11.7.3 Embryogenesis in Angiosperms: Dicots and Monocots

Question 1

Embryogenesis in Angiosperms: Dicots and Monocots

Answer 1

• The two classes of angiosperms, dicots and monocots, differ in several characteristics:
· leaf venation
· flower part numbers
· vascular bundle arrangement
· root systems
· number of cotyledons in seeds
• Embryogenesisis a process involving several cell divisions immediately after the egg is fertilized. In plants, embryogenesis is a facet of seed development.
• A seed consists of an embryo and stored food enclosed within a protective shell.
• When the seed is mature, plant development is arrested. The seed can remain dormant for a given period of time before developing into a mature plant.

Question 2

note

Answer 2

• The two classes of angiosperms, dicots and monocots, are named after the number of cotyledons present in the embryonic form. Dicots have two cotyledons, while
  monocots have one. In addition to these distinctions, dicots and monocots differ in several key characteristics, as shown in the chart to the left.
• Review: Two sperm from a pollen grain fertilize the female gametophyte of an angiosperm. One sperm will fertilize the polar nuclei of the female gametophyte, which will form the triploid endosperm, and the other sperm will fertilize the egg cell to produce the diploid zygote.
• In a dicot, the first division during embryogenesis splits the fertilized egg into two cells; the terminal cell and the
  basal cell. The terminal cell will further divide to form most of the embryo. The basal cell divides to produce the suspensor, which is a string of cells that will anchor the embryo to the ovule.
• As the terminal cell divides it forms the proembryo, a
  spherical group of cells attached to the suspensor. Two bumps on the proembryo will continue to develop, forming the two cotyledons. In monocots, only one cotyledon will form.
• A mature monocot seed contains only one cotyledon (also called the scutellum). The thin outer layer of the seed is referred to as the aleurone. The endosperm is the nutrient-rich material that nourishes the embryo.

Question 3

True or false?

Monocots have flower petals in multiples of 3, while dicots have flower petals in multiples of 4 or 5.

Answer 3

• true

Question 4

Dicots are distinguished by their

Answer 4

• net-like veins in leaves.

Question 5

Which of the following statements does not apply to monocots?

Answer 5

• Monocots typically have a taproot

Question 6

Which of the following is not a characteristic of monocots?

Answer 6

• flower parts in multiples of 4 or 5

Question 7

Which of the following statements is incorrect?

Answer 7

• Monocots and dicots are two classes of gymnosperms.

Question 8

The first division that takes place in the zygote of angiosperms produces

Answer 8

• the terminal cell and the basal cell