Further Experiments on Wound-Vessel Formation in Stem Wounds of Coleus

Experiments were conducted on wound-vessel regeneration in stem wounds of Coleus blumei Benth. with a Safranin O whole-mount technique. 2. The whole-mount technique demonstrated that differentiated xylem cells possessed simple perforation plates. It is suggested that the terms "wound-vessel member" (single cell) and "wound vessel" (strand of contiguous cells) be adopted to describe lignified cells with unique wall striations and simple perforation plates arising from wound responses. 3. Wound-vessel formation in flowering Coleus formed an irregular branching pattern that was weakly oriented to the plant axis as compared with that in vegetative plants which had a predominantly vertical arrangement of wound vessels. The disposition of wound vessels in wounded segments of excised shoots was similar to that in flowering plants. 4. It was not possible by the selective wounding of vascular tissues with microneedle puncture wounds and by shallow cortical wounds to determine whether the factors involved in wound-vessel formation resulted from the rupture of the primary phloem or whether both the primary phloem and the primary xylem were involved. Rupture of the primary xylem by pith puncture wounds did not result in wound-vessel formation. 5. Further experiments were conducted on the treatment of wounds with various inhibitors suspended in lanolin. Within the concentration limits investigated, potassium cyanide and phenylthiourea have little or no effect on wound-vessel formation; thiouracil and malonic acid partly inhibited the differentiation of these cells; and traumatic acid and iodoacetic acid strongly inhibited the formation of wound vessels. Some of the limitations of this technique are briefly discussed.