Shoot dynamics and adaptive morphology of Ipomoea phillomega (Vell.) House (Convolvulaceae), a tropical rainforest liana


J Penalosa

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Annals of Botany


Ipomoea phillomega (Vell.) House (Convolvulaceae) is a common liana in undisturbed and disturbed patches of a primary tropical rain forest in Veracruz, Mexico. In this study a demographic-morphological approach to an understanding of its growth dynamics was attempted. Clonal spread via stolons accounts for nearly all population recruitment. The liana can produce a variety of shoot types. The balance among these is influenced by light intensity such that shaded conditions favour the production of creeping shoots (stolons) with high elongation rates, long internodes and short-lived rudimentary leaves, and in full sunlight most shoots twine, elongate more slowly, have short internodes and produce large long-lived leaves. The correlation between light intensity and shoot type is not absolute. Even in deep shade of primary forest some twiners are produced and in full sunlight some stolons are produced. This suggests that over a span of light intensity ranging from 0.4–100 per cent of full sunlight, the liana invests energy both in vertical climbing and horizontal spread. Different shoot types showed different patterns of survivorship of plant parts. Twiner leaves have higher mortality rates than stolon leaves, but twiner apices have higher mortality rates than stolon apices. Exploration by essentially leafless stolons represents growth subsidized by insolated canopies elsewhere in the shoot system. The ‘costs’ of this pattern of growth are unknown since the physiological relationships among the shoot types have not been studied.