Plant Hormones Flashcards
Why do plants respond to external stimuli
To increase their chance of survival eg by avoiding stress, avoiding being eaten, enhancing survival and improving chances of successful breeding
What is a positive tropism
Growth towards the stimulus
What is negative tropism
Growth away from the stimulus
What is a tropism
Growth responses to a directional stimulus (stimulus coming from a particular direction)
What is phototropism and what are shoots and roots
Growth of a plant in response to light
-shoots positively phototropic so grow towards light, roots negatively phototropic so grow away from lifht
What is geotropism
Growth of a plant in response to gravity, shoots are negatively geotropic and grow upwards, roots are positively geotropic and grow downwards
What is chemotropism and example
Growth of plant in response to chemicals, eg pollen tubes of flower positively chemotropic and grow down the style towards the ovary by chemicals where the pollen can fertilise the ova
What is thigmotropism and example
Growth of plant in response to touch by another stimulus, eg shoots of climbing plants eg ivy wind around other plants/objects to gain support
What are growth factors
How plants respond to stimuli, they are chemicals that speed up or slow down plant growth
How are growth factors transported around plant
Active transport/ diffusion/ mass flow in phloem sap/xylem vessels.
-produces in the growing regions of the plant and move to where they’re needed
What are antagonistic growth factors
Cancel out each others effect
What are synergetic growth factors
Hormones that amplify each others effect
What are auxins and their use
Growth factors that stimulate the growth of shoots by cell elongation(cell walls become loose and stretchy so cell gets longer)
-high concen in roots inhibits growth
-used in cuttings/herbicides
What are gibberellins and use
Delays senescence so used to stimulate flowering and seed germination
What is ethene
Stimulated fruit ripening and flowering
