Floral Induction of Xanthium strumarium in Long Days

An efficient method of inducing flowering in the normally strictshort-day plant, Xanthium strumarium L., in long days is described.Plants were grown in 16-h long days and subjected to two thermocycleswith a root application of gibberellic acid at the 8th h ofthe light period. A thermocycle was defined as follows. Forthe first 8 h of the 24-h cycle, the temperature was 4 °C;for the remaining 16 h, it was 23 °C. The light was on forthe first 16 h and off for the remaining 8 h. Xanthium strumarium L., floral induction, thermoperiod, gibberellic acid     

锦带花的花粉活力、柱头可授性及传粉者的观察

在野外实地观测锦带花(Weigela florida(Bunge)A．DC．)的开花动态和访花者,在显微镜下观测柱头和花粉的形态及花粉-胚珠比,用TTC法测定锦带花花粉的活力,用联苯胺-过氧化氢法测定柱头可授性。结果表明,锦带花的花粉活力在开花时达70％以上,且能维持3d,之后明显下降。锦带花的柱头在开花3h后多数呈白色、二裂、具可授性,柱头的可授期持续2～3d。柱头与花药之间有5．3士0．9mm的空间距离,自然条件下难于自花授粉．开花当天7．00～10．00之间访花者最丰富,开花第2天访花者减少,开花第3天时访花者更少。在锦带花上记录到的访花者隶属于膜翅目、鳞翅目和双翅目,其中,熊蜂和蜜蜂是主要传粉者。     

Experimental Induction of Dilatation Meristems in Melia azedarach L.

Dilatation meristems were induced experimentally in the barkof Melia azedarach L. by mechanical bark blocking, wounding,and by application of 1.0% of either naphthaleneacetic acid(NAA) or of ethrel. The treatments induced the formation ofdilatation meristems in the rays, in the axial phloem parenchyma,and in the primary cortex. Dilatation was the result of bothcell divisions and cell enlargement. The dilatation meristemswere sometimes several cells wide, and were formed in all possibleorientations; some were even branched. In many cases, whirlswere formed as the result of dilatation activity in many directionsover a small bark area. The possible hormonal regulation ofdilatation activity is discussed. Auxin, bark, cortex, dilatation, ethylene     

Floral Induction in Short-Day Lemna paucicostata 6746 by 8-Hydroxyquinoline, under Long Days

Lemna paucicostata 6746 is a short-day duckweed and flowersin response to a single photoinductive cycle. Its critical darkperiod requirement is ca. 10 h. Flowering in this duckweed couldbe induced by 8-hydroxyquinoline (8-HQ) under an otherwise non-inductivelong-day regime of 16 h light and 8 h darkness; the criticaldark period requirement for initiation of flowering was thusreduced by at least 2 h. However, 8-HQ was ineffective in initiatingflowering in strain 6746 under continuous illumination. Atomicabsorption analysis of the plant material revealed that thecontent of both iron and copper is markedly higher in the plantstreated with 8-HQ. A comparison of the effects of 8-HQ and thoseof EDTA and ethylenediamine-di(o-hydroxyphenylacetic acid),on flowering of strain 6746, has also been made. (Received August 23, 1983; Accepted October 18, 1983)     

Shoot Apical Meristems of Picea sitchensis Seedlings Accelerate in Growth Following Bud-set

First-year seedlings of Picea sitchensis were induced to setbuds by transferring them from long days (17 h) to short days(10 h at 20 °C, 12 h night at 12 °C). After 20 shortdays, the seedlings stopped growing in height, the shoot apicaldomes began enlarging and the transverse growth rates of theshoot apical dome tissues increased. For about 25 days thereafterprimordia were produced faster within the developing buds thanat the apices of seedlings which had been kept in long daysto prevent bud-set. Accelerated primordia production after bud-setenables the largest possible buds to be formed during the frost-freeperiod before winter. Picea sitchensis, apical meristem, bud-set     

Floral Induction in Wolffia microscopica by Salicylic Acid and Related Compounds under Non-inductive Long Days

Flowering in Wolffia microscopica, a short-day plant, couldbe induced with salicylic acid (SA), under long days. Aspirin,benzoic acid and salicylaldoxime were also effective for inductionof flowering in this duckweed. Amonsgt these, SA is the mosteffective compound, as it could induce flowering even at 10^–7M. Flowering was further enhanced when Wolffia fronds were subjectedto short days, in the presence of SA. However, SA neither showedany effect on flowering ofW. microscopica in the absence ofEDTA in the nutrient medium, nor could it, by itself, supporteven the vegetative growth. The probable mechanism of actionof SA has also been discussed. It appears that the effect cannotbe due simply to chelation of metal ions and perhaps the salicylmoiety itself exerts a specific effect. (Received March 15, 1983; Accepted May 6, 1983)     

Induction of Flowering in a Duckweed, Wolffia microscopica, under Non-inductive Long Days, by 8-Hydroxyquinoline

Wolffia microscopica, a duckweed, flowers in response to a singlephotoinductive SD cycle of 16 h dark and 8 h light. Floweringin W. microscopica could be induced, under non-inductive longdays, by 8-hydroxyquinoline (8-HQ). Flowering was initiatedwith 10^–6 M 8-HQ and maximum flowering (ca. 75%) was obtainedat 5 x 10^–6M level. Flowering was accentuated furtherwhen plants, supplied with 8-HQ, were subjected to SD cycles. (Received September 13, 1985; Accepted December 4, 1985)     

Induction of Multinuclear Cells in the Apical Meristems of Allium cepa by Geomagnetic Field Outrages

This paper is a result of a long-term study of the apical meristems of the Allium cepa L. seedlings against a background of naturally changing geomagnetic field. Multinuclear cells, large cells with large nuclei, and giant cells with giant nuclei were detected. Changes in cellular structures were revealed, and the time-course of this process was followed. Changes in the cellular structure of meristems were correlated with the fluctuations of magnetic field of the Earth. The experiments conducted with in vitro culture of apical meristems showed that the observed changes were regulated on the local level.     

The Interaction of knotted1 and thick tassel dwarf1 in Vegetative and Reproductive Meristems of Maize

In Arabidopsis, SHOOT MERISTEMLESS (STM) and CLAVATA1 (CLV1) competitively regulate meristem homeostasis. Here, we explore the interaction of their maize homologs knotted1 (kn1) and thick tassel dwarf1 (td1). kn1 mutants form fewer lateral organs and td1 inflorescences are fasciated with additional floral organs. Double mutants show kn1 epistatic to td1 in seedling and ear development but dose-sensitivity exists later to promote leaf initiation. Thus kn1 and td1 function in a pathway to maintain meristem homeostasis but their products may interact with different partners during development.     

超长住院日患者分布特征与影响因素分析

目的 分析新疆某三级甲等医院超长住院日患者分布情况及其影响因素。方法 采用Logistic回归模型。结果 费别、性别、病种、出院转归、是否转科与是否手术是住院日超长的影响因素。转科患者、手术患者以及病种是影响住院日超长的重要危险因素。结论 合理安排转科患者与手术流程,制定以病种为特点的平均住院日考核值能有效控制超长住院日,进而有效降低平均住院日。     

Promotion and Inhibition of Inflorescence Growth by Long Days in Short-day Plants

Results of previous investigators have indicated that long periodsof light intercalated between inductive short-day cycles havean inhibitory effect on inflorescence growth in short-day plants.The present experiments show that such light periods can eitherpromote or inhibit inflorescence growth in Xanthium pemtsylvanicumand Chenopodium amaranticolor depending on their previous degreeof induction. Intercalated light exerts an inhibitory influence on the inductiveprocesses occurring during the dark period which follows itwhen unifoliate Xanthium plants have been previously exposedto not more than one short day and when fully foliated Chenopodiumplants have been previously exposed to not more than one ortwo short days. When plants are more strongly induced initially,an intercalated light period has a very marked promoting effecton the dark period succeeding it. In Xanthium this stimulatoryeffect increases with the duration of the light period up toan optimum of approximately 80 hours. It is suggested on the basis of available evidence that thepromotive effect of such intercalated light possibly affectsthe sensitivity of the apex to inductive stimuli and that itsinhibitory effect acts on the inductive processes occurringin the leaves.     

Evidence for a Flowering Inhibitor Produced in Long Days in Kalanchoe blossfeldiana

Experiments with Kalanchoe blossfeldiana are described in whichperiods of short-day treatment were interrupted by intercalatedlong days or light breaks during long dark periods. The effectsof 24-hour dark periods preceding and following such intercalatedlong days were also investigated. The results of these experiments have shown that: Single longdays intercalated between numbers of short days have a positiveinhibitory effect on flower initiation and are not merely ineffective.The inhibitory effect expressed as the number of inductive cyclesannulled is approximately additive, provided the long days areinterspersed with short days, but not if several long days aregiven consecutively. On the average 1 long day is capable ofannulling the flower-promoting effect of about 1 short days.To a first approximation flower numbers in Kalanchoe increaseexponentially with the number of inductive cycles given—upto at least 12 short days; the inhibitory effect of long daysinterspersed with short days also fits an exponential curve;i.e. the inhibition is roughly proportional to the amount ofprevious photo-periodic induction. A light break of as littleas 30 seconds' duration given in the middle of a long dark periodis as inhibitory as a long day. If followed by a long dark periodthe inhibition of an intercalated long day is almost completelyneutralized; a long dark period preceding it has no such effect. These results have been interpreted as due to the interactionof a flowering inhibitor with a reaction leading to flowering.A mechanism involving competitive inhibition of an adaptivelyformed enzyme has been described as a possible example of thekind of reaction which could account for the results presented.     

Anatomy of Watermelon Embryo Sacs Following Pollination, Non-pollination or Parthenocarpic Induction of Fruit Development

There is little information on the fate of embryo sacs in plantovules if pollination is prevented. In this study embryo sacsfrom watermelon were observed over a 13 day period followingflowering with (a) normal pollination, (b) non-pollination and(c) induction of parthenocarpic fruit development with naphthaleneacetic acid. Following pollination, and prior to fertilizationapproximately 2 days later, the embryo sacs completed developmentand consisted of two synergids with prominent filiform apparatus,an egg cell, a central cell with two polar nuclei and threeantipodal cells. Sperm nuclei were observed within the embryosac at 2 days and by 4 days the endosperm was proliferating.In the non-pollination treatment the embryo sac was still intactafter 4 days although the antipodal nuclei were becoming hardto distinguish. By 7 days only the two synergids and the eggcell were still well defined, the polar nuclei appeared in somepreparations to be fused, and the antipodals had degenerated.By 10 days the embryo sac was a structure-less watery mass.In parthenocarpic fruit the fate of the embryo sac was similarto that in non-pollinated fruit except that final breakdownwas delayed past 10 days. Maturity of the majority of embryo sacs in an ovary appearedto be contemporaneous with penetration of the pollen tube, andon the basis of the anatomical results it seems possible thatembryo sacs could be fertilized up to 2 days beyond the normaltime. Citrullus lanatus, watermelon, embryo sac, anatomy, pollination, parthenocarpy     

Human Retinal Light Sensitivity and Melatonin Rhythms Following Four Days in Near Darkness

The rods in the retina are responsible for night vision, whereas the cone system enables day vision. We studied whether rod function in humans exhibits an endogenous circadian rhythm and if changes occur in conditions of prolonged darkness. Seven healthy subjects (mean age±SD: 25.6±12.3 yr) completed a 4.5‐day protocol during which they were kept in complete darkness (days 1 and 4) and near darkness (<0.1 lux red light, days 2 and 3). Electroretinography (ERG) and saliva collections were done at intervals of at least 3 h for 27 h on days 1 and 4. Full‐field ERGs were recorded over 10 low‐intensity green light flashes known to test predominantly rod function. As a circadian marker, salivary melatonin concentration was measured by radioimmunoassay. The ERG data showed that rod responsiveness to light progressively diminished in darkness (significantly lower a‐ and b‐wave amplitudes, longer b‐wave implicit time). The decrease in amplitude (b‐wave) from day 1 to day 4 averaged 22±14%. After correction for the darkness‐related linear trend, the circadian variations in ERG indices were weak and usually non‐significant, with slightly higher responsiveness to light during the day than night. Rod sensitivity (by K index) tended to decrease. Strikingly, the overall amount of melatonin secretion (area under 24 h curve) also decreased from day 1 to day 4 by 33.1±18.9% (p=.017). The drift of the melatonin rhythm phase was within the normal range, less than 56 min over three days. There was no significant correlation between the changes in ERG responses and melatonin. In conclusion, scotopic retinal response to (low‐intensity) light and the amount of melatonin secreted are diminished when humans are kept in continuous darkness. Both processes may have a common underlying mechanism implicating a variety of neurochemicals known to be involved in the regulation of both photoreceptor and pineal gland function.     

水稻长日照开花因子Lfm1的图位克隆

开花期是水稻最重要的农艺性状之一,水稻的花期决定着水稻的地区适应性和最终产量。人工选择使水稻从短日照向长日照、低纬度向高纬度扩张,因此水稻已逐渐进化出适应长日照条件下的开花调控机制。目前,虽然鉴定了一些影响水稻长日照的开花基因如SDG724、RFT1、EHD4、DTH2,但是挖掘水稻长日照开花基因还十分有限。本研究通过筛选水稻突变体库,获得一批在长日照下花期有显著差异的突变体材料,其中一份突变体lfm1(late-flowering mutant1),在长日照条件下开花延迟,在短日照条件下开花时间正常。通过图位克隆,将Lfm1基因初定位至第8染色体端粒附近。进一步的精细定位将Lfm1基因定位于分子标记8-0.269和与8-0.283之间,范围为12 kb,该区域包括3个候选基因。经测序分析发现,在突变体lfm1中,LOC_Os08g01420基因的第六外显子2800处缺失9个碱基,突变体lfm1等位于已报道的突变体ehd3。在适度(中日照条件下,~12 h/12 h)的光照条件下,突变体lfm1表现为穗粒数增多,生育期略延长,具有应用于生产的潜力。Lfm1基因的克隆为培育适应不同生态区域的水稻材料提供了重要的基因资源。     

Induction of Rat Brain Tubulin Following Ammonium Ingestion

The effect of oral administration of ammonium acetate for 2, 15, 30, and 100 days on protein synthesis in rat brain was investigated. Although protein synthesis changes were modest, i.e., maximal increase of 24%, there was induction of synthesis and accumulation of a protein with an Mr of 55,000. We show, on the basis of its position on two-dimensional electrophoresis and its immunological reactivity, that this protein is tubulin. Its content increased by 33% as determined by isolation of tubulin after 15 days of oral administration of ammonium and to 49% after 100 days as determined by quantitative immunoblotting.     

Localization of Nucleic Acid Synthesis in Root Meristems

Adenine-8-C1¹⁴ was supplied to roots of Vicia faba and Alliumascalonicum and its incorporation into DNA was studied fromautoradiographs of hydrolysed sections. These roots have a quiescentcentre to the meristem where the cells do not synthesize DNAand probably, therefore, play no part in the construction ofthe root. The boundary between the quiescent centre and thecentral cap initials is clearly denned and this suggests thatthere is as little cell interchange between the histogens asthere is in roots with visibly discrete histogens.