Chapter 11: Plants Flashcards
Plants
Multicellular, eukaryotic, photosynthetic autotrophs.
What Allowed Plants to Move to Land?
- Cell walls
- Roots and root hairs
- Cutins
- Stomates
- Xylem and Phloem
- Seeds and pollen
The Leaf
Maximizes sugar production while minimizing water loss.
Has a palisade layer (tightly packed) and spongy mesophyll (to allow easy transfer of gases).
Guard cells
Epidermal cells that contain chloroplasts, stomates, and are photosynthetic.
Stomates
The openings where plants lose water by transpiration. When the stomata cells absorb water and become turgid they curve and open the stomate, and the stomate closes when the cells lose water and become flaccid.
Short Distance Transport
- Diffusion
- Osmosis
- Aquaporins (Osmosis of water)
- Cell swelling (Stomates)
Long Distance Transport
- Bulk flow: movement from high to lower pressure.
- Phloem: transports sugars from photosynthesis.
- Transpirational pull: Fluid in the xylem can be pulled upwards.
- Root pressure: fluid in the xylem can be pushed down.
Transpiration
The evaporation of water from the leaves.
Cohesion
The attraction of water to water. Makes it possible to pull a column of water from above within the xylem.
Transpirational Pull-Cohesion Tension Theory
For every molecule that is evaporated at the leaf through transpiration, another is pulled in at the root to replace it.
Factors that Affect the Rate of Transpiration
- High humidity will slow down transpiration, and vice versa.
- Strong winds can reduce humidity, thus increasing transpiration.
- Increased light intensity can increase transpiration.
- Closed stomates will stop transpiration.
Plant Hormones
Can affect the growth, development, and responses to environmental stimuli. Hormones usually do not depend on the raw amount given, but on the relative amounts. Examples include auxin, gibberellins, abscisic acid, cytokinins and ethylene gas.
Signal Transduction Pathways
Can amplify the hormonal signal.
Tropism
Growth of a plant towards or away from a stimulus. Toward a stimulus is a positive tropism, and away is a negative tropism.
Phototropisms
Result from an unequal distribution of auxins on once side of plant away from the light. Since auxins cause growth, the cells on the shady side enlarge, which cause the plant to move toward the light.
