plants and meiosis - BIO Flashcards
4 reasons why plants respond to stimuli?
to avoid stress
to avoid being eaten
enhance/ensure survival
to improve their chances of having offspring
model answer for a plant growing upwards towards light using auxin:
auxin is a plant ? produced at the base of the ? of the plant/shoot. When light is directly ?, auxin ? evenly down the sides of the shoot. In a shoot, auxin promotes cell ? and ? elongation. Even distribution of ? causes even growth so the shoot grows ? evenly towards light. this is called ? phototropism
hormone, tip, above, diffuses, division, cell, Auxin, upwards, positive
model answer for a plant bending diagonally towards light using auxin:
auxin is a plant ? produced at the base of the ? of the plant/shoot. When light is shining from one ?, auxin ? unevenly down the shaded side of the shoot (the side away from the ?). In a shoot, auxin promotes cell ? and ? elongation. Uneven distribution of ? causes uneven growth of the ? side so the shaded ? grows ? , causing it to bend towards ?. this is called ? phototropism
hormone, tip, side, diffuses, light, division, cell, Auxin, shaded, side, quicker, light, positive
Model answer for negative geotropism (when the shoot lays sideways)
Auxin is a plant hormone produced at the base of the tip of a plant/shoot. When the shoot lays sideways, gravity causes the auxin to fall to the lower surface. In shoots, Auxin promotes cell division and cell elongation. As there is an uneven distribution of Auxin on the lower surface, there is uneven growth (the lower side grows more quickly than the upper side) and because of this the shoot grows upwards - against gravity - hence negative geotropism
model answer for a root growing downwards towards gravity using auxin:
Auxin is a plant hormone produced in the base of the tip (in the shoot). When the shoot lays sideways, gravity causes Auxin to fall to the lower surface. IN roots, Auxin inhibits cell division and cell elongation. There is an uneven distribution of Auxin on the lower surface, so therefore there is uneven growth and the upper side/surface grows more quickly , so the root grows downwards , therefore positive geotropism.
what 6 main things do plants respond to?
humidity, light, gravity, temperature, physical touch and water
what is positive thigmotropism??
growth towards physical touch
positive/negative geotropism?
growth with(towards)/against gravity
positive/negative hydrotropism?
growth towards/away from water
positive/negative phototropism?
growth towards/away from light
plant germination required practical, key method points?
- collect 3 petri dishes,
- place 8 seedlings on cotton wool in each petri dish,
- put each dish in a different type of light - one in full light (eg: the window), one is partial light (eg: in a box with a hole cut in it), and one in darkness (eg: a closet/cupboard),
- measure the height of each seedling beforehand and record this in a table,
- then leave the petri dishes in their appropriate areas for 5 days, - - once this time is up - measure the new heights and record these in the same table.
plant germination required practical, results/hypothesis points?
- ones in full sunlight should grow the most and grow upwards - positive phototropism
- ones in partial sunlight should grow more diagonally towards the light source and slightly less so - positive phototropism
- ones in no sunlight should initially grow due to their energy source - and they naturally grow to search for light, but will then die when there is no light
plant germination required practical, key analysis points?
- draw a table of heights before and after and calculate the height difference between these two
- calculate a mean of change in height for each petri dish
- maybe also repeat experiment for increased accuracy
- draw a graph to show and compare results (maybe a bar chart) with change in height on the y axis and the light condition on the x axis
plant germination required practical, key variables points?
- control variables: same amount of seedlings, same amount of dampness and water, same light intensity, same type of seedlings
- independent variable : type of sunlight - full, partial, or none
- dependent variable(s) : change in height, how many plants have grown, direction of growth
3 ways that Auxin can help commercial farming??
can grow plant clones by adding an Auxin growth medium, can grow cuttings using rooting powder (which contains Auxin), can use Auxin in weedkillers as it can disrupt the plant’s growth patterns
3 ways that Giberrellins can help commercial farming??
can expose plants to it to induce germination as it controls plant dormancy ( allowing farmers to grow mutliple crops per year and at better times), can make more or bigger flowers, and can make fruit especially seedless ones grow bigger fruit
ways that Ethene can help commercial farming??
it can control the ripening process, so people pick the fruit before it’s ripe, so it doesn’t decompose while travelling and then expose to ethene with big Ethene chambers. However plants can often produce their own ethene so they block this by chilling it or blocking with a chemical inhibitor.
what happens in interphase?
the organelles duplicate, as well as the DNA - so there are 4 chromatids (but still 2 chromosomes - one mother, one father)
what happens in prophase?
each chromosome is made of 2 sister chromatids, nuclear membrane disappears and spindles start to form
