By Eben van Tonder, 19 March 25

Abstract

Putrescine and cadaverine, two biogenic amines commonly produced by plants, are integral to diverse physiological processes, including growth regulation, stress response, and senescence. In a select group of plants, notably Stapelia species, these compounds are emitted as volatiles to mimic carrion and attract pollinators—a striking example of evolutionary deception. Beyond this unique ecological role, cadaverine and putrescine are prevalent in many plant species, including legumes like soybeans, where they influence flavour and food quality. This paper explores the roles of cadaverine and putrescine beyond Stapelia, examining their functions in plant metabolism, their ecological significance, and their impact on sensory properties in food products.

1. Introduction

Cadaverine and putrescine are naturally occurring biogenic amines synthesized through the decarboxylation of lysine and ornithine, respectively. As polyamines, they are critical regulators in plant growth, development, and responses to environmental stress (Tiburcio et al., 1997). While these compounds are widespread across plant taxa, their external release as volatiles is rare, and typically associated with plants employing deception to attract pollinators.

The remarkable role of cadaverine and putrescine in plant mimicry was explored in The Carrion Flower: An Evolutionary and Cultural Study of Stapelia, where we examined how Stapelia evolved to exploit the perceptual biases of carrion flies. This was further developed in The Carrion Flower and the Unanswered Questions of Evolutionary Precision, which raised fundamental concerns about how such precise mimicry could evolve through natural selection alone. Finally, The Carrion Flower and the Coordinating Principle of Intention suggested that the fly’s own perception—its intention—might act as an organizing force in shaping the plant’s evolution.

While Stapelia represents one of the most extreme cases of biogenic amine exploitation in nature, the presence of cadaverine and putrescine is not confined to carrion-mimicking plants. These compounds are widespread in plant metabolism, and in some cases, their accumulation can influence food quality. This paper builds on the themes of deception and chemical manipulation in Stapelia, expanding the discussion to include broader plant physiology and the sensory implications of these amines in crops like soybeans.

2. Biogenic Amines in Plant Physiology

2.1 Biosynthesis and Biological Function

Putrescine is synthesized from ornithine via ornithine decarboxylase, while cadaverine is produced from lysine via lysine decarboxylase. Both compounds serve as precursors for higher-order polyamines, including spermidine and spermine, which are essential for nucleic acid stabilization, membrane integrity, and cellular proliferation (Tiburcio et al., 2014). These polyamines also contribute to stress tolerance by modulating ion channels, scavenging free radicals, and stabilizing proteins and membranes under abiotic stress conditions (Alcázar et al., 2010).

2.2 Distribution Across Plant Species

Both cadaverine and putrescine are widely distributed in plant species, with putrescine being particularly abundant. Cadaverine, while less ubiquitous, is commonly found in legumes (Fabaceae), including soybeans (Glycine max), and often accumulates in response to environmental stress or pathogen attack (Bouchereau et al., 1999).

3. Ecological Roles of Putrescine and Cadaverine

3.1 Sapromyiophilous Pollination Strategies

In a limited number of plant species, cadaverine and putrescine are emitted as volatile organic compounds to mimic the olfactory signature of decaying flesh. This strategy, termed sapromyiophily, deceives carrion-associated insects into visiting flowers under the false pretence of locating oviposition sites or food.

Stapelia species, along with other carrion-mimicking plants such as Amorphophallus titanum, Rafflesia arnoldii, and Hydnora africana, produce complex bouquets of volatile compounds, including putrescine, cadaverine, dimethyl disulfide, and dimethyl trisulfide, to attract pollinators such as flies and beetles (Jürgens et al., 2006).

3.2 Non-Pollination Ecological Roles

Outside of carrion mimicry, cadaverine and putrescine function in plant defence and allelopathy. They have been shown to deter herbivory and inhibit the growth of competing plants or pathogenic microbes (Walters, 2003). These compounds also serve as nitrogen storage molecules and contribute to signalling during biotic stress events.

4. Cadaverine and Putrescine in Soybeans

4.1 Physiological Functions in Glycine max

In soybeans, cadaverine and putrescine play crucial roles in growth regulation, nitrogen metabolism, and stress adaptation. Their synthesis is upregulated under drought and salinity stress and during infection by pathogens (Piñol et al., 2013). As part of the polyamine biosynthetic pathway, they help maintain cellular homeostasis and mediate defence responses.

4.2 Accumulation During Fermentation and Storage

Fermentation and post-harvest storage conditions significantly influence the concentration of cadaverine and putrescine in soy products. Controlled fermentation in products like miso, tempeh, and natto maintains biogenic amine levels within acceptable ranges. However, contamination with spoilage bacteria—particularly decarboxylase-positive strains of Enterobacteriaceae and Pseudomonas—can lead to elevated levels of cadaverine and putrescine (Santos et al., 2003).

These amines can contribute to off-flavours, described as bitter, fishy, or ammonia-like. Cadaverine is particularly associated with a sour, putrid note that differs from the acidity generated by lactic acid bacteria. Excessive accumulation not only degrades flavour quality but may pose health risks, particularly in individuals with impaired amine metabolism (Shalaby, 1996).

5. The Souring Effect in Soy: Cadaverine as a Sensory Defect

5.1 Sensory Attributes

Cadaverine imparts distinct off-notes in spoiled or poorly fermented soy products. Sensory analyses describe its contribution as sour, metallic, and fishy, with an astringent mouthfeel. These attributes are exacerbated when soybeans are stored in conditions favouring anaerobic bacterial growth or when fermentation is poorly controlled.

5.2 Implications for Food Quality and Safety

Although regulations on cadaverine and putrescine in foods are less stringent than for other biogenic amines like histamine and tyramine, their presence is considered an indicator of microbial spoilage and poor processing hygiene. Monitoring these amines can be crucial for maintaining food quality and consumer safety (Silla Santos, 1996).

6. Conclusion

Cadaverine and putrescine are integral to plant metabolism and ecological strategies. While their combined use as volatiles in carrion mimicry is a rare and fascinating adaptation—best exemplified by Stapelia—these compounds are also pervasive in plant physiology, particularly in legumes like soy. Their role in contributing to off-flavours in soy products highlights the importance of understanding and controlling their production in agricultural and food processing contexts.

Further research into the ecological and sensory roles of these amines may uncover additional applications or reveal novel evolutionary strategies in plant-animal interactions.

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