NAME: DATE: PERIOD: FOCUS on the LEAF Plants are organisms, made of two organ systems: the shoot system, and root system The plant leaf is an organ of the shoot system where photosynthesis occurs. It absorbs water, carbon dioxide (CO 2 ) and light energy to release oxygen (O 2 ) and make sugar for the whole plant. Organs are always made of two or more different tissues that work together. Tissue is a group of two or more similar cells that work together. Plants have three types of tissue, and many leaves have all three: Dermal tissue covers and protects other tissue. Vascular tissue transports water and minerals to the leaf and sugars from the leaf. Ground tissue is usually protected inside the dermal tissue, and is the main site of photosynthesis in the leaf. Cells of the dermal tissue have cellulose walls which are often thickened. They are usually covered with a waxy water- proof cuticle, which keeps water in. The bottom epidermis usually has stomata. Stomata are openings, surrounded by two guard cells that look like a doughnut. These guard cells expand to close off the opening, and open to let carbon dioxide in and oxygen out. Xylem is the vascular tissue that carries water to leaves, is usually towards the top of a vein. Phloem is the vascular tissue that carries sugar from the photosynthetic cells to the rest of the cells in the plant. These cells are towards the bottom of the vein. They often have fibers cells underneath, which protect the vascular tissue. There are two layers of ground tissue in most leaves. The palisade layer is on the top. These cells absorb most of the light, and are packed with chloroplasts, which make sugar. The spongy layer underneath lets carbon dioxide in the air get into the palisade layer, and oxygen out. A cell is the basic unit of life. Every organism is made of at least one cell, and multicellular organisms like plants often have large numbers of cells of many different types. Cells are surrounded by a membrane and have genetic material, DNA. shoot system root system dermal tissue vascular tissue ground tissue epidermal cells ground tissue vein vascuar tissue parenchyma

Take one of the PRIVET LEAF (TYPICAL DICOT) c.s. slides from the of the slide box. This slide is a thin slice across a leaf of a flowering vascular plant. Follow steps in the Focus packet to focus on the slice of leaf slide with the 4X objective lens. Move the slide to center the leaf. Switch to 10X, focus USING ONLY FINE ADJUSTMENT knob. Use p. 289 to help learn these cells and tissues To see cells in more detail, center those cells in your field and view, then Switch to 40X, focus USING ONLY FINE ADJUSTMENT knob. Draw a detailed sketch a few cells wide of the leaf cross section, showing and labeling: a layer of epidermal cells (2 + in detail) on both the upper and lower surfaces, which make up the dermal tissue; the waxy cuticle covering the epidermis; a pair of guard cells surrounding a stoma in the lower epidermis; parenchyma cells in the palisade layer ( 2 + in detail) and in the spongy layer (2 + in detail) of ground tissue in the mesophyll; vascular tissue bundles (veins) scattered in the center, with 2+ cells of xylem tissue and 2+ cells of phloem tissue NAME: DATE: PERIOD: FOCUS on the LEAF