water movement in plants
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Water Movement In Plants. Forces that move water in plants. Osmosis - allows water to enter root cells Capillary Action - forces that allow water to be drawn up through xylem tubules - PowerPoint PPT PresentationTRANSCRIPT
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Water Movement In Plants
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Forces that move water in plants
• Osmosis - allows water to enter root cells
• Capillary Action - forces that allow water to be drawn up through xylem tubules (cohesion, surface tension, adhesion)
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Forces that move water in plants• Transpiration - process by which plants lose water vapor through the leaves
a) Water enters leaf through veinsb) Water leaves xylem & enters mesophyllc) Water evaporates from wet cell surface = vapord) Water vapor diffuses into airspaces of mesophylle) Water vapor passes out into air through stomata
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Forces that move water in plants
Transpiration (continued)
*more water moves in to replace lost water = a continuous process that helps pull water through the plant & cools the leaves
**Over 90% of water taken in by plants is lost through the process of transpiration
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Rate of Tranpiration• Controlled by guard cells & stomata
-guard cells take in water through osmosis = increased turgor pressure (guard cells swell & open)
-guard cells lose water through osmosis/evaporation
(guard cells shrink & close)
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Rate of Transpiration (cont.)
• Stomata are open during the day - take in carbon dioxide for photosynthesis; stomata close at night but on a hot, dry day, they may close to prevent excessive water loss
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Environmental Factors Affecting Water Loss:
• Humidity - rate of water loss decreases when humidity levels are high
• Wind - rate of water loss increases during windy conditions (evaporation rate increased)
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Environmental Factors Affecting Water Loss:
• Temperature - rate of water loss increases as temperature goes up due to increased rate of photosynthesis
• Light - rate of water loss increases as light levels increase; due to increased photosynthsis
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Leaf Modifications to Prevent Water Loss
• Smaller leaves - reduced surface area limits water loss (curled leaves, needles, or spines)
• Succulents - thick, fleshy leaves that store water (aloe vera, jade)
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Leaf Modifications to Prevent Water Loss
• Stomata only on leaf bottom - not exposed to direct light = reduced evaporation rates
• Hairs - trap moisture, help prevent water loss
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