We assessed clonal variation in morphological variables, mineral nutrition, root growth capacity, net photosynthesis, tannin distribution, and cuticle and epicuticular wax features within four families of white spruce (Picea glauca (Moench) Voss). Seeds were collected from four families obtained through controlled crosses among selected genotypes. For each family, plants were produced either from seeds (zygotic) or by somatic embryogenesis (clones). Each family was therefore represented by its zygotic seedlings and three clones. Within a family and under similar growth conditions, several clones differed significantly from the zygotic seedlings in height, root-collar diameter, needle dry mass, branch density, shoot dry mass, root dry mass, and length of needles. Branch density (number of first-order branches per cm height) of zygotic seedlings and clones varied from 0.8 to 1.4 branches cm(-1) and from 0.6 to 1.3 branches cm(-1), respectively. Mean needle length of zygotic seedlings and clones ranged from 11 to 14 mm and from 11 to 17 mm, respectively. For many variables (height, dry mass of new roots, needle dry mass and branch density), differences among clones were significantly greater than differences among zygotic seedlings within a family. Tannins were more abundant in needles of clones than in needles of zygotic seedlings. In some clones, tannins occurred as a ribbon along the central vacuole, whereas in others they appeared as aggregates dispersed in the vacuole. Within a family, N, P and K showed considerable variations in their use efficiency. Interclonal variations were observed in root growth potential and net photosynthesis. Variations in growth and physiology reflect genetically determined differences among clones within a family.

No abstract

An exoglucanase, purified from a cellulase produce by the fungus Trichoderma harzianum Rifai., was successfully bound to colloidal gold and used for ultrastructural detection of intracellular cellulosic β-(1 → 4) glucans. These saccharides were found to be present in great amount in the walls of Ophiostoma ulmi (Buism.) Nannf., the Dutch elm disease agent, whereas they were randomly distributed in the walls of Fusarium oxysporum Schlecht f. sp. radicis-lycopersici Jarvis and Shoemaker (FORL), the agent of tomato crown and root rot. In O. ulmi cell walls, the β-(1 → 4) glucans were predominantly concentrated over the central portion of the inner walls. In both colonized elm wood and infected tomato root tissues, the compound middle lamella and secondary walls of parenchyma cells, fibers (absent in tomato roots), and vessel members were always intensely labeled, but gold particles appeared somewhat irregularly distributed. In fibers having an S3 gelatinous layer, the latter was always preferentially labeled. Penetration of O. ulmi in elm wood tissues resulted in the digestion of host wall areas free of labeling. Such areas were not observed in infected tomato tissues; instead, an accumulation of gold particles was noted along the fungal portion that was in close contact with the host wall. Results of this study confirm the potential value of gold-labeled exoglucanase and provide some new information about wall topochemistry during host-pathogen interactions.

The nature of the wall layers observed in suberized tyloses was studied in Populus basalmifera L., Ulmus americana L. and Quercus rubra L. As the suberin layers were present only in tyloses that had completed their expansion, most of the results concern mature tyloses. The cyto-and immunocytochemical tests were conducted, respectively, with an exoglucanase having a binding affinity for 13(l~4)-D-glucans, the subunits of cellulose, and with two monoclonal antibodies specific for un-esterified and esterified pectic molecules. In the three species, labelling for pectic compounds was intense over the external layer of tyloses but usually more dispersed or nearly absent over the layer corresponding to a primary wall that was, however, intensely labelled for 13(1 ~4)-Dglucans. The outer wall layer, comparable to a middle lamella in mature tyloses, was continuous with similar material that appeared to be secreted by the tylosis. This material was particularly abundant in pit chambers, in void spaces between the tylosis and the vessel wall, particularly at the junction of the vessel and two adjacent cells, and close to the rim of vessel perforation plates. In P. balsamifera, a single suberized layer or occasionally a succession of suberized and cellulose-containing layers was observed internal to the tylosis primary wall. In U. americana, the wall of tylosis was similar to that of P. balsamifera except that, at times, a secondary-wall-like layer was formed and only a single suberized layer was observed. In Q. rubra, the suberized layer was always observed internal to the tylosis secondary wall. Simple pits were also constantly noted in Q. rubra tyloses. The occasional occurrence of a cellulosic layer internally to the suberized layer was observed in the three species. Histochemical tests revealed that lignin was also an important component of the tylosis wall. The tyloses frequently contained phenolic compounds in close association with the suberized layers. The significance of the formation of suberized tyloses in trees is discussed.Abbreviation: TEM = transmission electron microscope

When Ophiostoma ulmi or Ophiostoma novo-ulmi are grown on either 0.22- or 0.45-μm millipore filter membranes placed on impoverished agar medium, the fungus grows through these membranes and takes on various irregular pleomorphic growth forms (P-forms). Links of continuity between these forms and the more regular ones have been shown using light, confocal, and transmission electron microscopy. Tests with labelled probes, such as gold-complexed wheat germ agglutinin for chitin and β-exoglucanase for cellulosic β-1,4-glucans, have indicated that in P-forms deposition of chitin is much altered but is less so in the case of cellulosic glucan. The cytology of these forms compared with the regular fungal ones is also very different, particularly with reference to mitochondria and nuclei. Also, numerous vesiculate structures were noted in the rarely septate P-forms. Similar irregular forms with opaque contents were produced by these fungi when they were grown on sterilized elm wood sections. When these latter samples were fixed by high-pressure freezing, the following main features were noted: fungal cells with a very thin wall, slightly labelled for chitin but more intensely for cellulosic glucans; well-preserved structures, such as plasmalemma and endoplasmic reticulum; and a slightly opaque, fibril-containing extracellular sheath. Differences in labelling for galactose, whether of wall layers or cell contents, were also observed in regular and P-forms. Electron opaque bodies that labelled strongly for galactose were also numerous in P-forms in some samples.Key words: transmission electron microscopy, high-pressure freezing, gold labelling, extracellular sheaths, wall constituents.