Reproduction in plants Flashcards
1
Q
What is the conversion to a floral meristem?
A
- Shoot meristems must be converted into a floral meristem to promote flowering, for this to happen a change in gene expression in the shoot apex must occur
- Each plant species needs a unique set of conditions to flower
2
Q
What are the requirements for flowering?
A
- Internal factors: age of plant, molecular signally for food storage and plant health, concentration of hormones
- External factors: temperature, photoperiod (length of day and night), environmental stimuli
3
Q
What role does photoperiod play in flowering? What are ‘long-day’ plants?
A
- Photoperiod triggers flowering
- The length of darkness is measured by phytochromes (photoreceptors)
- ‘long-day’ plants develop flowers when phytochromes detect a period of darkness shorter than a critical length
- In summer and spring the nights are shorter, hence they bloom in those seasons
4
Q
What are ‘short-day’ plants?
A
- They flower when phytochromes detect a period of darkness longer than a critical length
- The nights need to be long enough to activate the flowering genes
- Hence bloom in autumn
- When a long night is interrupted by a burst of light, the plants behave as if it were a short night (long-day plants will flower)
- Long-day and short-day flowering is both stimulated by the duration of the night
5
Q
How can phytochrome detect patterns of light and dark?
A
- It changes between Pr and Pfr
- In daylight it rapidly converts to Pfr
- In darkness slowly or fast converts to Pr
- The names refer to the wavelength of light
6
Q
What doe Pr and Pfr determine?
A
- The more Pr is present, the more time has passed in darkness. As soon as daylight is present most of the phytochrome is in Pfr form
- Pr is sensitive to red light, when phytochrome absorbed red light, it will convert Pr to Pfr (during daylight) fast conversion
- Pfr converts to Pr by exposure to far-red light (slowly) can also be fast
- Sunlight contains more red light than far-red light
- A long exposure to darkness would cause high amount of Pr
7
Q
To what form is phytochrome converted during the night?
A
- Converted to its inactive form (red)
- Phytochrome is slowly converted from its active form (far-red –> Pfr) to its inactive form (red –> Pr)
8
Q
To what form is phytochrome converted in the day?
A
- Converted to its active form (far-red Pfr)
- At night it is Pr, during day Pfr
Check book
9
Q
What is pollination and pollen?
A
- Pollination: The transfer of pollen from the anther of a flower to the stigma. When pollen sticks to the stigma of the flowering plant.
- Transfer of pollen by wind, animals and sometimes water. Most flowering plants rely on animal (insect) pollinators. Done to ensure genetic diversity
- Pollen: multicellular structure containing one of two sperm are produced by anthers
10
Q
What is fertilization?
A
- Fertilization: the fusing of sperm-bearing pollen and the egg to create a diploid zygote and occurs inside the ovule
- They form a pollen tube for the pollen to travel to the ovule
- The ovule develops into a seed, it contains the embryonic plant and a supply of food for germination. They develop into a fruit (any plant structure containing seeds)
11
Q
What is seed dispersal?
A
- Seed dispersal: distribute seeds to new locations for them to colonise in new areas. This can happen through wind, animals and water. Mainly mammals and birds. Done to reduce competition
- Depending on the method of dispersal, the seeds are adapted. Water-dispersed seeds are buoyant (float) and wind-dispersed are light and have spores
- Animal dispersed seeds, are constructed for the mutualistic relationship, defecate seeds after animals consumed them. In non-mutualistic relationships, the seeds have needles
12
Q
Why do flowering plants have mutualistic relationships with pollinators?
A
- The plants receive the benefit of the animal’s delivery service and transport pollen
- Pollinating animals receive the benefit of nutritious sugar-rich nectar (food source) sometimes assist in attracting a mate
- Some flowers are very specific and can only be pollinated by single species of insect called obligated mutualism, one relies on the other for survival
13
Q
What are the female structures of a half-views of animal pollinated flowers?
A
- Pistil (carpel): female part of the flower which is made out of:
Stigma: the sticky area where pollen grains deposit
Style: stalk that supports the stigma and connects with the ovary (pollen tube grows through it)
Ovary: base of the style, one or more ovules (egg which develops into a fruit)
14
Q
What are the male structures of a half view of animal-pollinated flowers? What are the other 3 structures?
A
- Stamen: the male part which is made out of the anther and filament
- Anther: the part that produces pollen
- Filament: stalk that supports the anther
- Petals: structures surrounding the reproductive parts of the flower evolved from leaves and are often coloured to attract pollinators
- Sepals: structures that enclose and protect the developing flower bud, support the flower, underneath the petals
- Receptacle: the thickened part of the stem at the base of the flower
15
Q
Be able to draw a half-view of animal-pollinated flowers.
A
