The Initiation and Growth of Tulip Bulbs

Tulip mother bulbs contain daughter bulbs, and second-generationdaughter bulbs are initiated within these daughter bulbs, fromFebruary to July. Initiation takes place progressively, thefirst-initiated bulbs being in the axils of the outermost scales.The innermost second-generation daughter bulbs are finally initiatedat the same time as the flower within the daughter bulb. Thelatest-formed bulbs grow much more rapidly than the others,and soon become larger than the first-formed ones. Later inthe season, growth of daughter bulbs falls into three phases,corresponding roughly with autumn, winter, and spring; growthis rapid in autumn and spring, and slower in winter. The ratesof daughter bulb growth in the autumn are affected by the amountof suppression by the mother bulb apex, but later these differencesdisappear. The durations of the phases of growth also vary withthe position of the daughter bulb. The outer daughter bulbsgrow for a longer time during the autumn phase than the innerones, so that differences in size due to variation in growthrate are partly nullified. In early spring, all daughter bulbsresume rapid growth simultaneously. Final bulb weight is thenapproached asymptotically, with the innermost bulbs having thehighest weights.     

Rhythmic Growth in Excised Sprout-leaves of Onion Bulbs

Sprout leaf preparations, consisted of the inner 6 or 7 sprout leaves attached to the base plate of bulbs of Allium cepa cv. Downy Yellow Globe. The preparations excised from dormant bulbs were capable of sprouting. The elongation of the sprout leaves in the light was inhibited by a field pretreatment of 2000 mg/1 M.H.-30 (30% maleic hydrazide) and stimulated by incubation in the dark. Rapid cooling of the bulbs prior to excising of the preparations had no effect on sprouting. The ability of the sprout leaf preparations to elongate followed a cyclical time course, displaying maxima 8 to 12 weeks apart. Pretreatment with M.H.-30 inhibited this periodicity.     

The Initiation, Growth, and Characteristics of a Tissue 2

The rate and extent of initiation of callus from potato tuberdiscs depends on the concentrations of auxin and kinetin inthe medium on which they are grown. NAA is the most effectiveauxin, initiating callus at a concentration (0. 01 mg/1) anorder of magnitude lower than for IAA or 2,4-D. There is a week'slag before initiation begins with IAA or 2,4-D. In combinationwith each auxin, kinetin is inhibitory to initiation of callusand its growth on the explant. High-intensity light and lowtemperature are also inhibitory. In isolated callus subcultured so as to prevent dilution ofits accumulated auxin, the only effect of varying exogenousauxin levels is as a progressive inhibition by NAA. If thisdilution is permitted, however, 2,4-D and IAA have an optimumgrowth promoting activity at 1 mg/1, whereas the effect of NAAincreases up to 10 mg/1. The growth of the callus is affectedby agar concentration (1 per cent optimum), and is halted bypH values below 5. The callus grows on various carbon sourcesbut is dependent upon one or more components of N. Z. Amine;it also requires a number of micronutrients. A suspension culture from the callus exhibits the usual growthcurve. The phenolic content follows a pattern different fromthat of growth, protein, and RNA content, and phenolics arerapidly synthesized as active growth ceases. In contrast tothe callus tissue, the suspension culture grows at a wide rangeof pH values and buffers the medium. At low temperatures in the light, potato discs produce greencallus with a chlorophyll content corresponding to that of thediscs from which they grew. The isolated callus tissue doesnot require kinetin and produces and excretes its own cytokinin(s).The amount synthesized varies over the growth cycle.     

Factors Affecting the Growth of Daughter Bulbs in the Tulip

The relative growth rate (R_w) of daughter bulbs of the tulipcultivar Rose Copland was remarkably constant during the springperiod of growth in four seasons at two sites. The Q₁₀ of R_wwas 2.2, and the long period of constant R_w is attributed tocompensation of a fall with age by increasing temperatures inthe spring. Final bulb weight differed among four cultivarsbecause of differences in R_w and in initial daughter bulb weights. Partial defoliation reduced R_w roughly in proportion to theleaf area removed, and removal of mother bulb scales resultedin reduced leaf area, fewer daughter bulbs, and a lower daughterbulb R_w. Heat-treatment of mother bulbs before planting (blindstoken)killed the flower within the bulb, inactivated the apical dominanceexerted by the flower, and resulted in a higher initial daughter-bulbweight at the start of the spring period of exponential growth.The R_w of heat-treated and control daughter bulbs were not different,neither were the leaf areas, so it is assumed that final daughter-bulbweights were higher following treatment because of increasedsink strength. The economic implications of these findings arediscussed.     

The Contractile Roots of Narcissus

All the tissues in the contracted region of the contractileroot of Narcissus become adjusted to the shortening of the root,which is brought about by vertical contraction and radial expansionof the inner cortical cells. Consequently the outer cortex includingthe exodermis is lifted passively in large wrinkles over thesurface, while the vertical walls of cells in the stele becomeundulated or indented as in the case of the vessels. These phenomenaare primarily brought about by the mechanical process of liftingand pulling due to the shortening and radial expansion of theinner cortical tissue. The possible mechanism of contractionof this cortical tissue is discussed.     

Basal Plate Tissue in Narcissus Bulbs and in Shoot Clump Cultures: Its Structure and Role in Organogenic Potential of Single Leaf Cultures

Light microscopy demonstrated that the apparently amorphous,achlorophyllous tissue at the base of in vitro shoot clump cultureof Narcissus was comparable in structure to the basal plateof Narcissus bulbs. Both had very complex vascularisation andsmall, densely packed parenchymatous cells. In shoot clump cultures, primordia were produced by meristematiczones at the surface of this achlorophyllous tissue, very closeto the base of leaves. Single leaf units excised from the invitro shoot clump cultures with a wedge of basal achlorophylloustissue were highly organogenic when used as secondary explantsfor in vitro culture of Narcissus. No organogenesis occurredin the absence of the leaf base and achlorophyllous (basal plate)tissue and little organogenesis occurred unless the leaf baseand basal plate tissue were immersed in the culture medium (i.e.explants inoculated into liquid medium or upright in agar-solidifiedmedium). After two 5-week culture passages in liquid medium, more thanfive leaves were produced per leaf base inoculated. Thus rapidmicropropagation of Narcissus can be achieved using only thebase of single leaf units excised from shoot clump cultures.Copyright1993, 1999 Academic Press Anatomy, basal plate, bulb, in vitro, leaf culture, Narcissus, organogenesis     

Initiation of Staphylococcal Growth in Laboratory Media

The effects of pH and NaCl concentration on the probability of aerobic growth initiation in Brain Heart Infusion broth at 30 C by five staphylococcal strains producing enterotoxins A, B, C, and D were studied in a factorial design experiment. Statistical analysis of the data indicated: (i) significant effects of pH, NaCl, and strain on the probability of growth; (ii) diverse effects of NaCl with various pH levels and strains; (iii) essentially a linear relationship between NaCl concentration and probability of growth initiation when data for all strains were pooled; (iv) the relationship between NaCl concentration and probability of growth initiation varies from linear to sigmoid, depending on the pH of the broth, when the statistically untreated (raw) data are plotted for each strain. Equations were derived which relate the decimal reductions of the number of cells of a staphylococcal population to the concentration of NaCl and pH of broth to which the population was exposed. From the equations, the probability that one cell is capable of initiating growth can be calculated. The impact of these types of studies on the development of realistic staphylococcal standards in foods is discussed.     

2种石蒜生长发育期鳞茎内源激素的动态变化

应用酶联免疫吸附测定法（ELISA）研究了石蒜与中国石蒜不同生长发育期鳞茎内源激素质量摩尔浓度的动态变化,分析了内源激素与2种石蒜生长发育的关系。结果表明,花芽分化前期2种石蒜鳞茎IAA浓度较低,而iPAs、ABA与GAs浓度较高;临近抽葶IAA浓度均有所增加,而iPAs与Zrs、ABA与GAs浓度均降到极值。花期ABA、GAs与ZRs浓度均有所回升,说明高浓度的ABA与GAs对2种石蒜的开花可能起正向调控的作用,但对叶生长的协同规律不明显。内源激素比例分析表明,ZRs/IAA、GAs/IAA、ABA/GAs三者比例高有利于2种石蒜的花原基分化,三者比例低则有助于2种石蒜的叶生长。     

Initiation of Staphylococcal Growth in Processed Meat Environments

The probability of staphylococcal growth initiation in laboratory-made cured meats is investigated and compared with growth initiation in broths.     

The Growth of the Shoot Apex and the Apical Dome of Barley During Ear Initiation

The growth of the floral main shoot apex of spring barley wasstudied during the period of ear initiation (that is, from initiationof the collar primordium until maximum primordium number wasattained). While floral primordia were being initiated the relativelength growth rate of the shoot apex was low. After maximumprimordium number there was about a twofold increase in relativelength growth rate. Estimates of the volume, fresh and dry weightof the floral apex indicated that the relative weight growthrate was also low at first and increased after maximum primordiumnumber. The rates of growth and the size at initiation of thefloral primordia was affected by their position on the floralshoot apex. The relative volume growth rate increased acropetallyfrom the first initiated (collar) primordium. The collar wasthe smallest and each subsequently-initiated primordium increasedin length. The diameter of the newly-initiated primordium alsoincreased until more than half the primordia had been initiatedand then it declined. The apical dome increased in both lengthand diameter and both were at a maximum at the time of the double-ridgestage and then both measurements declined. Length and diameterwere at a minimum at maximum primordium number. Subsequentlythere was an increase in the length of the dome, after whichboth the dome and some of the last formed, distal primordiadied. The period of spikelet initiation therefore is a stage duringwhich the relative growth rate of the floral shoot apex is low,there are changes in the size of the dome and the primordiashow a progression of increasing relative growth rates acropetallyalong the shoot apex. These changes produce the embryo ear inwhich the most advanced spikelets are in the lower mid-partof the ear. Changes in size of the apical dome prior to maximumprimordium number may be related to the subsequent death ofspikelet primordia and therefore also to grain number in themature ear.     

Initiation and Growth of Callus and Cell Suspensions of Theobroma cacao L

Callus and suspension cultures of Theobroma cacao L., initiatedfrom immature cotyledons of beans from pods harvested 120–130days after pollination were established. A modified B-5 or Murashige—Skoogagar medium sustained growth of callus without loss of vigourafter each sub-culture. A 15-fold weight increase occurred duringthe 4 week culture periods at 30 ± 1 °C. Coconutwater improved callus growth substantially. The optimum hormonalconcentrations for growth of suspensions were 0.5 mg 1^–1of 2, 4-dichlorophenoxyacetic acid and 0.1 mg I^–1 of kinetinin a Murashige—Skoog basal medium liquid medium. The optimumtemperature for growth of suspensions was 25–30 °C.The cell number and cell mass of suspensions increased 20-foldin 14 days. No organogenesis or embryogenesis was observed. Theobroma cacao L., acao, cell culture, suspension culture, tissue culture.     

Initiation, Growth and Nuclear Characteristics of Tissue Cultures of Paeonia suffruticosa

Tissue cultures of the garden paeony, Paeonia suffruticosa have been established using explants of etiolated stems. Callus formation was induced on agar-solidified media containing ammonium ions or amino acids together with the hormones 2,4-dichlorophenoxyacetic acid and kinetin, but not on media lacking the reduced nitrogen component. Attempts to induce callus from explants from green plants were completely unsuccessful and were characterized by the production of intense brown colorations, both of the explant and the medium. Subcultured tissue without the added hormones produced roots, both on solid and liquid media. Growth was tested on a range of liquid media, SH/2, SH, SH × 2 and SH—M, containing 1250, 2500, 5000 and 2500 mg/l potassium nitrate. The SH—M medium also contained 1650 mg/l ammonium nitrate. Growth measured as increased fresh weight was best in the SH/2, SH and SH—M media and was curtailed in the SH × 2 medium. Soluble protein content was highest at the lowest nitrogen concentration. A histochemical comparison of tissue grown on the SH/2, SH—M and SH—M lacking hormones showed that the cells in all the cultures remained diploid while differences were established in total nuclear protein, measured using the ninhydrin-Schiff procedure. Nuclei from SH—M grown cells have a higher protein content than those from the SH/2 medium while cells from the SH—M medium lacking hormones show a further increase in nuclear protein. This raises the question whether this change in nuclear protein is related to the morphogenesis of roots which occurs in this medium.     

不同温度下贮藏的食用百合种球发根和完好率以及嗣后的植株生长

在采用的温度2、7、12和18℃中,随着贮藏温度升高和时间的延长,食用百合种球腐烂程度加重。2℃处理130d对种球质量无明显影响。随着种球贮藏时间延长,鳞茎产量递增。但贮藏时间过长,影响植株生长。兰州百合于2℃下贮藏的鳞茎产量高于7℃下贮藏的,12℃下贮藏的种球种植后不萌发;龙牙百合以7℃下贮藏的产量为最高,2℃下的次之;宜兴百合以2℃下贮藏的产量为最高,12℃下为最低。兰州百合和宜兴百合适合于2℃下贮藏,龙牙百合的最佳贮藏温度为7℃。     

A Growth Initiation Factor for Host-Independent Derivatives of Bdellovibrio bacteriovorus

Host-independent (H-I) derivatives of Bdellovibrio bacteriovorus 109 Davis could not be isolated when concentrated suspensions of host-dependent (H-D) cultures, washed free of spent medium, were plated on host-free media. However, H-I colonies did appear when spent broth was incorporated into the isolation medium, indicating the presence of a factor in the spent medium essential for the growth of H-I cells. This growth factor (GIF) was also present in cell-free extracts of Escherichia coli and a variety of other microorganisms including H-D and H-I derivatives of strain 109 Davis. GIF was heat stable, non-dialyzable, and present in both soluble and particulate fractions of extracts. Heating of extracts at 70 C for 10 min resulted in 10- to 40-fold stimulation in GIF activity, and evidence for a heat-labile inhibitor was obtained. Colonies appearing on host-free medium in these experiments were shown to be those of typical H-I derivatives by isolation and subsequent host-independent cultivation of these organisms. GIF was a conditional requirement dependent on age and size of inoculum for all H-I derivatives characterized. Although GIF stimulated the growth of washed exponential phase cells transferred to fresh medium, it was not essential for growth. However, it was essential for the initiation of growth of washed stationary phase cells from small inocula transferred to fresh medium. It is proposed that GIF is required to initiate growth of metabolically quiescent cells.