bundle sheath definition by American Heritage Dictionary
nounThe American Heritage® Dictionary of the English Language, 4th edition Copyright © 2010 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
A layer or region of cells surrounding a vascular bundle.
bundle sheath - Science Definition
A layer or region of compactly arranged cells surrounding a vascular bundle in a plant. The bundle sheaths regulate the movement of substances between the vascular tissue and the parenchyma and, in leaves, protect the vascular tissue from exposure to air.