an integrated group of cells with a common structure and function 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

Apical meristem In shoot tips and root tips Region of cell differentiation/maturation 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 Guard cells Trichomes Root hairs Functions Absorption Secretion of cuticle Protection Control of gas exchange Epidermis Cuticle

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 root of the word sclerenchyma is the Greek word root (sclero) meaning “hard”

The Vascular Tissue System

Complex Vascular Tissues Xylem Conducts water and dissolved minerals from the roots Phloem 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 monocot stem Young dicot stem