Phenotypic plasticity in Bromelia serra Griseb.: morphological variations due to plant size and habitats with contrasting light availability

摘要

In the understory of the Schinopsis balansae Engl. forests of the Wet Chaco there are dense populations of Bromelia serra. The individuals of this strictly terrestrial bromeliad grow in the sun as well as in the shade of the understory. Studies carried out with a facultative epiphytic bromeliad, Aechmea distichantha Lem., that also lives in the understory of these forests and whose foliar bases form a tank (phytotelmata), verified the existence of differences in plant architecture and biomass allocation due to plant size (apparent phenotypic plasticity) and to environmental conditions (true phenotypic plasticity). Thus, to evaluate whether the architecture and biomass allocation of a strictly terrestrial bromeliad is also affected by habitat and by plant size, we selected 22 plants of B. serra from open areas and 22 from the understory covering the whole range in plant size. For each plant, we characterized its rosette (height, diameter and number of leaves) and we measured the length and width of the longest leaf. The plants were split into stem and leaves (sheaths and blades), weighed, and then several biomass allocation indexes were derived. At a similar biomass, plants grown in the sun had shorter leaves, with a lower length:width ratio than those from the understory, but there were no differences between habitats with regard to plant height, diameter or different biomass fractions. These results suggest that B. serra (a strictly terrestrial bromeliad) shows a high apparent plasticity in most variables, but low true phenotypic plasticity in response to environmental differences.