1. Monocot vs. Dicot Angiosperms are divided into monocots and dicots
As the zygote grows into the embryo, the first leaves of the young plant develop and are called cotyledons (seed leaves)
Monocots have one cotyledon (corn, lily, etc).
Dicots have two cotyledons (bean, oak, etc).

5. FEATURE
MONOCOTS
DICOTS
Cotyledons 1 2
Leaf venation
parallel
broad
Root system
Fibrous
Tap
Number of floral parts
In 3’s
In 4’s or 5’s
Vascular bundle position
Scattered
Arranged in a circle
Woody or herbaceous
Herbaceous
Either

6. Life cycles
From Outlaw’s lecture series

7. Angiosperm life cycle Floral structure Gametophytes Today
From Outlaw’s lecture series

8. Monocot seed development
typical monocot (maize)
seed with ovary wall (pericarp)
Monocots have one cotyledon (scutellum in grasses) that matures during germination
Source of nutrition for seed germination: endosperm
(compare to dicot)
Maize fruit and seed

9. Dicot seed development
dicot - two cotyledons
mature
immature
Three tissue systems:
Dermal
Vascular
Cortex or Ground
All cells of the primary growth in dicots are part of these three systems and originate at meristems
. . . A reminder that endosperm is formed in all angiosperms, but does not persist in dicots. In dicots, cotyledons are the primary source of nutrients for germination.

11. Seed germination What causes a seed to resume growth? What is growth?
Broadly, where do the energy and basic elements required for growth come from?
What observations did you make while germinating seeds?
Plants-In-Motion
Time-lapse videos of plant growth and response

13. Dicot germination and seedling
An example of epigeous (epi=above, geo=earth) germination

14. Dicot germination and seedling
An example of hypogeous (hypo=below, geo=earth) germination

15. Monocot germination and seedling

16. Root the first structure to emerge from the germinating seed
Typical dicot
Taproot persists and grows deep into the ground
Typical monocot
Taproot does not persist and adventitious roots originate from the shoot
Notice the high surface volume: area ratio

17. Roots - Comparisons Fibrous roots: Taproots:
Typical of dicots, primary root forms and small branch roots grow from it
In monocots mostly, primary root dies, replaced by new roots from stem

18. Tap Root vs. Fibrous Root
What are the functions of roots?
From Outlaw lecture
Typical of a dicot
Typical of a monocot

19. Organization of the plant body
Meristem = group of perpetually “embryonic” cells
Apical = at the tip (of the root, the shoot, including laterals)

20. Diagram of major parts of primary dicot plant body
Vascular tissue is throughout the plant body

21. Ground tissue of typical dicot root and shoot
Buttercup (Ranunculus)
Shoot
Alfalfa (Medicago)

22. Vascular tissue of typical dicot root
Buttercup (Ranunculus)

23. Dicot Root
The Casparian strip is a layer of impermeable lignin and suberin that does not permit water and mineral ions to pass between adjacent cell walls. The only access to the vascular cylinder is through the endodermal cells themselves.

24. Monocot Roots

25. Secondary Growth (root)
Example cross section of the dicot root in primary growth
The cambium (perpetually meristematic layer between xylem and phloem) divides mitotically, producing either:
A secondary xylem cell to the inside and a replacement cambial cell. OR
A secondary phloem cell to the outside and a replacement cambial cell.
Secondary growth rare in monocots
From Outlaw’s lecture

27. Roots – Structure and Development
Epidermis
Primary phloem
Primary xylem
Pith
Monocot
Eudicot
Endodermis
Cortex
Pericycle
48 µm
385 µm
8 µm
Location of
Casparian strip

28. Vascular tissue of typical dicot shoot
Alfalfa (Medicago)

29. Herbaceous dicot stem

30. Monocot stem

31. Primary tissues differently organized in angiosperm shoots
Typical of monocots
Typical of dicots

32. Example dicot stem cross section
Primary tissues differently organized in angiosperm shoots
Example dicot stem cross section
vascular bundles in ring with defined pith and cortex
Shoot
Alfalfa (Medicago)

33. Example monocot stem cross section
Primary tissues differently organized in angiosperm shoots
Example monocot stem cross section
vascular bundles scattered
Maize (Zea)

34. Secondary Growth (shoot)
Example cross section of the dicot shoot in primary growth
The cambium (perpetually meristematic layer between xylem and phloem) divides mitotically, producing either:
A secondary xylem cell to the inside and a replacement cambial cell. OR
A secondary phloem cell to the outside and a replacement cambial cell.
From Outlaw’s lecture