BIOL 227 Lecture Notes - Lecture 10: Sieve Tube Element, Ultimate Tensile Strength, Cell Wall
3 May 2016
School
Department
Course
Professor
Document Summary
Biol 227 tutorial 10 plant anatomy. Plants initially grow in 2 directions, up and down beginning with apical centers of cell division, from generative cells to 3 tissues generally making 3 organs, cells that differentiate with their inside-outside location. Primary walls: thin plastic, highly hydrated structures synthesized primarily during growth. Characteristics: strong, extensible, incorporative, tissue and organ yet to be determined. Secondary walls: provide strength and rigidity in cells that have stopped growing, they need to supply bending strength and withstand high negative pressures. Characteristics: have compressive and tensile strength but not extensibility (generally) and determinant. Vascular tissues the fossil records suggests vessel members evolved from trachids they occur in: gnetales and dicots except the most basal, monocotyledons, a few ferns and interestingly, The evolution of phloem is more speculative because it is composed of cellulose and does not have hard lignified tissue.
