Plan Responses To The Environment Flashcards
Define the term abiotic components
-components of an ecosystem that are non-living
What are alkaloids
- organic nitrogen-containing bases that have important physiological effects on animals; including nicotine and morphine
Define the term biotic components
-components of an ecosystem that are living
What are pheromones
- any chemical substance released by one living thing, which influences the behaviour or physiology of another living thing
What are tannins
-phenolic compounds, located in cell vacuoles or in surface wax on plants
Define the term tropism
-a directional growth response in which the direction of the response is determined by the direction of the external stimulus
What 2 type of external stimuli do plants respond too
-biotic (living) components
-abiotic (non-living) components
How does responding to the environment help plants
-aids in them surviving long enough to reproduce
What is an example of a way in which plants may respond to an external temperature such as high temperatures
-by depositing thicker layers of was on their leaves
What is an example of a way in which plants may respond to an external temperature such as wind
-by making their vascular tissues more lignified
What type of response do plants show to herbivores
-chemical defences
Name 3 types of chemical defences plants put up to protect themselves from herbivores
1) tannins
2) alkaloids
3) pheromones
Name the 4 types of tropisms
1) phototropism
2) geotropism
3) chemotropism
4) thigmotropism
Define the term phototropism
-shoots grow towards light, which enables them to photosynthesis
Define the term geotropism
-roots grow towards the pull of gravity
- anchors then in the soil and helps them take up water (needed for support) and raw material for photosynthesis and to help cool the plant
Define the term chemotropism
-where the growth of a plant is directed by a chemical stimulus
-e.g. on a flower pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation can take place
Define the term thigmotropism
-shoots of climbing plants, such as ivy wind around other plants or solid structures to gain support
A plant responding towards a stimulus is called what
-a positive tropic response
A plant responding away from a stimulus is called what
-a negative tropic response
What are non-directional responses to external stimuli called
-nastic responses
Where are hormones produced in plants
-by cells in a variety of tissues in the plant
How do hormones move around in the plant
-active transport
-diffusion
-mass flow in the phloem sap or in xylem vessels
What is the effects of cytokinins in plants
-promote cell division
-delay leaf senescence(aging)
-overcome apical dominance
-promote cell expansion
What are the effects of abscisic acid in plants
-inhibits seed germination and growth
-causes stomata closure when the plant is stressed by low water availability
What are the effects of auxins in plants
-promotes cell elongation
-inhibits growth of side-shoots
-inhibits leaf abscission (leaf fall)
What is the effect of gibberellins in plants
-promote seed germination and growth of stems
What is the effect of ethene on the plant
-promotes fruit ripening
Define the term apical dominance
-inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of a plant shoot
What are auxins
-plant hormones which are responsible for regulating plant growth
What are gibberellins
-plant hormones which are responsible for control of stem elongation and seed germination
What hormone does auxin promote
-abscisic acid
What does auxin and abscisic acids mean the plant does
-this helps maintain high abscisic acids levels in buds which reinforces bud dormancy
What happens to the amount of abscisic acids when the shoot tip is removed and what does this mean
-there is a drop in abscisic acid which allows for the buds to start forming and forming lateral shoots
What do cytokinins override when directly applied to buds and what does this mean
-apical dominance, this means that buds start to grow even if auxins are present
What happens to the level of auxin when the apical shoot is removed and what does this mean for cytokinins
-auxin levels drop, which means cytokinins spread more evenly which promotes growth in lateral buds
What way do cytokinins travel in a plant, why and what does this mean
-travel to the shoot tip because they are attracted to the auxins and this means that the cytokinins aren’t distributed evenly
What triggers gibberellin release in seeds
-absorption of water by the seed
Where is gibberellin released from in a germinating seed
-the embryo
Where does gibberellin travel after being released
-the aleurone layer in the endosperm
What does amylase do in seed germination
-it breaks down starch into glucose
How does glucose help the growing embryo
-by providing energy for respiration and is used for protein synthesis
What does the cell wall limit the cell’s ability to do in plant cells
-its ability to divide and expand
What are meristems
-
What limits the cell’s ability to divide and expand
-the plant’s cell wall
Where is the only place that growth happens
-where there are groups of immature cells that are still capable of dividing
What are groups of cells that are still capable of dividing called
-meristem cells
What are apical meristems
-meristems that are eat the tip of roots and shoots and are responsible for the roots and shoots getting longer
What are lateral bud meristems
-meristems that are found in the buds and give rise to side shoots
What are lateral meristems
-meristems found in the buds and give rise to side shoots
What are lateral meristems near the outside of roots and shoots responsible for
-the roots and shoots getting wider
What other type of meristem are located between the nodes and what are responsible for
-intercalary meristems
-and it is responsible for the shoot getting longer
Briefly describe how you could investigate phototrophic and geotropic responses
Briefly describe how you could investigate the effect of plant hormones on photoropisms
How has the role of auxin as a chemical messenger been confirmed
-agar blocks are impregnated with different concentrations of auxin and gave the same results
Where is auxin produced
-at the apex of the shoot
What enzyme does gibberellin stimulate the production of
-amylase
