BRAINCAKEPlant Responses
Revision notes for Plant Responses in OCR Biology A (H420). 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.