Weed Biology and Identification-203

Target students: M .Sc. Students in Weed Science

Lecture:

Dr. Majid AghaAlikhani (Ph.D.)

Academic position :

Associate Prof. of Tarbiat Modares Universitymaghaalikhani@modares.ac.ir

1

Plant Parts

Chapter #3

Modified by Georgia Agriculture Education Curriculum Office

June 2002

What are the parts of a plant?

Node: swollen part of stem where buds form (leaves or stems grow here)

Cotyledons: leaves formed at first node (cotyledonary node)

What are the parts of a plant?

Epicotyl: all of plant formed above cotyledonary node

Internode: stem tissue between nodes

What are the types of stems?

1) Woody Stem: trees, shrubs, woody perennials

2) Grass Stem: hollow or filled3) Herbaceous Stem: like

woody but softer (clover, alfalfa)4) Modified Stem:

Types of Modified Stems

• Bulbs: (onion)• Tubers: (potato)• Stolons: above ground runner (strawberry)• Rhizomes: below ground runners (field

bindweed or creeping jenny)

What are the functions of stems?

1) transport water, nutrients, sugars

2) support leaves3) store food

What are buds?

• special tissue on stems that can grow into new plant parts

• buds are described according to:

• 1) structures into which they grow– -Vegetative: leaves or stems– -Floral: flowers– -Mixed: both

• 2) where buds appear on stem– -Apical: tips of stems

• -if floral = bush• -if vegetative = vine

– -Axillary: where leaf joins stem– -Adventitious: near wounds

• 3) How buds are arranged

Bud Arrangements

–Alternate (alfalfa)–Opposite (beans)–Whorled (not common)

What is Apical Dominance?

• apical bud tries to make plant grow taller or longer

• if we remove apical bud, we remove the apical dominance

What are leaves?

• undergo photosynthesis, exchange gases

What is the difference between a simple leaf and a compound leaf?

• simple leaf = 2 parts (leaf blade and petiole)

Petiole

Leaf

Blade

What is the difference between a simple leaf and a compound leaf?• Compound leaf: leaf blade divided into

leaflets

What are the different types of compound leaves?

• Palmately compound

What are the different types of compound leaves?

• Pinately compound

What are the different types of compound leaves?

• Trifoliate (alfalfa)

What is the Hypocotyl?

• part of the plant below the cotyledonary node

What purpose does the hypocotyl serve?

1) anchor plant

2) absorb water & nutrients

3) store food

What are the types of root systems?

-Taproot: one main root, has no nodes– (carrot, evergreen, kochia)

-Fibrous root: many nodes, branching root system (grasses)

To help prevent soil erosion, which root system would be best?

• Fibrous

What are the parts of a grass plant?

• Leaves = Sheath is the part of leaf that wraps around the stem

• Joints = internodes• Culm = stems

Grass Plant Parts

• Tillers = branches, all branch from the base of the plant

• Crown = union of roots and stem

• Jointing stage = stems elongate rapidly