Self-supporting capacity of tropical lianas:: Growth strategies

Lianas are defined as non-selfsupporting woody climbing plants. However, during their life history they are capable of phases of self-support in the following special conditions: (i) when there are environmental limitations such as low light conditions; (ii) during juvenile phases of growth; and (iii) during episodes of expansion, renewal, or repair (after trauma) growth. The capacity to be self-supporting may involve part or the entirety of an individual, i.e., a single branch or the entire aerial system. Aerial systems that have both nonself- and self-supporting portions may be considered an expression of the duality inherent in biological functions: sexuality and asexuality, climbing and nonclimbing, exploration and establishment. A concise synthesis of personal observations of anatomical patterns as correlated to growth strategies in lianas is presented. Information gathered from over 400 angiosperm species growing in 40 tropical forest sites in America, Africa and Mayotte, are analysed. Variation in liana growth habit, reflective of differing microhabitats within tropical forests, finds its greatest expression in the contrast between the two extreme forms: self- and nonself-supporting. With regard to the origin of the lianescent habit in angiosperms, it seems likely that if lianas originated in a forest, they already had acquired the ability to produce both growth habits. Finally, it is stressed that the environmental milieux wherein the liana grows should be considered when discussing the occurrence of self- and nonself-supporting forms as these are tightly linked to the micro- and macro-habitat.