Action of gibberellic acid on the mitotic activity of the different zones of the shoot apex ofRudbeckia bicolor andPerilla nankinensis

Summary The influence of GA on the mitotic activity of each zone of the shoot apex is studied in two species having strikingly different morphogenetic responses to the chemical.InRudbeckia bicolor, the stimulation of mitoses mostly occurs in the central zone. This fact is related to the subsequent flowering of the plant. InPerilla nankinensis, the activation is more general and affects the central and the peripheral zones. It is connected to an acceleration of the plastochronic functioning.Therefore, the action of GA differs following the species and following the meristematic zones.In the pith, no increase of the length of the cells is apparent in either case, but the mitotic activity is enhanced. This increase of the number of cell divisions provokes the bolting ofRudbeckia and the elongation ofPerilla.With 1 Figure in the Text     

Über den Verzweigungsvorgang beiPsilotum undSelaginella mit Anmerkungen zum Begriff der Dichotomie

After a critical evaluation of the concept of dichotomous branching in Cormophytes the shoot apical meristems ofPsilotum triquetrum andSelaginella speciosa are described. InPsilotum only the terminal meristems of the cryptophilic shoots have a three sided apical cell. Those of the photophilic shoots lack a typical apical cell.Selaginella has a two sided apical cell. The process of branching is independent from apical cells. It is due to an equal or unequal fractionation of the initial zone of the shoot apex which embraces all tissues above the leaf producing zone of the apical meristem.

Herrn Univ.-Prof. Dr.Walter Leinfellner zum 70. Geburtstag gewidmet.     

Ontogeny of the reproductive shoot apex ofClethra barbinervis,especially on the superficial view

The structure and the ontogenetic process of the reproductive shoot apex forming a terminal inflorescence ofClethra barbinervis were examined, especially concerning the superficial view of the apex. The system of contact parastichies is 2+3 in phyllotaxis in the vegetative phase, changing to 5+8 for bract arrangement in the reproductive phase. At the same time the size of the apex is conspicuously enlarged. The size of the foliage leaf primordia in the vegetative phase is larger than that of the bract primordia in the reproductive phase. The radial cell files, which are clear in the vegetative shoot apex, are not recognizable at least in the early stage of the reproductive phase. The author proposes a close correlation between the appearance of the radial cell files, as well as the construction of the apical sectors, and the sizes of the shoot apex and leaf primordia. It may be proposed also that the construction of the apical sectors is closely correlated with the phyllotaxis.     

Hyphal tip ultrastructure ofAspergillus nidulans andAspergillus giganteus and possible implications of woronin bodies close to the hyphal apex of the latter species

Summary The hyphal tip ultrastructure ofAspergillus nidulans andAspergillus giganteus indicates that their apical organization is very similar to that found in other filamentous fungi. Both species have an area immediately behind the hyphal apex free of all large organelles and containing a high concentration of vesicles. InA. giganteus only one size class of vesicle is clearly evident, with a mean diameter of 72 nm. InA. nidulans two size classes of vesicle were found, with mean diameters of 75 nm and 31 nm. A Spitzenkörper is evident inA. nidulans as an area very close to the tip containing only the smaller vesicles. InA. giganteus one or more apparently mature Woronin bodies were found within the first 1 m of some hyphal apices. The possible significance of their presence is discussed.     

Application of soft X-ray microradiography to observation of cystoliths in the leaves of various higher plants

Soft X-ray microradiography was applied to observation of the cystoliths, calcified bodies of higher plants, in the leaves ofMorus bombycis, Humulus scandens, Ficus elastica, F. retusa (Moraceae),Boehmeria platanifolia, Pilea viridissima (Urticaceae) andMomordica charantia (Cucurbitaceae). It was proved that this technique is useful for examination of the shape, size, distribution and number of cystoliths in fresh leaves. The microradiographs revealed large cigar-shaped cystoliths in the leaf ofP. viridissima, and neighbor-cystoliths in somewhat restricted areas of the leaves ofM. bombycis andH. scandens, and two to seven radially arranged cystoliths in the leaf ofM. charantia. The number of cystoliths per unit area of leaf (nos./cm²) was estimated to be from 1,090 to 3,900 by means of the microradiographs, varying from species to species. The CaCO₃ content of the leaf calculated from the volume and number of cystoliths was approximately 0.4 mg/cm² in all species exceptF. retusa. InF. retusa, it was about 1.06 mg/cm², the highest value among all species tested. Hand-sections of the leaves showed that the lithocysts were localized in the upper and/or lower epidermis, and they were associated with many photosynthetic cells in all species, suggesting some relationship between CaCO₃ deposition in cystoliths and photosynthesis. This paper is dedicated to Professor Kurazo Furuya, Department of Biology, Tokyo Gakugei University, on the occasion of his retirement (1986).     

Structure and seasonal study of the shoot apex of two species ofAraucaria

Summary and Conclusions The shoot apices ofAraucaria columnaris andA. bidwillii exhibit a tunica-corpus organization. In the former the tunica is one-layered during spring and summer months and becomes more stratified during winter months. InA. bidwillii it is usually two-layered, with a tendency to further stratification.The corpus is divisible into three zones, the corpus initial zone, the flanking zone and the rib meristem zone. The corpus initial zone is the seat of formation of the rest two. The flanking zone is concerned with the production of leaf primordia, in which the covering tunica layer has no part.The rib meristem zone varies in depth according to the season of the year and the pith cells mature gradually in these species.InA. columnaris, where a seasonal study was undertaken, no period of complete dormancy was observed.     

Developmental anatomy of the shoot apical cell,rhizophore and root ofSelaginella uncinata

The developmental anatomy of the shoot apex, rhizophore and root ofSelaginella uncinata was examined by the semi-thin section method. The shoot apex has a single, lens-shaped apical cell with two cutting faces. Rhizophore primordia are initiated exogenously at the branching point of the second youngest lateral shoot. The rhizophore apex has a tetrahedral apical cell with three cutting faces. A pair of root primordia is initiated endogenously from inner cells of the rhizophore apex, after the rhizophore apical cell becomes unidentifiable losing its activity, and subsequently a root cap is formed from the distal face of the root apical cell. During the course of successive root branching the apical cell in an original root apical meristem becomes unidentifiable and then a new apical cell is initiated in each of the bifurcated root apical meristems. The root branching mode seems to be equivalent to the described dichotomous branching mode of fern shoots. Our results demonstrate a distinct morphogenetical difference between the rhizophore and the root, and confirm the exogenous origin of the rhizophore, as described for other species ofSelaginella. This evidence indicates that the rhizophore is not an aerial root but a leafless, root-producing axial organ.     

HISTOCHEMICAL AND AUTORADIOGRAPHIC STUDIES OF FLORAL INDUCTION IN CHENOPODIUM ALBUM

Gifford , Ernest M., Jr. , and Herbert B. Tepper . (U. California, Davis.) Histochemical and autoradiographic studies of floral induction in Chenopodium album. Amer. Jour. Bot. 49(7): 706–714. Illus. 1962.—Chenopodium album was induced to flower using short-day photoperiods. Changes in the chondriome, starch, total protein, ribonucleic acid (RNA), deoxyribonucleic acid (DNA), and histone distribution in cells of vegetative and inflorescence shoot apices were studied. The distal cells of the vegetative apex (especially the axial tunica cells) possess larger nucleoli and vacuoles, less granular mitochondria, and more differentiated plastids than do other cells of the apex; the distal cells stain lightly with dyes that indicate the presence of DNA and histone. RNA is distributed relatively uniformly in the shoot apex; the cells at sites of leaf initiation and young leaf primordia contain slightly higher concentrations of RNA than the axial cells of the shoot apex. Protein is uniformly distributed throughout the vegetative as well as the inflorescence apex. Upon induction, the chemical and morphological differences between cells in the shoot apex gradually disappear. RNA concentration of cells in the apex increases, reaching a maximum after 4 inductive cycles. Protein concentration of cells also increases, but this increase lags behind that of RNA.     

Effect of strictly plant-related factors on the response ofHevea brasiliensis andTheobroma Cacao nodal explants culturedIn vitro

Summary Nodal cuttings (primary nodal explants) were used to initiate microcutting cultures ofHevea brasiliensis andTheobroma cacao. The physiological stage of growth reached by the branches from which the explants were taken had a considerable influence on culture initiation and response. In both species, the buds of the nodal explants taken from dormant branches (stages 11, 12 and 13 inTheobroma; stage D inHevea) revealed greater opening abilityin vitro and shoot elongation than buds taken from branches in a phase of active meristem growth inTheobroma (stages F1 and F2) or during a foliar growth phase inHevea (stage C). InHevea, the branch growth phase effect persisted into the multiplication phase when shoots developedin vitro were used as the source of secondary nodal explants. However, it disappeared during subcultures of primary nodal explants. In both species, the position of the nodes on the branch with respect to the apex also had an effect on culture initiation. The buds of nodes furthest from the apex were more likely to develop into shoots. InHevea, the position of secondary nodal explants obtained from the primary shoot was seen to vary in effect depending on growth regulator applications during primary culture. These results are analyzed in terms of variations in the balance between endogenous growth promoters/inhibitors in the buds, depending on morphogenic stages and the bud position on the branch.     

Shoot structure and dynamics of saplings and canopies of three deciduous broad-leaved trees of a coppice forest in central Japan

Three deciduous broad-leaved trees, Quercus serrata, Castanea crenata and Carpinus laxiflora, were the main constituents of a coppice forest in central Japan. The shoot elongation and leaf emergence modes of both saplings and the canopy of the three species were investigated. The shoot elongation modes of Q. serrata and C. crenata were the same in saplings and the upper layer of the canopy. The second shoots of these two species were formed after the first shoots were elongated. C. laxiflora was different between saplings and the upper layer of the canopy. In saplings, only the first shoots took a long time to elongate. In the upper canopy layer, higher order shoots were formed in the same way as in the other two species. In the lower layer of the canopy, all three species showed the same shoot elongation mode, in which only the first shoot and its duration of elongation was short. Leaf longevity, individual leaf area, leaf mass per unit leaf area and the stem mass per unit stem length of C. laxiflora were significantly shorter or significantly smaller than those of Q. serrata and C. crenata. The length of the stem per unit leaf area of C. laxiflora was three times that of Q. serrata and five times that of C. crenata. The elongation growth of C. laxiflora was highly efficient as it occurred with a small leaf area. The shoot dynamics and the shoot structure of C. laxiflora are more suitable for elongation growth than in Q. serrata and C. crenata. Furthermore, the shoot structures of the three species were compared and ecological characteristics of the three species are discussed. Received: 29 September 1998 / Accepted: 17 September 1999     

Shoot development ofAucuba japonica I. Morphological study

The shoot development ofAucuba japonica was studied morphologically. The shoot shows dichasial branching in connection with the formation of a terminal inflorescence and shows a decussate phyllotaxis even in the reproductive phase. The sequence of initiation of successive foliar appendages is very precise, hence the foliage leaf, scale leaf and bract can be compared with each other even at their stages of initiation. In the stage of proximal foliage leaf formation the shoot apex is flat, while in the stage of formation of distal foliage leaves, bud scales and proximal bracts, it becomes concave. In the stage of formation of distal bracts the apex becomes domed. Plastochron durations are relatively long in the vegetative phase in comparison with other plants, and the duration from initiation of the first pair of appendages to that of the second is about one and a half months. Both male and female inflorescences exhibit basically a thyrsoid type of monotelic synflorescence.     

Changes in the anatomical structure of the shoot apex ofSenecio vulgaris L. during ontogenis in relation to the formation of leaves and inflorescence

An investigation was made of the anatomical structure of the shoot apex ofSenecio vulgaris L. a photoperiodically neutral plant, and compared with the formation of successive leaf primordia along the axis up to the initiation of the terminal inflorescence. In the shoot apex of a germinating plant a central zone can first be distinguished from the peripheral zone which is composed of small and intensely stained cells. Later, a rib meristem appears. At the time of the initiation of the middle (the largest) leaves, the shoot apex has a distinct small central zone and a well developed peripheral zone and rib meristem. Between these zones there is a group of cells dividing in all directions, the subcentral zone. At the time of initiation of the last leaves, the central zone extends to the flanks and gradually ceases to be distinguishable. At the same time, the subcentral zone increases in size. This is caused first by cell division and later, with the initiation of the last, most reduced leaves, by enlargement of the cells. Vacuolization in the inner part of the apex and the arrangement of the superficial cells in rows parallel to the surface of the apex, is a preparatory step to the initiation of the inflorescence.     

Distribution of chlorophyll-bearing organelles in the shoot apex of a range of dicotyledonous plants

Summary. Confocal laser scanning microscopy was used to study the distribution of the smallest detectable autofluorescing, chlorophyll-bearing structures in fresh, 40 μm thick longitudinal sections of the shoot apex of four dicotyledonous plants (Arabidopsis thaliana, Nicotiana glauca, Lupinus alba, and Spinacia oleracea). In all species, the smallest chlorophyll-bearing particles were found in the outermost cell layers (L1 and L2) of the shoot apex. Their distribution between these layers differed in each species. The smallest such particles were about 0.5–1.0 μm in maximum dimension, approximating the size of a single granum in the developing leaf. Their size and abundance increased with increasing cell age and distance from the peak of the apex. Immediately beneath the L1 and L2 layers was a zone largely devoid of these particles. Below this nonfluorescing zone, in the region where the derivatives of the meristematic zone differentiate into cells of the central pith region, the size and abundance of the chlorophyll-bearing particles increased progressively with increasing distance from the nonfluorescing zone. The presence of these small autofluorescing particles in the L1 and L2 cell layers of the shoot apex places the development of photosystem II fluorescence at an earlier stage of leaf development than previously observed. The use of confocal laser scanning microscopy to study unfixed sections provides another useful metabolic marker for mapping patterns of differentiation and development in the cells of the shoot apex. Correspondence and reprints: CSIRO Plant Industry, GPO Box 1600, Canberra, A.C.T. 2601, Australia.     

Morphactin-induced malmorphogenetic effect and its transmission inKalanchoë

Morphactin dispensed through shoot apex induced diverse malformations of plant organs in four species ofKalanchoë. The malmorphogenetic effect was freely transmitted to newly emerging axillary branches as well as across leaf lamina to differentiating epiphyllous buds.     

B-Chromosomen beiChironomus

In the population “Herrenmühle” ofChironomus plumosus 11% of the individuals contain one supernumerary chromosome. This B-chromosome is present both in germ-line and somatic cells. — InChironomus melanotus 6% of the larvae of the population “Falkau” carry supernumerary chromosomes. These B-chromosomes cannot be found in all nuclei of testis and soma, their number varies between cells within the individual. In both species the B-chromosomes represent centromeric fragments of chromosome IV as can be shown by their structure and pairing behaviour. — The polytene B-chromosome ofCh. plumosus exhibits a banding pattern in the salivary gland nuclei. Furthermore it is able to form an additional nucleolus in the nuclei of the malpighian tubules. InCh. melanotus band structures can be seen only in the B-chromosome of malpighian tubules. The larvae ofCh. melanotus, carrying B-chromosomes, show heterochromatic bodies in the salivary gland nuclei, varying in number and size in the nuclei of the same gland. These bodies are interpreted to be polytenic B-chromosomes divided into subunits.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Growth regulators in changing apical growth at transition to flowering

Reorganization of growth in the shoot apex ofChenopodium rubrum during transition to flowering is described. Growth and morphogenic changes — a rise in cell division rate, changes in leaf and bud formation and changes in directions of cellular growth — are viewed from the aspect of a possible role of growth hormones in controlling these changes. Growth and morphogenic effects of exogenous growth regulators in the shoot apex ofChenopodium are summarized and their floral effects explained in terms of changing apical growth correlations. New evidence concerning the timing of increased cell division rate and showing the limited requirement of axillary cell division and a shift to more vertical direction of growth in the apex in the floral developmental pathway was obtained in experiments with kinetin application and by surgical treatments.     

Localization of starch in shoot apices of vegetative and photoperiodically induced plants ofChenopodium rubrutn

Starch was determined by means of IKI reaction in shoot apices ofChenopodium rubrum plants induced to flowering by two short days and in non-induced plants. Small starch grains were already observed in the meristematic cells at an age of four days after sowing. Larger grains were found in the subapical region of the apex. Heterogeneity increases during further growth of the plants in induced, as well as in non-induced vegetative plants. Starch disappears from the cells potentially giving rise to axillary buds, while the number and size of starch grains increase in cells from which leaf primordia will be formed. This metabolic specifity of leaf and bud primordia is preserved during morphological differentiation and applies to vegetative, as well as to prefloral apices of photoperiodically induced plants. The amount of starch in the different regions of the apex is linked rather with organogenesis than with the quantitative growth in the apex.     

Cells within the nodal region of carnation shoots exhibit a high potential for adventitious shoot formation

Adventitious shoot formation was studied with leaf, stem and axillary bud explants of carnation (Dianthus caryophyllus L.). The shoot regeneration procedures were applicable for a wide range of cultivars and shoot regeneration percentages were high for all explant types. Using axillary bud explants, shoot regeneration efficiency was independent of the size of the bud and of its original position in the plant. In contrast, shoot regeneration from stem and leaf explants was strongly dependent on their original position on the plant. The most distal explants (just below the apex) showed the highest level of shoot regeneration. The adventitious shoot primordia developed at the periphery of the stem segment and at the base of leaf explants. In axillary bud, stem and leaf explants, shoot regeneration originated from node cells, located at the transition area between leaf and stem tissue. Moreover, a gradient in shoot regeneration response was observed, increasing towards the apical meristem.Abbreviations BA benzyladenine - NAA naphthaleneacetic acid     

Structure of the vegetative shoot apex ofCassiope lycopodioides

The structure of the vegetative shoot apex ofCassiope lycopodioides D. Don, which has a decussate leaf arrangement, was analyzed using trans- and longisections to generate a three-dimensional viewpoint. The apical dome of this species is relatively high from the middle to the maximal area phase of a plastochron. Therefore, the initial protrusion of a pair of leaf primordia occurs laterally on an apical dome conspicuously in contrast to the cases ofDaphne pseudo-mezereum andClethra barbinervis whose apices are nearly flat or slightly convex. The structure of the apex ofCassiope, however, may be understood with the concept of “apical sectors” on the same basis asDaphne andClethra (Hara, 1961, 1962, 1971a, b, c).     

Biology and social behaviour of three species ofAnischnogaster (Vespidae,Stenogastrinae) in Papua New Guinea

Summary Level of social organization, adult behaviour, size and development of the brood in three species ofAnischnogaster are described. The normal colony size in all the three species was one female per nest, and colony size never exceeded two females per nest. The social interactions, which were only observed in one species, did not include any marked dominance behaviour, but there was clear caste differentiation, with the older female guarding the nest while the younger female foraged for food. InAnischnogaster sp. A only some eggs and larvae have abdominal secretion, while no secretion at all was found on the eggs and larvae ofA. laticeps. In spite of this, the Dufour's gland was found to be well developed. The significance of this is discussed. Females ofA. laticeps were found to fall into two groups distinguished by the length of the sting. The larvae seem quite similar to those of other Stenogastrinae and have, apparently, only four instars.