Plant Structure, Growth, and Reproduction

Question 1

meristem

Answer 1

Meristems are tissues containing totipotent/ undifferentiated cells (equivalent to animal embryonic stem cells) capable of indeterminate growth (can go through mitosis to grow/ add new structures forever - as long as have resources to do so)

Question 2

indeterminate growth

Answer 2

can go through mitosis to grow/ add new structures forever - as long as the organism has resources to do so

Question 3

node

Answer 3

where the buds are located. It is the site of great cellular activity and growth.

Question 4

phototropism

Answer 4

the orientation of a plant or other organism in response to light, either toward the source of light ( positive phototropism ) or away from it ( negative phototropism )

Question 5

Shoot

Answer 5

plant stem

Question 6

shoot apex

Answer 6

the very top of the shoot

Question 7

Shoot apical meristem

Answer 7

the meristem at the very top of the shoot. 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).

Question 8

pollination

Answer 8

When pollen (from the anther) is transferred to/ placed on the
stigma of a flower (by means/ vectors of animals, wind, or water)

Question 9

fertilization

Answer 9

Fertilization:
Pollen produces a pollen tube which grows down the style of the carpel
Pollen tube grows into ovary and enters ovule (at micropyle), allowing sperm to fertilize it and produce a zygote

Question 10

seed dispersal

Answer 10

Zygotes develop into seeds, which protect the plant embryo and allow it to be dispersed (by wind, water, fruits, or animals) to other locations (decreases competition for resources/ space)

Question 11

germination

Answer 11

Once a seed encounters favorable environmental conditions, it will germinate (process where a seed begins to sprout).

Question 12

self-pollination

Answer 12

Self-pollination (pollen from anther of same
plant falls on its own stigma – less genetic variation),

Question 13

cross pollination

Answer 13

Cross-pollination
(pollen from anther of one plant carried to stigma of different plant –
increased genetic variation, but longer distance for pollen to travel)

Question 14

photoperiodism

Answer 14

photoperiodism – a plant’s response to the lengths of the night

Question 15

angiosperms

Answer 15

flowering plants: monocots and dicots

Question 16

conifers

Answer 16

seeds are in cones

Question 17

filicophytes

Answer 17

leaflets on stalks (ferns)

Question 18

bryophytes

Answer 18

non - vascular plants (no xylem/phloem) Ex: moss

Question 19

monocot vs. dicot

Answer 19

1 seed leaf vs. 2 seed leaf

Question 20

apical and lateral meristems

Answer 20

gymnosperms and dicots are the only types of plants that have both apical and lateral meristems.

Question 21

Apical Meristems

Answer 21

Allow plants to grow taller (gaining access to more light and CO2), and produce new leaves and flowers/ fruits, and allow roots to extend throughout the soil

Question 22

lateral meristems

Answer 22

Allow plant stems and roots to grow outward
and become thicker, producing secondary
xylem and phloem (vascular cambium) and
cork/bark (cork cambium)

Question 23

apical vs. lateral meristems

Answer 23

1. Apical Meristems (for primary 1° growth):
   -Found at the apex (tips) of roots and stems
   – Allow plants to grow taller (gaining access to more light and CO2), and produce new leaves and flowers/ fruits, and allow roots to extend throughout the soil
2. Lateral Meristems (for secondary 2° growth):
   -On the side (in the cambium)
   –Allow plant stems and roots to grow outward
   and become thicker, producing secondary
   xylem and phloem (vascular cambium) and
   cork/bark (cork cambium)

Question 24

similarities between apical and lateral meristems

Answer 24

Dicots (flowering plants with two seed leaves) and gymnosperms (cone-bearing plants like pines) contain both apical and lateral meristems
Both apical and lateral meristems rely on totipotent cell divisions for growth – this increases plant volume & mass

Question 25

the role of auxin in apical growth in plant stems and in apical dominance

Answer 25

Auxin (IAA - Indole-3-acetic acid) promotes growth in the shoot apex by promoting cell division AND cell elongation by changing patterns of gene expression!
Auxin also 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

Question 26

the role of auxin in phototropism in plants

Answer 26

Auxin promotes growth by lengthening plant cells and altering gene expression (produced by the shoot tip in coleoptiles = the protective sheaths around apical meristems)
Normally, auxin is distributed evenly throughout plant cells in stems so plant stems grow evenly
Auxin efflux pumps (membrane proteins) can actively transport (using ATP) auxin out of cells to redistribute it within plant tissues, creating auxin concentration gradients and causing certain plant tissues to contain higher concentrations of auxin than others.
In stems/ shoots, high concentrations of auxin stimulate cell elongation/ promote growth (cells become larger/ longer and stems grow) by changing patterns of gene expression!

Question 27

micropropagation

Answer 27

Micropropagation is a technique used to asexually reproduce large numbers of identical plants (clones) in vitro (“in glass”)
Micropropagation of plants utilizes tissues from the shoot apex, nutrient agar gels, and growth hormones.

Question 28

micropropagation process

Answer 28

1. Plant tissue is removed from shoot tip (which contains meristematic tissue) & it is sterilized
2. Removed tissue (called explant) is placed on sterile nutrient agar gel to grow. Gel contains high auxin concentration (stimulates cell growth & division)
3. As roots and shoots grow create new tissue (called a callus), shoots can be continuously divided and separated to form more and more new samples
4. Once roots and shoots are developed, plantlets are separated and transferred to soil

Question 29

micropropagation and its applications (as well as pros and cons)

Answer 29

Rapid Bulking
Stock plants with desirable characteristics are cloned, which maintains ALL of the desirable characteristics (because new plants are genetically identical to original plants) - more reliable than selective breeding
Used to quickly create large numbers of genetically modified plants too
Production of Virus-Free Strains
Plant viruses can wipe out crops, cause famine, and harm economies
Plant viruses spread via vascular tissue, which meristems do not contain, so using micropropagation can quickly produce large numbers of virus-free plants from the original non-infected meristems
Propagation of Rare/ Endangered Species
Used to increase numbers of rare or endangered species or species that are difficult to breed (such as orchids, which have very small seeds), or species that are in “high commercial demand”
EXPENSIVE

Question 30

Darwin’s experiments

Answer 30

Darwin cut the tip of the shoot off: He noticed that the plant no longer bent towards the sun. He concluded that the tip of the plant sends messages to the rest of the plant, telling it to bend towards the sun.

Darwin covered the tip in foil: This shows that the reactions were light - based.

Darwin covered the base of the shoot: The plant still bended towards the sun, which shows that the messaging was dependent on the tip

Question 31

Mutualistic relationship

Answer 31

the plant gets pollination and genetic diversity, the animal gets nutrients

Question 32

adaptations of flowers to attract animal pollinators

Answer 32

bright colors, smells, lots of pollen to feed on that is sticky

Question 33

vectors for seed dispersal

Answer 33

Zygotes develop into seeds, which protect the plant embryo and allow it to be dispersed (by wind, water, fruits, or animals) to other locations (decreases competition for resources/ space)

Question 34

environmental conditions necessary for seed germination

Answer 34

Necessary favorable conditions:
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)
Additional favorable conditions required by some seeds:
Fire (sprouting occurs after intense heat exposure - fires clear areas for new seeds to germinate with less competition)
Freezing (germination occurs in spring, only after exposure to winter/ extreme cold)
Digestion (enzymes in animal digestive tracts help remove seed coat)
Washing (inhibitors on some seeds must be washed away before germination can occur)
Scarification (seed sprouts after seed coat is weakened by physical damage)

Question 35

seed germination

Answer 35

1. Water is absorbed by the seed, which triggers synthesis of gibberellin (gibberellic acid – GA) in the seed
2. GA (a plant growth hormone) turns on genes that synthesize the enzyme amylase
3. Amylase hydrolizes (breaks down) starch (stored in the seed) into the sugar maltose
4. 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)
   
   5. 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)
   6. The cotyledon emerges and produces the shoot’s first leaves

Question 36

long day plants

Answer 36

Long-day plants (short night plants): flower when days are
longer and nights are shorter (midsummer)

Question 37

short day plants

Answer 37

Short-day plants (long night plants): flower when days are
shorter and nights are longer (spring/ autumn)

Question 38

phytochrome

Answer 38

Phytochrome exists in two different forms:
1. Pr (biologically inactive form): in the day, absorbs red light (660nm), which rapidly converts it into Pfr
2. Pfr(biologically active form): in the day, absorbs FAR-red light (730nm), which rapidly converts it back into Pr

Question 39

Pfr and Flowering

Answer 39

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

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

Question 40

red light

Answer 40

Sunlight contains more red light (than far-red light), so Pfr is more predominant during the day and Pr form is more predominant at night

Question 41

far red light

Answer 41

more at night

Question 42

Baby leaves

Answer 42

leaf premordium

Question 43

proton pumps

Answer 43

auxin triggers proton pumps, which sends protons from the cytoplasm to the cell wall, which loosens the cell walls so that they can bend.