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.

Autogamy ensures reproductive success in the bromeliad Dyckia dissitiflora Schult.f., endemic to the Brazilian caatinga domain

“…The peculiar and slow opening of D. dissitiflora flowers is probably related to the maturation of the anthers and stigmas in response to temperature, light, and humidity conditions (Dalrymple et al, 2020). Moreover, the morphology and complex and gradual floral movements before and after the flower opening, and the absence of herkogamy, may play an essential role in facilitating the deposition of self‐pollen on the stigma (Domingos‐Melo et al, 2020; Evans et al, 2011; Naghiloo et al, 2019). In Dyckia , autogamy appears to be inversely correlated with the number of pollinators since species with more pollinators are likely to be self‐incompatible and those with only one pollinator or only one syndrome type tend to be self‐compatible (Lenzi & Paggi, 2020; Rogalski et al, 2009; Vosgueritchian & Buzato, 2006).…”

Occurrence and Prevention of Delayed Autonomous Selfing in Salvia umbratica (Lamiaceae)

“…The effects of pollination on floral longevity variation have been evaluated in several plant species, showing, for example, that it may be curtailed after pollination to prevent further expenditure on floral resources (Roddy et al, 2021 ) and/or to direct pollinators to non-pollinated flowers (Milet-Pinheiro et al, 2015 ). In contrast, floral longevity may be extended when rain reduces pollen viability, thus increasing the probability of pollinators depositing viable pollen on stigmas and securing high seed set (Domingos-Melo et al, 2020 ). In some species, flower wilting or abscission have been shown to trigger DAS to increase seed set in the absence of pollinators or when pollen is limited (Costa and Machado, 2017 ; Domingos-Melo et al, 2018 ).…”