Plants Flashcards
Palisades mesophyll
tightly packed cells containing chloroplasts
Spongy mesophyll
loosely arranged cells with lots of intercellular spaces.
Stomata
Openings in leaves that lead to air spaces.
Transpiration
The loss of water through stomata in plants
Guard cells
specialized leaf cells that control the opening and closing of stomata
Sunken stomata
Stomata that are sunken in order to decrease the rate of wind-caused transpiration
Flowers
Reproductive organs of plants
How does gas exchange in plants work?
- Stomata lets CO2 diffuse into the leaf
- CO2 diffuses into the water lining the leaf
- CO2 enters photosynthesizing cells
- O2 enters through gas pockets in soil, allowing the plant to perform respiration.
How do guard cells work?
- An electrical gradient is established
- An osmotic gradient is established
- Water enters the guard cell and the stomata open
- Water leaves, stomata closes
What are the two types of tissue involved in transport of materials in plants?
Xylem and phloem
Xylem tissue
Transports water and minerals, and provides mechanical support. Basically columns of cell-wall-ness (the cells are technically dead)
Phloem tissue
Transports the products of organic materials, like sugars.
How is water’s movement through xylem explained?
Cohesion-tension theory: TACT. Transpiration, Adhesion (attraction between different substances), Cohesion (attraction between the same substance to itself), Tension (which is created as water moves out of the leaf, pulling more water in)
Plasmolysis
the contraction of the cell away from the cell wall (In plants). Occurs when not enough water is available.
Cell turgor
Rigidity caused by the amount of water in a plant cell
What gas causes ripening?
Ethylene. Positive feedback; as the fruit ripens, more ethylene is released.
Abiotic
non-living
Describe the process of phototropism
Phototropism is plants’ response to light. Auxin is a growth hormone that causes lengthening. When light is unequal on the plant stem, auxin goes to the shady side, causing the plant to bend towards the light
What is gravitropism?
Plants’ response to gravity
What is thigmotropism?
Plants’ response to touch
Dormancy (plants)
Response to unfavourable conditions. Abscission is the loss of leaves or other parts, and Seed Dormancy is a mechanism that allows seeds to delay germination until they have ideal conditions.
On what stimuli does seed germination rely?
- Water
- Oxygen
- Temperature (optimal)
- Fire! Nutrients from burnt stuff, more light for seedlings
- Hormones
Photoperiodism
The response of plants to changes in the photoperiod, the relative length of day vs. night time.
Do plants have circadian rhythms?
Yup.
How do plants maintain their circadian rhythms?
Two forms of phytochrome that convert from one to the other.
- P(r) is synthesized in plant cells
- P(fr) is the active form
- P(fr) accumulates during the day as P(r) is exposed to 660 nm wavelength light (Red light).
- P(r) accumulates at night as it’s not converted
- At daybreak, P(r) is rapidly converted to P(fr)
- Night length resets the circadian rhythms.
When do different plants flower?
- Long day plants flower when daylight is increasing
- Short day plants flower in late summer when daylight is decreasing
- Day neutral plants don’t care. They care about some other stimuli
Structural defenses of plants
Stickyness, spines, etc.
Chemical defenses of plants
Toxins! (like caffeine or nicotine) that kill insects
