Flowers and fruits Flashcards
what is the function of flowers?
for pollination and fertilization
what are the 4 concentric rings in an ideal flower, what are they for? what are their parts?
- Sepals → outer ring
Enclose and protect the flower bud before it blooms - Petals →
Typically bright and fragrant to attract pollinators - Stamens → male parts
Filament → the stalk
Anther → produces pollen - Carpels (pistils) → female parts, center of flower
Can be one or more
Stigma → catches pollen
Style → the stalk; connects stigma to ovary
Ovary → contains 1 or more ovules. Ovules turn into seeds, while the ovary will turn into the fruit
what is pollination?
is the transfer of pollen grains from the anther of one flower (where it was formed) to the stigma of another flower. Does not guarantee fertilization.
what is pollination syndrome?
is the set of floral characteristics exhibited by a plant and is associated with a specific type of pollinator
what are floral characteristics?
Flower shape Flower size Colour Odour Timing of flowering Nectar Pollen production
what are the two types of pollinators? examples
Abiotic: Wind Water Biotic: Bats Bess Beetles Birds Butterflies Flies moths
how do plants attract animal pollinators?
use visual cues (colours/patterns) and odours to attract, and reward such as food (nectar and pollen)
what do plants with abiotic pollinators typically look like?
typically have small colourless flowers with no scent that produce a lot of pollen
what are angiosperms? what is there main characteristic?
(flowering plants) → produce seeds that develop inside of ovaries that mature into fruit
what are sporophytes? how are they identifiable?
- adult diploid generation → dominant generation
- Recognizable with roots, stems, leaves, cones/flowers
- Provides nutrition to the non-photosynthetic gametophyte
what is the simplified life cycle of an angiosperm?
Sporophyte → spores → gametophytes → gametes → fuse to form diploid cell
gametophyte adults in angiosperms are:
-microscopic and do not exist as independent photosynthetic plants
where is a male gametophyte plant found, what is it made of?
is found in the pollen grain
made of 2 parts:
1. a tube cell
2. generative cell
why are sperm dependent on pollen tube formation?
Sperm of seed plants are not flagellated and therefore depend on the processes of pollination and pollen tube formation for transport to the ovary
in what state do pollen grains arrive at the stigma? what are the steps involved in pollen tube formation?
- pollen grains arrive at stigma in dehydrated condition and need to take up large amounts of fluid to germinate and form a pollen tube
1. Pollen arrives at stigma
2. Pollen grain take up large amount of fluid;this fluid stimulates the germination of pollen tube
3. Growth of pollen tube involves a pattern of cytoplasmic streaming and allows for rapid construction of new plasma membranes and cell walls
4. As the tube grows, sperm that are produced by the generative cell are carried to the egg for fertilization
what happens to the generative cell? why is it called double fertilization? what happens to the sperm?
- A generative cells produces 2 sperm cells through single mitotic division
- 1 cell fertilizes the egg
- 1 cell joins the 2 polar nuclei of the female gametophyte to produce endosperm (tissue), which is a source of nutrition for the sporophyte embryo during growth (seed germination)
what did pollen/pollination/pollen tube formation allow?
- allowed for movement of life onto land.
- Allows fertilization to occur over great distances without the need for environmental water for sperm to move through
what happens to an ovule? what if there are more than one ovules?
- gets fertilized by sperms and produces a seed
- then each one will be fertilized by a different sperm, each from a distinct pollen grain, and will produce a seed
what are the 3 components of a seed? what do they do?
- Seed coat → hard outer covering which protects from disease and desiccation
- Embryo → the fusion of the sperm and egg; divides by mitosis to eventually form sporophyte plant
- Food source → endosperm; embryo uses this to form meristems until they are big enough to break through the seed coat and begin taking up water and nutrients from the environment
what happens to the ovary as seeds are developing?
the ovary walls thicken into a fruit
what is a pericarp? what are its parts, what are their features?
- Mature ovary
1. Exocarp → outermost layer “skin” - Can be soft, fuzzy, thin, leathery, thick, hard, peelable
2. Mesocarp → middle layer - fleshy, usually the layer that is eaten
3. Endo carp → innermost layer that directly surrounds seed - Can be hard/stoney, papery/thin, or soft/fleshy
what is the function of a fruit?
to protect the dormant seeds inside, and aid in dispersal by either wind or animals
what is the function of a seed?
dispersal and dormancy and nourishment of embryo
what are 4 types of dispersal? how do they do this, and what are an example?
- parachuting/propelling → fruits that have dry outer coverings which catch the wind and carry them away
Eg. wings of a maple fruit
Eg dandelion seeds - barbs/hooks → dry fruits may have barbs/hooks to enable them to cling onto animals fur and be carried away to new locations
eg. longspine sandbur - Explosive dispersal → seed pods of some dry fruits burst open and project seeds away from parent plant
eg. pea pods - Ingestion → fleshy fruits are sweet/nutrient dense/brightly coloured so that animals eat them. They go through the digestive tract and are excreted in feces in a different location
eg. cherries
where are female gametophytes found in angiosperms?
in the ovule
how is an egg produced?
Diploid cells within an ovule divide by meiosis to form haploid megaspores which then divide by mitosis to form a female gametophyte which produces an egg
how is a sperm produced?
Diploid cells within the anther divide by meiosis to form haploid microspores which then divide by mitosis to form the male gametophyte → pollen grain, which produces sperm
how do you calculate percent germination?
Number of germinated pollen grains/ total number of pollen grains X 100%
Eg. 9 grains had tails/21 pollen grains X 100% = 42.9% viable pollen grains
what are tepals?
petals and sepals that are formed together, and look the same
