Enviromentally Induced Changes in Clamp Connection Incidence in Hyphal Branching Systems of Coprinus disseminatus

The incidence of clamp connections among surface hyphae at thecolony margin of apparent dikaryons from four stocks of Coprinusdisseminatus has been investigated under several environmentalconditions. On 2 per cent malt agar, clamp connections are formed at allnodes of the main leader hyphae, but they are absent from theearlier-formed nodes of primary branch hyphae. Most primarybranches have begun to form clamp connections by their fifthcell division, and continue to do so subsequently. Onset ofclamp connection formation in primary branches is delayed whenthe concentration of malt in the medium is reduced. The occurrenceof clamp connections on main leader hyphae is reduced or preventedwhen nutrient supply in the medium is reduced, or when the mediumis ‘pre-staled’ by previous growth of C. disseminatus.Clamp-free main hyphal tips revert to formation of clamp connectionswhen the intact hyphal system is transferred to more favourableenvironmental conditions. Presence of clamp connections on bothmain and branch hyphae is associated with high hyphal diameter,and in some instances, also with high hyphal extension rate. The significance of these observations to mechanisms of growthof hyphal branching systems and their relevance to other speciesthat form clamp connections intermittently, are discussed.     

Analysis of Branching in Spring-sown White Lupins (Lupinus albusL.): The Significance of the Number of Axillary Buds

Plant density and sowing date were shown to affect branchingin spring-sown white lupin (Lupinus albusL.), but the responsevaried among environments. The patterns of primary and secondarybranching in the cv. Lublanc were studied as a function of boththe number of axillary buds and the plant growth rate. Fieldexperiments that used a wide range of sowing dates and plantdensities to alter plant architecture were conducted over 5years, and these were supplemented with data from additionalglasshouse and growth cabinet experiments. The number of axillary buds on the main stem or primary branches,which determined the potential number of branches, increasedlinearly with the number of nodes. In situations where all axillarybuds did not produce branches, it was found that the numberof primary and secondary branches produced was related to theplant growth rate at the beginning of branch elongation. Knowledgeof the number of axillary buds improved the analysis of theinteraction between cultural practices and environmental conditionson plant architecture. The variability of branching potentialamong genotypes was discussed. Lupinus albus; branches; axillary buds; growth; sowing date; plant density     

The Initiation and Development of Secondary Xylem in Axillary Branches of Populus deltoides

The initiation of secondary xylem in elongating axillary branchesof Populus deltoides Bartr. ex Marsh. is independent of thatin the main stem. Although secondary xylem differentiates acropetallyin the main stem, it does not differentiate from the stem intothe axillary branch. Secondary xylem is usually initiated ininternode 4 (occasionally 3) of the axillary branch, and fromthis site it develops both acropetally in the elongating branchand basipetally toward the main stem. Secondary vessel differentiationalways precedes fibre differentiation. Although secondary xylemdifferentiates in internodes that have ceased elongation, itdifferentiates first in traces of the vascular cylinder servingrapidly expanding and maturing foliage leaves. As younger leaveson the branch expand and mature, secondary xylem differentiatesin their traces eventually producing a complete secondary vascularcylinder. Scale leaves do not initiate secondary xylem independentlyin their traces; they are activated by adjacent traces in thevascular cylinder serving foliage leaves. Once established,the primary-secondary vascular transition zone advances acropetallyin a branch just as it does in the main stem. Populus deltoides Bartr. ex Marsh., cottonwood, axillary branches, secondary xylem, plastochron index, post-dormancy development, xylem.     

Internal Changes in Hyphae of Rhizopus sexualis (Smith) Callen and Mucor hiemalis Wehm. associated with Zygospore Formation

The distribution of nucleic acids, nuclei, mitochondria, andreserve foods in vegetative hyphae, zygophores, and developingzygospores of Rhizopus sexualis and Mucor hiemalis were examinedby differential staining. The extreme tips and growing zones of vegetative hyphae containeda high concentration of RNA and numerous mitochondria. Nucleiwere not present at the extreme tip but were numerous just behindit. In older parts of the hyphae the concentration of RNA waslow and both nuclei and mitochondria were fewer than in thezone of elongation. Glycogen and lipids were present in all parts of the livinghyphae except the extreme tips and were more highly concentratedin the older parts of the hyphae. Young zygophores showed a much lower RNA/DNA ratio than thatfound in the vegetative hyphal tips. Transfer of colonies from20? C to temperatures of less than 10? C, which is known toprevent zygospore initiation, caused some but not all recognizablezygophores of R. sexualis, but not those of M. hiemalis, torevert to the RNA/DNA ratio characteristic of vegetative hyphae.Some zygophores of Rhizopus and most of those of Mucor developedinto sporangiophores at low temperature, retaining the relativelylow RNA/DNA ratio throughout development. It is suggested thata reduction in the RNA/DNA ratio is an early step in the changefrom the vegetative state to the reproductive one. At firstthis step is reversible, but soon becomes irreversible by anadditional step, the nature of which is unknown. For some timeafter this the reproductive hyphae are capable of either producingasexual sporangia or of conjugating to produce zygospores. Onceconjugation has taken place development either ceases or continuesuntil the spore is fully mature, but it cannot under any circumstancesthen be reversed. The development and maturation of the zygospore involves a greatincrease in number of both nuclei and mitochondria and in theconcentration of glycogen and lipids.     

The Development and Behaviour of Mycelial Strands in Merulius lacrymans (Wulf.) Fr.: II. Hyphal Behaviour during Strand Formation

The system of hyphal branching by Merulius lacrymans was observedin mycelium which had grown from a wood food-base on to glassslides during incubation in sterile moist chambers. A hierarchyof branches and sub-branches arose from the region of clampconnexions, or nodes, of relatively wide main hyphae. Therewas evidence that the sequence of branches occurring at nodesin basipetal succession represented the time sequence of branchdevelopment at any one node. Later-formed branches at any nodewere smaller than earlier branches, but such earlier branchesusually became smaller towards the tip as growth continued.Mycelial strands were built up by growth and branching of thigmo-tropicallysensitive ‘tendril’ hyphae in association with thewide main hyphae. Tendril hyphae were characteristically narrow,thin-walled hyphae arising both as later-formed branches fromthe nodes of the main hyphae and as the narrowed tips of earlierbranches. Although this branching behaviour could be seen amongstaerial hyphae growing over agar media, hyphae growing in contactwith or within the agar behaved differently and did not formstrands.     

Mathematical Growth Analysis of Young Terminalia superba Plants in a Controlled Environment: Comparison of Growth Rhythms of the Principal Axis and of Axillary Branches

A Fourier analysis was used to study the marked variations inthe rate of shoot elongation and branch formation of young Terminaliasuperba plants. The growth of aerial parts of 3-month-old Terminaliaseedlings was measured daily during the following 7 months ofgrowth, and then weekly over a 15-month period of study. Measurementswere carried out in a controlled glasshouse at 27 °C and16 h photoperiod. The Fourier method clearly demonstrated thatthe main axis of young T. superba showed periodical regularvariations, with rest periods. This study revealed that theplagiotropic branch formation by apposition and elongation ofaxillary units was equally rhythmic and directly related tothe main shoot growth rhythm. However, the dates of outbreakof these new units on branches seemed relatively independentfrom variations in shoot growth rate. This developmental patternended in a characteristic and particular stratified branch systemin young Terminalia superba, comparable to the system shownby adult plants in their natural environment. Terminalia superba, Fourier analysis, growth rhythms     

Bathymetric adaptations of reef-building corals at davies reef,great barrier reef,Australia. I. Long-term growth responses of Acropora formosa (Dana 1846)

In situ rates of linear growth (branch extension) were measured for Acropora formosa (Dana) at depths of 5, 10, and 15 m. Estimates of radial branch growth and internal accretion were made at the shallowest and deepest sites. In addition, reciprocal transplant experiments between these two sites were conducted using branches of different lengths. The in situ results showed that individual branches at the deep site extended twice as fast, and deposited more calcium carbonate than branches at the shallow site. Branch initiation, however, was more rapid at the shallow site. Thus, if the extension of new lateral branches were included to obtain a measure of overall growth, rates were highest at the shallow site. The initial length of the transplanted branches significantly affected growth rates. Longer branches showed greater overall growth within all treatments. Branch extension rates, however, increased with initial branch length at the deep site, while tending to remain constant at the shallow site. This result is interpreted as evidence that the extension of each branch tip at the deep site was supported by translocated metabolites derived from a greater volume of zooxanthellae-bearing tissue than at the shallow site. A. formosa exhibits different growth patterns at different depths. At the deep site, extension is favoured over branch initiation. Consequently, translocation from a greater volume of tissue is presumably available to sustain the higher extension rate at each tip. At the shallow site, where extension is less rapid but branch initiation is more rapid, each tip probably receives translocate from a smaller volume of tissue. These mechanisms result in different growth forms at the two sites and are apparently adaptations to different environmental conditions. Light or water motion, or a combination of the two are proposed as probable controlling factors.     

Branching is coordinated with mitosis in growing hyphae of Aspergillus nidulans

Filamentous fungi like Aspergillus nidulans can effectively colonize their surroundings by the formation of new branches along the existing hyphae. While growth conditions, chemical perturbations, and mutations affecting branch formation have received great attention during the last decades, the mechanisms that regulates branching is still poorly understood. In this study, a possible relation between cell cycle progression and branching was studied by testing the effect of a nuclei distribution mutation, cell cycle inhibitors, and conditional cell cycle mutations in combination with tip-growth inhibitors and varying substrate concentrations on branch initiation. Formation of branches was blocked after inhibition of nuclear division, which was not caused by a reduced growth rate. In hyphae of a nuclei distribution mutant branching was severely reduced in anucleated hyphae whereas the number of branches per hyphal length was linearly correlated to the concentration of nuclei, in the nucleated hyphae. In wild type cells, branching intensity was increased when the tip extension was reduced, and reduced when growing on poor substrates. In these situations, the hyphal concentration of nuclei was maintained and it is suggested that branching is correlated to cell cycle progression in order to maintain a minimum required cytoplasmic volume per nucleus and to avoid the formation of anucleated hyphae in the absence of nuclear divisions. The presented results further suggest the hyphal diameter as a key point through which the hyphal element regulates its branching intensity in response to the surrounding substrate concentrations.     

适宜河北省旱寒区的冬油菜品种的筛选

筛选适宜河北省低平原地区种植的油菜品种,同时实现生态效益和经济效益,为相似气候区油菜品种的种植选择及种植结构的调整提供理论依据。以16个油菜品种为材料,对品种间农艺性状的变化进行方差分析、相关性分析和聚类分析。各品种间分枝部位存在差异,变异系数为61.82%,品种JR5分枝部位最低,14T×38最高;其次差异较为明显的是产量和二次分枝数,变异系数分别为26.69%和24.89%,14T×38产量最高,20SY-13最低。二次分枝数最大和最小的品种分别为20SY-13和天油142。油菜产量与一次分枝数和主花序角果数呈极显著正相关(P<0.01),株高与分枝部位、主花序长度和主花序角果数呈显著正相关关系,一次分枝数与主花序角果数呈显著正相关(P<0.05),二次分枝数与主花序角果数呈极显著负相关。当欧式距离为5时,16个油菜品种可分为五大类。选择株高较高、一次分枝数和主花序角果数较多、二次分枝数较少且可以在当地正常越冬的油菜品种进行种植,可以获得较高水平产量;20SY-13在当地秋季种植应注意安全越冬。     

Axillary Bud Development in White Clover in Relation to Defoliation and Shading Treatments

A period of growth under shade netting in the glasshouse allowedthe cultivation of white clover stolons with an accumulationof undeveloped axillary buds similar to that often found onstolons from grass/clover swards. The subsequent capacity ofthese nodes to develop branches under different circumstanceswas investigated in three experiments. Removal of the laminaeand petioles subtending sets of four buds along a stolon reducedthe rate at which branches were initiated from the buds. Treatmentsin which petioles, or petioles plus laminae, were retained initiatedbranches more quickly. Shading the stolons reduced both therate of initiation and the percentage of buds which developed,unless both petioles and laminae were retained. There was someevidence that conditions applied to individual buds may actin the same way as the same conditions applied to sets of fourbuds and that illuminated nodes may depress the performanceof neighbouring shaded notes. Fewer buds developed at older nodes than at younger nodes duringthe summer, but during the autumn younger buds initially developedmore slowly than older buds. This suggests that buds can developat a younger nodal age in summer than in winter. When leafless stolons were cut up into component internodesbuds developed faster than on intact stolons, provided the budwas located at the end of the internode nearest the main stolongrowing point. If the bud was at the other end, branch developmentwas slower than on intact stolons. The results are discussedin relation to clover growth in sward conditions. White clover, Trifolium repens, axillary bud development, branching, growing points, defoliation, shading     

Evidence for the independent regulation of hyphal extension and branch initiation in Fusarium graminearum A3 5

Abstract Addition of 100 μM choline chloride to the medium increased (by approx. 36%) both the length of the hyphal growth unit ( G a measure of mycelial branching) and the mean hyphal extension rate ( E ) of Fusarium graminearum but did not increase the maximum rate of extension of the hyphae ( E _max). The paramorphogen, edifenphos (Hinosan) reduced G and E without affecting specific growth rate (μ). However, when mycelia were treated with edifenphos plus choline, μ was reduced, G was increased by approx. 35%, but E and E _max were not affected. The results suggest that the primary effect of edifenphos is inhibition of hyphal extension, whilst the primary effect of choline is inhibition of branch initiation.     

Crown Spread Patterns for Five Deciduous Broad-leaved Woody Species: Ecological Significance of the Retention Patterns of Larger Branches

Patterns of crown spread and branch retention of two shade-intolerantspecies (Betula platyphyllaandB. maximowicziana) were comparedwith three more tolerant species (Quercus mongolica,Acer sieboldianumandMagnoliaobovata). Branching height (height of the lowest living branch)rose more rapidly with age for the twoBetulaspecies than forthe shade tolerant species. Branching heights ofA. sieboldianumandM.obovatawere similar, irrespective of tree height and age, andlarger trees tended to produce wider crowns than theBetulaspecieswhen trees of similar height were compared. In all species,the branch basal area (cross-sectional area of a branch at itsbase) and the leaf area per branch generally increased as thebranch position on a stem became lower. Therefore, retaininglarger branches contributed significantly to the support ofa larger leaf area per tree. The number of larger branches (branchbasal area >80 cm²) for bothBetulaspecies was significantlysmaller than that of the shade tolerant species. The branchretention pattern ofBetulaspecies was probably a consequenceof intolerance of the leaves to shade. The decline ofBetulaspecieswith forest succession is likely to occur through their inabilityto retain branches with a large base area in closed forests.Copyright1997 Annals of Botany Company Shade tolerance; crown spread; branch retention; branch size; broad-leaved woody species; leaf area index per tree     

Cyclic AMP control of hierarchical growth pattern of hyphae inNeurospora crassa

Wild-typeNeurospora crassa shows a clear hyphal dominance growth pattern with a hierarchy of hyphal diameters containing wide main hyphae, narrow primary branch hyphae, and still narrower secondary branches. Mutants (cr-1), lacking cyclic AMP, lack this size hierarchy when grown in medium without cyclic AMP. When grown in media containing sufficient cyclic AMP or 8-bromocyclic AMP to correct other morphological aberrations, these mutants still lack hierarchical growth. When grown in the presence of very high levels (3 mM) of 8-bromocyclic AMP, there is a long delayed formation of hyphae of different diameters. It is suggested that differences in cyclic AMP concentrations among the hyphae of wild type may be central to the production of the hierarchical growth pattern.     

Growth Dynamics and Morphology of Annual Shoots, According to their Architectural Position, in Young Cedrus atlantica (Endl.) Manetti ex Carriere (Pinaceae)

The influence of shoot architectural position on growth andbranching pattern of young Cedrus atlantica (Endl.) Manettiex Carrière trees were studied. Extension growth andtype of axillary products (lateral bud, sylleptic short or longshoots) of annual shoots of increasing branching order (mainstem, branches and branchlets) were recorded weekly during the1993 growing season. Annual final shoot length, duration ofextension, and maximum extension rate decreased with increasingbranching order. Sylleptic axillary shoots occurred only onannual shoots of the main stem and branches and were producedwhen extension rate was at its highest. Differences in growthrate and final length of annual shoots, according to their architecturalposition, were related to differences in the total number anddiversity of types of sylleptic axillary shoots produced. Itis suggested that types and numbers of sylleptic axillary shootsproduced are linked with threshold values for both final lengthand extension rate of the parent shoot. Copyright 1999 Annalsof Botany Company Atlas cedar, extension growth, sylleptic branching, tree architecture, morphology.     

On-line study of growth kinetics of single hyphae of Aspergillus oryzae in a flow-through cell

Using image analysis the growth kinetics of the single hyphae of the filamentous fungus Aspergillus oryzae has been determined on-line in a flow-through cell at different glucose concentrations in the range from 26 mg L-1 to 20 g L-1. The tip extension rate of the individual hyphae can be described with saturation type kinetics with respect to the length of the hyphae. The maximum tip extension rate is constant for all hyphae measured at the same glucose concentration, whereas the saturation constant for the hyphae varies significantly between the hyphae even within the same hyphal element. When apical branching occurs, it is observed that the tip extension rate decreases temporarily. The number of branches formed on a hypha is proportional to the length of the hypha that exceeds a certain minimum length required to support the growth of a new branch. The observed kinetics has been used to simulate the outgrowth of a hyphal element from a single spore using a Monte Carlo simulation technique. The simulations shows that the observed kinetics for the individual hyphae result in an experimentally verified growth pattern with exponential growth in both total hyphal length and number of tips.     

Branch development in Lupinus angustifolius L.#II. Relationship with endogenous ABA, IAA and cytokinins in axillary and main stem buds

The concentrations of indole-3-acetic acid (IAA), cytokinins (CK) and abscisic acid (ABA) were measured in buds of different regions (main stem and lateral branches) of Lupinus angustifolius L. (cv. Merrit) and at different stages in the development of branches. In lupin, branching patterns are the result of discrete regions of axillary branches (upper, middle and basal) which elongate at much different rates. Early in development only the main shoot elongates, followed usually by basal branch growth and then rapid upper branch growth. Branches in the middle of the main stem grow only weakly or fail to develop. Levels of IAA were generally high in the apical buds of slowly growing branches and low in buds from strongly growing branches, whereas CK levels showed the opposite relationship. CK:IAA ratio showed a closer relationship with the rate of growth of a particular branch better than the levels of either CK or IAA alone. During early stages of growth ABA concentration did not follow the rate of branch growth. However, later in development, where growth did not closely match the ratio of CK:IAA, ABA level showed a strong negative relationship with growth. A significant decrease in ABA was associated with continued strong growth of the main stem apex following a decline in CK:IAA ratio. Overall, the best relationship between the level of growth factors in apical buds and branching pattern in lupin was the ratio of CK:IAA, implying that high CK:IAA at a given bud would promote growth. ABA level appeared to play a secondary role, as a growth inhibitor.     

不同密度下凤仙花重要形态性状与花朵数的关系

对30cm×30cm和50cm×50cm种植密度下的凤仙花(Impatiens balsamina L.)的地径、株高、冠幅、叶面积、花期、花径、一级分枝数、二级分枝数、一级分枝部位高和二级分枝部位高10个重要形态性状与花朵数的关系差异进行了相关性及通径分析,为凤仙花栽培与性状选择提供科学基础。结果表明:30cm×30cm种植的凤仙花的一级分枝数、二级分枝部位高都与花朵数呈显著正相关,地径、冠幅、二级分枝数与花朵数呈极显著正相关,对花朵数的直接效应大小顺序为:二级分枝数>一级分枝数>花径>花期;50cm×50cm种植的凤仙花,其地径、冠幅和二级分枝数都与花产量呈显著正相关,对花朵数的直接效应大小顺序为:二级分枝数>冠幅。二级分枝数对两种密度栽培的凤仙花花产量都起着重要作用。不同种植间距下凤仙花采用了不同的适应方式以获得最大花朵数目,进而获得最大数量的种子,获得较多的繁殖机会。在30cm×30cm下,是通过获得较多一级分枝数;在50cm×50cm下,是通过增加冠幅来产生较大花产量,而且与前者相比,植株茎秆粗壮,对霜霉病的抗性也强,因此,在栽培中,应以适合的低密度栽培比较好。     

On-line study of fungal morphology during submerged growth in a small flow-through cell

A flow-through cell is designed to measure the growth kinetics of hyphae of Aspergillus oryzae grown submerged in a well controlled environment. The different stages of the growth process are characterized, from the spore to the fully developed hyphal element with up to 60 branches and a total length lt up to 10,000 micrometer. Spore swelling is found to occur without change in the form of the spore (circularity index constant at about 1.06) and the spore volume probably increases exponentially. The germ tube appears after about 4 h. The branching frequency and the rate of germ tube extension is determined. After about 10 h growth at a glucose concentration of 250 mg L-1, 6-7 branches have been set, and both the total hyphal length lt and the number of tips increase exponentially with time. The specific growth rate of the hyphae is 0. 33 h-1 while the average rate of the extension of the growing tips approaches 55 micrometer h-1. The growth kinetics for all the branches on the main hypha have also been found. The main hypha and all the branches grow at a rate which can be modeled by saturation kinetics with respect to the branch length and with nearly equal final tip speeds (160 micrometer h-1). Branches set near the apical tip of the main hypha attain their final tip speed in the shortest time, i.e., the value of the saturation parameter is small. Finally, the influence of substrate (glucose) concentration cs on the values of the morphological parameters has been determined. It is found that saturation type kinetics can be used to describe the influence of cs on the growth. Experiments with recirculation of effluent from the cell back to the inlet strongly suggest that the fungus secretes an inducer for growth and branching.     

Biochemical purification of a mammalian slit protein as a positive regulator of sensory axon elongation and branching

Many neurons in both vertebrates and invertebrates innervate multiple targets by sprouting secondary axon collaterals (or branches) from a primary axon shaft. To begin to identify molecular regulators of axon branch initiation or extension, we studied the growth of single sensory axons in an in vitro collagen assay system and identified an activity in extracts of embryonic spinal cord and of postnatal and adult brain that promotes the elongation and formation of extensive branches by these axons. Biochemical purification of the activity from calf brain extracts led to the identification of an amino-terminal fragment of Slit2 as the main active component and to the discovery of a distinct activity that potentiates its effects. These results indicate that Slit proteins may function as positive regulators of axon collateral formation during the establishment or remodeling of neural circuits.     

Stand Density Effects on Branching in an Annual Legume (Senna obtusifolia)

Effects of proximity to nearest neighbours on shoot morphologyand branch growth were examined for Senna obtusifolia (L.) I.& B., an annual legume species that displays wide variationin branching. Periodic surveys described location and type ofgrowth at all nodes on plants in regularly spaced monocultures.Stands with interplant distances of 15-50 cm (51-5 plants m^-2)formed closed canopies with similar amounts of leaf area andbiomass. Number of lower primary branches, their degree of curvature,and location of branch apices relative to the main stem respondedto interplant distance relatively early in shoot growth, beforecanopy closure. The final effects of ten-fold differences inplanting density on the formation of these ascending lower brancheswere only two-fold differences in number of vertical shoot axeswithin the stand. An additional study examined response of lowerbranches to an adjacent gap in the stand. Initial number anddirection of branch growth were not affected by location ofthe gap. The first effect of crowding by neighbours was on number ofbranches initiated by developing shoots. Differences in branchingsubsequently increased through differentiaI survival and directionof branch growth. Such alterations principally affected lateralexpansion of individual shoots, with little effect on radialsymmetry or vertical distribution of leaves.Copyright 1994,1999 Academic Press Branch morphology, canopy, competition, light quality, Senna obtusifolia, shoot growth, sicklepod