Quasi Carnivorous Plants
Quasi Carnivorous Plants
In order for a plant to be considered carnivorous, it must 1) attract prey, 2) capture prey, and 3) digest the prey. Many plants are able to do the first two criteria, but few (only about 670 worldwide) actually do all three. Many plants attract insects, especially for pollination, like honeybees to flowers. Some even trap insects and/or other prey for defense, such as the water filled leaf wells near the stems of thistle plants. However, some plants are very close to being carnivorous, but fall into a gray area and are considered quasi or semi carnivorous.
Capsella (Shepherd's Purse): The seeds of Capsella bursa-pastoris secrete chemicals which attract many smal invertebrates, and they release toxins which kill the prey and then release enzymes which digest them. This creates a nutrient rich area around the seed which gives the emerging plant an advantage over its competitors.
Stylidium (Triggerplant): These, mostly Australian plants, have stalked mucous glands, frequently on and near the flowers, their sepals, and stems. The glands do produce digestive enzymes. They may well prove to be carnivorous, but currently the research is inconclusive. Several sources do consider Trigger Plants to be carnivorous.
Dipsacus (Teasel): These plants have wide leaf bases that form deep "wells" where they are attached to the stem of the plant. They fill up with rain water or dew and can often be seen with dead, drowned insects and other invertebrates. Their decaying remains may well provide a type of leaf fertilizer, but there is not evidence of enzymetic activity or digestion.
Hepatics (Liverworts): Liverworts are common wetland plants that look like small pads of green leather upon the soil surface. They are primitive plants, older than the ferns, and grown in very wet conditions. They have been found to trap a variety of protozoa, but as of yet, there is no evidence of carnivory.
Ibicella and Proboscidea (Devil's Claw): Devil's Claw or Unicorn Plants, get their name from the shape of the seed pots. They are a relatively common "weed" in the desert southwest, and have punctured many bicycle tires. They have sticky leaves similar to Pinguicula, and do indded capture insects, but here is no evidence of enzyme activity.
Paepalanthus: This group of bromeliad relatives do have a central rosette of leaves that form a cistern filled with fluid, much like a pitcher plant. No evidence of digestive enzyme secretions has been discovered yet. Research is underway to prove any carnivorous nature, but none have been reported as of yet.
Passiflora (Passion Flower): These vining tropical plants have beautiful and elaborate flowers. One species P. foetida, does have glandular bracts, and research has found digestive enzymes with the plant tissue, but none on the plant surface. There is currently no evidence of carnivory.
Geranium viscosissimum: The Sticky Purple Geranium is considered a proto-carnivorous plant. It produces enzymes that can digest proteins, but it lacks traps. It is a herbaceous perennial native to the western Rocky Mountains. The enzymes are found on the plant's very sticky tentacle like hairs.