Flowers Flashcards
What part of the life cycle happens in the ovary of angiosperms/female cone of gymnosperms?
The growth of the sporangium and the production of the spores. The spores grow into whatever remains of the gametophyte, which then produces gametes. Fertilization happens and creates an embryo
What type of leaf did flowers originate from?
Sporophylls
What type of leaf did the carpel originate from?
Megasporophylls
What type of leaf did the anther originate from?
Microsporophylls
What type of leaf did the sepals and petals originate from?
Vegetative leaves
What type of leaf did gymnosperm cones originate from?
All sporophylls, but only either the microsporophyll that became the male cone or megasporophyll that became the female cone
What is spiral phyllotaxy?
Flower pattern seen in some of the dicots. Resembles spiral clusters of sporophylls that got compressed into a flower
What is a complete flower?
A flower with all 4 whorls
What are the 4 whorls in a flower?
- Calyx: all sepals
- Corolla: all petals
- Androecium: male reproductive parts
- Gynoecium: female reproductive parts
What is the calyx? What does it do?
All the sepals of a flower. It protects the developing flower but has been modified in some plants
What is the corolla? What does it do?
All the petals of a flower. They’re usually brightly coloured and/or produce nectar to attract pollinators
What are tepals? What do they do?
Sepals that look identical to the petals in a mature flower. They have the same function as the petals
How are the petals and sepals modified in Lasiopetalum species?
Petals are reduced to just produce nectar, and the sepals have become larger and brightly coloured to attract the pollinators instead of the petals
What are the 2 parts of the stamen? What type of leaf did each one originate from?
Anther and filaments. They both came from the microsporophylls, but the anthers came from the reproductive portions and the filaments came from the vegetative portions
What happens inside the anther?
Microsporogenesis. The microsporocyte undergoes meiosis, which produces 4 haploid microspores. Each one germinates into the microgametophyte, which matures into pollen
What is the difference between gymnosperm and angiosperm pollen?
Gymnosperm pollen has 3 cells instead of 2, it has the generative cell, the pollen tube, and the prothallial cell. Angiosperms only have the generative cell and the pollen tube
What is the megasporangium in angiosperms?
The ovule
What happens inside the carpels?
Megasporogenesis. The megasporocyte undergoes meiosis and produce 4 megaspores, but only 1 will develop further. That one undergoes 3 rounds of mitosis to 7 cells with a total of 8 nuclei among them
What is the structure of the remains of the megagametophyte in angiosperms?
3 Antipodal cells at the top, one large cell with the polar nuclei in the middle, 2 synergids at the bottom on either side of the egg cell
What do the antipodal cells do?
Organizes the other cells of the megagametophyte
What do the polar nuclei do?
Form the endosperm with double fertilization
What do the synergids do?
Guide the pollen tube to the egg cell
How is megasporogenesis different in gymnosperms?
The megasporocyte still 4 megaspores where only 1 survives and develops. But that one develops into a proper megagametophyte in the female cone with archegonia
Why is having the ovary enclosed in the carpal advantageous?
Lets the plant be selective about what pollen pollinates it. Only pollen from the correct species will be able to make the correct interactions with the stigma to germinate
What are 6 modifications of flowers?
- Fusion of sepals or petals into tubes
- Fusion of stamen
- Fusion of all reproductive structures in hibiscus
- Column in orchids
- Ray and disk flowers in Asteraceae
- Reduction of certain flower parts in wind pollinated flowers
How do Drakaea orchids get pollinated?
The labellum mimics a female wasp by secreting pheromones, so when a male wasp lands and tries to fly off with it, the labellum flings it back into the column and covers it in pollen
What are bracts?
Vegetative leaves that are not part of the 4 whorls but can take over function of petals or sepals
