5.5 Plant and animal responses Flashcards
Define abiotic components
components of an ecosystem that are non-living
Define alkaloids
Organic nitrogen-containing bases that have important physiological effects on animals; including nicotine, quinine, strychnine and morphoine.
Define biotic components
components of an ecosystem that are living.
define pheromone
any chemical substance released by one living thing, which influences the behaviour or physiology of another living thing.
define tannins
pherolic compounds, located in cell vaculoes or in surface wax on plants.
define tropism
a directional growth response in which the directionof the response is determined by the direction of the external stimulus.
give some examples of some of plants tropisms
Phototropism - shoots grow towards light, which enables them to photosynthesise
geotropism - roots grow towards the pull of gravity. This anchors them in the soil and helps them to take up water, which is needed for support (to fill vacule to stay tugid) as a raw material for photosynthesis and to help cool the plant. there will also be minerals, such as nutrate in the water needed for the synthesis of amino acids.
Chemotropism - on a flower, pollen tubes grow down the style, attracted by chemicals, towards the ovary where fertilisation can take place.
thigmotropism - shoots of climbing plants, such ivy, wind around other plants or solid structure to gain support.
Explain the effect of cytokinins
promote cell division
delay leaf sequence
overcome apical dominance
promote cell expansion
explain the effect of abscisic acid
Inhibits seed germination and growth
Causes stomatal closure when the plant is stressed by low water availabilty
explain the effect of auxins
Promote cell elongation
inhibit growth of side-shoots
inhibit leaf abscission
explain the effect gibberellins
promote seed germination and growth of stems.
explain the effect of ethene
Promotes fruit ripening
define apical dominance
inhibition of lateral buds further down the shoot by chemicals produced by the apical bud at the tip of a plant shoot.
define auxins
plant hormones which are reponsible for regulating plant growth.
define gibberellins
plant hormones which are reponsible for control of stem elongation and seed germination.
State the obsivation when an shoot tip is broken of the plant.
the plant starts to grow from the lateral buds that were previously dormant.
State the first theory of apical domiance
the apical bud produces auxins which inhibits lateral buds from growing, and so when removed latical buds can grow.
Suggest how the scientist tested the effect of oxygen to the apical cut.
the oxygen could of produced a hormone which promotes lateral bud growth. to get around this they placed a ring of auxin transport inhibitors below the apex of the shoot. The lateral bud grew.
Explain the suggested season for apical domiance with the evidance from the auxin ring inhibitor.
when normal auxin level in lateral buds inhibits growth, whereas low auxin levels promote growth,
However a third variable may be the reason, years later it was discovered that auxin levels increase when apex is cut off, and is caused by two other hormones, Abscisic acid and cytokinins.
explain the current understanding of apical dominance
it was discovered that auxin levels increase when apex is cut off, and is caused by two other hormones, Abscisic acid and cytokinins.
Abscisic acid inhibits bug growth. high auxin in the shoot may keep abscinic acid levels high in the bud. when the bud is removed Abscisic acid conc drops, and lateral starts to grow,
Cytokines - promotes bud growth, directly apling cytokinin to buds can override the apical dominance effect,the apex is a sink for cytokinins produced by roots. when apexs is removed spreads evenly around the plant,
describe how a fungus caused disease causes cell elongation.
the fungal compounds involed are gibberellins and include gibberellic acid(GA3),
It made rice, maize peas rosette all grow taller.
explain why cell elongation might not be caused by GA3 in nature.
An expirmient which uses concentrations of gibberellins within natural ammounts.
Researcher compared GA1 levels of tall pea plants and dwarf pea plants, which were otherwise genetically identical. GA1 values were higher in taller plants/
It was found that the Le gene (tall gene) causes the production of an enzyme that converts GA20 to GA1.
then a pea plant with a mutation that blocks gibberellin production between ent-kaurene and GA12-aldehyde in the pathway. those plants produce no gibberellin and grow only about 1cm tall.
describe the synthesis pathway for gibberellins
ent-kaurene -> GA12-aldehyde -> GA12 -> GA52 -> GA44 -> GA19 -> GA20 -> (enzyme produced by Le gene) GA1
define geotropism
a directional growth response to gravity`
define phototropism
a directional growth response to light
State what kind of plant cells that can grow and how,.
meristem as they are immature and are still capable of dividing.
state where are apical meristem is found
at the tips or apices of roots and shootsm and are responsible for the roots and shoot getting longer
State where are lateral bud meristems found.
found in the buds these can give rise to side shoots.
state where the lateral meristem found.
it forms a cylinder near the outside of roots and shoots are responsible for roots and shoots getting wide.
State what causes growth between nodes.
intercalary meristem which are located between nodes.
