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Plants Structure and Fuction.docx

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BIOL 1115

 For photosynthesis, gas exchange, and transpiration.  Epidermal layer secretes an external layer of waxy cuticle that reduces water loss by evaporation from the leave surface.  Stomata are the primary site of transpiration. Transpiration is a process that contributes to the movement of water and dissolved substance up the shoot from the roots.  Guard cells surround the stomata. It regulates the passage of water vapor.  They are cells that are mainly found in dicot leaves. They contain chloroplasts that are important for photosynthesis.  Venation, arrangement of mesophyll cells and distribution of stomata.  Monocots have only spongy mesophyll, but dicots have both palisade (closely packed) and spongy mesophyll. Stomata for monocots are equally distributed between upper and lower leaf surfaces, but dicot most of the stomata is located on the bottom of the leaf. Dicot leaves are held horizontally off the stem, but monocot is held vertically.  The greatest changes are the leaves because they are the primary site of water loss.  The leaves that transpiration and photosynthesis occurs. The most surface area so the plants will invest more time in modifying the leaves to better suit the environment.  Because only the upper surface is exposed to the air.  Lower half of the leaf, the spongy mesophyll cells are narrow and thin and surround large air cavities to help the leaf float in water. They are large so they can float.  Reducing surface area of the leaf, turning them to needles or spines. Absence of stomata on the epidermis. Large thin walled cells in the cortex that stores water.  Thin walled water storing parenchyma, thick cuticle covering the entire epidermis and stomata is located in the pits in the epidermis.  Billiform cells are full of water and turgid, this cause the blade of the leaf to open flat. When the plant is placed in a hot environment the bulliform cells will lose water and collapse. This will cause the leaf to roll up to protect the stomata from direct sunlight.  When the guard cells are turgid it will open, and when water is lost it will close.  When it is in light photosynthesis will go up which will actively transport H ions out which will passively transport K ions therefore solute in the guard cells will go more concentrated water will move in passively (open stomata) when it is in the dark photosynthesis is down so K ion will be diffused out of the guard cells which will decrease solute concentration water will move out
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