Plants Flashcards
Root system-
underground- absorbs
water and minerals from the soil
Shoot system-
aboveground- absorb light and CO2 Stem o Leaves o Flowers/ fruits
Ground tissue system-
plant body–functions in photosynthesis, storage, and support
Vascular tissue system-
conducting system–transports water, minerals, food
Dermal tissue system-
provides covering for plant
Ground tissue system
Composed of 3 different types of tissue. Growing plant cell secretes thin flexible primary cell wall. After stops growing- secondary cell wall- inside primary cell in between plasma membrane and primary cell wall
more rigid and cell can no longer grow after scw
put down. Each of the three tissues contain different types of cell walls, making the structure of the cells range from very soft and flexible (most common parts of plants) to very hard (cells found in wood, bark, nuts, etc)
Xylem
Vascular. conducts water and dissolved nutrient materials from roots to stems and leaves. Cells are hollow and dead at maturity
Phloem
Vascular. conducts food materials (carbs formed by photosynthesis). Cells alive at maturity
Epidermis-
Dermal tissue system. outermost layer of herbaceous plants. Transparent- no chloroplasts. Secrete waxy cuticle which restrict water loss. has stomata.
stomata
pores in epidermis that allow for gas exchange
Guard cells-
surround stomata
Trichomes-
outgrowth or hairs in epidermis (called root hairs in roots)
Periderm-
replaces epidermis in woody plants
Leaf tissues
Upper epidermis covers upper layer, lower epidermis covers lower layer. Mesophyll, bundle sheath, veins
Mesophyll-
photosynthetic ground tissue of the leaf. Loosely arranged with many air spaces- allows for rapid gas diffusion. Palisade mesophyll- closely packed, spongy mesophyll looser.
Bundle sheath-
nonvascular cells surrounding larger veins
Veins-
vascular bundles containing xylem and phloem
Transport in Plant Body
Water and dissolved nutrient minerals are transported from roots to other parts of the plant in xylem- only moves upward. Dissolved sugar is translocated in phloem- can move upward or down. Driven by physical forces, not by a pumping organ
Transpiration-
loss of water vapor by evaporation , mostly through stomata
Environmental factors affecting transpiration:
Higher temps and more light–>stomates to open more
wind and dry air–more transpiration
humidity–less transpiration
Importance: transpiration
responsible for water movement from soil to leaves
cools stem and leaves and Distributes dissolved minerals through plants
how might transpiration be harmful?
Too much transpiration- plant can wilt and die
what cycle is transpiration a part of?
Part of hydrologic cycle- water cycles from ocean and land back to atmosphere, then back to ocean and land Water evaporates from leaves and stems to form clouds in atmosphere
Guttation-
liquid water is forced out of plant. Occurs at night, when no transpiration is occurring but there is moist soil
xylem (water potential)
Remember that water moves from an area of higher water potential to an area of lower (more negative) water potential, meaning an area with more dissolved solutes. When soil is moist, it has a high water potential, although it is slightly negative because it has some dissolved minerals (pure water has water potential of zero). Root cells have a more negative water potential due to many dissolved solutes- therefore water moves by osmosis from soil into root
Tension-cohesion model (or transpiration-cohesion model)
Loss of water through transpiration in leaves causes a tension that extends from leaves down to stems and roots, drawing water up the stem xylem to the leaf cells. Possible only as long as there is an unbroken column of water in xylem throughout the plant- maintained by cohesion of water molecules to each other and adhesion of water molecules to xylem. Because there is a water potential gradient from the least negative (soil) up through the plant to the most negative (atmosphere), water is pulled up from soil through plant. Tension-cohesion model is powerful enough to pull water upward 500 ft.
phloem system
Before loaded into phloem, glucose produced during photosynthesis is converted into sucrose. Fluid can move both upward and downward. Sucrose moves from a source to sink
Controlling water loss at the stomata
Controlled by changes in shape of guard cells
guard cells opening up
Water moves into guard cells- they become turgid and bend slightly, moving apart to produce a pore
guard cells closing
Water leaves guard cells- they become flaccid and the cell walls collapse, closing the pore
How does blue light open stomata?
Pigment in guard cells is stimulated by blue light. Triggers activation of enzymes called kinases located in the cell membrane. These enzymes cause potassium ions to flow in, followed by water bc of water potential, and the stomata open
Closing of stomata
Caused by a hormone called abscisic acid (ABA), which binds to receptors on a guard cell’s plasma membrane. Potassium ions leave the cell, and water follows by osmosis. stomata close.
low conc of CO2 does what to stomata?
opens them
dehydration does what to stomata?
closes
Circadian rhythms-
24 hour cycle of opening and closing stomata
Alternation of generation-
portion of life cycle in multicellular haploid stage, portion in multicellular diploid stages. diploid sporophyte, haploid gametophyte
Gametophyte generation-
haploid- give rise to gametes by mitosis
Pollination-
transfer of pollen grains from anther to stigma.
Double fertilization step 1
Two sperm cells from generative cell move down pollen tube of pollen grain and enter ovule.
Germination
the process of seed sprouting and growth of young seedlings into mature plants
Requirements for germination:
Imbibition, Large supply of oxygen required to power aerobic respiration to energy for germination, between 25 and 30 C, some require light, some require long low temperature period before seeds can break dormancy and germinate
Imbibition
absorption of water by dry seed
Photoperiodism-
response of plant to lengths of daylight and darkness. there is a group that doesn’t respond to photoperiodism
Short-day plants-
flower when night is > 12-14hr
Long-day plants -
Flower when nights are < 12 hr
Intermediate-day plants-
Do not flower when night length is too short or long
Phytochrome-
type of photoreceptor that absorbs light. Absorbs two forms of light- red and far-red
Red light-
present at sunrise, causes phytochrome to shift from inactive form to active form
Far red light
at sunset and darkness shift phytochrome to inactive
pfr
active form phytochrome
What would happen if a pulse of red light interrupted the dark phase in a plant?
activated the phytochrome, which made the plants act as if the night were short
Nastic movements-
quick responses that are temporary and reversible
Tropism-
slower, directional growth response- results in change in position in part of the plant. + or -, but irreversible. Under hormonal control
Phototropism-
growth caused by light.
Gravitropism-
growth in response to direction of gravity.
Thigmotropism-
growth in response to mechanical stimulus, such as contact with solid object. Ex- twirling of stems of vines
why do higher temps and more light cause higher rate of transpiration
more light –> more heat
more light/heat –> stomates to open more
why wind and dry air–more transpiration
bc water potential causes dry air to be less conc than water in stomata; wind blows water vapor away and causes more water to take place
why humidity–less transpiration
bc a lot of water in air already so water potential difference isn’t so stark
pollen grain
A pollen grain contains a tube cell, which forms a pollen tube towards the egg, and a generative cell, which contains two sperm cells.
double fertilization step 2
One sperm cell unites with egg, forming zygote. Second sperm fuses with a central cell found within the ovule that contains two haploid nuclei, forming a triploid (3n) endosperm.
endosperm
surround developing plant in seed, functions as nutrients.
double fertilization reason for name
Called double bc two cell fusions. (“One sperm cell unites with egg, forming zygote. Second sperm fuses with a central cell”)
In flowers- sporophyte and gametophyte n and locations ish
In flowers- diploid sporophyte is large and independent, haploid gametophyte is located in the flower
negative gravitropism-
Stems- grows away from direction of gravity,
positive gravitropism-
Roots- grows toward gravity.
Root cap-
site of gravity perception in roots.
Positive phototropism-
shoot tips bend towards the light. Auxin moves down from the coleoptile, making it grow
Auxin
a plant hormone
coleoptile
the tip of the plant
why do plants bend toward light in phototropism?
Auxin moves faster on through the cells on the side less exposed to light, making them grow longer, so plant bends toward light.
what happens to the ovule and ovary after fertilization?
Ovule develops into a seed, ovary develops into a fruit.
Sporophyte generation-
diploid- forms spores by meiosis
(Pr)
inactive phytochrome
active form phytochrome results
When in active form (Pfr), the phytochrome can induce gene transcription
what happens when genes of plants are transcribed?
seed germination, shoot elongation and branching, leaf expansion, and flower, fruit and seed formation
source (phloem)
area of excess sugar supply (leaf)
sink (phloem)
area of storage/use for sugar
