Summary Wound-induced changes in the protein content, the protein pattern, the patterns of peroxidase and malate dehydrogenase isoenzymes and the nucleic acid content were investigated in the tuber tissue of Solanum tuberosum L. (cv. Saskia ) with regard to their localisation in the tissues beneath the wound surface. These investigations, which were carried out 4 days after wounding when the induced reactions had stabilized, were pursued to complement earlier findings indicating that the volume of the physiological influenced tissue determines the intensity of the histological reactions which can be observed only directly below the wound surface ( Rosenstock et al., 1972). The protein content in the tissues shows a significant localized increase after wounding, compared with that of the intact tuber. This increase is most evident in the cell layers nearest the wound surface and continously decreases to a depth of approximately 2 mm below this surface. The protein content at greater depths is similar to that in the tissues of the intact tuber. Polyacrylamid gel electrophoresis yielded an electropherogram from the uppermost cell layers (0–0.5 mm below the surface) exhibiting two additional bands (Z and W) not) observed in the protein pattern of the intact tuber. In addition, the colouring of bands 1 and 15 from the intact tissue was enhanced, whereas the intensity of other bands (5, 6, 7, 8, 10, 12 and 16) was diminished. Moreover a dedifferentiation of the basic pattern and a greater degree of background staining on the gels could be observed. In the subsequent cell layers (0.5–2.5 mm below the surface) these woundinduced changes were progressively less pronounced. The additional protein band W could not be dedected at a depth of 1–1.5 mm, and band Z was no longer in evidence at a depth of 2 mm below the surface. The electrophoretic pattern at deeper tissue levels resembled quite closely that of the intact tissue. To complement these experiments special enzymes were also investigated. The pattern of malate dehydrogenase isoenzymes exhibited no change after wounding at any depth below the surface; only the activity of MDH generally was slightly more intense up to a depth of 2 mm. The peroxidase isoenzyme pattern displayed a remarkable increase in the intensity of all bands in the tissue layers nearest the wound. This enhancement of activity diminished continously up to a depth of 2 mm below the surface, beneath which the intensity of the bands was the same as in the intact tissue. In addition, three new bands with peroxidatic function (A, B, C) were detected in the cell layers nearest the wound. At a depth of 0.5–1 mm below the surface the isoenzyme band A had completely disappeared and the intensity of bands B and C had diminished. In the subsequent cell layers these bands likewise disappeared, first band B and finally band C. At a depth of more than 2 mm below the surface the pattern corresponded with that of the intact tuber tissue. Additional investigations concerning the nucleic acids showed that the DNA content increased after wounding only in the cells nearest the wound, in the region where histological wound reactions (mitoses) could be observed. The RNA content was, however, not only greater near the surface of the wound, but also in subsequent layers up to a depht of 3–4 mm below the surface. The results, as a whole, confirm and complement the results of previous investigations which indicated that the physiological activity after wounding is enhanced not only in the cells nearest the wound, but also in the tissues further beneath the surface where no histological reactions take place. This increased physiological power may be an essential factor for regulating the intensity of the superficial histological processes of wound healing.
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Jun 1, 1979
Shawn Doonan + 2
Open Access