1. Weed Biology and Identification-201
Target students:
M .Sc. Students in Weed Science
Lecture:
Dr. Majid AghaAlikhani (Ph.D.)
Academic position :
Associate Prof. of Tarbiat Modares University

2. Basic Plant Structure
Roots
Stems
Leaves

4. General Organization A plant has two organ systems: the shoot system
Found above ground and includes the organs such as leaves, buds, stems, flowers (if the plant has any), and fruits (if the plant has any).
the root system
Found below ground and includes roots, tubers, and rhizomes

5. Classifying Plants Nonvascular plants: have no vessels no stems
No leaves
No roots
Examples: Mosses & Liverworts

6. Classifying Plants Vascular Plants:
have vessels to transport food and water
Xylem: transports water
Phloem: transports food & nutrients
have roots, stems and leaves
Example: Grass, corn, trees, flowers, bushes

7. Gymnosperm Flowerless plants "naked seeds"
cone bearing plants (seeds grow on cones)
needle like leaves
usually stay green year round
Examples: pine trees & evergreens

8. Angiosperm flowering plants seeds are enclosed in a fruit
have finite growing seasons
Examples: grasses, tulips, oaks, dandelions
Divided into two main groups: Monocots & Dicots

9. Monocot Seed Angiosperms that have 1 seed leaf (cotyledon)
parallel veins on leaves
3 part symmetry for flowers
fibrous roots
Example: lilies, onions, corn, grasses, wheat

11. Dicot Seed Angiosperms that have 2 seed leaves (cotyledons)
net veins on leaves
flowers have 4-5 parts
have a taproot
Examples: trees and ornamental flowers

13. A. MONCOTS B. DICOTS 1. Have only 1 cotyledon 1. Have 2 cotyledons
2. Fibrous roots
2. Thick single main roots called taproots
3. Long thin leaves with parallel veins
3. Fan-like leaves with net veins
4. Flower parts are in groups of 3’s
4. Flower parts are in 4’s and 5’s
5. Stem has vascular tubes that are scattered
5. Stem has vascular tubes that are organized into rings
6. E.g. corn, wheat, grasses
6. E.G. beans, maples, peanuts, peas

14. Roots Roots absorb NUTRIENTS and water anchor the plant in the soil
provide support for the stem
store food
usually below ground
There are two major types of root systems in plants..
Taproot and fibrous root.

16. Root Types Taproot systems have a stout main root with a
limited number of side-branching roots.
Examples of taproot system plants:
nut trees, carrots, radishes & dandelions.
Fibrous root systems have many branched roots.
Examples of fibrous root plants:
most grasses, marigolds and beans

17. Stems The stem is the main trunk of a plant.
provide structure and support for leaves, flowers and fruits
may also store food
carry nutrients and water
Most stems grow above ground BUT…
many stems grow below ground or are ground hugging
Some modifications include:
bulbs, rhizomes, runners, tubers

18. Leaves are lateral outgrowths from the stem
main function is food production through photosynthesis
most commonly flat, broad and green.
maximizes their function of absorbing sunlight and transforming it into food.

20. Buds Buds are undeveloped shoots and flowers
classified terminal or lateral.
Terminal buds can be identified by their location
at the tip of a stem.
Lateral buds are located at the sides of the stem.
Cabbage and head lettuce are examples of very large
terminal buds
Brussels sprouts are edible lateral buds.
Broccoli is an example of edible flower buds.

21. Flowers Reproductive organ of the plant – produce seeds
Flowers are usually both male and female
The male part of the flower is the STAMEN
The female part of the flower is the PISTIL
See your sheet for more detail on flower anatomy

22. Flowers Continued Other external parts of flowers include:
SEPALS - usually green and enclose other
parts of the flower in the bud.
PETALS are usually brightly colored and may
contain aromatic substances as well as nectar glands.

23. MALE - STAMENS Stamens produce pollen which contain the sperm
Stamens are made of a head called the anther and a stock called the filament.

24. FEMALE – PISTIL Pistil holds the egg cells.
The pistil is made of a sticky head called the stigma, a stock called the style, and the ovary that holds the egg cells.

26. Petal
Pistil
Corolla
Stamen
Calyx
Sepal
Pollen
Stigma
Anther
Style
Filament
Ovary

27. Fruit A ripened ovary or group of ovaries containing the seeds
More on classification of fruits!
Fruit
A ripened ovary or group of ovaries containing the seeds
the ovary enlarges forming the mature fruit.
A simple fruit forms from the ripening of the ovary of a single pistil.
Eg. Tomatoes & oranges

28. More on Fruit
A complex fruit is derived from more than one ovary resulting in a clustering of smaller fruit elements
Eg. Raspberries, strawberries – not really berries!

29. The parts of the flower and what part they become in the fruit.

30. Fruit or Vegetable?? Botanically:
fruit always develops from a flower and is
composed of at least one ripened ovary.
a vegetable is any edible part of a plant other than the flower.
Most people think:
a fruit is an edible plant part that is sweet and eaten as a dessert.
vegetable is a plant part that is edible, but not particularly sweet.

31. Which is it?
Many fruits, such as tomatoes, squash, cucumbers, corn and eggplant, are popularly called vegetables.
However, only one vegetable, rhubarb (the edible petiole), is used as a fruit.