Green leaves in the growing season, bright colors in the fall, and evergreen pine needles all year long provide one of nature’s beautiful sights to behold.
There’s more to leaves than just looks! Like the human species, they inhale and exhale. Only thing is, they breathe in our exhale (carbon dioxide) and put out what we breathe in (oxygen). Now that’s quite a balance, isn’t it? Basically, there are two kinds of leaves, the common deciduous types (leaves drop each fall) that have a “fan” or “net” patterns of veins while grasses, evergreens, and most plants with bulb-like roots (iris, tulips) have veins that run top to bottom and carry the handle, parallel veination.
In either case, the veins provide the way for water and food to be carried inside the leaf and also stiffen the softer tissue and help the leaf hold its’ shape. The soft tissue is green because it contains the chlorophyll that, along with sunlight, changes the carbon dioxide and dissolved foods into sugars, which flow down the steams to be circulated throughout the tree for energy and growth.
The stems are pliable and flexible to allow the leaf to flatten in the breeze without snapping off. This same flattening helps with the evaporation of excess water (transpiration – we call it sweating) to help cool the plant. The excess water flows outward through millions of tiny “windows” on the leaves’ undersides called stomata. This is where the carbon dioxide goes in and the oxygen exits. On extremely hot days these stomata can literally “shut the window” to conserve moisture.
Leaves come in all kinds of shapes. Most have “drip tips”, natural drain spouts, so excess rainwater can run off. In desert and arid areas all the water possible is collected and help on the leaves so drip tips aren’t needed. Elm leaves are broader on one side so they tip sideways to spill excess water; cottonwood vegetation can turn edgewise to lessen hot sun damage; thin pine needles can take lots of strong winds by filtering it between their “leaves”.
Fall color? The bronzes, yellows, reds, and other colors are there all the time on deciduous trees. The green is just stronger until the tree quits making food in the fall and the other great colors get a chance to do their thing. The more you learn about these marvelous food-manufacturing factories, the harder it is to “leaf” them alone!
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