Wall structure and bud formation in Rhodotorula glutinis

Summary The first stage in the formation of a bud in Rhodotorula glutinis is the production of a tapered plate of new wall material between the existing wall and the plasmalemma. The parent cell wall is lysed, allowing the bud to emerge enveloped in this new wall. Mucilage is synthesised to surround the developing bud. As the bud grows a septum forms centripetally dividing the two cells. When the daughter cell reaches maximum size the septum cleaves along its axis, producing the bud scar on the parent cell and the birth scar on the daughter cell. The birth scar is obliterated later as the wall of the young cell grows. A system of endoplasmic reticulum and vesicles is found in young buds and is thought to be responsible for the transport of wall material precursors.     

Temperature induced atypical morphogenesis of the obligately psychrophilic yeast,Leucosporidium stokesii

The obligately psychrophilic yeast, Leucosporidium stokesii increased in size, produced irregular wall growth and formed atypical buds when incubated within one to three degrees above 20 °C, the maximum growth temperature. Incubation of cells anaerobically or aerobically in the presence of 2,4-dinitrophenol at the elevated temperatures prevented the development of atypical buds. An investigation of subcellular morphology revealed that the atypical bud was anucleate, did not form a septum between bud and parent cell and produced numerous cytoplasmic vesicles. On shift-down to 15 °C, the optimum growth temperature, nuclear division, migration and septum formation resumed.     

Changes in the lanthanum distribution following decapitation of the sporophytes of an aquatic fern,Marsilea drummondii A. Br.

Summary The active terminal bud and the quiescent lateral buds and corresponding nodes inserted at different levels on the main rhizome ofMarsilea drummondii were examined with the EM afterin vivo feeding with lanthanum nitrate. These tracer experiments demonstrate that all the buds are fed by their phloem cells. In the lateral bud axis the labelling of the sieve elements apoplast indicates that a solute transfer took place in the node between xylem and phloem via xylem transfer cells. La³⁺ deposits are completely absent from the apical dome of inhibited buds indicating that the walls of the quiescent meristematic cells are not permeated by the tracer. The removal of the terminal bud has two effects. It rapidly (in 2 hours) allows the lanthanum to penetrate the lateral bud tip walls at a stage when no fine structural changes are discernable and to bind to the outer surface of the plasmalemma as it does in the active terminal bud. This study including inhibited buds and buds released from apical dominance support the view that changes in the state of the cell surface (cell wall and plasma membrane) may be a prerequisite for the resumption growth activity.This study was supported in part by a grant from the Centre National de la Recherche Scientifique to L.Sossountzov (AI 031275).     

TENDRILS OF PASSIFLORA FOETIDA: HISTOGENESIS AND MORPHOLOGY

Passiflora foetida bears an unbranched tendril, one or two laterally situated flowers, and one accessory vegetative bud in the axil of each leaf. The vegetative shoot apex has a single-layered tunica and an inner corpus. The degree of stratification in the peripheral meristem, the discreteness of the central meristem, and its centric and acentric position in the shoot apex are important plastochronic features. The procambium of the lateral leaf trace is close to the site of stipule initiation. The main axillary bud differentiates at the second node below the shoot apex. Adaxial to the bud 1–3 layers of cells form a shell-zone delimiting the bud meristem from the surrounding cells. A group of cells of the bud meristem adjacent to the axis later differentiates as an accessory bud. A second accessory bud also develops from the main bud opposite the previous one. A bud complex then consists of two laterally placed accessory bud primordia and a centrally-situated tendril bud primordium. The two accessory bud primordia differentiate into floral branches. During this development the initiation of a third vegetative accessory bud occurs on the axis just above the insertion of the tendril. This accessory bud develops into a vegetative branch and does not arise from the tissue of the tendril and adjacent two floral buds. The trace of the tendril bud consists of two procambial strands. There is a single strand for the floral branch trace. The tendril primordium grows by marked meristematic activity of its apical region and general intercalary growth.     

Electron Micrography of Bud Formation in Metschnikowia krissii

The fine structure of bud formation of Metschnikowia krissii was studied by means of ultramicrotomy and transmission electron microscopy. Bud protrusion and development were observed by scanning electron microscopy. Bud formation in this yeast takes place by an extension of a small localized area of the existing parent wall. The parent cell and its bud are initially separated by the plasmalemma, creating an intercellular site within which the generation of new cell wall (bud and birth scar areas) occurs centripetally. When the dividing wall is complete and new cell wall material is formed, a narrow cleavage plane becomes increasingly defined. This cleavage plane apparently proceeds laterally toward the direction of the existing outer walls which rupture, resulting in the separation of the bud from the parent cell. The bud scar is prominently convex in shape; the birth scar is less conspicuous and initially concave in shape. Comparison of bud formation in M. krissii is made with that observed in Saccharomyces cerevisiae and Rhodotorula glutinis.     

Isolation and characterization of prosthecae ofAsticcacaulis biprosthecum

The budding process of the yeast form of Mucor rouxii was examined by electron microscopy of thin sections with particular reference to wall ontogeny. In most instances the bud wall is seen as a continuation of the inner layers of the parent cell wall. As the bud emerges it ruptures the outer layers of the parent wall. The bud wall is much thinner than the parent wall and remains so while the bud grows into a sphere of about one half the diameter of the parent cell. Then a septum begins to form centripetally, at the neck, by invagination of the plasmalemma. Before the neck canal is completely occuluded, electron-dense wall material is deposited into the septum space. Two separate septum walls are deposited, one on the parent side and one on the bud side of the invaginating plasmalemma. Septum wall formation extends to the surrounding neck walls. In this manner, the parent and bud cytoplasms become fully separated and each is surrounded by a continuous wall. The two cells remain attached to each other by the original neck wall; eventually, the bud abscisses leaving a birth scar on the bud cell and a more pronounced bud scar on the parent cell. In general, the mechanism of budding in this zygomycetous fungus resembles that of an ordinary ascomycetous yeast such as Saccharomyces cerevisiae.     

Effect of Assimilate Supply on Development and Growth Potential of Axillary Buds in Roses

The effect of assimilate supply on axillary bud developmentand subsequent shoot growth was investigated in roses. Differencesin assimilate supply were imposed by differential defoliation.Fresh and dry mass of axillary buds increased with increasedassimilate supply. The growth potential of buds was studiedeither by pruning the parent shoot above the bud, by graftingthe bud or by culturing the bud in vitro. Time until bud breakwas not clearly affected by assimilate supply during bud development,Increase in assimilate supply slightly increased the numberof leaves and leaf primordia in the bud; the number of leavespreceding the flower on the shoot grown from the axillary budsubstantially increased. No difference was found in the numberof leaves preceding the flower on shoots grown from buds attachedto the parent shoot and those from buds grafted on a cutting,indicating that at the moment of release from inhibition thebud meristem became determined to produce a specific numberof leaves and to develop into a flower. Assimilate supply duringaxillary bud development increased the number of pith cells,but the final size of the pith in the subsequent shoot was largelydetermined by cell enlargement, which was dependent on assimilatesupply during shoot growth. Shoot growth after release frominhibition was affected by assimilate supply during axillarybud development only when buds sprouted attached to the parentshoot, indicating that shoot growth is, to a major extent, dependenton the assimilate supply available while growth is taking place.Copyright1994, 1999 Academic Press Assimilate supply, axillary bud, cell number, cell size, defoliation, development, growth potential, meristem programming, pith, Rosa hybrida, rose, shoot growth     

Shoot preformation in clones of Fraxinus pennsylvanica in relation to site and year of bud formation

Summary Shoot preformation was investigated in buds of four clones of Fraxinus pennsylvanica var. subintegerrima (Vahl) Fern. at two sites in Manitoba in the second (1988) and third (1989) growing seasons after grafting. More preformed primordia were produced in terminal buds in 1989 compared to 1988 at each site. Both terminal and lateral buds at Morden contained significantly more primordia than those at Winnipeg. The numbers of preformed primordia were significantly different among clones. Clone 3 produced the most and clone 1 the fewest primordia in terminal buds. Despite quantitative variation, the pattern was similar among clones for terminal buds at each site and in each year. A similar pattern was evident for lateral buds at the Winnipeg site in 1989 but at Morden, clones 4 and 1 had the largest number of preformed primordia. Data from 1989 revealed that numbers of primordia were correlated with bud dimensions, parent shoot length, diameter and number of leaves, and location of the bud on the parent. Shoot dry weight was also related to these variables and revealed a non-linear increase in dry weight with shoot length. Multiple regression, with parent shoot length and location of buds along the parent axis as independent variables provided a reliable indicator of preformation in the crown. Although there is a genotypic component to preformation, variation between sites, years and crown locations suggests plasticity in bud development.     

Histological Study of Adventttious bud Formation on Lactuca Sativa Cotyledons Cultured In Vitro

Abstract

Cyto-histological changes accompanying the formation of adventitious buds in excised cotyledons of Lactuca sativa were studied during the first 12 days after planting in vitro. Prospective proliferating cells can first be recognized, already on the first day after planting, by a marked increase in nuclear and nucleolar volumes, followed on the second day by a burst of cell divisions involving particularly mesophyll cells. Then lignified elements develop together with meristematic center, forming a callus-like tissue in the inner part of the cotyledons. At the third day of culture, the epidermal cells start to divide with a periclinal wall followed by an anticlinal division. In the following days of culture the epidermal cells, which divide mainly with periclinal walls, form layers of cells below the surface, gradually filling up the intercellular spaces. From the 8^th day on, the buds protude above the surface and develops into shoots. These results are discussed in relation to DNA content of nuclei of Lactuca sativa cotyledons and to the time course of cell division and tracheary element formation. The very regular sequence of changes associated with the initiation and development of the bud makes the in vitro culture of Lactuca cotyledons an appropriate System for histochemical and biochemical studies.     

LEAF-OPPOSED BUDS IN MUSA: THEIR DEVELOPMENT AND A COMPARISON WITH ALLIED MONOCOTYLEDONS

A single, lateral, vegetative bud which is positioned 180° from the axil of a leaf is a generic feature of Musa (Musaceae). Such leaf-opposed buds occur in all ten species and five cultivars examined, representing all four sections of the genus and all groups of cultivated bananas and plantains. The bud arises relatively late and is first visible as a vascular-free “clear zone” in the axis directly below the future bud meristem site. It is first associated with the fifth or sixth leaf primordium from the apex. A defined superficial meristem develops on the stem directly above the insertion of the leaf margins one or more plastochrons later. Normal, basically axillary, vegetative buds occur in the closely related genera: Orchidantha (Lowiaceae), Heliconia (Heliconiaceae), Strelitzia, and Ravenala (Strelitziaceae). These buds arise in the axil of the first to the third leaf primordium in a manner similar to most other monocotyledons. Axillary vegetative buds also occur in the remaining families of the Zingiberales: Cannaceae, Costaceae, Marantaceae, and Zingiberaceae.     

Development and Growth Potential of Axillary Buds in Roses as Affected by Bud Age

The effect of axillary bud age on the development and potentialfor growth of the bud into a shoot was studied in roses. Ageof the buds occupying a similar position on the plant variedfrom 'subtending leaf just unfolded' up to 1 year later. Withincreasing age of the axillary bud its dry mass, dry-matterpercentage and number of leaves, including leaf primordia, increased.The apical meristem of the axillary bud remained vegetativeas long as subjected to apical dominance, even for 1 year. The potential for growth of buds was studied either by pruningthe parent shoot above the bud, by grafting the bud or by culturingthe bud in vitro. When the correlative inhibition (i.e. dominationof the apical region over the axillary buds) was released, additionalleaves and eventually a flower formed. The number of additionalleaves decreased with increasing bud age and became more orless constant for axillary buds of shoots beyond the harvestablestage, while the total number of leaves preceding the flowerincreased. An increase in bud age was reflected in a greaternumber of scales, including transitional leaves, and in a greaternumber of non-elongated internodes of the subsequent shoot.Time until bud break slightly decreased with increasing budage; it was long, relatively, for 1 year old buds, when theysprouted attached to the parent shoot. Shoot length, mass andleaf area were not clearly affected by the age of the bud thatdeveloped into the shoot. With increasing bud age the numberof pith cells in the subsequent shoot increased, indicatinga greater potential diameter of the shoot. However, final diameterwas dependent on the assimilate supply after bud break. Axillarybuds obviously need a certain developmental stage to be ableto break. When released from correlative inhibition at an earlierstage, increased leaf initiation occurs before bud break.Copyright1994, 1999 Academic Press Age, axillary bud, cell number, cell size, pith, shoot growth, Rosa hybrida, rose     

Preformed and neoformed extension of shoots and sylleptic branching in relation to shoot length in Tsuga canadensis

Summary Shoot systems developed over 3 successive years were investigated on 55 understorey Tsuga canadensis (L.) Carr. trees. Paired comparisons of preformed-leaf content of terminal buds and numbers of leaves produced on new shoots showed that neoformed leaves were produced in large numbers. Parent-shoot character was not useful in predicting numbers of preformed leaves, was better related to total leaves produced, but left the majority of the variation unexplained. This reflected the capacity of any terminal bud to produce a shoot with more or less neoformation, depending on conditions for growth. All shoots over 6 cm long produced sylleptic shoots that bore from two to many leaves and were arranged in a mesitonic pattern along the parent. Some of the longer sylleptic shoots produced lateral buds or second-order sylleptic shoots. Monopodial second-year extensions of sylleptic-shoot axes followed an acrotonic pattern, as did proleptic shoots from the few lateral buds borne on the parent shoots. Such lateral buds were more frequent on shorter parent shoots: they typically occurred near the proximal and distal ends. Duration of shoot extension was positively correlated with shoot length: terminal buds became evident as shoot extension neared cessation.     

Developmental study onHypolepis punctata (Thunb.) Mett.

The origins of the first and second petiolar buds ofHypolepis punctata were clarified in relation to the early development of the leaf primordium, which arises from a group of superficial cells of the shoot apical meristem. One of these superficial cells produces a two-sided leaf apical cell which subsequently cuts off segments to make a well-defined cell group, called here the leaf apical cell complex, on the distal part of the leaf primordium. Meanwhile, cells surrounding the leaf apical cell complex also divide frequently to form the basal part of the leaf primordium. Two groups of basal cells of the leaf primordium located on the abaxial and the adaxial sides initiate the first and the second petiolar buds, respectively. The initial cells are usually contiguous to the leaf apical cell complex, constructing the abaxial and adaxial flanks of the very young leaf primordium. However, the first petiolar bud sometimes develops from cells located farther from the leaf apical cell complex. These cells are derived from those originally situated in the peripheral region of the shoot apical meristem. This study was supported by a Grant-in-Aid for Encouragement of Young Scientists by the Ministry of Education, Science and Culture, of Japan No. 474322 in 1979.     

Shoot development and bud mite infestation in hazelnut (Corylus avellana)*

The interaction of environmental and genetic variation in hazelnut (Corylus avellana) shoot development and the behaviour, survival, and colonisation of eriophyid bud mites (Phytoptus avellanae and Cecidophyopsis vermiformis) were studied. The distribution of galled buds on shoots indicated that mites colonised only those buds formed during the mite migration period. The point of entry is probably the growing shoot tip. Once within this structure, as the shoot develops the mites have access to a succession of newly-formed, bud primordia that are unprotected by bud scales. The relative accessibility of the apical meristem and bud primordia may affect host susceptibility.     

Erratum

The number of nodes produced by a bud meristem before differentiation into a flower is defined as its developmental potential. Decapitation, rooting, and grafting experiments were used to measure the developmental potential of the vegetative axillary bud meristems on Nicotiana tabacum. Decapitation experiments measure the in situ developmental potential while rooting and grafting experiments measure developmental potential in isolation and at a new location on the organism, respectively. A rooted or grafted bud exhibits one of two patterns of development: (1) It develops like an in situ bud or (2) It develops according to its new environment. For example, second axillary buds below the inflorescence produced 18.8 ± 0.8 nodes in situ, 17.9 ± 0.9 or 39.8 ± 1.1 nodes when rooted, and 22.2 ± 0.6 or 34.2 ± 0.7 nodes when grafted to the base of the plant. These results suggest that the buds which develop like in situ buds are developmentally determined while buds that develop according to their new environment are undetermined. On an individual plant, determined and undetermined buds are separated by one internode and only first, second, and third buds below the inflorescence exhibit determination.     

Nuclear behaviour during ascus formation in Saccharomyces rosei (Guilliermond) Lodder et Kreger-van Rij

Stained cells of Saccharomyces rosei prepared from 4 to 10-day-old cultures were studied under the light microscope. Mitotic and meiotic divisions involving a ring-like structure as well as preceding and subsequent stages were observed. Cells presenting supernumerary mitoses in a varying number were frequent. These mitoses, having terminated their multiplication activity, suspended the process shortly before its conclusion and, in a development which was identical at all, assumed a curious arrangement forming a mitoses-ring. Meiosis-buds were detected. These especial buds, where karyogamy and meiosis took place, resulted from the development of the mitoses-ring, whose mitoses upon resuming their activity moved toward the cell wall giving rise to the appearance of these appendices. Each one of these buds received the corresponding pair of daughter nuclei, diploidization occurring subsequently. Meiosis was usually processed in a single bud (effective-meiosis-bud) and all four meiotic nuclei migrated to the mother cell, and gave rise to a tetra-nucleate spore or binucleate spores if two were formed.Other modalities of sporulation were observed. These may result either from the association of two cells, in which one assumed the function of meiosis-bud (false-meiosis-bud), or from a cell association in which this function was performed for several linearly arranged cells forming a protuberance.Conjugation between mother cell and an attached bud, or between independent cells, was not observed.     

Non-destructive measurement of dormant bud respiration rates

The lack of an indicator of the state of bud development during the dormant period has been a major difficulty in studying the effects of winter chilling on subsequent shoot growth and flowering. We considered that respiration rate (R _D ) might provide such an index, so developed a technique for the non-destructive measurement of the R _D of individual dormant buds of kiwifruit (Actinidia deliciosa). A closed configuration gas exchange system was used. The low R _D of dormant buds required the use of an unusually small system volume. As a consequence, it was necessary to modify the conventional closed system so that most of the system volume could be sampled for analysis. Increases in CO₂ concentration during a measurement were determined by injecting gas samples into a stream of air flowing through an infrared gas analyser. The technique was found to be reliable even at R _D as low as 20 pmol s-1. Error analysis showed that under normal operating conditions the coefficient of variation was approximately 3 %. With two operators, measurements could be made at the rate of one bud every four minutes. The ability to make non-destructive measurements has the advantage of enabling us to make sequential measurements on individual buds and monitor subsequent development. The system could be readily adapted to other woody fruit species, providing that gas-tight seals can be established on individual buds. Use of the system is illustrated by measuring the temperature response of the R _D of dormant buds grown under contrasting conditions. All buds showed increasing R _D with increasing temperature in the range 15 to 25 °C. Buds which had grown in the coolest region, where bud break is usually the earliest, had the highest R _D when measured during early spring. This revised version was published online in September 2006 with corrections to the Cover Date.     

Natural and Induced Rooting of the Stem Apex in Rubus

European Rubi of the subgenus Eubatus spread vegetatively bythe rooting of stem apices at the end of the growing season.The rooting reaction involves a cycle of changes beginning atthe time of the equinox with an acceleration of extension growthand the assumption of positive geotropism. Entering the ground,the stem apex forms a rooting boss, from which a short negativelygeotropic shoot terminating in a resting bud arises. This restingbud develops in the subsequent spring to establish an independentdaughter plant. A sequence of events re-sembling the naturalrooting reaction can be induced in midsummer by darkening theapical 25 cm. of vegetative stem apices whilst still attachedto the parent plant. Roots are formed within 3 weeks of darkening,and a dormant bud after 4 weeks. It seems probable that thenatural rooting reaction is a response to shortening day lengthin the late summer.     

VARIATION IN HYDRA'S TENTACLE NUMBERS AS A FUNCTION OF TEMPERATURE

Chlorohydra uiridissima whose tentacle number is altered at different temperatures, was studied to see how other developmental variables changed as a function of temperature. The results suggest that temperature is instrumental in establishing the size of bud and tentacle primordia, but the number of primordia present may play a limiting role.

Animals were cultured at 18, 23 and 28°C and shifted between the extreme temperatures. Large animals with 8 tentacles, small animals with 5 tentacles, and intermediate animals with 6 and 7 tentacles served as parents. Buds and parents were monitored daily and scored for numbers of buds and tentacles.

Temperature, not parental size, determined the size of the buds. At the lower temperature buds were produced more slowly and initiated less frequently, but occurred in greater numbers per parent and had more tentacles than at the higher temperatures. The duration of bud development also increased at lower temperature, but at the lowest temperature the duration of bud development was not correlated with tentacle numbers on buds.

Changes in the frequency of bud initiation and the duration of bud development induced by changing temperature did not parallel changes in the number of tentacles produced on buds. Animals shifted from 18°C to 28°C underwent rapid increases in the rate of bud initiation and rapid shortening in the duration of bud development, while animals shifted from 28°C to 18°C underwent equally rapid changes in the opposite directions. The number of tentacles produced on buds, however, changed slowly to that characteristic of buds acclimated to the new temperatures. The frequency of bud initiation and the duration of bud development, therefore, do not determine tentacle number.

The number of tentacles already present seems to limit possibilities for adding new tentacles. Parents with five tentacles were especially likely to undergo upward changes in their tentacle number while parents with eight tentacles were resistant to such changes.     

DEVELOPMENT AND PHYLLOTAXIS OF THE VEGETATIVE AXILLARY BUD OF MICHELIA FUSCATA

Tucker, Shirley C. (Northwestern U., Evanston, III.) Development and phyllotaxis of the vegetative axillary bud of Michelia fuscata . Amer. Jour. Bot. 50(7): 661–668. Illus. 1963.—The vegetative axillary buds of Michelia fuscala are dorsiventrally symmetrical with 2 ranks of alternately produced leaves. The direction of the ontogenetic spiral in each of these buds is related both to the symmetry of the supporting branch and to the position of the bud along the branch. On a radially symmetrical branch, all the axillary buds are alike—all clockwise, for example. But in a dorsiventrally organized branch the symmetry alternates from clockwise in 1 axillary bud to counterclockwise in the next bud along the axis. Leaf initiation and ontogeny of the axillary apical meristem conform with those of the terminal vegetative bud. The axillary bud arises as a shell zone in the second leaf axil from the terminal meristem. During this process the axillary apex develops a zonate appearance. The acropetally developing procambial supply of the axillary bud consists wholly of leaf traces. At the nodal level the bud traces diverge from the same gap as the median bundle trace of the subtending leaf. Only the basal 1–2 axillary buds which form immediately after the flowers elongate each year, while the majority remains dormant with 3 leaves or fewer.