Plants as Living Organisms Plant Parts and Their Functions Plant and Soil Science Topic 2014

Basic Parts of the Plant Roots Stems Leaves Flower (not included in this lecture)

Root Functions 1. Anchor Plant 2. Absorb water and minerals 3. Translocate water and minerals to stem 4. Store Food

Root Parts Primary root – First root that the seed sends out – Anchors root Secondary root – Branches off of primary root Root Cap – Protects roots while they grow

Root Parts Root hairs: – Tiny one celled hair like extensions of the epidermal cells located near the tips of the roots where vascular tissues have formed. – Increase surface area – Absorb water and minerals from soil Adventitious roots Roots that begin growth from the stem

Different type of Roots A. Tap Root – Continuation of the primary root – Ideal for anchorage – Penetration is greater for water – Storage area for food made by photosynthesis

Different type of Roots B. Fibrous Roots – Many finely branched secondary roots – Shallow roots cover a large area More effective absorption of water and minerals Roots hold the soil to prevent erosion

Types of Roots

Stem Function 1. Translocate water, minerals and food to the leaves 2. Support the leaves and display them to light 3. Store food and water 4. Produces new stem tissue

Stem Tissues Xylem – Provide structural support – Transports water and minerals from roots to leaves Phloem – Transports food made in leaves to the rest of the plant

Buds Bud scales – Protect under developed parts Terminal Bud – Tip of twig Apical Meristem – Primary growing point Lateral buds – Can develop into secondary branches Apical dominance – Hormones that prevent lateral buds from developing

Buds

Leave Function 1. Make food through photosynthesis 2. Provide site of gas exchange 3. Store food

Cross section of Leaf

Principal Tissues of the Leaf Epidermis – Cuticle Waxy substance covers the leaves and stems Waterproof layer that keeps water in plants – Stomata Openings in the epidermis mainly located on underside of leaves Exchange of gases – Guard Cells Two cells located on each side of stomata Open and closes stomata

Principal Tissues of the Leaf Mesophyll layer – Palisade mesophyll Primary site of photosynthesis – Spongy mesophyll Contains air and chloroplasts Site of photosynthesis and gas exchange Veins or vascular bundles – In spongy mesophyll – Phloem tissues conduct food from photosynthesis to rest of plant – Xylem tissues conduct water and minerals up to cells in leaves and stems

Simple vs. Compound Simple – Single leaf blade and a petiole Compound – A petiole and more then one leaf blades

Shapes of leaves