Rough Bark Formation and Food Reserves in Pine Roots
Abstract:One of the principal symptoms of the littleleaf disease of shortleaf pine is a marked deterioration of the roots, as shown by the scabby appearance of the small laterals and excessive dieback of the mycorrhizae-bearing roots. In the advanced stages of the disease, an excessive and premature formation of rough bark termed "brown-patch" occurred on all roots. It appeared likely that brown-patch over large root areas could result in a serious loss of phloem wherein much of the reserve food is stored. The purpose of this study was to trace the events from the known reduced photosynthetic capacity of the littleleaf trees to the excessive formation of rough bark on the roots. The histology of brown-patch is described and illustrated with photomicrographs. Monthly analyses were run throughout a single year on the total carbohydrate content of root wood and bark to determine whether root starvation precedes and leads to formation of brown-patch. The food content of root bark on healthy trees reached a minimum in early fall and a maximum in early spring. Root bark on diseased trees had only half the food content of the healthy trees over the year. These data showed that excessive brown-patch formation follows the starvation of the phloem which resulted from either impeded synthesis or translocation of food.
Document Type: Journal Article
Affiliations: Principal Research Scientist, Forest Service, U. S. Dept. Agric., Asheville, N. C.
Publication date: June 1, 1964
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