Plant Structure, Growth and Reproduction Flashcards
Which process is linked to the plant adaptation of having bright colors
Pollination
Describe the conditions needed for seed germination.
-water needed to rehydrate the seed
-gibberellin active after water absorbed
-gibberellin needed to produce amylase;
-water needed to allow substances inside the seedling to be transported;
-oxygen needed for (aerobic) cell respiration;
-warmth needed to speed up metabolism/enzyme activity;
-warmth indicates that it is a favourable season for germination/spring;
-some seeds need a cold period to stimulate germination;
-some seeds need fire to stimulate germination
-some seeds need to pass through an animal (gut) to stimulate germination
In long day plants…
Levels of Pfr activate genes to promote flowering
In short day plants…
high levels of Pfr inhibit flowering by inhibiting gene expression
Pfr levels increase when..
there is more sunlight exposure
What is the active form of phytochrome?
Pfr
What is the inactive form of phytochrome?
Pr
Short day plants must have…
at least 12 hours of uninterrupted night in order to flower
Define seed dispersal and its purpose.
Process in which seeds move away from the parent plant to prevent resource competition.
What is the process of pollination?
When pollen (from the anther) is transferred to/ placed on the stigma of a flower (by means/ vectors of animals, wind, or water)
What happens when a seed germinates?
The seed begins to sprout (dependent variable in seed germination experiment)
Describe the effect of drop height on distance traveled by seeds.
Lower drop height means the seed as an increased chance of simply landing on the ground. Higher drop height means increased chance that the distance will increase because the likelihood of being caught by wind increases.
State some advantages of seed dispersal via animals.
-Deposited in feces with organic matter
-Digestion may crack seed coat, allowing better germination
-Further distance travelled
State the disadvantages of seed dispersal.
-Deposited in a poor environment
-Predation
Magnification=
image size/actual size (in um)
What aspects must be included in a seed germination experiment?
-Control
-Independent variable
-Dependent Variable (how many seeds have sprouted)
Clue: Plant has Flowers
Classification: Angiospermophyta
Clue: Plant has cones
Classification: Coniferophyta/ Gymnospermophyta
Clue: Plant does not produce seeds, has fern-like leafs
Classification: Phylum Filicophyta
Clue: Plant does not have vascular tissue
Classification: Phylum Bryophyta
What allows almost all plants to have indeterminate growth?
meristems
What is auxin?
A plant hormone that shifts gene expression in a plant to loosen plant cell walls to cause elongation on the shaded side of the plant, resulting in phototropism
What is the role of auxin efflux pump?
Utilizes ATP to pump auxin to the shaded side of the plant stem.
Cell division occurs at a high rate in the….
plant meristem
Steps of Micropropagation
- Uses the shoot apex which is sterilized and placed into a sterile nutrient agar gel.
- This agar gel contains high concentrations of auxin which stimulates growth and cell division.
- The shoots, after the roots have developed, can be separated and transferred to soil to create additional plants.
What are the two types of meristems found in plants?
Apical and Lateral
Compare growth due to apical vs. lateral meristems.
-Both apical and lateral meristems rely on totipotent cell divisions for growth.
-Meristems are regions where cells continue to divide and grow.
-Apical meristems contribute to vertical growth while lateral meristems increase diameter.
-Apical meristems produce new leaves and flowers while lateral meristems produce new xylem and phloem.
Auxin always changes….
gene expression
What is photoperiodism?
Response of the plant to length of night
Sunlight contains more…
red light
Pfr absorbs more…
red light
Pr absorbs more…
FAR red light
In plant shoots, auxin…
promotes cell elongation
In plant roots, auxin…
inhibits cell elongation (creates a negative phototropism)
What are meristems?
Undifferentiated cells in the roots or stems of a plant that allow indeterminate growth.
What is a node?
a section of growth located in the stem
What is self-pollination?
pollen from the anther of a plant falls on its own stigma
What is cross-pollination?
Pollen from the anther of one plant is carried to the stigma of another (increases variation)
What is a monocot?
One seed leave (grasses, orchids)
What is a dicot?
Two seed leaves (roses)
What are the two types of plants that have both apical and lateral meristems?
Gymnosperms and dicots
What is apical dominance?
Promotes growth in the apex and inhibits growth in the buds
What are the adaptations of flowers pollinated by animals?
-Heavily scented
-Brightly colored
-Sticky pollen to attach to animals
What are the pros of micropropagation?
-Used to save rare and endangered plant species
-Used to improve crops by singling out traits such as disease and pest resistance.
-Prevent famine caused by plant viruses.
-Viruses infect vascular tissue not present in the meristems used, allowing the production of large amounts of virus free plants.
What are some cons of micropopagation?
-Mistrusted by the general population
-Plants all become clones of one another, meaning a single strand could wipe out an entire population
-Expensive
-High Tech
What are some examples of vectors of seed dispersal?
Fruit, animals, wind, water
Darwins’ Experiment #1
removed the coleoptile tip and the response did not change, demonstrating that the tip played a crucial role in carrying out phototropism
Darwins’ Experiment #2
covered the coleoptile tip which indicated that the tip require a response to light to carry out phototropism
Darwins’ Experiment #3
Covered the lower portion of the stem which determined that the tip played the sole role in the plant’s response to light.
What is the function of anthers?
Where male sex cells (pollen) is produced
What is the function of the stigma?
Sticky to collect pollen grains
What is the function of the style?
Transport pollen to the ovule
What is the function of the ovary?
Helps to protect the ovules once they become seeds, can be in the form of fruit
What is the function of the filament?
To support the anther
What is the function of sepals?
To protect the reproductive organs
What is the function of petals?
To attract pollinators
What does xylem transport?
water and dissolved minerals
What does phloem transport?
Nutrients
What is the epicotyl?
Embryo shoot
What is the radicle?
Embryo root
What is the micropyle?
Hole through which water can enter
What is the Cotyledon?
Contains food stores
What is the testa?
Seed coat
Explain apical growth in plant shoots, including the role of auxin.
-Occurs at apexes of stems and roots
-Add vertical growth to roots and stems for increased absorption
-Produce new leaves and flowers
-Develops into primary xylem and phloem
-Growth at these regions is due to cell elongation AND mitosis
-growth in shoots is indeterminate
-phototropism towards the light
-Activates proton pumps in cells; Protons (H+ ions) are pumped from cytoplasm to cell walls which decreases the pH, loosening cellulose fibers by breaking the bonds between them (more elastic)
What is apical dominance?
Auxin promotes growth and cell division in the shoot apex by inhibiting growth in the lateral buds
What is the shoot apical meristem and what occurs there?
-At the very top of the shoot is the shoot apical meristem
-Cells in the shoot apical meristem actively carry out mitosis & cell division repeatedly to generate the cells needed for extension of the stem and development of the leaves (and flowers).
Explain the process of phototropism in plants, including the role of auxin.
-auxin is a plant hormone produced by the tip of the stem
-Normally, auxin is distributed evenly throughout plant cells in stems so plant stems grow evenly
-auxin efflux pumps set up concentration gradients;
-causes transport of hydrogen ions from cytoplasm to cell wall;
-decrease in pH breaks bonds between cell wall fibres
-makes cell walls flexible
-positive phototropism is growth towards light
-If one side of a plant receives more light (detected by shoot tip), auxin efflux pumps redistribute auxin so that the SHADED side of the plant has a HIGHER concentration of it.
-More auxin = more growth/ cell elongation
-Upregulates the expression of expansin genes, further increasing elasticity of cell walls, so cells on SHADED side of stem elongate (turgor pressure), and plant stem bends TOWARD the light
What are coleoptiles?
Produce auxin, the protective sheaths around apical meristems
How does auxin work?
-Upregulates the expression of expansin genes, further increasing elasticity of cell walls, so cells on SHADED side of stem elongate (turgor pressure), and plant stem bends TOWARD the light
What is the relationship between flowers and pollinators?
-Animal-pollinated plants have large, brightly colored, scented flowers (to attract birds, bats, bees/ other insects etc.), and “sticky” pollen grains (to adhere to pollinator bodies)
-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
What is the process of fertilization?
The fusion of haploid nuclei (the male pollen grain fuses with the female ovule to produce a diploid zygote)
Explain the process of photoperiodism in long-day and short-day flowering plants (including the role of phytochrome).
-flowering affected by light
-phytochrome exists in two forms: Pfr and Pr
-Pr (red absorbing) converted to Pfr (far-red absorbing) in red or day light;
-sunlight contains more red than far red-light so Pfr is more abundant during the day because more Pr is produced and converted to PFr;
-gradual reversion of Pfr to Pr occurs in darkness;
-Pfr is active form / Pr is inactive form
-in long-day plants, flowering induced by dark periods shorter than a critical length / occurs when day is longer than a critical length;
-enough Pfr remains in long-day plants at end of short nights to stimulate flowering;
-Pfr acts as promoter of flowering in long-day plants;
-short-day plants induced to flower by dark periods longer than a critical length/days shorter than a critical value;
-at end of long nights enough -Pfr has been converted to Pr to allow flowering to occur
-Pfr acts as inhibitor of flowering in short-day plants
Outline how knowledge of photoperiodism can be used to induce short-day plants to flower out of season.
Long-day plants (spinach, carnations, lettuce): to promote flowering, plants are purposefully exposed to a light source or a burst of light during the night (lengthening light exposure and minimizing time of darkness)
Short-day plants (chrysanthemums, poinsettias): to promote flowering, plants are purposefully covered with a black cloth for 12-15 hours a day until flower buds begin to grow/ show color. Note that if the period of darkness is interrupted with a burst of light, short-day plants will not flower.
Plant Hormones
-Called phytohormones
-Plant hormones released from the shoot apex control stem growth and the formation of new nodes
