Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Photosynthesis (leaf structure) Leaf Structures • To understand photosynthesis it is important to understand the leaf structures and functions. • Leaves are the plants “food supply factory.” – In higher plants the leaf structures is adapted to maximize light absorption and carbon dioxide diffusion. Leaf structures • • • • • • • • Veins (xylem and phloem) Mesophyll Palisade layer (parenchyma cells) Spongy Layer Cuticle Upper and Lower epidermis Stomates Guard cells Veins (xylem and phloem) • This is a network that acts like a plumbing system that supplies water and minerals to the leaf and that carries the products of photosynthesis away to other parts of the plant. • Xylem: carries water and dissolved minerals from the roots to the leaves • Phloem: carries the food made in the leaves to the rest of the plant Mesophyll • The green leaf cells between the upper and lower epidermis of a leaf which is loaded with chloroplasts. • The mesophyll consists of 2 layers: – Palisade layer (parenchyma cells) – Spongy Layer Palisade layer (parenchyma cells) • This layer is found right below the upper epidermis, which is made of parenchyma cells. • Most photosynthesis in plants takes place in the palisade layer of the leaves Spongy Layer • This layer is found below the palisade layer and above the lower epidermis, which contains many air spaces. • The spongy layer is involved in gas exchange. Cuticle • This is a thin non-living waxy substance that covers leaves. • The cuticle helps reduce water loss and protection from most bacteria, fungi, and insects. Upper and Lower epidermis • This is a single layer of cells, which covers the upper and lower surfaces of leaves. • The epidermis also provides protection to the leaves from most bacteria, fungi, and insects. Stomates • Are minute pores found in the epidermis of leaves, which allows diffusion of gases in and out. • During the day, stomata absorb carbon dioxide from the air and release oxygen and water. • Evaporation of water from the leaf is referred to as transpiration, is the major source of water loss in leaves. Guard cells • Are two bean-shaped cells that surround the stomata. • The guard cells control the size of the stomata. • When the guard cells swell, the stomata open. • When the guard cells shrink, the stomata close. Chloroplast Chloroplast- a organelle in plant cells and algae that contain the chlorophyll pigments and the enzyme systems for photosynthesis. Diagram of A Chloroplast Chlorophyll Chlorophyll a light absorbing pigment that gives plants their green color and converts the energy of sunlight to food in the process known as photosynthesis. Plant leaf pigments