Friday, October 7, 2011

A Plant's Guide to Water

(originally posted August 14, 2011)

As I sat trying to brainstorm what I wanted to write about this week, I found myself drawing a blank. Maybe it’s because it’s a Sunday, maybe it’s because I can’t think, or maybe it’s because it has been gloomy and raining most of the day. It’s interesting the effect that rain has on us; we feel compelled to bundle up, stay inside, find something comforting to eat or drink, and put everything on our to do list on hold.

Which got me to thinking of all the effects water has on plants and some of the neat ways they have evolved to address these issues. Ah-ha! It seems rain can provide motivation after all!

Plants have some of the most fascinating adaptations to deal with water (or the lack thereof). On their leaves and stems, they have microscopic openings called stomata which are used for respiration. On hot days, plants risk dehydration through these openings, so many respond by wilting their leaves. By keeping the underside of their leaves shaded (which is where the highest concentration of stomata are found), the plants reduce evaporation. Jewelweed, a common plant in the eastern US, Pacific Northwest, and Canada, takes this to daily extremes. Plants in the sun have wilted leaves, while their immediate neighbors in the shade will have erect leaves. You can literally trace the shadows of the overhead trees in the jewelweed below.

Cypress trees, on the other hand, are adapted to the other extreme, living their lives in saturated swamps. Their wide trunks and vertical protrusions of their roots called knees give the trees a stable hold on the ground, more so than their thin-trunked neighbors. It’s like the difference between standing with your legs together and seeing if your friend can push you over and then standing in a sumo wrestler stance and accepting the same challenge.

When it comes to dealing with frozen water, pines, firs, and spruces are the clearcut (oh crud, never say “clearcut” around a tree) winners in this category. We all know that these evergreens have needles instead of broad, flat leaves, but did you know that needles are just broad, flat leaves rolled up? The rolled up leaves coupled with a waxy coating reduce water loss, which means that the leaves can be used for photosynthesis year-round. As an added bonus, the needle shape of the leaves makes it easier for snow accumulation to slide off of their branches.

Plants have all sorts of incredible ways to deal with water, whether it be a lack of it, an abundance of it, or the frozen form of it. Since the rain is forecasted to continue on into tomorrow here, tomorrow when I don my full rain suit, I won’t be able to help thinking how I’ll kind of look like a rolled up leaf with a waxy coating. Ok, a blue and gray pine needle with a waxy coating.

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