Plants are made up of: -organs, tissues, and cells The three major plant organs are: -Roots, stems, and leaves -Each asexual organs Plants have a Root System beneath the ground that us a multicellular organ which: -Anchors the plant -Absorbs water and minerals -Stores sugars and starches Additional Root Structures: -At the tips of the roots vast number of tiny root hairs increase the surface area enormously, making efficient absorption of water and minerals possible -Plants may also have a symbiotic relationship with fungi and the tips of the roots, termed mycorrhizae (fungus root) -Mycorrhizae assist in the absorption process and are found in the vast majority of all plants
Plants have a Shoot System above the ground that works as a multicellular organ -Leaves are the main photosynthetic organ inmost plants -Stems function primarily to display the leaves Plant organs-leaf, stem, and root- are composed of three tissues types: -Dermal tissue -Vascular tissue -Ground tissue Dermal Tissue -Is a single layer of closely packed cells that cover the entire plant and protect it against water loss (cuticle) and invasions by pathogens like viruses and bacteria Vascular Tissue -Is continuous through the plant an transports materials between the roots and shoots -Is made up of xylem, which transports water and minerals up from the roots and phloem, which transports food from the leaves to the other parts of the plant -Xylem cells have two types of water conduction cells: tracheids and vessels that are dead at functional maturity -Phloem cells conduct sugar and other organic compounds. Phloem is composed of two types of cells, sieve tubes and companion cells, both alive at maturity
Ground Tissue -Is anything that isn t dermal tissue or vascular tissue -Used for storage and photosynthesis Plant Growth -For growth, plants have meristems that generate cells for new organs -Meristems are perpetual embryonic tissue that are responsible for indeterminate growth (growth throughout the plant s life) Plant Meristems: -Perpetual embryonic regions -Zones for cell division Two Types of Plant Meristems -Apical Meristems are located at the tips of the roots and in the buds of shoots -These are the sites of cell division, allowing the plant to grow in length, Primary growth occurs when the plant grows at the apical meristems (length) -Lateral Meristems result in the growth which widens or thickens the shoot and roots, this is termed secondary growth Leaf Anatomy -Stem outgrows for Ps -Blade: the flattened portion of a leaf -Peptiole: stalk of a leaf Tissues within a Leaf: -Upper Epidermis -Mesophyll -Lower Epidermis -Veins
Upper Epidermis -Cuticle present -Usually one cell layer thick -Cells tightly packed together, have stoma, guard cell with chloroplasts -Function: Protects the mesophyll Mesophyll -Palisade: upright cells (Ps) -Spongy: loosely organized cells with air spaces (Gas Exchange) -Function: Major sites for Ps Lower Epidermis -No cuticle present -Usually one cell layer thick -Cells tightly packed together -Function: Many stomata, guard cells present for gas exchange Stomata -Regulated by guard cells which have chloroplasts
Veins -Xylem: transport water -Phloem: transport sugar -Veins located in mesophyll and are often surrounded by bundle sheath cells for support