B3.2 Endocrine System Flashcards
Tropism
Growth response made by a plant in response to a particular stimuli in their environment
Groups of responses that can be split into phototropisms (response to light) and gravitropisms (response to gravity)
Controlled by auxins
Difference between positive and negative tropism
Positive = growing towards direction of stimulus
Negative = growing away from direction of stimulus
Phototropism
Plant growth towards/away from a light source
Stems = positively phototropic
Roots = negatively phototropic
Gravitotropism
Growth of the parts of plants in response to the force of gravity
Stems = negatively gravitrophic
Roots = positively gravitrophic
Another term used for gravitropism
Geotropism
Auxin
Plant hormone that enables a plant to grow towards or away from a stimulus
Produced in roots and shoots
How does auxin cause a response to a stimulus
Stimulus causes an uneven distribution of auxin,
which causes cell elongation on side with auxin resulting in an unequal growth rate,
causing the root or shoot to bend
How plants respond to light
When light hits one side of a shoot the auxin on that side both moves away from the light, and is denatured by the light
This lead to a build up of auxin on shaded side
The cells on the shaded side elongate
Shoot bends towards light
How plants respond to gravity
Gravity causes auxins to gather on the lower side of the root and shoot
In roots auxins collect on lowest side of roots, causing the cells to elongate and grows down towards the force of gravity
In shoots auxins stimulates growth so side with the most auxins elongates and grows down away from the force of gravity
3 plant hormones commonly used in agriculture and horticulture
Auxins
Gibberellins
Ethene
Why is ethene unique to the other two hormones
It is a gas
Hormone is used to help to regulate fruit development, without it fruit is often small.
Auxins
ethene
Ethene is a hormone that stimulates the conversion of starch into sugar which causes fruit to ripen – this is why unripe fruit is not as sweet as ripe fruit.
This hormone is the only plant hormone that is a gas
How is ethene used commercially
To ripen fruit
Stimulate the conversion of starch into sugar which causes fruit to ripen – this is why unripe fruit is not as sweet as ripe fruit.
Gibberellins
Plant hormone that ends dormancy period for seeds and buds causing shoots and flowers to open
Gibberellins cause stem elongations
List the common agricultural and horticultural uses of plant hormones.
Growing cuttings
Tissue culture
Ripening fruit
Killing weeds
Kromoting flowering
Producing seedless fruit
How can plant hormones be used to kill weeds?
Most weeds have broad leaves
Auxin in herbicides causes the broad-leafed weeds to grow too quickly.
They are unable to sustain the high growth rate, causing them to die
how a cutting can be grown.
A cutting is a part of plant removed from the main shoot, so it does not have roots, so it is unable to absorb water or minerals.
Rooting powder containing auxin can be used to stimulate root growth in cuttings.
Tissue culture
Horticulture method using auxin to grow whole plants from a plant tissue sample
Growth of tissues or cells in an artificial medium separate from the parent organism
How have gibberellins made farming more productive?
Gibberellins can be used to end seed dormancy by promoting germination
Enables farmers to control when crops begin to grow - can trigger winter germination in a greenhouse
Enables farmers that plants all grow at the same time - all ready to harvest at same time
Can use to extend growing season/have two growing seasons
How can seedless fruit be produced?
Gibberellins can be sprayed on flowers to stimulate fruit growth, even though there are no seeds.
How can ripening in fruit be delayed
By spraying plants with auxins.
Allows harvesting at the same time
Prevents fruit from dropping from trees to early
Why do horticulturists and gardeners take cuttings and develop them with auxins?
Why do horticulturists and gardeners take cuttings and develop them with auxins?
More cards to be made for b 3.2
Agriculture
farming, including cultivation of the soil for the growing of crops and the rearing of animals to provide food, wool, and other products.
Cutting
A sample of a plant
Dormant
When seeds cannot germinate, due to a lack of optimum conditions
Herbicide
Chemicals in weed killers, that only kill wide leaf plants, such as weeds
Horticulture
Garden cultivation and management
Parthenocarpic fruit development
Fruit without seeds
Stimulus
Conditions around the plant
Thyroxine
Regulates metabolism
Involved in digestion, how heart and muscles work, brain development and bone health
When thyroid gland does not make enough thyroxine (hypothyroidism), many of the body’s functions slow down
Adrenaline
Released at times of stress
Prepares the body for fight or flight responses
Ovulation
Process of releasing a mature ovum into the fallopian tube each month
FSH (pituitary gland)
Causes egg to mature and stimulates ovaries to start producing oestrogen
Oestrogen (Ovaries)
Stimulates build up of uterus lining,
inhibits FSH production,
stimulates LH production
LH (pituitary gland)
Triggers ovulation at peak
Progesterone
Maintains uterus lining
