The digestive systems of carnivorous plants

Abstract

To survive in nutrient-poor habitats, carnivorous plants capture small organisms comprising complex substances not suitable for immediate reuse. The traps of carnivorous plants, which are analogous to the digestive systems of animals, are equipped with mechanisms for the breakdown and absorption of nutrients. Such capabilities have been acquired convergently over the past tens of millions of years in multiple angiosperm lineages by modifying plant-specific organs including leaves. The epidermis of carnivorous trap leaves bears groups of specialized cells called glands, which acquire substances from their prey via digestion and absorption. The digestive glands of carnivorous plants secrete mucilage, pitcher fluids, acids, and proteins, including digestive enzymes. The same (or morphologically distinct) glands then absorb the released compounds via various membrane transport proteins or endocytosis. Thus, these glands function in a manner similar to animal cells that are physiologically important in the digestive system, such as the parietal cells of the stomach and intestinal epithelial cells. Yet, carnivorous plants are equipped with strategies that deal with or incorporate plant-specific features, such as cell walls, epidermal cuticles, and phytohormones. In this review, we provide a systematic perspective on the digestive and absorptive capacity of convergently evolved carnivorous plants, with an emphasis on the forms and functions of glands.

Quantification of Protein Uptake by Endocytosis in Carnivorous Nepenthales

“…The trapping mucilage of D. lusitanicum is much less prone to exsiccation [ 28 ] and therefore may not require constant replacement causing a slightly delayed start of endocytosis (60 min). In contrast, similarly to animals [ 3 ], D. muscipula and N. × ventrata form temporary stomachs [ 29 , 30 ], where the glands are more or less inactive until prey is trapped [ 30 ], which is in good consistency with their observed endocytosis latency of 16 h.…”

“…Carnivorous plants (CPs) attract, trap, degrade, and absorb tiny animals in order to supplement their nutrient supply [ 1 , 2 ]. Prey digestion and uptake in CPs is functionally similar to the processes observed in the digestive systems of animals [ 3 , 4 ]. However, in CPs the functional features are all performed in one spot: the trap leaf.…”

“…Uptake from the apoplast into the cytoplasm is usually believed to be performed by selective, active or passive membrane carriers [ 3 , 14 , 15 ]. Such carriers would be very efficient in the uptake of ions and small molecules, possibly up to the size of oligopeptides as in Sarracenia [ 16 ].…”

Plant structure and function: Evolutionary origins and underlying mechanisms

“…The most commonly secreted proteins in glands of carnivorous plants are pathogenesis-related proteins, and of the 19 non-carnivorous plants tested 15 species showed protease activity in their glandular secretions. Freund et al (2022) suggest that glandular functions in trap leaves could be convergent exaptations of the structures and exudates found throughout the angiosperms.…”

“…Transitioning from plant physiology to plant functional morphology, Freund et al (2022) delve into the fascinating world of carnivorous plants. The authors describe the trapping and secretory structures seen in various lineages of carnivorous plants and raise three important questions.…”