Ch 41 - Sensory Systems in Plants

Question 1

Phototopisms

Answer 1

Bending towards light of blue wavelengths

Question 2

Gravitropism

Answer 2

Roots grow in direction of gravity
Stems grow in opposite direction
Gravity sensed along length of stem in endodermal cells
The root cap also sense gravity
Auxin gathers on lower side of stem to curve stem up

Question 3

Mechanical Stimuli Response

Answer 3

Thigmomorphogenesis: responds to mechanical stress, permanent change
Thigmotrophism: direction growth in response to contact
Movement to catch more light
Tilting of leaves to catch light

Question 4

Mimosa pudica

Answer 4

Pulvini: swollen structures at base of leaflets

With stimulation, leaves fold

Question 5

Water & Temp Response

Answer 5

Affect length of growth
Dormancy often occurs
Dropping of leaves - called Abscission
Abscission Zone at base of petiole is where leaves fall off

Question 6

Hormones

Answer 6

Chemicals produced and transported to create a response

Question 7

Plant Hormones

Answer 7

Auxin
Cytokinins
Gibberellins
Ethylene
Abscisic acid

Question 8

Auxin

Answer 8

Promotes elongation of cells
Promotes formation of lateral roots
Plant bends towards the light by elongating cells on dark side
Stimulates ethylene production

Question 9

Cytokinins

Answer 9

Produced in root meristems and fruit
Guide cell division and differentiation
Promote growth of lateral buds into branches
If Auxin and cytokinin are in equal amounts, produces mass of undetermined cells

Question 10

Gibberellins

Answer 10

Acidic
Affect stem elongation
Hasten seed germination

Question 11

Ethylene

Answer 11

Gaseous hydrocarbon
Suppresses stem and root elongation
Controls leaf flower and fruit abscission
Hastens fruit ripening

Question 12

Abscisic Acid

Answer 12

Synthesized in mature leaves, fruits and root cap
incudes formation of dormant winter buds
Suppresses bud growth
Promotes senescence
Role in opening and closing stomata
Prevents early seed germination