Wound Responses in Girdled Stems of Lianas

Abstract

Nineteen species of lianas, some with typical secondary growth and some with anomalous secondary growth, were girdled by removing either one-half or the entire bark. Although regeneration occurred in stems with typical secondary growth, it was not as great as in stems with anomalous secondary growth. In stems with lenses of apotracheal parenchyma, most regeneration occurred from the parenchyma and was so great that the secondary xylem was fragmented into small individual pieces. In half-girdled stems of lianas with supernumerary cambia, proliferation occurred from the xylem and phloem rays, all cambia, and phloem nearest the exposed surfaces at the lateral edges of the girdle. In full-girdled stems, regeneration occurred from the innermost cambia as well as from internal phloem. All species with lobed xylem and disjunct cambium had prolific regeneration that always occurred from the furrows of phloem between the xylem lobes. In some full-girdled stems, callus that formed on the periphery of the stem developed a continuous cambium. Even though new xylem differentiated within this callus, the lobed pattern did not reappear. There were different responses to wounding in stems of different taxa with wide rays. Mikania cordifolia regenerated profusely, but Aristolochia gigantea regenerated much less. In Mikania, each callus from a wide ray eventually fused to neighboring callus produced by adjacent rays. Within each callus proliferation an individual segment of cambium developed and produced secondary xylem and phloem. However, these segments never became continuous as in the stem before wounding. From our studies, we concur with the suggestions that internal and included phloem reduces the chances of disruption of translocated materials to the root system and further suggest that the greater amount of living tissue occurring within the xylem, as well as in the phloem, gives an advantage in rapid and vigorous regeneration following wounding or girdling. [Other taxa studied were: Hippocratea volubilis, Passiflora coccinea, Vitis munsoniana, Stigmaphyllon ellipticum, Tetrastigma voinierianum, Serjania polyphylla, Mikania scandens, Pithecoctenium echinatum, Mansoa verrucifera, Saritaea magnifica, Chodanthus puberulus, Arrabidaea chica, Peixotoa glabra, Mascagnia psilophyla.].