Plants Flashcards
Collenchyma
- ground tissue that provide extra mechanical support to the plant, especially where the plant is actively growing
- thick but flexible cell walls
Imbibition
- The absorption of water by the seed
- begins the process of germination in plants
Casparian strip
Helps regulate the type and amount of substances that can enter through the roots and travel to the rest of the plant (via vascular tissue)
What cells make up the phloem
Sieve cells and companion cells
Sieve cells
Long cells with pores that allow substances to flow through them
They lack organelles in order to transport sugars
Companion cells
Have the organelles needed in order to carry out metabolic functions (loading sieve cells with sugars to transport)
Companion cells connect to sieve cells via plasmodesmata (gap between cells that connect their cytoplasms)
What structures make up the xylem
Tracheids and vessel elements
Tracheids
- Long, thin cells that connect to one another via their tapered ends
- Water flows through pits found at the ends of tracheid cells
- Also provides structural support (along with allowing the flow of water throughout the plant)
Vessel elements
- Shorter and stouter than tracheid cells
- Maintain contact with other vessel elements
- Water flows through perforations between vessel elements (perforations are better than pits because water flows more efficiently)
- Also provides structural support (along with allowing the flow of water throughout the plant)
Pith
Tissue found at the center of the root or stem
Stores and transports materials throughout the plat (functionally similar to vascular tissue)
Made up of parenchyma (ground tissue)
Dermal tissue of a plant
Found on the outer layer of the plant
Provides protection to the inside of the plant
Helps regulate how the plant is affected by the external environment
What is the function of the casparian strip
Regulates type and amount of substances that enters roots of the plant due to the fact that it is made up fatty, waxy substances that make it impenetrable (substances are forced into the cytoplasm of the root cell and forced to flow through the plasma membrane)
Helps filter substances coming in through the cell wall
What causes the opening of the stomata?
Low concentration of CO2 inside the plant which occurs during the daytime (photosynthesis occurring)
Plants need more CO2 to carry out photosynthesis
This causes the stomata to open (more carbon dioxide rushes in)
How does the stomata open?
K+ ions diffuse into guard cells —> this causes a higher concentration of solute within the guard cells which leads to water rushing into the guard cells making them turgid (swollen)
Swollen guard cells = open stomata
What causes the closing of the stomata?
High concentration of CO2 inside the plant (happens at night when photosynthesis is not occurring), the plant does not need [CO2] for photosynthesis causing plant to close stomata
High temperatures cause plants to close their stomata because they want to prevent transpiration (evaporation of water from the plant) so they close their stomata and water stays in the plant
How does the stomata close?
K+ ions leave the guard cells —> this causes the outside of the guard cells to have a higher concentration of solute which leads water to rush out of the guard cells, making them *flaccid (shrunken)**
Shrunken guard cells = closed stomata
Functions of auxins
- Promote plant growth and elongation of cells by increasing proton concentration in primary cell walls
- enzymes are activated that loosen cellulose fibers, increasing cell wall plasticity and thus tugor pressure expands cells to grow
- function with cytokinins to promote cell differentiation and division
- one of the main hormones responsible for plant tropisms (growth in a certain direction: phototrophism, gravitropism and thigmotrophism)
Function of cytokinins
- can regulate cell differentiation and division
- stimulates cytokinesis
- stimulates and influences the direction of organogenesis
- stimulate the growth of lateral buds which weakens the apical dominance created by auxins (growth of apical meristem)
- delay senescence (aging) in plants
Functions of gibberllins
- promote cell growth (stem elongation and flower)
- elimination of dormancy of a seed –> promote germination
- promote flowering and fruit production
- inhibition of agining in leaves
- can work with auxins to stimulate growth
Function of abscisic acid
- Function in times of plant stress
- Promotes/maintains seed dormancy (prevents premature opening), closes stomata (during drought), inhibits growth, forms scales
- The dormancy caused by this hormone can be broken by an increase in gibberllin or environmental stimuli (such as temperature or light)
What type of plants are bryophytes?
Nonvascular plants: they do not have vascular tissue or roots
Examples: mosses, liverworts, hornworts