Title: Annual report of the Quebec Society for the Protection of Plants
Identifier: annualreportofqu1317soci (find matches)
Year: 1921-1935. (1920s)
Authors: Société de Québec pour la protection des plantes
Subjects: Plants, Protection of; Plants, Protection of; Plant diseases; Plant diseases
Publisher: Quebec : The Society
Contributing Library: New York Botanical Garden, LuEsther T. Mertz Library
Digitizing Sponsor: The LuEsther T Mertz Library, the New York Botanical Garden

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I Efifect on the Plant As with mosaic the leaves of potatoes suffering from leaf roll do not function properl^^ The causal principle is translocated in the plant juices and in this case it especially affects that part of the vascular tissues known as the phloem. In the phloem it gives rise to a necrosis or death of the tissue. Since it is in the phloem that most of the conduction of elaborated food takes place, those parts awaiting supplies of food for their development will receive onh^ a much reduced amount. This is the case with the tubers and the stolons bearing the tubers. Hence those tubers which do develop are small and are borne on short underground stems. )Moreover the infective principle passes down the parts of the phloem not killed and reaches the vascular tissues of the developing tuber. In it, therefore, there may also be phloem-necrosis. When such a tuber is cut across, or when it is pared to expose the vascular tissues, these are seen to be browned. The general term "net-necrosis" is used to indicate such an appearance, but it must be recollected that net-necrosis may be caused by other conditions than those in leaf-roll. Moreover the tubers from a plant with leaf-roll do not necessarily develop net-necrosis, for they maj^ not be affected soon enough, nor sufficiently severely, to cause necrosis in the vascular tissues. A further effect on the plant is exhibited in the next generation for tubers from diseased plants, and especialh' those with net-necrosis, frequently develop very w^eak, spindling sprouts. The yield from leaf-roll plants is materially reduced, in many cases being nothing at all. Fig. 4—A leaf showirg the dwj.rf, curled, daik green symptoms of mosaic. There are no apparent light green patches.

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