Title: Contributions from the Botanical Laboratory and the Morris Arboretum of the University of Pennsylvania, vol. 14
Identifier: contributionsfro14univ (find matches)
Year: 1934 (1930s)
Authors: University of Pennsylvania. Botanical Laboratory; University of Pennsylvania. Morris Arboretum
Subjects: Botany; Botany
Publisher: Philadelphia : (s. n. )
Contributing Library: Penn State University
Digitizing Sponsor: Lyrasis Members and Sloan Foundation

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30 Phytopathology (Vol. 28
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cell a^n'-sletuent^TnU^StU^^^^^^ penetration showing vesicle in epidermal a subepidermal cell. C. Mycelium and haustorium S fhf TF '"P^^*^ haustorium within with short germ tube entering host shoSL ab^nc/nf ? ^"^ Parenchyma. D. Spore lular type of penetration. E? Diafframmatif ro^Zl\ i^'^^l^T"'^ ^"^ ^^e intercel- Uum of a typical unresisted infectfonh^on^h T. *^*'^ ""^ *^^ «P^^^^ «f the myce- spread is shown and the appearance of transv^^^^^^ T'*'^- ^^^^^^ longitudinal cated: a, point of penetration; b extent If «nh!-r' ^^^^"^ ^* ^^"«"« ^^^^Is is indi- growthjD, extent of Wread adjacent tfrLinLct^^^^^^^ T"^^' ^' P^*^ «^ radial r, the phloem. j no resm auct in inner cortex; e, cortical resin duct; >r > *t ->. ^^ r 4 ^ ⺠'â *â ^> ri- â¢^ w*** 1938) True: Gall Development on Pinus Sylvestris 31 and often dying cortical cells. Most of them showed isolated groups of living hyphae penetrating the more normal portions of the cortex and the inter- cellular remains of others where tissue abnormalities were more severe. In the case of one infection, discovered in sectioning, where no external symp- tom was present, the abundant and continuous spread of the large inter- cellular mycelium had produced almost no abnormality in the areas it pene- trated. This infection had penetrated as deeply into the cortex as most of the others, some of which were still confined to the outer cortex. Infections to which little or no resistance apparently is offered are those that cause but slight early abnormality in the host. The abundant large hyphae pass between or encircle nearly every cell in the infected area (PL I, 2 and 3), and many cells are penetrated by the ellipsoid to cylindric haus- toria, which are uninucleate and greatly attenuated where they pass through the cell wall (Fig. 3, C and Fig. 6, E). The haustoria often appear to seek out the nucleus of the host cell and those touching it appear at times to be flattened at the point of contact. The host cells in the infected zone are more spherical and regular in outline than those in the normal cortex, and there is a tendency toward hypertrophy, which is most pronounced in the cells invaded by haustoria. The hyphae of a mycelium whose invasion apparently is unresisted advance in characteristically different directions (Fig. 3, E). Some run parallel to the axis of the twig in the spaces between the first one or two cortical cell layers or just beneath the epidermis. The major portion of the mycelium, however, spreads radially inward through the outer cortex until the inner cortex is reached, and there a second vertical spread occurs, which is most pronounced in the intercellular spaces adjacent to and near the epithelial cells of the resin ducts. These cells often show a tendency to hypertrophy, increasing in size until they may partially or completely fill the ducts. (PL I, 2). The mycelium often spreads a considerable distance about the margin of the phloem before entering it. (PL I, 3). Fresh shoots of the current season's growth, collected September 20, 1933, and tested microchemically, indicated a possible physiological explanation for the diversified paths followed by the mycelium in unresisted infections. The layer of cells just below the phellogen, and at times the cells of the phellogen itself, well established at that date, were found containing starch, particularly near the bases of the needle fascicles, where every cell was filled with it. Elsewhere in these peripheral tissues starch was less abundant, appearing only in scattered cells. Internal to this layer the cells of the outer cortex seldom showed starch except below needle fascicles where starch-con- taining cells are few and scattered. The inner primary cortex, however, had numerous scattered starch-containing cells in the vicinity of the phloem and near the resin ducts. Droplets of fatty substances were present in scattered cortical cells, but were especially abundant in the cells surrounding the resin ducts. Compounds giving a positive reaction to the ferric chloride test for tannins were found in scattered cells in the inner cortex, but especially in the

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