Differences in xylem and phloem structure in living stumps of Norway spruce (Picea abies (L.) Karst.) and silver fir (Abies alba Mill.)

What is it about?

Living stumps that have been reported in many tree species were the first, circumstantial evidence of root grafting. Although stump overgrowth has been extensively studied in various tree species, anatomical observations have mainly focused on the xylem part, while the bark tissues are less investigated, despite their importance in the overgrowth process of injury. Here, we investigated the xylem and phloem structure in living stumps in Norway spruce and silver fir. We found that the mechanism of wound closure was similar in the two species; however, there were differences in the structure of wound tissues in wood and bark. Immediately after the injury, a callus consisting of parenchymal cells was formed, followed by wound-wood with wide increments, and the wood structure and morphology of tracheids were changed. Traumatic resin canals were present in both species but were more abundant in spruce, which also had normal resin canals. In both species, the typical structure of annual phloem increment was lost in the non-collapsed phloem and sclereids were very abundant in the collapsed phloem. In fir, the collapsed phloem was rich in swollen parenchyma cells, while in spruce, numerous large traumatic resin canals were conspicuous. The study showed that similar and species-specific patterns of vascular tissue restoration exist in spruce and fir in response to tree felling. _x000D_ _x000D_ _x000D_

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