Chapter 22: Early Development of the Plant Body 1. Mutations Describe how the st

Question

Chapter 22: Early Development of the Plant Body

1.    Mutations

Describe how the study of mutations that disrupt the basic patterns of development in plants have helped to identify key regulators of embryogenesis. Give an example

2.    Formation of the Embryo

Discuss the concept of polarity as it pertains to angiosperm embryogenesis.

3.    Formation of the Embryo

Define the term “primary meristem.” Name the three primary meristems, and name the tissue(s) into which each develops.

4.    Formation of the Embryo

List the principal stages of embryonic development in angiosperms, and describe the appearance of the embryo at each stage.

5.    Formation of the Embryo

Discuss the role(s) of the suspensor during embryogenesis in angiosperms.

6.    The Mature Embryo and Seed

Draw and label the parts of a typical dicot seed with cotyledonary storage (e.g.,garden bean). Draw and label the parts of the mature corn grain.

7.    Requirements for Seed Germination

Define seed dormancy. Discuss some of the ways in which seeds can overcome dormancy.

8.    From Embryo to Adult Plant

Define the terms “epigeous” and “hypogeous,” and give examples of each type of germination.

9.    From Embryo to Adult Plant

Onion (Allium cepa) and maize (Zea mays) are monocots, but they differ in certain features of germination. Outline these differences. Castor is a dicot; draw and label the parts of a castor bean seedling.

Explanation / Answer

Based on the given data,

3)

Apical meristems are located at or near the tip of the plant shoots and roots. These tissues exhibit primary growth and produce three types of primary meristems: protoderm, (produces the epidermis), ground meristem (differentiates into the primary xylem) and procambium (produce all the primary tissues other than the epidermis and vascular cambium).    

7)

Dormancy is the phase in the life cycle of the plant in which active growth is temporarily suspended. The main purpose of dormancy is to enable the plant endure unfavorable conditions. The breaking of the dormancy will takes place by the environmental conditions also by some action of the hormones.

Seed coat plays an important role in causing the dormancy of the seed. The seed coat or testa is composed of several layers of cells and is composed of polysaccharides, hemicellulose, fats, waxes and proteins. During seed ripening the chemical components of seed coat become dehydrated and form a hard tough protective layer around the embryo. Due to impermeability of seed coat, the germination of seed is delayed. After planting hydration of the seed takes place, which will release plant hormones and they helps overcome form dormancy.

8)

Seed germination is a process in which dormant embryo of seed resumes metabolic activities and grows to produce a seedling. There are two types of seed germination on the basis of behavior of cotyledons germination- hypogeal or hypogeous and epigeal or epigeous.

In hypogeal seed germination, epicotyls elongates quickly, pulling the plumule out of the soil surface. Hence, cotyledons do not come over the soil surface, but lie below it. E.g., - rice, wheat, jowar, gram, ground nut etc.

In epigeal germination, the hypocotyls elongates quickly, pulling cotyledons and plumule above the soil surface. E.g. - castor, tamarind etc.

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