The Structure of an exchange system in flowering plants.docx

The Structure of an exchange system in flowering plants (1) - The structure of the leaf is adapted to carry out both photosynthesis and gas exchange - The different cell types (palisade mesophyll, spongy mesophyll) and tissues are arranged in a specific way to carry out these processes Pathway of C...

The Structure of an exchange system in flowering plants (1) - The structure of the leaf is adapted to carry out both photosynthesis and gas exchange - The different cell types (palisade mesophyll, spongy mesophyll) and tissues are arranged in a specific way to carry out these processes Pathway of Carbon dioxide through photosynthesising leaf - There is a higher concentration of Carbon dioxide in the atmosphere than in the leaf - Carbon dioxide diffuses into the leaf through open stomata and into the air space of the spongy mesophyll - Carbon dioxide diffuses through the cell wall and cell membrane in mesophyll cells. - Carbon dioxide dissolves in the cytoplasm and diffuses into the chloroplast Adaptations of the leaf for gaseous exchange - Leaves are thin which gives a short diffusion distance - They are flat which provides a large surface area to volume ratio - They have many stomata which allow movement of gases in and out of the air spaces inside the leaf to maintain a steep concentration gradient - Have air spaces to allow gas movement around the loosely packed mesophyll cells - Many stomata in the lower epidermis open in sunlight to allow gas movement in and out of the leaf - Lenticels on the stem allow gaseous exchange between the atmosphere leaves of the plant Plant Excretion - Plants produce very little waste. Plant excretion consists mainly of carbon dioxide by night, and oxygen during the day. Plants store some waste in vacuoles and lose more when dead structures fall off. - Guard cells control the stomatal size in leaves and are thought to be sensitive to carbon dioxide concentration. This ensures sufficient CO2 for photosynthesis and prevents a build-up of excess CO22