. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. Black Rot, Leaf Spot, and Canker of Pomaceous Fruits 113 the cellulose tissues, cortical and medullary, are colored blue with methyl- blue and unstained with methyl-green. The woody parts stain red with phloroglucin. In the diseased part there is a very prominent general brownish deposit, located chiefly in the medullary ray cells, the thick-walled cortical parenchyma, and the phloem parenchyma. Such cells are not stained by any of the stains used. The sclerenchyma fibers and the cork
. Black rot, leaf spot and canker of pomaceous fruits. Black rot; Leaf spots; Canker (Plant disease); Apples. Black Rot, Leaf Spot, and Canker of Pomaceous Fruits 113 the cellulose tissues, cortical and medullary, are colored blue with methyl- blue and unstained with methyl-green. The woody parts stain red with phloroglucin. In the diseased part there is a very prominent general brownish deposit, located chiefly in the medullary ray cells, the thick-walled cortical parenchyma, and the phloem parenchyma. Such cells are not stained by any of the stains used. The sclerenchyma fibers and the cork are colored red by saf- ranine, whereas suberized cork cells are made green with a chlorophyll solution. Diseased wood shows a test for lignin phloroglucin. The more striking ex- ternal symptoms of the canker noted are the dis- coloration of the bark, a crevice at the margin of the lesion, and a sinking of the tissues. It has been noted elsewhere that the organism penetrates the wood to a limited extent only, so that the more notable changes occur in the bark. The canker is sometimes superficial, the attacks of the organism being confined to the cor- tical tissues. Attacks on the wood of old limbs are not frequent, but on twigs the wood is subject to common invasion by the parasite. In cross and lon- gitudinal sections the first and the second, and sometimes the third, layers of wood, and even the pith, are discolored. Closer examination shows the mycelium to be very abundant within the vessels of the xylem and in the woody parenchyma. In this region the characteristic brown deposit is found, but is located chiefly in the cells of the medullary rays and the wood parenchyma. Inoculations on young apple trees in the greenhouse with the ascospore strain (no. 82, from apple) show that. FlG. 35. HISTOLOGICAL CHANGES IN DISEASED WOOD Cross section of part of apple twig, showing brown deposit in wood fibers and wood parenchyma cells. Mycelium is also shown in the xylem ducts, but it s
Size: 1348px × 1853px
Photo credit: © Library Book Collection / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1900, bookdecade1910, booksubjectblackro, bookyear1916
