Plant Anatomy Unit 1 Chapter 6 Lesson 2

Stems Stems have 2 main functions: The movement of materials Movement of water and minerals from roots up towards the leaves Movement of manufactured food from the leaves down to the roots Support of the leaves and reproductive structures Flowers and fruit or seeds

Stems cont. Stems are also used for: Food storage Reproductive methods Irish Potato Reproductive methods Stem cuttings or grafting Green stems manufacture food just like leaves

Stems on the Outside Lenticels Breathing pores

Stems on the Outside cont. Bud scale scars Indicate where a terminal bud has been located The distance between two scars represents one year of growth Leaf scars Show where leaves were attached

Unique Stems Irish Potato & Gladiolus Very different stems Stems are used for food storage and plant reproduction                             

Stems on the Inside Vascular system Water and minerals travel up the XYLEM Manufactured food travels down the PHLOEM Comparative to animal circulatory system

Dicots Dicots (2 cotyledons - seed leafs) the xylem and phloem are separated by the cambium The cambium produces new cells Grow continually because the cambium builds new xylem and phloem cells Trees are a perfect example! Sap = new xylem Heartwood = old, inactive xylem Tree bark = old, inactive phloem

Monocots One cotyledon (seed leaf) Grasses, corn No outside cambium Vascular bundles that contain xylem & phloem Cells don’t increase in number, they grow in size (won’t keep growing like a tree)

Monocots vs. Dicots

What do we do with Stems? Food Building Materials Asparagus Irish Potato Celery Building Materials Wood

Key Stem Words Cambium Bud Bud scales Terminal bud Where cell division takes place Bud Structures containing undeveloped leaves, stem, or flowers Bud scales Cover and protect the bud Terminal bud Large bud at the tip of a stem

Key Stem Words Apical meristem Auxins Lateral buds Apical dominance Primary growing point of the stem Auxins Hormones that influence the growth of a stem Lateral buds Bus found on the sides of the stem Apical dominance Auxin influence causes the lateral buds closest to the apical meristem from developing so that the growth can be concentrated on an upward point vs. an outward point.

Key Stem Words Bulb Corm Rhizome Stem tuber Short, flattened stems that bear fleshy food storage leaves Corm Short, swollen underground stem Rhizome Underground horizontal stem Stem tuber Swollen tips of the rhizome

Key Stem Words Stolon Horizontal stem that is above ground Produces roots at tip or nodes to produce a new plant asexually