Estimates of hierarchical variation in flower morphology in natural populations ofScleranthus annuus (Caryophyllaceae), an inbreeding annual

The variation in two sets of morphological characters of the flowers of the highly inbreedingScleranthus annuus (Caryophyllaceae) was assessed using 15–20 plants from each of 20 natural populations from the southernmost region of Sweden. The stamen fertility data set consisted of 10 characters describing the degree of fertility of the ten stamens/staminoids, while the sepal/gynoecium data set comprised 10 sepal characters, together with style and stigma length. Substantial variation was found in both the degree of development and the fertility of the stamens, the degree of variability in stamen fertility being related to stamen position within the flower. Considerable variation was found in the characters of the sepal and the gynoecium. Hierarchical analyses of variance indicated that 29% of the variation in total male reproductive effort was distributed among populations, 28% among plants within populations and 43% represented within-plant variation. The corresponding averages for the characters from the sepal/gynoecium data set are 26, 38, and 35%: a greater proportion of the total variance in female reproductive characters is accounted for by among individual variation than is the case with the male reproductive characters. Significance tests of Mahalanobis distances derived by canonical variate analyses indicated that all populations were significantly separated using the sepal/gynoecium data set, while only 50% of the pairwise comparisons on the basis of the stamen fertility data set were significant. Cluster analysis did not reveal any aggregation of the populations. The incongruence of the two data sets and their ability to discriminate between the populations is discussed.     

Mutations associated with floral organ number in rice

How floral organ number is specified is an interesting subject and has been intensively studied in Arabidopsis thaliana. In rice (Oryza sativa L.), mutations associated with floral organ number have been identified. In three mutants of rice, floral organ number 1 (fon1) and the two alleles, floral organ number 2-1 (fon2-1) and floral organ number 2-2 (fon2-2), the floral organs were increased in number centripetally. Lodicules, homologous to petals, were rarely affected, and stamens were frequently increased from six to seven or eight. Of all the floral organs the number of pistils was the most frequently increased. Among the mutants, fon1 showed a different spectrum of organ number from fon2 -1 and fon2 -2. Lodicules were the most frequently affected in fon1, but pistils of more than half of fon1 flowers were unaffected; in contrast, the pistils of most flowers were increased in fon2 -1 and fon2-2. Homeotic conversion of organ identity was also detected at a low frequency in ectopically formed lodicules and stamens. Lodicules and stamens were partially converted into anthers and stigmas, respectively. Concomitant with the increased number of floral organs, each mutant had an enlarged apical meristem. Although meristem size was comparable among the three mutants and wild type in the early phase of flower development, a significant difference became apparent after the lemma primordium had differentiated. In these mutants, the size of the shoot apical meristem in the embryo and in the vegetative phase was not affected, and no phenotypic abnormalities were detected. These results do not coincide with those for Arabidopsis in which clavatal affects the sizes of both shoot and floral meristems, leading to abnormal phyllotaxis, inflorescence fasciation and increased floral organs. Accordingly, it is considered that FON1 and FON2 function exclusively in the regulation of the floral meristem, not of the vegetative meristem.Abbreviation DIC differential interference contrast This work was supported in part by Grant-in-Aid for Scientific Research on Priority Areas from the Ministry of Education, Science and Culture of Japan.     

Odor preference in honeybees as a function of amount of reward: Tests of two explanations

How does a foraging honeybee come to prefer a color or odor paired with the large of two amounts of sucrose solution to a color or odor paired with the smaller amount? One hypothesis is that the attractiveness of a color or odor is based on the strength of its association with the taste of sucrose, which increases with the duration of concurrent color-taste or odor-taste stimulation. Another hypothesis is that the attractiveness of a color or odor is based on association with the afferent consequences of feeding, which are different for the two amounts. Both hypotheses were tested in experiments on proboscis-extension conditioning, a technique that provides better control of stimulation than is possible in work with free-flying foragers. In Experiments 1–3, which were designed to test the first hypothesis, an odor that accompanied the ingestion of sucrose on training trials was found to elicit extension of the proboscis when subsequently it was presented alone, but the duration of concurrent stimulation had no significant effect on the probability or persistence of the response. In Experiments 4 and 5, which were designed to test the second hypothesis, an odor that immediately followed the ingestion of sucrose on training trials failed to elicit extension of the proboscis when subsequently it was presented alone. The results support neither hypothesis.     

Bi-directional inflorescence development inArabidopsis thaliana: Acropetal initiation of flowers and basipetal initiation of paraclades

In this study we investigated Arabidopsis thaliana (L.) Heynh. inflorescence development by characterizing morphological changes at the shoot apex during the transition to flowering. Sixteen-hour photoperiods were used to synchronously induce flowering in vegetative plants grown for 30 d in non-inductive 8-h photoperiods. During the first inductive cycle, the shoot apical meristem ceased producing leaf primordia and began to produce flower primordia. The differentiation of paraclades (axillary flowering shoots), however, did not occur until after the initiation of multiple flower primordia from the shoot apical meristem. Paraclades were produced by the basipetal activation of buds from the axils of leaf primordia which had been initiated prior to photoperiodic induction. Concurrent with the activation of paraclades was the partial suppression of paraclade-associated leaf primordia, which became bract leaves. The suppression of bract-leaf primordia and the abrupt initiation of flower primordia during the first inductive photoperiod is indicative of a single phase change during the transition to flowering in photoperiodically induced Arabidopsis. Morphogenetic changes characteristic of the transition to flowering in plants grown continuously in 16-h photoperiods were qualitatively equivalent to the changes observed in plants which were photoperiodically induced after 30 d. These results suggest that Arabidopsis has only two phases of development, a vegetative phase and a reproductive phase; and that the production of flower primordia, the differentiation of paraclades from the axils of pre-existing leaf primordia and the elongation of internodes all occur during the reproductive phase.     

Apios americana,a fly-pollinated papilionaceous flower?

In the flowers ofApios americana the vexillum remains ± in its bud position. In this way, a dark cavity is formed displaying a bright window at its base. Insect visitors are attracted to the hidden inflorescences by scent. In their attempt to reach the window they trigger an explosive release of stigma and pollen. Stigmatic fluid glues pollen to the visitor. All characters of the flower fit well into the myiophilous syndrome and thus flies are expected to be the proper pollinators.Apios americana seems to be the only myiophilous exception within the predominantly melittophilousFabaceae.     

Identification of genes expressed in the shoot apex ofBrassica campestris during floral transition

The vegetative-to-floral transition ofBrassica campestris cv. Osome was induced by vernalization. Poly(A)+RNA was isolated from the transition shoot apex after 6 weeks of vernalization, the floral apex after 12 weeks of vernalization and the expanded leaves just before vernalization, and cDNAs were synthesized. These cDNAs were used for subtraction and differential screening to select cDNA preferentially present in the transition and floral apices. Nucleotide sequences of the resulting 14 cDNA clones were determined, and northern blot analysis was carried out on six cDNAs. Two cDNA clones which did not show significant similarity to known genes were shown to be preferentially expressed in the floral apex.     

Odor, taste, and flavor perception of some flavoring agents

Psychophysical functions for the odor, taste, and flavor offive common flavorings were obtained by the method of magnitudeestimation. The stimuli included three simple compounds (vanillin,piperonal, and benzaldehyde) and two complex ones (natural vanillaextract and artificial almond essence). The odor intensity ofall the flavorings grew much less rapidly with concentrationthan did taste intensity. The growth of flavor for the complexsubstances and piperonal behaved very much like taste. For vanillinand benzaldehyde, the flavor functions resembled taste functionsat high concentrations but showed a tendency to flatten at lowerconcentrations. These findings implied that, at least for someflavorings, the growth of flavor reflects the most salient featureon the particular concentration range studied. At low concentrationsodor seems to be the most important feature and so flavor functionsare generally flat, but at high concentrations taste becomesthe salient feature and so flavor functions steepen.     

Studies in the morphology and systematics of berberidaceae

The floral vasculature in three allied genera,Plagiorhegma, Jeffersoria andAchyls is investigated, and the results are compared with those ofEpimedium andVancouveria which are related closely toPlagiorhegma andJeffersonia. The vasculature in the receptacle ofPlagiorhegma andJeffersonia is similar, but that ofAchlys is much simpler. Slightly different trace patterns are observed in the sepals ofPlagiorhegma andJeffersonia. InJeffersonia, the 3-trace condition leaving 2 or 3 gaps is most frequently observed, but inPlagiorhegma traces of a double nature leaving a single gap are more frequent. The traces to the innermost sepals, petals and stamens are usually of a double nature leaving a single gap in both genera. Regular division and fusion are not observed in the receptacular stele. The vascular differentiation between sepals and petals is more advanced inPlagiorhegma andJeffersonia than inEpimedium andVancouveria. InAchlys, the traces are all staminal and single throughout their course. Two parts recognized in the pistils ofPlagiorhegma, Jeffersonia andAchlys are traversed by independent vasculature. The comparisons of pistil morphology including vasculature ofPlagiorhegma, Jeffersonia, Achlys, Epimedium andVancouveria lead to the interpretation that the pistils are based on the same morphological plan. The probable evolutionary trend in pistil is then suggested in these five genera.     

Attraction of the grasshopper, Melanoplus sanguinipes, to host plant odors and volatile components

The attraction of the polyphagous grasshopper, Melanoplus sanguinipes (F.), to odors from plant foliage or to chemical components of these odors was tested in a glass Y-tube olfactometer. Humidified air was passed at equal flow rates through a sample chamber containing plant material and an empty control chamber and then through the Y-tube to the holding chamber containing the test insect. Solutions of volatile chemicals in water were metered at a constant rate into the sample air stream with a syringe pump. Insects moving upwind were recorded after entering either the sample or control arm of the Y-tube. Both nymphs and adults were strongly attracted to the odor of chopped and intact seedling foliage of perennial ryegrass and wheat. Chopped leaves but not intact leaves of sorghum and alfalfa also were significantly attractive. The major components of ryegrass odor from both chopped and stem-cut leaves were Z-hex-3-en-1-yl acetate, Z-hex-3-en-1-ol, and pent-1-en-3-ol, in that order, with lesser amounts of E-hex-2-enal. Chopped leaves released many more minor components. The major components when tested individually or in binary and ternary mixtures were significantly attractive to grasshoppers compared to humidified air but not to the degree of whole plant odor. However, a quartenary mixture simulating the odor blend had levels of attractancy equal to that of chopped grass odor. Blends of these 5- and 6-carbon unsaturated alcohols, esters, and aldehydes volatilizing from green plants probably play an important role as olfactory cues for orientation of grasshoppers to food plants.

---

Résumé L'attraction de M. sanguinipes (F.) par l'odeur du feuillage et des composés chimiques de ces odeurs a été examinée dans un olfactomètre en tube de verre en Y. Des flux identiques d'air humidifié étaient introduits dans une enceinte contenant le matériel végétal et dans une enceinte témoin, et, via le tube en Y, dans l'enceinte contenant l'insecte à étudier. Des solutions aqueuses de substances volatiles étaient introduites à un taux constant dans le courant d'air grâce à une seringue. Les insectes se déplaçant contre le vent étaient enregistrés après pénétration dans une branche déterminée du tube en Y. Larves et adultes étaient fortement attirés par l'odeur de feuillage intact ou coupé de semis de Lolium perenne et de blé (Triticum aestivum). Les feuilles coupées, mais non les feuilles intactes de sorgho (Sorghum bicolor) et de luzerne (Medicago sativa) étaient, elles aussi, significativement attractives. Les principales substances constituant de l'odeur de feuilles de Lolium perenne, tant coupées qu'intactes, étaient dans l'ordre de Z-hex-3-en-1-yl acétate, le Z-hex-3-en-1-ol et le pent-1-en-3-ol, et dans une moindre mesure, E-hex-2-enal. Les feuilles coupées libéraient beaucoup plus de composés secondaires. Les principaux constituants testés, seuls ou en mélanges binaires ou ternaires, étaient significativement attractifs, mais moins que l'odeur totale de la plante. Toutefois, un mélange quaternaire, simulant le mélange odorant, avait le même pouvoir attractif que l'odeur de la plante entière. L'union de ces alcools, esters et aldéhydes à 5- et 6-carbones non saturés, volatilisés à partir des plantes vertes, jouent probablement un grand rôle comme signaux orientateurs lors de l'attraction des criquets par leur plantes alimentaires.

     

外来入侵种--紫茎泽兰花芽分化和胚胎学研究

应用石蜡切片法对紫茎泽兰(Eupatorium adenophorum)从花芽分化到胚胎形成的全过程进行系统观察,结果表明:紫茎泽兰从刚孕花序至头状花序的直径(d)大小为1.6～1.8 mm时为花芽分化期;d在1.8～2.0和3.8～4.0 mm范围内为大小孢子及雌雄配子体发育期,其中d在2.3～3.5 mm之间时为减数分裂的主要过程;药壁分化过程为双子叶型,胞质分裂为同时型,绒毡层发育属腺质绒毡层,成熟花粉粒为3-细胞型;胚囊发育属蓼形,胚珠倒生,单珠被,薄珠心;胚胎发育过程中有双胚现象.