Wednesday, June 19, 2013
Our Saturday was a free day and some of us went to Bologna. While there we visited the University of Bologna’s garden, the Orto Botanico. It is one of Europe’s oldest gardens and was established in 1568. Today it has 5000 specimen.
I had a ton of fun walking around this garden. There are many trees and little circular planters, each containing a different species. The most interesting plants were the carnivorous ones kept in a cage. The fact that they were in a cage made me laugh. There were a few varieties including the cobra lily (Darlingtonia californica) and the venus fly trap (Dionaea muscipula). I have not seen carnivorous plants in person so it was fun to look at these. These plants became carnivorous through evolution to compensate for nutrient poor soil. Both the cobra lily and venus fly trap can tolerate fire and actually depend on fires to eliminate competition from other plants which I think is a useful characteristic. Although the cobra lily is a hardy plant, its roots are delicate and require a much colder temperature to survive than part of the plant above the soil. This is because the plant naturally grows in bogs and stream banks fed by cold mountain water. I would never have guessed the roots need to be kept at a cooler temperature than the rest of the plant.
What I find most interesting about these carnivorous plants are their trapping mechanisms. The cobra lily uses lubricating secretions and downward-pointing hairs to force their prey into their trap. This is common to all North American pitcher plants but this species also makes use of false exits. This confuses the insect, exhausting it after many attempts to escape through the false exit and not having the ability to climb the slippery walls, it falls into the digestive acids at the bottom of the plant.
Venus Fly Trap
The venus fly trap uses an active steel trap mechanism. The trap is a section of the plant’s leaf. The inside lobes of the trap have hairs that must be triggered twice in succession or two different hairs on the same leaf must be triggered in order for the trap to close. This redundant triggering mechanism is capable of distinguishing between living and non-prey stimuli and is a safeguard to conserve energy. But if non-prey triggers the trap, it will reopen in 24 hours. This mechanism is not fully understood and I think it’s very interesting that the plant has a way of determining if the movement is from prey. The fact that the plant can tell which hairs have been touched within a certain period of time is remarkable. This closure occurs in about 1/30 second in full sunlight. The speed of closure is dependent on temperature, cooler temperatures causing slower movement. When open, the lobes of the trap are convex but when closed it is concave, forming a cavity. The edges of these lobes are lined with stiff hairs intermeshing when closed, keeping large prey in the trap. But there are holes in the mesh allowing small prey to escape because the benefit of digesting the prey does not outweigh the nutrition gained. Bologna is a wonderful place to visit and I am glad we stopped by to see the university’s beautiful garden.
"Cobra Lily Plants." Cobra Lily Plants. N.p., n.d. Web. 19 June 2013.
"Darlingtonia californica - the Cobra Lily." Darlingtonia californica, Carnivorous Plants Online. Botanical Society of America, n.d. Web. 19 June 2013.
"Dionaea Muscipula - The Venus Flytrap." Venus Flytrap. Botanical Society of America, n.d. Web. 19 June 2013.