Histological Observations and Histophotometric DNA Measurements in Wounded Tissues5Pisum sativumL. infected withAgrobacterium tumefaciens

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Abstract
Crown gall tumours of pea seedlings have been studied, with special attention to the morphogenesis and cytology of wound tissues, infected wounds, and young and older tumours. Feulgen staining was used for histophotometric estimation of the relative amount of DNA per nucleus. Most cells of the cortex of normal elongated pea seedlings contained an 8-C amount of DNA. Wounding with or without infection had no great influence upon the amount of DNA per nucleus in the wound region during the first 3 d. By induced mitosis more 2-C and 4-C nuclei were formed. Later on, in uninfected wounds during wound regeneration, some 8-C nuclei were again formed. In infected tissues and tumours the pattern of DNA synthesis and mitosis was drastically changed. DNA measurements were performed at different stages and in different parts of the tumours. Root meristems and other meristematic tissues, which develop in the tumour, contained mainly 2-C and 4-C nuclei. Older roots, growing out from the tumour, contained mainly 8-C nuclei, and some 4-C and 16-C nuclei. In non-dividing tissues of the tumour 2-C, 4-C, 8-C, 16-C, and 32-C nuclei were found. Some nuclei even with higher DNA content were present. In the growth centres the same nuclei classes were observed. Certainly polyploidy occurs in the higher DNA classes. It is not clear whether poly-teny is also involved in the process.

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