Different biomechanical design and ecophysiological strategies in juveniles of two liana species with contrasting growth habit

Abstract

• Premise of the study: Lianas constitute a major functional type in tropical zones. While some liana species start climbing immediately after germination (shade-avoidance), others have a long self-supporting phase (shade-tolerance). The morphophysiological characteristics of these two growth habits are unknown. • Methods: We quantified growth traits, biomass allocation, mechanics, anatomy, and hydraulics for saplings of Ventilago calyculata (an immediate obligate climber) and Ziziphus attopensis (having a long self-supporting phase), both in the family Rhamnaceae. The mechanics, anatomy, and hydraulics for the mature individuals of the two species were also evaluated. • Key results: In the juvenile stage, V. calyculata had a higher slenderness ratio, height growth rate, and photosynthetic rate but similar biomass growth rate compared with Z. attopensis. In contrast, Z. attopensis had a higher leaf area growth rate, specific leaf area, and leaf mass fraction. Ziziphus attopensis had stiffer, but less conductive stems than V. calyculata. Stem rigidity of saplings decreased from base to apex in Z. attopensis, but increased in V. calyculata. Both species had similar resistance to xylem embolism. However, the leaves of V. calyculata were able to resist greater water deficits. At the mature stage, wider and longer vessels emerged in the xylem, and both species increased stem specific conductivity and drought resistance in stems and leaves. Ventilago calyculata had significantly higher specific conductivity and was more drought tolerant than Z. attopensis. • Conclusions: The two lianas differed significantly in growth, biomass allocation, anatomy, mechanics, ecophysiology, and hydraulic properties in line with their growth habits and shade adaptation strategies. © 2014 Botanical Society of America.