Weed Biology and Identification-202

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

Basic Parts of the Plant

• Roots• Stems• Leaves• Flower

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Taproot

Lateral roots

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Taproot

Lateral roots

Leaves

Stem

Sh

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Taproot

Lateral roots

BranchLeaves

Stem

Sh

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Taproot

Lateral roots

Apical bud

BranchLeaves

Stem

Sh

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mLateral bud

Taproot

Lateral roots

Apical bud

Branch

Node

Internode

Leaves

Lateral bud

Stem

Node

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Roots

• 1. Anchor Plant• 2. Absorb water and minerals• 3. Translocate water and

minerals to stem• 4. Store Food

•Root

Structure

Anchorage and support

Storage

Stems

• 1. Translocate water, minerals and food to the leaves

• 2. Support the leaves and display them to light

• 3. Store Food

Woody Dicot Stem

Morphology

Transport and support.

Cactus stems store water, photosynthesize.

Stolons produce new individuals at nodes above ground.

Rhizomes produce new individuals at nodes below ground.

Tubers store carbohydrates.

Thorns provide protection.

Leaves

• 1. Make food through photosynthesis

• 2. Provide site of gas exchange• 3. Store food

Transport of water, sugar, and nutrients through vascular tissue

CO2

Sunlight

Water

Nutrients(such as N, P, K)

Shoot

syst

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Root

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•Make food through photosynthesis

Vascular tissue

(b) Close-up of root tip

Ground tissue

Epidermal tissue

Apical mersitem

Sloughed-off root cap cells

Root cap

Root hair

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Matu

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Elo

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Div

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nLateral root

(a) Longitudinal section of root segment

mucilage

Primary Growth

Flowers

• 1. Contain organs for specialized sexual production

• 2. Produce seeds and fruit

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

ARE YOU PAYING ATTENTION?

• THERE JUST MAY BE A QUIZ!!!

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

Different type of Roots

• C. Aerial roots–Clinging air roots

•Short roots that grow horizontally from the stems

•Roots that fasten the plant to a support

–Absorptive air roots

Different type of Roots

• Adventitious Roots–Develop in places other than

nodes–Can form on cuttings and

rhizomes

Roots

• 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

Absorbing water and nutrients

Specialized Stems

• A. Corm (gladiolus, crocus)– underground–Solid, fleshy, scale covered

WAKE UP!!!!!!!!!!!!

• DON’T FALL ASLEEP• PAY ATTENTION!• THIS MEANS YOU!!!

Specialized Stems

• B. Bulb (tulips, lillies, onions)–Layers of fleshy scales that

overlap each other–Underground stem

Specialized Stems

• C. Tuber (potato, caladium)–Food storage area–Short, thick underground stem

Specialized Stems

• D. Crown (African Violets, fern)–Closely grouped stems or

plantlets–Just above ground or just below

Specialized Stems

• E. Spurs (pear and apple trees)–Short sems found on woody

plant limbs adapted for increased production of fruits

Specialized Stems

• F. Rhizomes (iris, lily of the valley)–Underground stems that produce

roots on the lower surface and extend leaves and flower shoots above the ground

Specialized Stems

• G. Stolon (Strawberry, airplane plant)–Stem that grows horizontally

above the soil surface

Principal Tissues of the Leaf

• Epidermis–Cuticle

•Waxy substance covers the leaves and stems

•Waterproof layer that keeps water in plants

Principal Tissues of the Leaf

• Epidermis (cont)–Stomata

•Openings in the epidermis mainly located on underside of leaves

•Exchange of gases

Principal Tissues of the Leaf

• Epidermis (cont)–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

Principal Tissues of the Leaf

• 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

Parts of the Flower

• Sepals–Outer covering of the flower bud–Protects the stamens and pistills

when flower is in bud stage

Parts of the Flower

• Petals–Brightly colored–Protects stamen and pistills–Attracts pollinating insects

Parts of the Flower

• Stamens–Male Reproductive part–Anther-produces pollen–Filament-supports the anther

Parts of the Flower

• Pistil–Female reproductive part–Ovary

•Enlarged portion at base of pistill•Produces ovules which develop into seeds

–Stigma•Holds the pollen grains

Parts of the Flower

• Style–Connects the stigma with ovary–Supports the stigma so that it can

be pollinated

Complete and Incomplete Flowers

• Complete: have all four main parts–Sepals–Petals–Stamens–Pistils