9.3 - 9.4 Flashcards
What are Meristems?
Stem cells, indefinite growth, with specific regions of development
Indeterminate Growth
Plants stems which have the potential for indefinite growth
Node
an area on the stem where buds are located
Tropism
a directional response in a plant to an external stimulus
Phototropism
A positive tropism in plant stems (growing towards the light) negative tropism in roots (grow away from light into the ground)
Shoot
The stem together with the leaves
Shoot apex
The top of the shoot, also called the shoot apical meristem
Pollination
When pollen (from the anther) is transferred to the stigma of a flower (through animals wind or water)
Fertilization
The fusion of haploid nuclei (male pollen fuses with the female ovule to produce a diploid zygote)
Seed Dispersal
Seeds are moved away from the parent plant to reduce competition for resources) in various ways (animals, water, wind, or fruit - note that fruits provide more protection too)
Steps of germination
- Water is absorbed by the seed, which triggers synthesis of gibberellin (gibberellic acid – GA) in the seed
- GA (a plant growth hormone) turns on genes that synthesize the enzyme amylase
- Amylase hydrolizes (breaks down) starch (stored in the seed) into the sugar maltose
- Maltose is hydrolized into glucose (for cellular respiration – ATP) or condensed/ polymerized (for production of cellulose to build cell walls in new cells being formed)
- Now that the seed is metabolically active, the seed coat (testa) ruptures and the radicle (embryonic root) grows into the ground (water, nutrients, and minerals)
- The cotyledon emerges and produces the shoot’s first leaves
Self-pollination
pollen from anther of same plant falls on its own stigma – less genetic variation
Cross - pollination
pollen from anther of one plant carried to stigma of different plant – increased genetic variation, but longer distance for pollen to travel
Photoperiodism
plant’s response to the lengths of the night
Angiosperm
-flowering plants
-have stems, roots, and leaves
-seeds (in fruit)
-ex: flowers
Gymnosperms (conifers)
-leaves roots and stems
-seeds (in cones)
-woody stems
-ex: conifers
Filicophytes
-leaves roots and stems
-reproduce with spores
-leaves are pinnate
-ex: ferns
Bryophytes
-no leaves roots or stems
-reproduction with spores
-anchored by rhizoids
-ex: mosses
What do gymnosperms and dicots have in common?
They are the only types of plants that have both apical and lateral meristems
Compare apical and lateral meristems
-Both apical and lateral meristems rely on totipotent cell divisions for growth
-apical meristem growth occurs at the apex of stems and roots, whereas lateral meristem growth occurs at the cambium
-apical meristems add vertical growth whereas lateral meristems adds lateral growth
-apical meristems produce new leaves and flowers whereas lateral meristems produce bark and wood
Auxin in apical growth
-Auxin promotes growth in the shoot apex by inhibiting growth in the lateral/ axillary buds (a condition called apical dominance)
-This allows the plant to use its resources to continue to grow upward toward more light/ CO2
Auxin in phototropism
-promotes growth by lengthening plant cells and altering gene expression
-Auxin efflux pumps transport (using ATP) auxin out of cells to redistribute it within plant tissues, creating auxin concentration and causing certain plant tissues to contain higher concentrations of auxin than others
-high concentrations of auxin stimulate cell elongation/ promote growth
Micropropagation
-A technique used to asexually reproduce large numbers of identical plants
-uses tissues from the shoot apex, nutrient agar gels, and growth hormones
Relationship between flowers and pollinators
-pollinators have a mutualistic relationship with flowering plants (both benefit - animal gets nectar/ pollen and flower is pollinated/ fertilized) and most flowering plants have coevolved with pollinator species
Adaptations of flowers to attract animal pollinators
have large, brightly colored, scented flowers (to attract birds, bats, bees/ other insects etc.), and “sticky” pollen grains (to adhere to pollinator bodies)
Environmental conditions necessary for germination
-Water (to rehydrate the seed, triggers gibberellin production, and triggers further metabolic reactions)
-Oxygen (for aerobic respiration – ATP!)
-pH (optimum in soil/ surrounding environment for enzyme function)
-Ideal temperature (for optimal enzyme activity)
typically warmer temps indicate optimal germination (spring)
Process of seed germination
- Water is absorbed by the seed, which triggers synthesis of gibberellin (gibberellic acid – GA) in the seed
- GA (a plant growth hormone) turns on genes that synthesize the enzyme amylase
- Amylase hydrolizes (breaks down) starch (stored in the seed) into the sugar maltose
- Maltose is hydrolized into glucose (for cellular respiration – ATP) or condensed/polymerized (for production of cellulose to build cell walls in new cells being formed)
- Now that the seed is metabolically active, the seed coat (testa) ruptures and the radicle (embryonic root) grows into the ground (water, nutrients, and minerals)
- The cotyledon emerges and produces the shoot’s first leaves
Role of phytochrome in long day plants
In long-day (short night) plants: more Pfr promotes flowering – when night is LESS than a certain critical length, Pfr levels are higher due to more sunlight exposure and shorter nights; high levels of Pfr activate genes to promote flowering
Role of phytochrome in short day plants
In short-day (long night) plants: more Pfr inhibits flowering (by inhibiting gene expression) – when night is GREATER than a certain critical length, Pfr levels are lower due to less sunlight exposure and longer nights; genes no longer inhibited = promotes flowering
