BRAINCAKEPlant Responses
Revision notes for Plant Responses in AQA Biology (7402). Read the start of any lesson here, then sign in free for the whole lesson, the R.E.C.I.P.E. recall steps and the quiz.
- Plant Growth ResponsesPlants show directional growth responses which are known as tropisms.
- Plant HormonesAuxins produced at the tops of roots and shoots cause cell elongation, prevent leaf abscission, maintain apical dominance, control tropisms and…
- Seed GerminationWhen the seed absorbs water the embryo is activated and produces gibberellins which switch on genes that code for amylases and proteases to break…
- Apical DominanceAuxins (e.g. indoleacetic acid - IAA) are made in the tips of. roots and shoots and in the meristems which occur just behind the tips of roots and…
- Gibberellins: Synergy and Antagonism.Gibberellins also affect the length of the internodes by stimulating cell elongation.
- Leaf LossAs light intensity and temperature decline in the winter the amount of glucose needed for respiration to maintain the leaves and produce chlorophyll…
- Flowering and Day-LengthPlants are sensitive to the absence of light (photoperiodism).
- Preventing FreezingIf cell membranes freeze, the cell will be damaged and die.
- Stomatal ControlTemperature and water availability are major abiotic factors for plants.
- Chemical DefencesCommon physical defences against herbivory are thorns, barbs, spikes, spiny leaves, fibrous, inedible tissue, hairy leaves, stings and trichonmes…
- PheromonesMaple trees release chemicals when attacked by insects.
- Response to TouchMimosa pudica contains a toxic alkaloid and has a sharp prickly stem which helps protect it against herbivores.
- TropismsTropisms are directional growth responses to stimuli.
- Growing inthe DarkPlants grow more quickly in the dark.
- GeotropismPlants are sensitive to gravity.
- Fruit RipeningEthene gas is a plant hormone involved in the ripening of climacteric fruits i.e. fruits that continue to ripen after they have been picked.
- Rooting PowderApplying auxin to cut shoots causes the growth of roots.
- Hormonal WeedkillersPlant hormones interact to allow the plant to grow.
- Other Uses of Plant HormonesAuxins are used to produce seedless fruit.