Carnivorous plants have earned their fame by unique trap and kill devices that catching or luring animals. There are some other species that share similarities with carnivorous plants but not quite the same. The determination factor solely depends on their relationship with the growing environment including the victim. Whether or not the killing mechanism is critical for survival in a particular environment, where other plants cannot or at least cannot grow well. Carnivorous plants rely on their victims for nutrients intake to survive on barren land. Besides, the lifestyle determines its carnivory level, which is the method of deriving nutrition via killing the prey in a conspicuous way. As a result, some plants can be murderous but not carnivorous because of their specialized structures that can catch and kill but never obtain nutrients directly from the corpse.
Ibicella lutea and Martynia annua which referred to as the devil’s claw in the sesame family of Pedaliaceae. The name is derived from the matured seedpod that looks like some horrific insect jaws that are black and spiny. Ibicella lutea also taxonomically known as Martynia lutea. They are commonly known as the unicorn plant due to the unique shape of the immature seedpod that looks like a horn or unicorn. Ibicella lutea originated from the Sonoran Desert of Mexico which has been naturalized and distributed in Southern California and Arizona. They can be propagated through the seed germination with the arrival of the summer thunderstorms. Morphologically, they look like some varieties of begonias, or melon plants with hairy leaves.
Proboscidea louisianica and Proboscidea parviflora are found in North America which morphologically similar to Martynia. The only difference is the color of the flowers. The whole plant is fully covered with tiny glandular hairs that look almost identical to that of Pinguicula (butterwort) and rainbow plants. The greasy and sticky hairs are the trapping mechanism for numerous tiny insects. However, they do not acquire any nutrients from the prey they killed, therefore, making them murderous plants rather than carnivorous.
There are many other non-carnivorous plants with sticky leaves that has killing abilities. Such as the following examples.
Saxifraga umbrosa (common name: London pride, in the family of Saxifragaceae)
Saxifraga rotundifolia (common name: round-leaved saxifrage, in the family of Saxifragaceae)
Primula sinensis (common name: Chinese primrose, in the family of Primulaceae)
Pelargonium zonale (common name: wildemalva, in the family of Geraniaceae)
Erica tetralix (common name: cross-leaved heath, in the family of Ericaceae)
Mirabilis longiflora (common name: sweet four-o’clock plant, in the family of Nyctaginaceae)
Nicotinana tabacum (common name: cultivated tobacco, in the family of Solanaceae).
In addition, there are murderous plants such as a number of Stylidium species (common name: trigger plants, in the family of Stylidiaceae)
Potentilla glandulosa (common name: sticky cinquefoil, in the family of Rosaceae)
Geranium viscosisimum (common name: sticky geranium, in the family of Geraniaceae)
Petunia violacea (common name: violet-flower petunia, in the family of Solanaceae)
Petunia nyctaginiflora (common name: white-flower petunia, in the family of Solanaceae)
Solanum tuberosum (common name: potato, in the family of Solanaceae)
Puya raimondii (common name: queen of the andes, in the family of Bromeliaceae) impales the birds with its spines on the margin of leaves.
Surprisingly, the sticky leaves and leaves with spines are not the only weapon that the murderous plants used. The leaves of Dipsacus fullonum (common name: wild teasel, in the family of Caprifoliaceae) store rainwater at the basal part of the leaves drown and kill insects from climbing the stem. The natural shape of the leaves is fused with the opposite leaf together with the stem, thus forming a natural container that able to retain water. Insects will be drowned in the rainwater that was accumulated at the natural “tank” at each node. This unique method prevents pests from attacking the actively growing meristematic tissue on the apical buds. The major function is to protect their vital organ, the flower. Some examples list as the following.
Passiflora foetida (common name: stinking passionflower, in the family of Passifloraceae)
Plumbago auriculate (common name: cape leadwort/ blue plumbago, in the family of Plumbaginaceae), and few species of Stylidium
Another “cruel” murderous species is Pisonia grandis that commonly known as bird catcher in the family of Nyctaginaceae. Their seeds coats are covered with down pointed “hard” hair or spiky structure that is capable of killing sea birds that are entangled and died in a mass of seeds. But those escaped disperse the sticky seeds that stuck on their feathers.
However, these murderous features do not qualify them as carnivores because they get very little or no nutrients benefit from the victims. There might be other species not mentioned in this article that are under discovery or less obvious murderous ability in nature. The specialized structures such as the sticky leaves with glandular trichomes, spines on the margin of the leaves, “spiky” or thick hairs on the vine are the self-defense mechanisms, which could be deadly weapons to some animals. Apart from the dispersal purposes (sticky seeds), these structures play a pivotal role in the protection of their reproductive parts, especially the flower from the predation of herbivores.
Further reading:
Werner, P. A. (1975). Predictions of fate from rosette size in teasel (Dipsacus fullonum L.). Oecologia, 20(3), 197-201.
Walker, T. A. (1991). The distribution, abundance and dispersal by seabirds of Pisonia grandis. Atoll Research Bulletin.
Ornduff, R. (1992). Historical perspectives on heterostyly. In Evolution and function of heterostyly (pp. 31-39). Springer, Berlin, Heidelberg.
Stenström, M., & Molau, U. (1992). Reproductive ecology of Saxifraga oppositifolia: phenology, mating system, and reproductive success. Arctic and Alpine Research, 24(4), 337-343.
Sgorbati, S., Labra, M., Grugni, E., Barcaccia, G., Galasso, G., Boni, U., … & Scannerini, S. (2004). A survey of genetic diversity and reproductive biology of Puya raimondii (Bromeliaceae), the endangered queen of the Andes. Plant Biology, 6(2), 222-230.
D’amato, P. (2013). The savage garden, revised: Cultivating carnivorous plants. Ten Speed Press.
Vandenbussche, M., Chambrier, P., Rodrigues Bento, S., & Morel, P. (2016). Petunia, your next supermodel?. Frontiers in plant science, 7, 72.
