Transpiration Lab
Water is essential to plants in many ways. It first provides the major substance for living, to keep cells from shriveling up and dying. The second major function is to keep the plants rigidity. As plant cells become turgid, full of water, the cells expand, filling the extent of their cell walls, which are kept taught with turgor pressure. If the cells lose water, two problems occur. First, the cells dehydrate, causing the organism to die. Second, turgor pressure is lost as cells become flaccid, limp and unfilled, causing a loss of support for the plants structure which makes it appear wilted. As aquatic plants evolved into large complex land plants, an adaptation occurred in the center of plants to allow full growth without the problem of water loss. A system of vascular bundles extending from the tips of the furthest leaves to the deepest roots of each plant developed, carrying water in xylem sap and sugar in phloem. While phloem can transport sugar in any direction within the plant, xylem can only move water up, from root to leaf. Once in the leaf, the water evaporates through stomata-tiny gaps in the lower epidermis of each leaf, which are regulated by guard cells-a process called transpiration
The plants were allowed to sit for ten minutes before the initial reading was made, to allow for equilibration. After recording levels of water for all plant environment simulations, readings were made in ten minute increments until thirty minutes elapsed. After this, the leaves were cut off of each plant to be weighed and measured. With these figures, we found the total surface area of each plant, after which we could calculate the rate of transpiration for each climate. We selected a bean plant on which to test varied environmental factors on transpiration. The different environments included excessive sunlight-a floodlight one meter from the plant, wind/dry air-a stationary fan approximately one meter away from the plant on low speed, humid/rainy climate-leaves misted, then covered with a clear plastic bag (open at the bottom for air exchange). Normal room conditions were also tested for the control. One bean plant was used for each simulated environment. Different environmental factors can have impacts on the intensity of water evaporation, and thus the rate of plant transpiration. Just like water in an open environment, a dry environment would increase the evaporation of water, and the rate of transpiration. A hot or very bright environment would do the likewise. Conversely, moist, dark, or cool environments would allow for a slower rate of transpiration because water would not be as readily evaporative. When testing the rate of transpiration for any given plant, I hypothesize that plants exposed to copious quantities of light will transpire more rapidly than those in a regular environment. To set up the experiment, four pieces of Tygon clear plastic tubing were cut to sixteen inches. Inside each was placed the ti
Some common words found in the essay are:
Introduction Water, Conclusion Figure, rate transpiration, negative pressure, water molecules, water evaporation, evaporation water, bean plant, turgor pressure, low rate transpiration, movement water, vapor plant, low rate, water vapor plant,
Approximate Word count = 1182
Approximate Pages = 5 (250 words per page double spaced)
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