long], pl [pods 9-10 mm], p2 [pods 11-13 mm], p3 [pods 14-27 mm long]) and used to assess reproductive development on a week by week basis. In all treatments, losses of flowers and pl pods accounted for 92% or more of total reproductive abscission and, of this, the majority was due to flower abscission. The number of abscised pl pods was relatively stable across treatments, but the number of p2 and p3 pods which abscised varied markedly with sowing date, possibly indicating a relationship with changes in environmental conditions. Examination of ovaries following cryosectioning and fluorescence microscopy showed that pollination of ovules occurred with a similarly high frequency in flowers destined to abscise (77%) compared with those destined to form pods (88%). The difference was due to a 50% probability of pollination of the fifth ovule in ovaries of flowers forming pods and only a 25% probability in those which abscised. The data are discussed in relation to the likely physiological basis for the regulation of reproductive abscission in the species.

Branching, flowering and pod-set patterns in snap-bean (Phaseolus vulgaris L.) as affected by temperature

The effect of temperature on branching, flowering and pod-set patterns of determinate snap-bean (Phaseolus vulgaris L.) cultivars has not been well documented. In this work, well-defined rigid gradients of branching and flowering were found in determinate snap-bean. However, in spite of the great developmental stability of these gradients, pod production and distribution along the main axis of the bean plant was highly plastic in its response to environmental conditions. Under controlled conditions, high temperature (32/27 °C) drastically reduced pod production even though branching and flowering were greatly increased. Under lower temperatures most (>50%) mature pods were produced by branches of the first and second trifoliolate leaves. Low night temperature (12 °C) increased branching and relative pod production by more basal nodes, mainly by primary leaves branches. Large shifts in the relative contribution to mature pod production by main inflorescence and branches at different nodal positions along the main shoot were observed also in the field. It appears that in determinate cultivars of snap-bean the rigid gradients in branching and flowering do not limit pod production because of compensatory rapid developmental adaptation to transient environmental stresses. Key words: Snap-bean, Phaseolus vulgaris L., branching, pod-set, temperature

ステルンベルギア(<i>Sternbergia lutea</i> Roem. & Schult.)の開花に及ぼす温度の影響

In this study, the growth periodicity of Sternbergia plants grown outdoors was clarified and the effect of temperature on the initiation and development of flower buds was investigated.1. The Sternbergia bulb develops a sympodial branching system. Each unit has about 8 foliage leaves and terminates in 2 or 3 inflorescences. The bases of the foliage leaves, except the uppermost leaf, encircle the vertical axis of the bulb and gradually enlarge into scales which serve as food storage organ.2. Floret initiation on the primary inflorescence occurs between April and early May. Carpel primordia are visible in early July and the pollen tetrad are formed in early September. Anthesis occurs in late September. Floral differentiation on secondary and tertiary inflorescences follows that of the primary inflorescence after a short delay.3. Flower initiation occurs at temperatures between 10°and 30°C, but the optimum range was 20°-25°C. Once initiated, floral differentiation and development progressed most rapidly at 25°-30°C.4. The development of flower bud from carpel formation stage to flowering was faster at 20°-25°C than at 30°C. At 10°C flower buds ceased to develop and became blasted.5. Bulbs kept at 20°C after July 1, when the main inflorescence attained the carpel formation stage, bloomed earlier but produced fewer inflorescences as compared to those placed at 25°or 30°C from July 1 to August 19 and thereafter shifted to 20°C. This result suggests that bulbs should be kept at 25°-30°C after carpel formation in the main inflorescence to optimize the development of secondary and tertiary inflorescences.6. To retard development of flower bud until the Christmas season, bulbs were stored at 5°and 30°C after August 20. Bulbs stored at 30°C and planted in late November flowered in late December when forced in a glasshouse kept above 20°C, but those stored at 5°C did not flower because the flower buds became blasted.