Plant Hormones Flashcards
define tropism
when plants detect stimuli in their environment and respond by growing in a particular direction
define positive tropism
when the plant grows towards the stimulus
define negative tropism
when the plant grows away from the stimulus
define phototropism
growing towards the light
define gravitropism
growing in the same direction as gravity
what is the effect of phototropism
because the stem grows towards the light the plant can photosynthesise more meaning more food is produced for the plant, it grows faster, increasing the plants chances of survival
what is the effect of gravitropism
by the roots growing downwards and deeper into the soil, this helps provide anchorage. Also takes the roots nearer to water.
what is auxin?
a plant hormone they enables a plant to grow towards or away from the stimulus.
where is auxin made in a plant
in the roots and shoots
how does auxin help a plant respond to light?
when light hits the left side of a plant (for example) auxin would move to the right, the cells on that side respond by elongating. This increases the length of the side of the shoot so it bends towards the light.
what are the main three hormones in plants?
ethene, gibberelins, auxin
what does ethene do?
ripens fruits by stimulating the conversion of starch into sugar; this is why ripe fruit is sweeter. It’s the only plant hormone that exists as a gas
what does gibberelins do?
promotes growth, mostly stem elongation, also ends the dormancy period of seeds and buds.
what are the commercial uses of plant hormones?
to speed up/slow down plant growth killing weeds delay ripening promote root growth controlling dormancy producing seedless fruit
suggest an advantage and disadvantage to gardeners of using weed killer
advantage: kills weeds
disadvantage: only kills broad leaved weeds
