. De récentes recherches sur les maladies du feuillage : conference proceedings : Carlisle, Pennsylvanie, du 29 mai au 2 juin 1989. Maladies et ravageurs des feuilles United States Congrès. Moins bien connus sont les questions suivantes : 1) Quel est le rôle du stade imparfait ? 2) Quand est-ce hysterothecia et les ascospores matures, et quelles sont les conditions qui favorisent la libération des spores, in- fection, et l'expression des symptômes ? 3) Quel est l'environnement ou de conditions microclimatiques qui permettent à l'éclosion d'une épidémie de la maladie ? 4) Quelles sont les conditions climatiques qui permettent en outre de développer les épidémies endémiques de lev

• Contributeur: The Book Worm / Alamy Banque D'Images
• ID de l’image: RF3TBK
• Taille du fichier: 7,1 MB (310,7 KB Téléchargement compressé)
• Autorisations: Modèle - non | Propriété - non
• Dimensions: 1830 x 1365 px | 31 x 23,1 cm | 12,2 x 9,1 inches | 150dpi

Informations supplémentaires

Cette image appartient au domaine public, ce qui signifie que le droit d’auteur a expiré ou que le titulaire du droit d’auteur a renoncé à ses droits. Les frais facturés par Alamy couvrent l’accès à la copie haute résolution de l’image.

Cette image peut avoir des imperfections car il s’agit d’une image historique ou de reportage.

. Recent research on foliage diseases : conference proceedings : Carlisle, Pennsylvania, May 29-June 2, 1989. Leaves Diseases and pests United States Congresses. Less well understood are the following questions: 1) What is the function of the imperfect stage? 2) When do hysterothecia and ascospores mature, and what are the conditions that favor spore release, in- fection, and symptom expression? 3) What are the environmental or microclimatic con- ditions that allow for epidemic outbreaks of the disease? 4) What are the conditions besides climate that allow epidemics to develop from endemic levels of in- fection? 5) Is there resistance to the disease within and be- tween species of pine? Life Cycle Conflicting reports exist on the function of the imper- fect stage of the fungus, development of the hysterothe- cia, and maturation and release of ascospores. Weir (20) refers to the imperfect stage as "spermagonia, " implying that the conidia function in sexual reproduction of the fungus. Waters (19) suggested that the conidia were essential for sexual reproduction rather than as infecting spores. Laurent (8) never found mature fruiting bodies of both spore stages on the same needle and, when both stages were present, only one or the other was mature. Lightle (9) found mature pycnidia with conidia in May and June. The spores appeared in tendrals or spherical droplets, and germinated in water after 3 days. Lightle (9) did not know if conidia played a role in infection. In California, I observed what appeared to be "recep- tive hyphae" originating from the hymenial layer and protruding through the surface of developing hysterothe- cia during June when the imperfect stage was mature and releasing conidia (fig. 1). Whether these hyphae are fer- tilized by conidia and function as trichogynes could not be determined and needs further investigation.. Please note that these images are extracted from scanned page images that may have been digitally enhanced for

Recherche dans la banque de photos par tags

• bookcentury1900
• bookpublis