The dark side of the rain: self-pollination setbacks due to water exposure in Pavonia varians Moric (Malvaceae), a species with rain-dependent flowering

ABSTRACT

Plants that occur in arid or semi-arid environments may restrict their flowering to the rainy season to ensure water availability for reproductive functions. However, the exposure of flowers to rainfall can compromise their functionality, such as complex self-pollination mechanisms. We experimentally tested how rainfall exposure affects the sequence of anthesis and reproductive success of Pavonia varians. This species is endemic to the Caatinga, and it has a rainfall-dependent flowering and a specialized mechanism of delayed self-pollination by style curvature. Our results demonstrate that wet flowers have difficulty in distending their petals, and although they maintain the sequence of anthesis, style curvature and corolla closure are delayed. Water exposure also compromised reproductive success by spontaneous self-pollination in bagged flowers but did not prevent fruit set by exposed flowers. These conditions allow cross-pollination in P. varians if rainfall is transient or localized, which is a common condition in the Caatinga. We believe that this type of experimental approach can bring important clues about how reproductive systems respond to abiotic factors, especially in the context of imminent climate change.

Keywords:
autogamy; Caatinga; delayed self-pollination; floral anthesis; style curvature