The functional relevance of heteroblasty, an abrupt morphological change in the ontogeny of a considerable number of angiosperm species, is unresolved. Some epiphytic bromeliads show an abrupt heteroblastic change when small plants with narrow leaves suddenly develop broader leaves to form a watertank-like leaf architecture, commonly interpreted as a strategy to cope with drought.
Beyschlag and Zotz quantify the effects of the heteroblastic change on whole-plant light capture by reconstructing plant models. They used a functional structural plant model (Yplant) to construct digital replicas of atmospheric and tank-forming individuals of four species, two of them naturally growing in exposed conditions and two occurring in understorey sites. This allowed them to determine leaf display efficiencies as well as make a systematic analysis of leaf architectural traits and their effect on light interception.
Modelling morphology and ontogenetic trajectories of leaf architectural traits revealed that rising total leaf number in atmospheric individuals constantly increased self-shading. The effects of changes in leaf morphology and leaf architecture on plant light capture may explain the common occurrence of heteroblastic species in the understorey of Neotropical forests, which does not negate a simultaneous positive effect of heteroblasty on plant water relations.
This paper is part of the Special Issue on Morphology and Adaptation. It is FREE access for a limited period to the end of January 2018. It will then be free access from November 2018.
Beyschlag, J., & Zotz, G. (2017). Heteroblasty in epiphytic bromeliads: functional implications for species in understorey and exposed growing sites. Annals of Botany, 120(5), 681–692. https://doi.org/10.1093/aob/mcx048