2.6a the need for transport in plants
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What do plants need transport systems for?
To move substances such as water from one place to another
Why do plants need water?
To transport materials and carry out photosynthesis
How is water and minerals transported through in plants?
in xylem vessels
What are xylem vessels strengthened by?
lignin rings and spirals
Where is the upper epidermis found and what is its function?
• at the very top of the leaf, above the palisade mesophyll cells • skin-like tissue forming the upper covering of leaves
Where are palisade mesophyll cells found and what are their function?
• below the upper epidermis and above spongey mesophyll cells • main photosynthetic tissue in the left containing many chloroplasts
Where are spongey mesophyll cells found and what are their function?
• bellow the palisade mesophyll cells and above the lower epidermis • plant leaf tissue with loosely packed cells and air spaces between them to allow gas exchange
Where is the lower epidermis found and what is its function?
• at the very bottom of the leaf, bellow the spongey mesophyll cells • skin-like tissue forming the lower covering of leaves
What are stomata?
tiny pores in the leaf epidermis that allow gas exchange. They also allow water to leave the cell by evaporation and carbon dioxide and oxygen to enter/ leave the cell.
What are guard cells and what is their function?
• Cells that are found on either side of the stomata - they control gas exchange in leaves by controlling the opening and closing of the stomata.
What is transpiration?
water loss through the leaves of a plant by evaporation through the stomata.
Describe the flow of water through the plant
• water passes into the root hair cells by osmosis • water passes up the stem through the xylem • water lost through the stomata (evaporation) by transpiration
State the factors that can increase the rate of transpiration
• higher temperature - higher windspeed
State the factor that can reduce the rate of transpiration
-increased humidity
How is sugar transported up and down the plant?
living phloem cells
Why do plants need water?
• photosynthesis-hydrogen from water combines with carbon dioxide to produce water • transport-minerals are transported dissolved in water • support-water sweets vacuoles making cells turgid • cooling-evaportion of water from leaves has a cooling effect
What apparatus can be used to measure transpiration rate?
potometer
Describe the structure of xylem vessels
made up of dead tube-shaped cells with no cell contents but with lignin rings and spirals to give support.
Describe the structure of phloem cells
living phloem tissue made up of sieve tube cells connected by sieve plates with no nucleus. They have companion cells.
What is the function of a leaf vein?
tissue consisting of xylem vessels and phloem tubes running through a leaf.
What is the roles of xylem vessels?
• transport water from the roots to all other areas of the plant • transport of minerals which are dissolved in the water • helps strengthen the stem of the plant
What do the guard cells do to the stomata if there is little water supple?
they close the stomata
What do the guard cells do the the stomata if there is a good water supply?
they open the stomata