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Adapted from What a Plant Knows: A Field Guide to the Senses, byDaniel Chamovitz, by arrangement with Scientific American/Farrar,Strauss and Giroux, LLC (North America), One World (UK), Scribe(AUS/NZ), Kawade Shobo Shisha (Japan). Copyright 2012 byDaniel Chamovitz. To learn more visit, books.scientificamerican.com . Cuscuta pentagona is not your normal plant. it is a spindly orange vine that cangrow up to three feet high, produces tiny white flowers of fivepetals and is found all over North America. What is unique about Cuscuta [commonly known as dodder] is that it has no leaves. And itisn"t green, because it lacks chlorophyll, the pigment thatabsorbs solar energy, allowing plants to turn light into sugars and oxygen through photosynthesis. Cuscuta gets its food from its neighbors. It is a parasitic plant. Inorder to live, Cuscuta attaches itself to a host plant and sucks off the nutrientsprovided by the host by burrowing an appendage into theplant"s vascular system. What makes Cuscuta truly fascinating is that it has culinary preferences: it chooseswhich neighbors to attack. A Cuscuta seed germinates like any other plant seed. The new shoot growsinto the air, and the new root burrows into the dirt. But a youngdodder left on its own will die if it doesn"t quickly find ahost to live off of. As a dodder seedling grows, it moves its shoottip in small circles, probing the surroundings the way we do withour hands when we are blindfolded or searching for the kitchenlight in the middle of the night. While these movements seem randomat first, if the dodder is next to another plant (say, a tomato),it"s quickly obvious that it is bending and growing androtating in the direction of the tomato plant that will provide itwith food. The dodder bends and grows and rotates until finally itfinds a tomato leaf. But rather than touch the leaf, the doddersinks down and keeps moving until it finds the stem of the tomato plant. In a final act of victory, it twirls itselfaround the stem, sends microprojections into the tomato"sphloem (the vessels that carry the plant"s sugary sap), andstarts siphoning off sugars so that it can keep growing andeventually flower. Consuelo De Moraes even documented this behavior on film. She is anentomologist at Pennsylvania State University whose main interestis understanding volatile chemical signaling between insects andplants and between plants themselves. One of her projects centeredon figuring out how Cuscuta locates its prey. She demonstrated that the dodder vines nevergrow toward empty pots or pots with fake plants in them butfaithfully grow toward tomato plants no matter where she putthem—in the light, in the shade, wherever. De Moraeshypothesized that the dodder actually smelled the tomato. To check her hypothesis, she and her students put thedodder in a pot in a closed box and put the tomato in a secondclosed box. The two boxes were connected by a tube that entered thedodder"s box on one side, thereby allowing the free flow ofair between the boxes. The isolated dodder always grew toward thetube, suggesting that the tomato plant was giving off an odor thatwafted through the tube into the dodder"s box and that thedodder liked it. If the Cuscuta was really going after the smell of the tomato, then perhaps DeMoraes could just make a tomato perfume and see if the dodder wouldgo for that. She created an eau de tomato stem extract that sheplaced on cotton swabs and then put the swabs on sticks in potsnext to the Cuscuta . As a control, she put some of the solvents that she used to makethe tomato perfume on other swabs of cotton and put these on sticksnext to the Cuscuta as well. As predicted, she tricked the dodder into growing towardthe cotton giving off the tomato smell, thinking it was going tofind food, but not to the cotton with the solvents. I am an expert from hydraulic-pressmachine.com, while we provides the quality product, such as Punch Press Machine , H Frame Presses Manufacturer, Mechanical Power Presses,and more.
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