摘要:

SUMMARYIn thick transverse sections through carefully sampled pieces of the developing early‐wood zone ofFraxinus excelsior, the shape of the developing vessel elements is circular.On the basis of this shape and of some considerations on the mode of cellular adjustments and preliminary counts of cell‐division figures in this zone, it is concluded that a two‐stage process for the enlargement of the vessel elements, as proposed by Zasada&Zahner(1969), is unl

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00847.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYDuring the formation of cell wall thickenings in primary tracheary elements of the hypocotyl of cucumber, the morphology or topography of cell organelles was studied in relation to the size of the developing thickenings.In the initial stage, endoplasmic reticulum is smooth and vesicular, whereas afterwards it is rough and cisternal. The diameter and the electron density of the contents of Golgi vesicles in the successive stages differ. In the initial stage, cortical microtubules are present along the whole plasmalemma; in the following stages they occur only around the thickenings; and, in the final stage, they are again present along the whole plasmalemma. Lomasomes and cytoplasmic fibrils are present only in the beginning of thickening formation.The changing morphology of the endoplasmic reticulum in the different stages is related to different functions in thickening formation. The smooth vesicular form buds off vesicles which are probably added to the lomasomes. The rough cisternal form synthesizes proteins (enzymes). In addition, it seems that it transports substances and conducts vesicles. The changing morphology of Golgi vesicles is probably related to varying amounts and nature of substances in the vesicles in various stages. The orientation of microtubules and the distance between them indicate that microtubules form a barrier against Golgi vesicles. Lomasomes probably deposit substances during the initial stage in the developing thickenings. There are no indications that cytoplasmic fibrils are involved in thickening formation.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00848.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYThe relationship between the endoplasmic reticulum and the Golgi vesicles and the formation of cell wall thickenings in primary tracheary elements of the hypocotyl of the cucumber was investigated. In order to study the degree to which the endoplasmic reticulum and the Golgi vesicles might contribute to thickening formation, the relationship between the size of the thickening and the density of these cell organelles in the cytoplasm near the thickening was studied quantitatively. It appeared that the density, and hence the contribution, of the endoplasmic reticulum and the Golgi vesicles reaches an optimum in the mid‐stage of the process of thickening formation.The endoplasmic reticulum and, to some extent, the Golgi vesicles occur in the cytoplasm between the cell wall thickenings in higher densities than in the cytoplasm facing the thickenings. This supports the hypothesis that cell wall substances brought by the endoplasmic reticulum and the Golgi vesicles pass through the plasmalemma between the thickenings and are then transported through the primary cell wall towards the sites of the thickenings.Lomasomes seem to be involved in the initiation of the thickenings. It seems likely that cell wall substances pass through the plasmalemma by way of the lomasomes. The substances are then transported sideways through the primary cell wall and the thickenings arise at each side of the vanishing lomasome

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00849.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYBoth pulse and continuous labelling experiments were performed to study cap genesis in the primary root ofAvena sativaL.The cap meristem comprises one tier of initial cells situated immediately distal to the root cap junction. In the periphery of this tier, the cells have lost their initial character. Compensation for this loss of initial cells is provided by anticlinal divisions of more centrally situated initial cells.Pulse labelling experiments indicated an average cycle time of the cap initials of 10 to 12 hours. From this cycle time and the number of cells in the central rows of the cap it was inferred that forAvenait takes at most 5 to 6 days before a derivative cell is sloughed off.The results are compared with data from Clowes(1971) and Phillips&Torrey(1971, 1972).

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00850.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYThe cuticular characters of the leaves of all Malesian species belonging to 25 genera of the Icacinaceae and those ofPennantiafrom Australia and New Zealand and some taxa from Continental Asia have been studied and are described in detail. Five stomatal types and nine different hair types are recorded for this part of the family. Haberlandt's interpretation of the slender papilla‐like hairs ofGonocaryumas hydathodes is challenged. Penetrating asteroscleroids in the cuticular flanges of twoStemonurusspecies are reported for this family for the first time.A synoptical key to the genera on the basis of cuticular characters only is given. The diagnostic and taxonomic value of the characters used is discussed.Taxonomic implications of this study are the indication of a close relationship between Phytocreneae and Iodeae (all climbers), the isolated position of the generaPlateaandGonocaryum, and the impression thatMappianthusshould be treated as a genus separate fromIodes.The combined characters of indumentum and stomatal type do not show an absolute correlation with the levels of specialization found in wood‐ and nodal anatomy for this family by Bailey and Howard. The distribution of stomatal types over the genera, however, suggests that the paracytic and anomocytic types are primitive for Icacinaceae and that the cyclocytic and anisocytic types are more deri

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00851.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYMicroorganisms are used for gaining a better insight into the structure of the woody cell wall. For obtaining maximal effects from this branch of studies, microorganisms also need to be studied more intensively. Examples are given where microorganisms and cellulase preparations degraded the woody cell wall: differences in soft rot attack in Angiosperm and Gymnosperm fibre walls; soft rot attack in wood which was used inTeredotests in coastal waters; the influence of ponding and immersion in cellulase preparations. It is proposed that the mucous layer around the hyphae ofChaetomium globosumand other soft rot fungi plays a role in producing the geometrical cavities. It was found that bacteria attacking ponded wood destroy the very thick membrane of the half bordered pit‐pair to a considerable degree, leaving a thin membrane which is considered to be the S2 layer of the parenchyma cell wall. Bacteria also remove the membranes of the bordered pit pairs, most probably by digesting the margo, leaving the torus free to float away. The cellulase preparations are able to digest the margo‐fibrils of the bordered p

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00852.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYThe morphogenesis of groundnut plants from an age of 0 to 21 days is described. The opinion that flower primordia are present in groundnut seeds is not confirmed. Further observations prove that the early development of the groundnut is less fixed than former conceptions about the structure of the seed suggest.

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00853.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYOne‐ to four‐year‐old callus cultures of the Lombardy poplar (Populus nigraL. ‘Italica‘) are able to form roots and leaves or shoots. There may be single leaves, small buds, elongating shoots, or a combination of these organs. Of the four cytokinins used to stimulate organ formation, zeatin was the most active, stimulating shoot formation at a concentration as low as 10–8M. The highest zeatin and BA concentrations (10–5M) stimulated leaf formation, but fewer elongated shoots were formed than at a lower cytokinin concentration. 2,4‐D was inhibitory to organ formation, even in low concentrations that stimulated callus growth (0.05–0.1 mg/1). This 2,4‐D‐inhibition is discussed in relation to the suppression of t

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00854.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYYoung adventitious roots formed by tissue cultures or stem cuttings of the Lombardy poplar produce buds when treated with kinetin or 6‐benzylaminopurine (BA). These buds originate from the superficial layers of the root, often close to the apex. When the buds are in a terminal position the apical tissues have been disturbed by callus formation. The normal activity of the apical root meristem is stopped by cytokinin, and in most cases the cells lose their meristematic appearanc

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00855.x

年代:1973

数据来源: WILEY

摘要:

SUMMARYJerusalem artichoke tissues were cultured for 1–4 days on media containing different labelled auxins (IAA‐1‐14C and 2,4‐D‐14C) before being transferred to a medium without growth substances. The development of tissues and the fate of the incorporated substances were studied and compared with those of tissues maintained on the same medium throughout.Explants had absorbed enough IAA in 2 or 3 days to develop like others kept on the original medium. In the case of 2,4‐D development of the explants was even better when transferred after 3 days to a medium without auxin.When IAA was used incorporated radioactivity was found in IAAsp and an unidentified substance A; growth is determined by the ratio of substance A to IAAsp. With 2,4‐D label is retrieved as 2,4‐D itself as well as another unidentified substance D: here also growth is determined by the ratio of 2,4

ISSN:0044-5983    

DOI:10.1111/j.1438-8677.1973.tb00856.x

年代:1973

数据来源: WILEY