Morphological differentiation of current-year shoots of deciduous and evergreen lianas in temperate forests in Japan

Morphological variation in current-year shoots within plants was examined in five deciduous and four evergreen liana species from temperate forests in Japan to elucidate the role differentiation in shoots. All lianas had both shoots that twined or developed adventitious roots to gain support on host materials (searcher shoots) and self-supporting shoots with no climbing structures (ordinary shoots). Searcher shoots were 20–295 times longer than ordinary shoots. The allometric relationships between stem length and leaf area differed between searcher and ordinary shoots, and the stem length for a given leaf area was greater in searcher shoots. Leaf area per shoot mass was 1.4–4.3 times higher in ordinary shoots because of the greater allocation to leaf biomass. Searcher shoots comprised only 1–6% of total shoots but 30–85% of total shoot length in deciduous lianas. Ordinary shoots accounted for 70–95% of the total leaf area in these liana species. These results suggest that the exploration of new space was primarily achieved by searcher shoots, whereas a large proportion of current photosynthetic production was achieved by ordinary shoots. The range of stem length and leaf mass ratio of ordinary shoots was similar to that in shoots of tree species. Specialization of shoots in lianas is discussed.