Plant Nutrition

• Green plants make their own food, they use simple inorganic substances (carbon dioxide, water, and minerals) from the soil.
• Plants build substances like carbohydrates, lipids, proteins, and vitamins by using carbon dioxide, water, and minerals.
• Green plants make glucose from carbon dioxide and water.
• If you just mix carbon dioxide and water together, it won't make glucose.
• Green plants use the energy of sunlight from photosynthesis to make glucose.
• Sunlight shining on carbon dioxide and water won't make glucose. The sunlight needs to be trapped and then used in the reaction. Chlorophyll traps the sunlight in.
• Chlorophyll is the pigment that makes plants green.
• Chlorophyll is stored in the chloroplasts of plant cells.
• When sunlight falls on a chlorophyll molecule, some of the sunlight is absorbed. The chlorophyll molecule then releases energy, which makes carbon dioxide and water combine (with them help of enzymes inside the chloroplasts)
• Carbon Dioxide + Water

  (sunlight and chlorophyll) -->

  Glucose + Oxygen
• 6CO2 + 6H2O --> C6H12O6 + 6O2
• Photosynthesis happens in the chloroplasts where enzymes (catalyst) and chlorophyll (energy supply) are present.
• Leaves are specially adapted to allow photosynthesis to take place as quickly and efficiently as possible.
• A leaf consists of a broad, flat part called the lamina, which is joined to the rest of the plant by a leaf stalk.
• Running through a leaf, there are vascular bundles, which then form the veins of the leaf. These contains tubes that carry substances to and from the leaf.
• A leaf is made up of several layers.
• The bottom and top of a leaf are covered with a layer of closely fitting cells called the epidermis.
• The epidermis does not contain chloroplasts.
• The function of the epidermis is to protect the inner layers of the cells in the leaf.
• The cells of the upper epidermis often secrete a waxy substance on top of them called the cuticle.
• The cuticle in the leaf helps to prevent the water from evaporating from the leaf.
• There is sometimes a cuticle on the underside of a leaf as well.
• In the lower epidermis, there are small openings called stomata (singular: stoma)
• Each stoma is surrounded by a pair of guard cells which can open or close the hole.
• Guard cells contain chloroplasts.
• The middle layers of the leaf are called mesophyll.
• Mesophyll cells contain chloroplasts.
• The palisade mesophyll is arranged like a fence.
• The spongey mesophyll is below the palisade mesophyll and is are round and arranged loosely, with large air spaces between them.
• Running through the mesophyll are veins or vascular bundles.
• Each vein or vascular bundle contains a xylem vessel and a phloem tube.
• Xylem vessels are large and thick celled tubes that carry water.
• Phloem tubes are small and thin walled and carry away sucrose and other substances the leaf has made.
• Carbon dioxide is hard to obtain and therefore the leaf must be very efficient when absorbing it.
• The leaf is held out into the air by the stem and the leaf stalk, and it's large surface area helps to expose it to as much air as possible.
• The cells that need carbon dioxide are the mesophyll cells.
• Carbon dioxide gets through the leaf through the stomata. It does this by diffusion.
• Behind each stoma there is an air space that connects with all the other air spaces between the spongey mesophyll cells.
• Water is obtained from the soil and is absorbed by the root hairs and carried up to the leaf through the xylem vessels.
• Water travels from the xylem vessels to the mesophyll cells by osmosis.