  Being the polymorphs of calcium carbonate (CaCO3), vaterite and calcite have
attracted a great deal of attention as promising biomaterials for drug delivery
and tissue engineering applications. Furthermore, they are important biogenic
minerals, enabling living organisms to reach specific functions. In nature,
vaterite and calcite monocrystals typically form self-assembled polycrystal
micro- and nanoparticles, also referred to as spherulites. Here, we demonstrate
that alpine plants belonging to the Saxifraga genus can tailor light scattering
channels and utilize multipole interference effect to improve light collection
efficiency via producing CaCO3 polycrystal nanoparticles on the margins of
their leaves. To provide a clear physical background behind this concept, we
study optical properties of artificially synthesized vaterite nanospherulites
and reveal the phenomenon of directional light scattering. Darkfield
spectroscopy measurements are supported by a comprehensive numerical analysis,
accounting for the complex microstructure of particles. We demonstrate the
appearance of generalized Kerker condition, where several higher order
multipoles interfere constructively in the forward direction, governing the
interaction phenomenon. As a result, highly directive forward light scattering
from vaterite nanospherulites is observed in the entire visible range.
Furthermore, ex vivo studies of microstructure and optical properties of leaves
for the alpine plants Saxifraga 'Southside Seedling' and Saxifraga Paniculata
Ria are performed and underlined the importance of Kerker effect for these
living organisms. Our results pave the way for a bioinspired strategy of
efficient light collection by selfassembled polycrystal CaCO3 nanoparticles via
tailoring light propagation directly to the photosynthetic tissue with minimal
losses to undesired scattering channels.
