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Tissues an integrated group of cells with a common structure and function Plant Tissues Four tissue systems in plants: Meristematic tissue: rapid cell division, lengthening of shoots and roots Dermal tissue: provides covering for the plant body. Ground tissue: variety of functions including support, photosynthesis, and storage Vascular tissue: “plumbing system” throughout plants; conducts water, food (CH2O), and dissolved minerals; also strengthens and supports the plant. Plants Exhibit Localized Growth at Meristems Meristematic Tissue specific areas of plant growth composed of cells that do not differentiate cells retain the ability to divide, which other plant cells lose allow plants to grow their entire lives Types: Apical – primary growth at root and shoot tips Lateral – secondary growth in trees and shrubs Intercalary – secondary growth in monocot stems Region of cell differentiation /maturation Apical meristem Region of cell elongation In shoot tips and root tips Allium cepa root tip shown here Parenchyma cells Region of cell division Apical meristem Root cap Apical Meristems Stem buds have a dome-like apical meristem in addition to leaf primordia and bud primordia, which protect the apical meristem. Dermal Tissue System Dermal Tissues Single layer of cells called the epidermis in herbaceous plants Epidermis Guard cells Trichomes Root hairs Functions Absorption Secretion of cuticle Cuticle Protection Control of gas exchange The Ground Tissue System Parenchyma cells Spherical-shaped cells; most common type of tissue (most of apples & potatoes); found throughout plant Have thin primary walls Living, metabolizing tissue Functions: Photosynthesis & respiration Storage (starch, oil droplets, water, and salts) Wound healing & regeneration Collenchyma Beneath the epidermis in young stems and in large veins of leaves (“strings” in celery) Elongated cells that have unevenly thickened cell walls (especially in the corners) Flexible support system (like our skeletal system) Found uniformly throughout the plant Alive at maturity Sclerenchyma Specialized for structural support; occurs in many areas Two types: Fibers – support in wood, bark, leaves, stems Sclereids – protection in fruits, seeds, other plant organs Primary and secondary cell walls. Dead at functional maturity The Vascular Tissue System Complex Vascular Tissues Xylem Phloem Conducts water and dissolved minerals from the roots Conducts dissolved food materials, carbohydrates, in solution Continuous throughout plant Support plant body All 4 types of tissues are present in the root tip Young dicot stem Young monocot stem