Chapter 29.3

1. Chapter 29.3 Primary Structure of Shoots AP Biology Spring 2011

2. Behind the Apical Meristem • Terminal buds: shoot’s main zone of primary growth • Underneath the terminal bud surface is a shoot apical meristem which constantly produces more cells during the growing season • Cells that divide from the shoot apical meristem differentiate into specialized tissues

3. Behind the Apical Meristem • Below the terminal bud, along sides of apical meristem, tiny bulges of tissue develop • Each is the start of a leaf • Each stem region where one or more leaves have formed is a node, and the region between two successive nodes is an internode

4. Behind the Apical Meristem • Lateral buds (auxillary buds): form in leaf axil, region between the upward growing stem and outward growing leaf • Each auxillary bud is a dormant shot of mostly meristematic tissue • Hormones secreted by the terminal bud keeps the lateral buds dormant

5. Inside the Stem • Vascular bundle: multistranded cord of primary xylem and phloem running lengthwise through the ground tissue of shoots

6. Inside the Stem • The arrangement of vascular bundles differes between eudicots and monocots

7. Inside the Stem • Eudicots: vascular bundles arranged in a ring underneath the epidermis that divides the ground tissue into the outer cortex and inner pith • Cortex: portion between ring of vascular bundles and the epidermis • Pith: part inside the ring

8. Inside the Stem • Monocots: the vascular bundles are scattered throughout the ground tissue