Detection and Responses Flashcards
What is Phytochrome involved in?
It is a pigment found in many plants and it is involved in several plant growth responses
What are three of the plant growth responses?
- Seed germination: inhibited by far red light and stimulated by red light in many plants
- Shoot elongation: lack of red light and shoots elongate
- Detection of plant spacing: crowded plants receive far-red light from neighboring plants and increase their height
Describe red light and far red light?
- Red light: more direct
- Far red light: reflected light
What is Phototropin?
It is the bending of growing stems toward light sources that have blue wavelengths
Describe how gravity effects plant growth?
- Gravity is sensed along the stem in endodermal cells
- The signaling structures are amyloplasts that sink in the cytoplasm
Describe how a plant moves?
- Plant movement is controlled by cell surface proteins, water potential, and plant hormones
- They do not have muscles
What are the five types of plant movement?
- Photomorphogenesis
- Thigmomorphogenesis
- Phototropisms
- Thigmotropism
- Gravitrophisms
Describe Photomorphogenesis?
-Development in plants is triggered by light
Describe Thigmomorphogenesis?
- Effects the way the plant grows due to “touch”
ex. If a plant is growing on a hill, it will grow larger trunks
Describe Phototropisms?
-Plants will grow toward the light
Describe Thigmotropism?
- Plants grow toward mechanical stimuli
ex. vines grow up walls because they grow toward pressure/touch
Describe Gravitrophisms?
- Plants grow directionally due to earths gravity
ex. Plants detect gravity so they know which end their roots should go
Describe turgor and touch related turgor?
- Turgor: the rigidity of cells, mainly due to fluid absorption
- Touch induced plant movements involve reversible changes in turgor pressure
- If water leaves turgid cells, they may collapse
- If water enters limp cells, they become turgid
- These cells are known as pulvini (area of stem that is effected by turgor changes)
What are two examples of touch responses?
- Snapping of a venus fly trap
- Curling of tendrils
Describe light related turgor?
- Some turgor movements are triggered by light which maximizes photosynthesis
ex. Sunflowers face the sun ALL DAY which is a turgor light response (not a growth response)
ex. Bean leaves are horizontal during the day when their pulvini are rigid but are more/less vertical at night as pulvini lose turgor
Describe gravitrophism?
- Shoot exhibit = negative gravitrophism (grow away from gravity)
- Roots exhibit = positive gravitrophism (grow with gravity)
Describe Auxin and what it causes in plants?
- It accumulates on the lower side of the stem due to amyloplast position
- It causes asymmetrical cell elongation and curvature of the stem upward
ex. If a plant is turned sideways, its stem will begin to grow longer on the bottom side so that the plant will be growing upright still
Where is gravity percieved in a plant?
- In the roots, the cap is where gravity is detected
- Once detected, signaling triggers differential cell elongation and division
Describe dormancy?
- Dormancy = results in cessation of growth during unfavorable conditions
- Often results in Abscission (dropping of leaves/petals)
- This conserves resources
Describe hormones in plants?
- Chemicals produced in one part of an organism and are transported to another where they exert a response
- In plants, hormones aren’t produced by specialized tissues
Describe Auxin?
- One effect is that is causes an increase in plasticity of the plant cell wall
- It is produced in the lit tip of plant and then migrates to the opposite side (dark side)
- It causes elongation of the cells on the dark side of the plant which therefor causes the plant to bend
Describe Cytokinins?
- Produced in the root apical meristems and developing fruits
- It stimulates cell division and differentiation and promotes growth of lateral buds into branches
- There is also a plant pathogen that introduces genes into the plant genome that increase production of both cytokinin and auxin = causes massive cell division and formation of crown gall tumor
Describe Gibberellins?
- Gibberellins acid hastens seed germination
- Used to extend internode length in grapes which results in larger grapes
Describe Ethylene?
-It’s a gas
-It retards growth by…
Suppressing stem and root elongation
Controlling leaf, flower, and fruit abscission
Hastens fruit ripening
Describe Abscisic Acid?
- Is synthesized main in mature green leaves, fruits, and root caps
- It induces the formation of dormant winter buds
- Counteracts gibberellins and auxin
- It is needed for dormancy in seeds and is important in opening and closing the stomata
What are the three systems that cause animal responses to the environment?
- Sensory
- Endocrine
- Nervous
What are exteroceptors and interceptors in sensory receptors?
- Exteroceptors: sense external stimuli
- Interoceptors: sense internal stimuli