Plants

• Epidermis Covers the outer surfaces of the plant for protection
• Palisade Mesophyll is the main site of photosynthesis in the leaf
• Spongy mesophyll has air spaces between the cells which allow gases to diffuse through the leaf. Oxygen enters and carbon dioxide diffuses out
• Xylem transpots water and minerals through the plant from roots to leaves. Also supports the plant
• Phloem vessel transports dissolved food material through the plant
• Meristem tissue found mainly at the tips and shoots of the plant, where it can produce new cells for growth
• The loss of water from the leaves is called transpiration
• There are many factors that can affect the rate of transpiration:

  -An increase in temperature will increase the rate, as more energy is transferred to the water to allow it to evaporate

  -Faster air flow will increase the rate, as it will move away water vapour allowing more to evaporate

  -increased light intensity will increases the rate, as it will cause the stomata to open
• An increase in humudity decrease the rate of transpiration because the air contains more water vapours so the concentration gradient is lower because transpiration is the loss of water from the leaves
• In the leaf Guard cell role is to open and close stomata. At night the stomata are closed because photosynthesis does not take place in the dark, so carbon dioxide is not needed. Closing the stomata reduces water loss
• Guard cell function is to control water loss and gas change by opening and closing the stomata
• When water is plentiful, guard cell take up water and bend.This causes the stomata to open, so gases for photosynthesis are free to move in and out of the stomata along with water from transpiration.
• Translocation phloem tissue transports disssolved sugars from the leaves to the rest of the plant
• xylem cells have hallow tubes strengthened by lignin adapted for the transport of water in the tarsnspiartion stream
• Phloem tissues transports dissolved sugars from the leaves to the rest of the plant for immediate use or storage. Has tubes of elongated cells. Cell sap can move from one phloem cell to the next through pores in the end walls
• Transpiration helps the xylem vessels from the roots