restricted to the gland cells surrounding the amphidial sense organs (the sheathcells). In addition to providing the rst description of SXP proteins from a plant parasitic nematode, this work provides the rst detailed characterisationof a protein secreted from the amphids of a plant parasite. Résumé
-15, uniseriate and multiseriate, 2–5(–6) cells in width (up to 7 cells in AO 67-15) . Rays exceeding 1 mm in height occur in all samples except AO 66-15 ( Fig. 3 ). Multiseriate rays 4–53 cells high, composed of procumbent body cells, with upright and square cells in 1–4(–7) marginal rows, sheathcells
bundle-sheathcells of Zea mays L. Planta 1977 136 77 89
Fahn A. Secretory Tissues in Plants. Academic Press London 1979
Feder N. O'Brien T.P. Plant microtechnique: Some principles and new methods. Am. J. Bot. 1968 55 123 142
Fenner C.A. Beiträge zur Kenntnis der Anatomie, Entwicklungsgeschichte
sixteen neurons. The four dendrites beneath each papilla have basal bodies and cilliary microtubules typical of mechanosensors. The region close to the tips of the dendrites is surrounded by non-cellular material and the dendrites are separated from each other by a series of sheathcells. On the basis of
The presence of thin-walled parenchymatous cells in the inner bundle sheath of species of the liliaceous genera Aloe, Chamaealoe, Astroloba, Lomatophyllum, Gasteria, Haworthia, Asphodeline, Asphodelus, Bulbine, Eremurus and Trachyandra was observed and described. Some species, however, have lignified sclerenchymatous cells in this position and this is general in Kniphofia. Cells in this region produce a secretion in the form of a copious exudate in many species of Aloe, or much sparser contents in the case of related genera. The leaves of most species contain small amounts of anthraquinones, while the related anthrone-C-glycosides accumulate in others. A wide range of other phenolic substances occurs, recognized as distinct zones on thin layer chromatograms, but mainly consisting of unidentified compounds. It is not certain if synthesis occurs in the thin-walled bundle sheath cells or if these have only a storage function. Another layer of rather smaller parenchymatous cells in the outer bundle sheath is distinct in the majority of genera and these cells typically contain amorphous globules of unidentified material. Infrequently, similar globules are seen in the inner bundle sheath cells. It is postulated that synthesis of secretory compounds takes place perhaps in the inner mesophyll and in the outer bundle sheath cells. The presence of a thin-walled secretory tissue, together with the compounds secreted in many species, suggests close affinity between most of the genera mentioned, although the ubiquitous lignification excludes Kniphofia.
A silicified wood, Welkoetoxylon multiseriatum, gen. et sp. nov., is described from the late Early Eocene Green River Formation of southwestern Wyoming. The combination of features observed in W. multiseriatum, including latex tubes (laticifers) in the rays and abundant sheath cells, indicates affinities with the Moraceae. This is the first report of fossil moraceous wood from the Eocene of the western interior of the U.S.A. and it provides reliable evidence for the Paleogene occurrence of Moraceae in this region. The indistinct growth rings of this fossil indicate this tree did not experience a distinct dormant season.
Developmental changes in the xylem were studied in a stem of Bocconia vulcanica Donn. Smith with a xylem radius of 3.0–4.5 cm. Growth rings are absent. The vascular cambium is nonstoried with fusiform initials averaging 282 µm long. The specialised vessel members are short, with oblique to transverse end walls, simple perforations, and alternate intervascular pitting. Vessels are relatively uniform in diameter and arrangement throughout the wood. Fibres have moderately thin walls and do not increase in length from the primary xylem to the cambium. Axial parenchyma is paratracheal, scanty to vasicentric. Rays are exclusively multiseriate, tall, and heterocellular with a predominance of erect and square cells. Sheath cells occur along the sides. There are no fibres in the secondary phloem and a periderm is not present. The xylem and bark are similar in many respects to that formed in some groups of dicotyledons that are basically herbaceous with evolution toward woodiness.
Length-on-age curves are presented for tracheids of three stems of bristlecone pine (Pinus longaeva). In the oldest stem tracheid length has steadily increased over the last 2200 years, and there are no signs of a levelling off. In the younger stems, which have the innermost rings dated 1484 and 1445 A.D., it appears that the 'juvenile' phase of steep increase in tracheid length of Pinus longaeva lasts several centuries. The methods of measuring tracheid length from narrow increment cores with a high percentage of damaged tracheids in macerations and in tangential sections using Ladell's method are compared. The wood anatomy of P. longaeva is described and found very similar to that of P. aristata. Both species differ in minor details from the related P. balfouriana. All three species share minute crystals in the epithelial and sheath cells of the resin ducts.
Structural variations in cambium, xylem and phloem collected from main trunks of Sterculia colorata, S. alata, S. villosa, S. urens and S. foetida growing in the South Dangs forests were studied. In all five species, the cambium was storied with variations in the length of fusiform cambial cells. Compared to other species S. foetida had the longest and S. urens the shortest fusiform cambial cells. Cambial rays in all the species were compound (tall) and heterocellular with sheath cells. Their height and width were maximal in S. foetida and in S. villosa respectively. In all the species the storied nature of fusiform cambial cells was maintained in derivative cells that developed into sieve tube elements; vessel elements and axial parenchyma of both phloem and xylem. However, fibres of phloem and xylem were nonstoried. The dimensions of elements in phloem and xylem varied among the species. The variation in the mean length of sieve tube elements and vessel members coincided with that of fusiform cambial cells.
present in each receptor and extend into the tip of the pore. The pore contains a channel filled with amorphous material. Each pair of neurons is surrounded by two accessory cells, the socket and the sheathcell. Structural similarities with pores on the anterior part of the body of other phytoparasitic