Seed Dormancy and Development

Question 1

Dead layer of cells that act as the protective layer of the seed

Answer 1

Testa (Seed coat)

Question 2

Protective structure on fruits

Answer 2

Pericarp

Question 3

Absorbing organ of grains

Answer 3

Scutellum (Modified cotyledon)

Question 4

Seeds with starchy or oily and fatty endosperms

Answer 4

Endospermous Seeds

Question 5

Food source of non-endospermic seeds

Answer 5

Cotyledons

Question 6

May arise from the embryo itself or from the surrounding tissues, such as the endosperm and seed coat. It is a physiological state where a viable seed fails to germinate, even under favorable environmental conditions

Answer 6

Seed Dormancy

Question 7

Primary hormones regulating seed dormancy

Answer 7

Abscisic Acid and Gibberellins

Question 8

Causes pre harvest sprouting

Answer 8

Extensive wet weather

Question 9

Causes embryos to germinate directly on the cob while attached to the parent plant

Answer 9

ABA deficiency

Question 10

ABA and GA levels during seed development

Answer 10

• During early stages: ABA is high while GA is low promoting dormancy
• During germination: ABA declines while GA increases

Question 11

Breaks dormancy in many small seeds

Answer 11

Light

Question 12

Also capable of breaking seed dormancy

Answer 12

Nitrate (NO3-), Nitric Oxide (NO), and smoke

Question 13

Process where seeds are subjected to specific temperature and moisture conditions to stimulate germination and overcome dormancy

Answer 13

Stratification

Question 14

Reasons why isolated embryo grows faster than when in intact seeds

Answer 14

• Devoid of protective layers
• Faster absorption of water

Question 15

Phase 1 of Seed Germination

Answer 15

The dry seed takes up water rapidly via imbibition (water potential), which ceases when all binding sites of water become saturated. The hydration activates basal metabolic processes

Question 16

Effect of Phase 2 on solute potential

Answer 16

The solute potential becomes more negative due to the breakdown of stored food reserves

Question 16

Phase 2 of Seed Germination

Answer 16

Water uptake declines until the water potential gradient is reestablished. The metabolic processes, transcription, and translation are reinitiated. The embryo expands and the radicle emerges from the seed coat.

Question 17

Signifies the end of germiantion

Answer 17

Radicle Emergence

Question 18

Phase 3 of Seed Germination

Answer 18

Water uptake resumes and the stored food reserves of the seed are fully mobilized

Question 19

Stimulated by gibberellins to secrete hydrolytic enzymes (such as alpha-amylase) into the surrounding embryo making starches available to the embryo. Enhanced via mRNA expression

Answer 19

Cereal Aleurone

Question 20

Constitutes the endosperm

Answer 20

Starch stored in amyloplast

Question 21

Gibberellin receptor that promotes the degradation of negative regulators of alpha-amylase production, including DELLA proteins, thereby up-regulating GA-MYB proteins and alpha-amylase transcription

Answer 21

GID1

Question 22

Inhibits alpha-amylase transcription

Answer 22

Abscisic Acid

Question 23

Roles of alpha and beta amylase

Answer 23

Alpha-amylase: Hydrolyze large starch chains consisting of alpha 1-4 glucose residues
Beta-amylase: Degrades oligosaccharides into maltose

Question 24

Period between radicle emergence and exhaustion of seed reserve, appearance of first leave, stage at which environmental factors exert selective pressure on seedling survivorship

Answer 24

Seedling Establishment

Question 25

Growth in response to stimuli

Answer 25

Tropism

Question 26

Lateral redistribution of auxin in response to gravity

Answer 26

Gravitropism

Question 27

Hypothesis that suggests that auxin accumulates on the lower side of a plant organ in response to gravity, promoting differential growth

Answer 27

Cholodny-Went Hypothesis

Question 28

Second messengers in the signaling that occurs during gravitropism

Answer 28

pH and Ca2+

Question 29

Auxin transport towards the root-shoot junction

Answer 29

Basepatal

Question 30

Auxin transport towards apex of the root

Answer 30

Acropetal

Question 31

Redirects auxin laterally back into the vascular parenchymal tissue. Found in the hypocotyl

Answer 31

PIN3

Question 32

Directs vertical auxin back movement from shoot to root. Also responsible for auxin recirculation in the shoot apical meristem

Answer 32

PIN1

Question 33

Mediates auxin movement to root tip

Answer 33

ABCB19

Question 34

Regulates auxin levels in root hairs

Answer 34

ABCB4

Question 35

Lateral redistribution of auxin in response to light

Answer 35

Phototropism

Question 36

First step in phototropic bending

Answer 36

Phototropin 1 phosphorylates the ABCB19 auxin transporter to inhibit rootward auxin transport

Question 37

Developmental process where seeds develop in the dark

Answer 37

Skotomorphogenesis

Question 38

Suppresses photomorphogenesis in etiolated shoots

Answer 38

Gibberellins and Brassinosteroids