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Plant Tissues Plant structures are composed of 4 main tissues. They are: Epidermis – outer layer of cells which protect the plant from water loss and from fungi and bacteria Vascular Tissues – transport water, sugars and other materials through the plant Ground Tissues – tissues that the vascular tissue is embedded in…. usually storage cells Meristematic – cells that divide Plant Tissues • • • • • Meristematic- growth Epidermal- protection Parenchyma- storage Sclerenchyma- strengthen and support http://www.lima.ohioVascular- transportation state.edu/biology/image – xylem = water + nutrients s/zeaxs.jpg – phloem = plant products in solution Plant Tissues In Most Plants • Glucose is produced in the leaves through photosynthesis. • The glucose is converted to sucrose (by dehydration synthesis) for transportation. • The sucrose is converted to starch and stored. Roots Roots have many functions. 1. anchor the plant 2. bind soil… stops erosion 3. absorb water and minerals 4. store food (usually as starch) Root Types Taproots • look large and fleshy, • are mostly found in plants with two seed-leaves (dicots), • grow deep into the ground to search for food, • are able to store food, which is particularly necessary for perennial plants during periods of dormancy. Fibrous roots • lie close to the surface of the soil, • are mostly found in plants with one seed-leaf (monocots) • collect precipitation before it sinks deep into the ground, • can often be found growing side by side with taprootsthe two types of roots combine efforts to maximize efficiency. Adventitious roots • are common in both dicots and monocots • develop to help the plant climb: for example, ivy • help develop modified underground stems, such as bulbs Aerial Roots modified to absorb water from the air Aerial roots of an Orchid Orchids in bloom Root Hairs are actually epidermal cells adapted to absorb water Root Hairs * Water enters the cells by Osmosis * Minerals enter by Active Transport Regions of the root tip • Region of Maturation - Most cells differentiate into various distinctive cell types. – Root hairs form. • Region of Elongation - Cells become several times their original length. – Vacuoles merge • Region of Cell Division - Composed of apical meristem in the center of the root tip. – Most cell division occurs at the edge of the inverted cup-shaped zone. • Root Cap - Thimble-shaped mass of parenchyma cells covering each root tip. – Protects tissue from damage. – Function in gravity perception. The Root Tip The Function of Root Tissues • Epidermis – outer layer of cells, provide protection from drying out, water loss and infection. • Cortex – area made up of parenchyma cells. Parenchyma cells are usually storage cells • Endodermis – regulates materials entering the center of the root. • Pericycle –the outermost layer of cells of the stele • Xylem – transports water • Phloem – transports sugar • Stele – Also known as the “Vascular Cylinder”…… made up of the xylem and phloem • Pith – tissue located in the center of the stem • Apical Meristem - (Meristematic Tissue) – tissue that in a constant state of growth… apical means “located at the tip” • Meristem accounts for the increase in length of the roots and stems. Dicot Root X-section Monocot root X-section Dicot root X-section Most Dicot roots have an “X” of xylem cells in the center of the root. The Casparian Strip regulates the movement of water into the root Stele