The development of pistillate and perfect florets in Xeranthemum squarrosum (Asteraceae)

The formation of capitulum inflorescence with two different types of floret is an interesting issue in floral biology and evolution. Here we studied the inflorescence, floral ontogeny and development of the everlasting herb, Xeranthemum squarrosum, using epi‐illumination microscopy. The small vegetative apex enlarged and produced involucral bracts with helical phyllotaxy, which subtended floret primordia in the innermost whorl. Initiation of floret primordia was followed by an acropetal sequence, except for pistillate peripheral florets. The origin of receptacular bracts was unusual, as they derived from the floral primordia rather than the receptacular surface. The order of whorl initiation in both disc and pistillate flowers included corolla, androecium and finally calyx, together with the gynoecium. The inception of sepals and stamens occurred in unidirectional order starting from the abaxial side, whereas petals incepted unidirectionally from the adaxial or abaxial side. Substantial differences were observed in flower structure and the development between pistillate and perfect florets. Pistillate florets presented a zygomorphic floral primordium, tetramerous corolla and androecium and two sepal lobes. In these florets, two sepal lobes and four stamen primordia stopped growing, and the ovary developed neither an ovule nor a typical stigma. The results suggest that peripheral pistillate florets in X. squarrosum, which has a bilabiate corolla, could be considered as an intermediate state between ancestral bilabiate florets and the derived ray florets.     

蛇足石杉的形态学及不同光照处理下气孔特征的研究

对蛇足石杉的形态学特征进行了重新描述,并对不同光照处理下蛇足石杉叶片的气孔特征进行比较。结果表明：在一定范围内,随着环境中光照强度的增加,气孔长度和宽度、单个气孔面积、气孔密度及气孔总面积都呈增加的趋势。当光照强度超过某一阈值时其气孔指数和气孔密度仍呈增加的趋势,但气孔长度、宽度和单个气孔面积呈变小趋势。小而密的气孔是其适应旱生环境的表现,表明其具有一定的生态适应能力,但进行人工栽培时应避免光照过强。     

Methods for Physical Characterization of Phase-Separated Bodies and Membrane-less Organelles

Membrane-less organelles are cellular structures which arise through the phenomenon of phase separation. This process enables compartmentalization of specific sets of macromolecules (e.g., proteins, nucleic acids), thereby regulating cellular processes by increasing local concentration, and modulating the structure and dynamics of their constituents. Understanding the connection between structure, material properties and function of membrane-less organelles requires inter-disciplinary approaches, which address length and timescales that span several orders of magnitude (e.g., Ångstroms to micrometer, picoseconds to hours). In this review, we discuss the wide variety of methods that have been applied to characterize the morphology, rheology, structure and dynamics of membrane-less organelles and their components, in vitro and in live cells.     

Seasonal,unimodal lunar‐day oscillations in potato O2‐consumption

Abstract

O₂‐consumption of sprouting potato plugs in constant conditions was monitored hourly over ten years. The data for each month was reorganized to obtain the mean rate for each hour of the lunar day. All the data revealed a very low amplitude residual lunar‐day pattern, range less than 1%, with a lesser minimum at upper transit of the moon and major maximum at lower transit. Hourly variances disclosed a significantly greater range from upper transit to lower than for the rest of the day. To discover possible inverting tendencies for the lunar cycles, the mean monthly days were divided into quarters with each quarter expressed as its deviation from the daily mean. Greater negative correlation than random (—0.333) would indicate an inverting semidiurnal cycle if found between adjacent quarters, and a diurnal if between alternate ones. A diurnal cycle was demonstrated (P<.001) using all data when the quarters included centering on upper transit but not when the quarter terminated at this time. Using the upper‐transit‐centered quarterly series an annual modulation was found, with a highly significant diurnal cycle (P<.000001) for the months September‐February and only randomness for March‐August. The results during fall and winter indicate a family of inverting diurnal lunar‐day cycles with maxima at upper transit, lower transit, moonrise, or moonset. Neither diurnal nor semidiurnal lunar cycles occurred the remainder of the year.     

The full moon as a synchronizer of circa-monthly biological rhythms: Chronobiologic perspectives based on multidisciplinary naturalistic research

Biological rhythmicity is presumed to be an advantageous genetic adaptation of fitness and survival value resulting from evolution of life forms in an environment that varies predictably-in-time during the 24 h, month, and year. The 24 h light/dark cycle is the prime synchronizer of circadian periodicities, and its modulation over the course of the year, in terms of daytime photoperiod length, is a prime synchronizer of circannual periodicities. Circadian and circannual rhythms have been the major research focus of most scientists. Circa-monthly rhythms triggered or synchronized by the 29.5 day lunar cycle of nighttime light intensity, or specifically the light of the full moon, although explored in waterborne and certain other species, have received far less study, perhaps because of associations with ancient mythology and/or an attitude naturalistic studies are of lesser merit than ones that entail molecular mechanisms. In this editorial, we cite our recent discovery through multidisciplinary naturalistic investigation of a highly integrated circadian, circa-monthly, and circannual time structure, synchronized by the natural ambient nyctohemeral, lunar, and annual light cycles, of the Peruvian apple cactus (C. peruvianus) flowering and reproductive processes that occur in close temporal coordination with like rhythms of the honey bee as its pollinator. This finding led us to explore the preservation of this integrated biological time structure, synchronized and/or triggered by environmental light cues and cycles, in the reproduction of other species, including Homo sapiens, and how the artificial light environment of today in which humans reside may be negatively affecting human reproduction efficiency.     

Variations in the locomotor activity of the Mexican wolf (Canis lupus baileyi) respect to moon periodicity: a study in an outdoor enclosure

It is assumed that the response of the regulatory system of mammal activity depends on the changes in light intensity throughout the 24-h cycle. The aim of this study was to determine whether the moon luminosity cycle exerts an effect on the locomotor activity of the Mexican wolf (C. lupus baileyi). Data collection was carried out with the actimetry, of 11 individuals were analyzed using ANOVA to determine the effect of the lunar cycle. Significant differences were encountered between moon phases (p = 0.001), with a decrement of activity during new and full moon. However, effects were dependent also on the age of the individuals and the daylight period. On the other hand, it is a possible regulation of the activity pattern by the effect of lunar periodicity. This periodicity needs a more detailed examination to determine its adaptive function.     

Geographical variation in reproductive biology is obscured by the species problem: a new record of brooding in Porites cylindrica,or misidentification?

Little is known about the reproductive biology of corals from the Philippines, despite this archipelago being at the center of coral reef biodiversity. Here, we report on the reproductive biology of a branching poritid species provisionally identified as Porites cf. cylindrica in the Bolinao‐Anda reef complex (BARC), northwestern Philippines. Histological examination and ex situ planulation observations reveal P.cf. cylindrica colonies to be gonochoric brooders that release actively swimming zooxanthellate larvae. Planulation appeared to occur throughout the year and there was significant lunar periodicity in planular release. The mean peak of release occurred from the 25th to 29th lunar day or just before the new moon, while peak in diel timing in planulation occurred during daytime between 08:00–11:00 h. Elsewhere in the Pacific, Porites cylindrica colonies are reported to broadcast spawn. If our species identification is correct, then this is the first report of brooding in P. cylindrica. Although there are no apparent morphological differences between the coral in this study and P. cylindrica reported from other sites, an alternative explanation for our findings is that our provisionally identified Porites cf. cylindrica is a different species. If so, our findings further highlight how difficulties with species identification in corals can influence our understanding of geographical variation in reproductive biology.     

Activity-driven sharpening of the retinotectal projection in goldfish: Development under stroboscopic illumination prevents sharpening

Blocking or synchronizing activity during regeneration of the retinotectal projection prevents both the sharpening of the retinotopic map recorded on tectum and the refinement of the structure of individual arbors within the plane of the map, and this refinement is triggered by N-methyl-d-aspartate (NMDA) receptors. We tested whether activity-driven refinement also occurs during development of the projection in larval and young adult goldfish. Shortly after hatching, larval goldfish were placed into tanks within light-tight chambers illuminated by a xenon strobe at 1 Hz for 14 h of each daily cycle. Fish were reared for 1.5–2 years, until large enough to record in our retinotectal mapping apparatus (6 cm length). Age- and size-matched controls had normal maps with multiunit receptive fields (MURFs) recorded at each tectal point of 10.8° (0.16 S.E.M., n = 5), whereas the strobe-reared fish had only roughly retino-topic maps with much enlarged MURFs averaging 26.7° (1.41 S.E.M., n = 5). This enlargement represents an abnormal convergence onto each tectal point, as the maps failed to sharpen during development. The arbors of individual retinal axons were stained with horseradish peroxidase (HRP) in larval fish and in adult strobereared and control fish. They were drawn with camera lucida from tectal whole mounts, and analyzed for spatial extent in the plane of the retinotopic map, order of branching, number of branch endings, depth of termination, and caliber of the parent axon. Arbors from larval fish (1–2 weeks) were small (approximately 50 × 40 μm) with less than 10 branches, occupied a single strata, and could not be separated into different classes by caliber of axon. The 87 arbors stained in control adult fish (6 cm long) were much like previously examined adult arbors, with those from fine, medium, and coarse axons averaging 115, 166, and 194 μm in extent, respectively, and having 17–24 branch endings. The 110 arbors from 12 strobe-reared fish were often abnormal. Although the fasciculation was normal, the extrafascicular routes were abnormal with reversing turns. The axons often had branches along their course, and these branches were scattered across a wider extent, rather than forming a distinct cluster. In contrast, neither the number of branches nor the depths of termination was significantly changed in any group. The coarse caliber arbors were most abnormal, being 64% longer and 30% wider than controls. The fine caliber arbors were also significantly larger by about 20%, but the medium caliber arbors were not enlarged. The enlarged arbors partially account for the unsharpened electrophysiological maps. Together the results show that during development, as well as during regeneration, the retinotectal map is subject to an activity-driven sharpening process. © 1993 John Wiley & Sons, Inc.     

化学调控剂对减轻水稻抽穗灌浆期阴害效应的综合评判

应用灰色关联选择受阴害水稻的主要受害指标,以层次分析法和模糊综合评判分析了化学调控剂对减轻水稳在抽穗灌浆期不同时段阴害的效应,结果表明,阴害危害的最大3个指标为结实率、净同化率和根系活性强度;在水稻抽穗后6－20d出现阴害时,喷施化学调控剂的增产效果最明显,隶属度达0.7869。