Plant structure and transport

Leaves

• Upper epidermis - covered by a waxy cuticle
• Palisade mesophyll cells - do most of photosynthesising
• Spongy mesophyll cells - sosme photosynthesising, but less than palisade cells
• Parenchyma - packages the plant
• Lower epidermis - contains stomata
• Vascular bundle - contain xylem and phloem

Stomata

• Used for gas exchange
• Found on lower epidermis
• Sunlight triggers the release of potassium ions inside the guard cells. This lowers the water potential and so water comes in by osmosis. The guard cells then become turgid and the stomata open.

Roots

• Main part is the tap root
• On the outside are root hair cells - increases surface area of roots to absorb more water
• Epidermis - outer layer
• Cortex - contains parenchyma cells
• Stele - contains vascular bundle and the pith (made of parenchyma cells)
• Vascular bundle contains xylem and phloem
• From the root, the water needs to get to the stem, and so transported up. The water enters the root by osmosis and continues to travel to area of low water potential, such as the xylem in the stem

Pathways water takes

• There are three pathways the water can take from the root to the stem: apoplastic, symplastic, vacuolar
• Apoplastic - the water moves through the gaps inbetween the cell membrane and cell wall
• Symplastic - Through the cytoplasm of plants cells, avoiding the vacuole, from cell to cell through the plasmodesmata(gaps between walls)
• Vacuolar - Straight through the cell and the vacuoles
• These pathways continue until the water reaches the Casparian *****. This cell contains suberin wax which is between the cell wall and membrane, stopping water taking the apoplastic pathway. This puts all…