Chapter 22 (Raven)

Question 1

How is polarity important in embryonic development of plants?

Answer 1

essential first step, because it fixes the structural axis of the body (“backbone”) on which the lateral appendages will be arranged.

Question 2

What are the three primary meristems of plants and which tissues do they form?

Answer 2

1. protoderm forms the dermal tissue system
2. procambium forms the vascular system
3. ground meristem forms the ground tissue system

Question 3

Through what stages do embryos of eudicots develop? How does embryo development in monocots differ from that in eudicots?

Answer 3

1. globular stage (no development of cotyledons)
2. heart stage (monocots form only one cotyledon and become cylindrical instead)
3. torpedo stage (elongation of cotyledon and primary meristems) (in monocots, the cotyledon often looks like the dominating structure due to size.)
   4.

Question 4

What are the main parts of a mature monocot or eudicot embryo?

Answer 4

it consists of an axis bearing one or two cotyledons. (in flowering plants) the shoot and root apical meristems are at opposite ends. epicotyl with a plumule, hypocotyl below the cotyledons, radicle below the hypocotyl.

Question 5

What phenomena, or processes, characterize seed maturation, the second phase of seed development?

Answer 5

build up of stored food, dessication occurs, and seed coat hardens.

Question 6

Of what significance is seed dormancy to the plant?

Answer 6

ensures that the conditions will be favorable when growth does occur, allows passage of seeds through the digestive tract of some animals, and are closely linked to the ecological conditions in their particular habitats.

Question 7

What are the two phases of seed development?

Answer 7

embryogenesis and seed maturation

Question 8

What is embryogenesis?

Answer 8

it establishes the body plant of the plant, by two superimposed patterns: apical-basal pattern and radial pattern.

Question 9

What is the apical-basal pattern in embryogenesis?

Answer 9

it is the first three stages of embryo development, where the seed is dividing into two cells (apical and basal, asymmetrically), then three (basal remains, apical divides again), then proliferates.

Question 10

What is the radial pattern in embryogenesis?

Answer 10

it refers to concentrically arranged tissue systems.

Question 11

What is the name of the upper pole in plant polarity?

Answer 11

the chalazal

Question 12

What is the name of the lower pole in plant polarity?

Answer 12

the micropylar

Question 13

What names does the seed go through as it develops?

Answer 13

1. one and two celled zygote
2. three celled proembryo
3. four celled proembryo
4. embryo proper with formation of the protoderm (2 celled suspensor at bottom)
5. embryo proper forms a notch, all three meristems present, suspensor present and mature
6. embryo is mature, with all typical parts, and the suspensor is gone.

Question 14

How is the protoderm formed?

Answer 14

by periclinal divisions (divisions parallel to the surface)

Question 15

the ground and procambium meristems are formed by…

Answer 15

vertical divisions within the embryo

Question 16

in angiosperms, the apical meristem arises between the…

Answer 16

cotyledons, or on one side of the cotyledon, in the case of monocots. in monocots, its also surrounded by a sheathlike extension from the base of the cotyledon.

Question 17

True or False. the suspensor of angiosperms is metabolically active.

Answer 17

True.

Question 18

the suspensor goes through programmed cell death during which stage?

Answer 18

the torpedo stage.

Question 19

True or False. the embryo transmits inhibitory signals to the suspensor to keep it from developing into an embryo.

Answer 19

True.

Question 20

If a radicle cannot be distinguished, the embryonic axis below the cotyledon is referred to as…

Answer 20

the hypocotyl-root axis.

Question 21

What is the first structure to immerge from most seeds?

Answer 21

the root (or radicle) called the primary root or taproot.

Question 22

What are the branches of the primary root called?

Answer 22

lateral roots.

Question 23

In monocots, the primary root is…

Answer 23

shortlived.

Question 24

How do monocots form roots after the loss of the primary root?

Answer 24

they form stem-borne roots which arise at the nodes and then produce lateral roots.

Question 25

What is the difference between epigeous or hypogeous seed germination?

Answer 25

in epigeous germination, the cotyledons extend above ground. With hypogeous germination, they remain below ground.

Question 26

What does it mean when a seed is established?

Answer 26

it no longer depends on the stored food of the seed for nourishment, it is a photosynthesizing, autotrophic organism, and the seedling phase has come to an end.