the Pitcher world

One of the many interesting plants found in watery places like bogs are Pitcherplants, some of the carnivores of the plant world.  Digestion of animal matter is essential to their existence in a boggy, wet environment that routinely dissolves and carries away nutrients the plants need.

Big Bog, a black spruce bog near Red Lake MN

Black Spruce dominate the northern temperate bog landscape, but let in ample light for low-growing bog plants to flourish.

Bogs not only have water-laden soil, but an acidic content that further leaches the nutrients from the matrix.  When flooded with spring snow melt or heavy rainfall, bog plants are inundated with fresh water almost devoid of nutrients.  Where will they get the carbon and nitrogen they need to grow?

Purple Pitcherplant leaves

Some leaves of the Purple Pitcherplant form tubular, trumped-shaped structures, usually filled with rainwater.  New leaves are formed after the plant flowers each year, but leaves can last up to two years, even through the extended, sub-zero weather of the northern temperate winter.

Purple Pitcherplant leaf filled with rainwater

The upper rim of the leaf secretes nectar and a floral scent designed to attract insects. A waxy coating makes the edge of that rim slippery, and the vertical sides of the trumpet ensure that the insect falls into the watery reservoir, where it will drown.

But rather than the true carnivory (using digestive enzymes secreted by the plant) exhibited by some pitcher, sundew, or venus flytrap plants, Purple Pitchers contain a complex ecosystem within their tubular trumpets that release the nitrogen and carbon they require.  In turn they provide their aquatic inhabitants with the oxygen they need to sustain their own metabolism.

Here’s how it works:

Purple Pitcherplant leaves

The waterworld of Purple Pitchers supports a collection of bacteria that decompose animal matter, protozoans that eat them, and at least three types of fly larvae that consume the bacteria and protozoans, as well as attacking the carcass of drowned insects.

The consumers (protozoans and fly larvae) and decomposers (bacteria) all produce carbon dioxide and excrete ammonia through their metabolism of the decomposing carcasses or each other.  The plant is more than happy to take up these waste products directly through its leaves, lowering their potentially toxic concentration in the water.  Photosynthetic pigments in the leaves produce the necessary components to fix that carbon dioxide into plant sugars, and release oxygen (as a byproduct of photosynthesis) directly into the water for the aerobic metabolism of its consumer population.  It’s a sustainable system!

Purple Pitcherplant leaves and flower

A single flower towers above the collection of old and new leaves of a Purple Pitcherplant, the only species that tolerates the cold weather of northern bogs, like this one at Red Lake, Minnesota.  The height of the flower ensures that pollinators avoid the insect-trapping leaves below.

Purple Pitcherplant flower

A Purple Pitcher flower starts out upright, but the heavy anthers and ovaries eventually cause it to bend over.  The ovary is the big bulbous structure right below the sepals.  The style extends into a wide umbrella shape, with stigma surfaces only at its upturned tips.

Purple Pitcherplant flower anatomy

A cut-away of a Pitcherplant flower shows the unusual shape of some of the structures.  From Wikipedia.  Anthers drop their pollen into the umbrella-shaped style, which pollinators walk through on their way to obtain nectar from compartments near the umbrella.  As they force their way into the style chamber, past the stigmas of the next flower they visit, they deposit the pollen they acquired from the previous one.

Added to the unique features of this plant in sustaining its own micro-ecosystem, and its strange floral anatomy that prevents self-pollination, are the myriad adaptations for tolerating fluctuating water levels in a bog over the course of the year, and surviving the frozen state during a long winter.  What an amazing plant!

6 thoughts on “the Pitcher world

  1. Fascinating. I don’t think I’ve ever encountered one of these plants. Reading about it makes me think of the Audrey 2 from Little Shop of Horrors.

  2. Sue,

    I attached 3 pictures on the original email.  Can you see them now?

    I can ask Irene.  I thought of her, too, especially as we talked about gardening at book club this morning.  Maybe I’ll try to save one and ask all the ladies.  I have a feeling it’s one of those dried type flowers that lives for a long time.  

    Sure enjoy your post!

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