After having missed a summer kayaking, I was overjoyed when I finally slid my little blue otter into the waters of North Pond for the first time this year. It was a blue and gold day when I paddled out to see if the rose pogonias were still in bloom in the bog at the southwest end of the pond. These delicate pink and white native orchids with their fringed tongues that rise above a rich sphagnum moss community are a sight to behold for any orchid lover. I was amazed by this year’s abundance of flowers.
Attaching my line to a couple of cattails so I could drift and contemplate this marvelous boggy neighborhood, I was initially struck by the sheer diversity of plants that inhabited the nitrogen poor ‘island’.
That’s when I saw the pitcher plant flowers. Why is it that I am so enamored by these solitary dark crimson and green flower spikes? Perhaps because they seem so improbable in an otherwise low growing community of plants, except for a few, none of which tower over the pitcher plant in florescences except for the occasional swamp maple and cattails. After examining one perfect five lobed flower with its central starred balloon like center I looked for its companion, the pure white flower of the diminutive sundew, also held high above tiny rosettes of sticky red clusters, but they had already gone by.
For the millionth time I wondered why it was that these two carnivorous plants grew in such close proximity to each other. I suspected some kind of mutualism or relationship must occur between the two, one that benefited both plants, but had never found any research to support this idea. I did know that the flowers of the two carnivorous plants, held high above the plants on stalks prevented the carnivores from trapping those insects that would pollinate them, an adaptation like most, that always amazed me. Both kinds of flower heads followed the sun, that is, they were heliotropic. I pulled myself in close to the bog to inspect both the pitcher plant and its friend the sundew with my usual curiosity. Carnivorous plants occur in locations where the soil is too poor in minerals and/or too acidic for most other plants to grow (although in this seemingly diverse bog one might argue that point).
The pitcher and sundew have evolved traps to lure, drown and digest animal prey to supplement nutrient-poor soils, providing us with a perfect example of the complex relationship between plants and the places they grow. Both are deadly traps for mosquitoes.
The pitcher plant consists of a group of hollow, reddish-green leaves, each connected to a stem that extends roots downward into the bog. Each “pitcher” has an upper, flared lip that has hairs that curve downward and is generally partially filled with water. Insects attracted to the pitcher crawl inside the modified leaf and are prevented from leaving by the downward pointing hairs. Eventually the insects tire and fall into the water where they are digested for the most part, by bacteria. The products of digestion, high in nitrogen and containing amino acids, are absorbed by the leaf, supplementing photo-synthetically produced organic matter. The water contained by the leaves supports a community of interesting organisms that include bacteria, protozoa, rotifers, and other creatures. In some places, pitcher plants even devour spiders, salamanders, and small frogs.
The round-leaved sundew has a number of small rounded leaves attached to a central stem. The modified leaves form a sort of rosette. Each leaf has glandular hairs around itsedge and most leaves have a drop of a sticky substance attached to the end of each hair. Insects like mosquitoes and ants become trapped in the drops. When they try to escape, their frantic motions cause the leaf to fold over the insect. The whole process takes about 30 minutes. The prey is subsequently digested and the digested nutrients, also containing essential nitrogen and amino acids, are absorbed into the plant, supplementing food produced
photo-synthetically.
Amazing, don’t you think? Another observation suddenly occurred to me while I was examining the two plants. Both plants were primarily reddish and green. This color correspondence might be another clue supporting my idea that these two plants benefited from each other in very specific ways…
Suddenly my eye caught the loon floating high and then sinking in the water nearby. This one was fishing. The loon dipped his/her head and bill into the water searching for fish with his very red eye that, come
autumn would turn gray for the winter. The red eye, it is believed, filters out blue and green light making for more effective summer fishing. The brilliant red may also help a loon attract a mate. The dark shadow on the water caused me to look up into a late afternoon sky, just in time to see the white eagle’s tail. A top predator was flying over my head. And it was late. Reluctantly, I decided to paddle back to the dock. Hours had passed while I was enthralled by what I had seen at the bog and my never-ending unanswered questions.
Pitcher plants growing in wetlands across Canada have long been known to eat creatures – mostly insects and spiders – that fall into their bell-shaped leaves and decompose in rainwater collected there. But researchers have discovered that vertebrates – specifically, salamanders – are also part of their diet.
Loons only sport their famous red eyes during the summer. In winter, they have gray eyes. … One possible reason for the red eyes of the loon is that the color helps them to see underwater, filtering out blue and green light. It is also thought that the brilliant red color helps them to attract other loons.
Passive Traps
Perhaps the most familiar examples of passive traps are the sundews (Drosera) and the pitcher plants (Sarracenia and Darlingtonia in temperate climes and Nepenthes in the tropics). The sundews capture their prey by producing from stalked glands an adhesive, or glue (the drop of “dew”), which captures and holds fast the insect. As the prey struggles, it is covered with the sticky mucilage and, as a consequence, suffocates. The stalked glands then bend in toward the prey; in some species, the entire leaf enfolds the prey. A second type of gland on the leaf secretes digestive enzymes and acids, initiating the breakdown and subsequent absorption of nutrients.
The unusual relationship between insect-eating pitcher plants and ants that live exclusively on them has long puzzled scientists. The Camponotus schmitzi ants live only on one species of Bornean pitcher plants (Nepenthes bicalcarata), where they walk across slippery pitcher traps, swim and dive in the plant’s digestive fluids and consume nectar and prey that fall into the trap. Though the benefits to the ants are obvious, it has been harder to tell what exactly the plants gain. However, plants that harbor the insects grow larger than those that do not, suggesting a mutualistic relationship exists between the two. In this new study, researchers demonstrated a flow of nutrients from ants to their plant hosts, and found that plants colonized by insects received more nitrogen than those that did not host ants. Ants appeared to increase the pitchers, capture efficiency by keeping traps clean, and also protected the plants by actively hunting mosquito larvae that otherwise bred in pitcher fluids and sucked up plant nutrients.
“Kneeling down in the swamp amidst huge pitcher plants in a Bornean rainforest, it was a truly jaw-dropping experience when we first noticed how very aggressive and skilled the Camponotus schmitzi ants were in underwater hunting: it was a mosquito massacre!” says Scharmann. “Later, when we discovered that the ants’ droppings are returned to the plant, it became clear that this unique behavior could actually play an important role in the complex relationship of the pitcher plant with the ants.”
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