Xylem Passive transport Transport medium Driving mechanism Role Xylem tissue consists of: Water and dissolved inorganic salts. Transpiration stream Chemical substances that are needed for photosynthesis e.g water mineral ions, are carried by xylem tissue from the roots (site of absorption) up to the leaves where they will be used for the manufacture of food (photosynthesis Xylem vessels Tracheids Fibres Parenchyma cells
Phloem Transport medium Driving mechanism Active transport Process Role Movement Phloem tissue consists of: Dissolved sugars (organic nutrients) Pressure-flow/translocation "Source to sink" Phloem loading involves sugar moving by active transport into the sieve tube Water then follows due to osmosis and then transpiration pull draws the water up the stem. Cohesion between the water molecules causes the water to form a continuous stream up the plant and "pulls" the water up. Adhesion between the water molecules and the walls of the xylem vessels also helps draw water up the plant and at night when the flow ceases it prevents back flow. Most photosynthesis occurs in plant leaves. Phloem vessels are involved in the transport of organic nutrient products e.g sugars, amino acids and plant hormones to all parts of the plant. Occurs in two directions - up towards the flowers and down to the roots. Phloem fibres Phloem parcnchyma Sieve cells Companion cells
The role of transport in plants is mainly to carry materials for photosynthesis to the cells and move cell products away to other parts of the plant.
Transport in plants
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