Patterns and drivers of heat production in the plant genus Amorphophallus

Abstract

SUMMARYThermogenesis – the ability to generate metabolic heat – is much more common in animals than in plants, but it has been documented in several plant families, most prominently the Araceae. Metabolic heat is produced in floral organs during the flowering time (anthesis), with the hypothesised primary functions being to increase scent volatilisation for pollinator attraction, and/or to provide a heat reward for invertebrate pollinators. Despite in‐depth studies on the thermogenesis of single species, no attempts have yet been made to examine plant thermogenesis across an entire clade. Here, we apply time‐series clustering algorithms to 119 measurements of the full thermogenic patterns in inflorescences of 80 Amorphophallus species. We infer a new time‐calibrated phylogeny of this genus and use phylogenetic comparative methods to investigate the evolutionary determinants of thermogenesis. We find striking phenotypic variation across the phylogeny, with heat production in multiple clades reaching up to 15°C, and in one case 21.7°C above ambient temperature. Our results show that the thermogenic capacity is phylogenetically conserved and is also associated with inflorescence thickness. Our study paves the way for further investigations of the eco‐evolutionary benefits of thermogenesis in plants.

Floral thermal biology in relation to pollen thermal performance in an early spring flowering plant

“…2013; Claudel et al . 2023). However, sex stage‐specific thermogenesis in other taxa often lasts for multiple days over which a given sexual stage persists in the flower or inflorescence (Claudel et al .…”

“…However, sex stage‐specific thermogenesis in other taxa often lasts for multiple days over which a given sexual stage persists in the flower or inflorescence (Claudel et al . 2023). We suggest that thermogenesis in H. arifolia is unlikely to aid in increased pollinator attraction through a direct heat reward or by increased emission of volatiles.…”

“…To define incidences of thermogenesis, we used a cutoff of the floral interior exceeding 1.5 °C or above ambient temperature, following Claudel et al . (2023), for at least 4 consecutive minutes. To do this, we calculated the difference between floral interior temperature and ambient temperature (ΔT), recorded the start time, duration (minutes and seconds), and range of warming during each period of thermogenesis for each flower.…”

“…The duration of floral thermogenesis has been associated both temporally and spatially with distinct sexual phases of flowers (e.g., thermogenesis only occurs in the male zone of dimorphic Amorphophallus especially immediately after anthesis; Claudel et al . 2023). Heliotropism is another well‐studied mechanism of floral warming in which floral orientation is adjusted to maximize the absorption of solar radiation.…”

Visual-, Olfactory-, and Nectar-Taste-Based Flower Aposematism

“…In parallel to common visual signaling, many flowers attract pollinators (and herbivores) via olfactory signals and cues (e.g., [1,4,11]). Flower colors may also serve to regulate their temperature [12][13][14][15]; as such, they not only help with gamete development in cold environments (e.g., [16,17]) but even provide a reward for pollinators in habitats or during hours characterized by low temperatures (e.g., [6,14,18,19]). It should be remembered that excess sunlight, especially in the UV (ultraviolet) spectrum, may cause damage to reproductive mechanisms, especially gametes [17,20]; indeed, sunlight was found to influence flower color polymorphism in Lysimachia arvensis [21] and in many other species [22].…”