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Weed Biology and Identification-202

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1 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 University

2 Basic Parts of the Plant
Roots Stems Leaves Flower

3 Shoot system Root system

4 Shoot system Lateral roots Root system Taproot

5 Shoot system Leaves Stem Lateral roots Root system Taproot

6 Shoot system Branch Leaves Stem Lateral roots Root system Taproot

7 Apical bud Lateral bud Shoot system Branch Leaves Stem Lateral roots Root system Taproot

8 Apical bud Node Lateral bud Internode Node Shoot system Branch Leaves Stem Lateral roots Root system Taproot

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

10 Root Structure

11 Anchorage and support

12 Storage

13 Stems 1. Translocate water, minerals and food to the leaves
2. Support the leaves and display them to light 3. Store Food

14 Woody Dicot Stem Morphology

15 Transport and support.

16 Cactus stems store water, photosynthesize.

17 Stolons produce new individuals at nodes above ground.

18 Rhizomes produce new individuals at nodes below ground.

19 Tubers store carbohydrates.

20 Thorns provide protection.

21 Leaves 1. Make food through photosynthesis
2. Provide site of gas exchange 3. Store food

22 Sunlight Shoot system CO2 Transport of water, sugar, and nutrients through vascular tissue Root system Water Nutrients (such as N, P, K)


24 Make food through photosynthesis

25 Sloughed-off root cap cells
(a) Longitudinal section of root segment Primary Growth Lateral root Cellular Maturation Zone of Root hair (b) Close-up of root tip Vascular tissue Cellular Elongation Zone of Ground tissue Epidermal tissue Zone of Cellular Division Apical mersitem Sloughed-off root cap cells mucilage Root cap

26 Flowers 1. Contain organs for specialized sexual production
2. Produce seeds and fruit

27 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


29 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

30 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

31 Different type of Roots
Adventitious Roots Develop in places other than nodes Can form on cuttings and rhizomes

32 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

33 Absorbing water and nutrients

34 Specialized Stems A. Corm (gladiolus, crocus) underground
Solid, fleshy, scale covered


36 Specialized Stems B. Bulb (tulips, lillies, onions)
Layers of fleshy scales that overlap each other Underground stem

37 Specialized Stems C. Tuber (potato, caladium) Food storage area
Short, thick underground stem

38 Specialized Stems D. Crown (African Violets, fern)
Closely grouped stems or plantlets Just above ground or just below

39 Specialized Stems E. Spurs (pear and apple trees)
Short sems found on woody plant limbs adapted for increased production of fruits

40 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

41 Specialized Stems G. Stolon (Strawberry, airplane plant)
Stem that grows horizontally above the soil surface

42 Principal Tissues of the Leaf
Epidermis Cuticle Waxy substance covers the leaves and stems Waterproof layer that keeps water in plants

43 Principal Tissues of the Leaf
Epidermis (cont) Stomata Openings in the epidermis mainly located on underside of leaves Exchange of gases

44 Principal Tissues of the Leaf
Epidermis (cont) Guard Cells Two cells located on each side of stomata Open and closes stomata

45 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

46 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

47 Parts of the Flower Sepals Outer covering of the flower bud
Protects the stamens and pistills when flower is in bud stage

48 Parts of the Flower Petals Brightly colored
Protects stamen and pistills Attracts pollinating insects

49 Parts of the Flower Stamens Male Reproductive part
Anther-produces pollen Filament-supports the anther

50 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

51 Parts of the Flower Style Connects the stigma with ovary
Supports the stigma so that it can be pollinated

52 Complete and Incomplete Flowers
Complete: have all four main parts Sepals Petals Stamens Pistils


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