Plants as organisms Unit 3 Lesson 3 Stems

Plants as organisms Unit 3 Lesson 3

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 – 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 –In all stems: – Water and minerals travel up the XYLEM – Manufactured food travels down the PHLOEM

Dicots – Dicots 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 – 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)

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