Plant responses

• plant response to Herbivore include physical and chemical responses
• Pheromones are chemicals that are released and affect other members of that species
• plants use pheromones to communicate about danger
• Alkaloids are bitter tasting nitrogenous chemicals that affect the metabolism of herbivore resulting in death, E.G nicotine
• Plants response to a stress includes high wind, excess water or lack of water
• Examples of response to abiotic stress include leaf loss day length sensitivity obsidian, prevent freezing and stomach control
• Leaf Loss


  This is when plants willThis is when plants willThis is when plants willThis is when plants will lose their leaves due to colder climates this is due to the decrease in daylight therefore the decrease in rate photosynthesis
• abscission: the natural detachment of parts of a plant, typically dead leaves and ripe fruit
• plants are able to control when the depart can open or close in response to different stimuli the evaporation of water out the stomata provides a cooling effect.
• Positive tropism is going towards the stimuli
• Negative tropism is when the plant grows away from the stimuli
• tropism is a term given when a plant grows in response to stimulus
• auxin can control elongation and cells and shoots and inhibits the growth of cells in roots
• Ppant hormones control range of responses in the plant such as ripening of fruits, sea germination and lengthening of stems
• auxin


  this causes cell elongation in stems and inhibits growth in roots. They also maintains apical dominance.
• Ethene


  A gas that causes fruit to ripen
• Gibberellin


  Stimulate seed germination stem elongation and pollen tube growth in fertilisation
• Abscisic acid(ABA)


  Stimulates stomatal closing and maintains dormancy of seeds
• apical dominance is the ability of a plant to produce a single shoot from a single node
• auxin stimulates growth of shoots particularly the apical shoot
• Boxing results in apical dominance which means one main shoot growing which inhibits growth of lateral shoots due to high concentration of oxen at apical
• The higher the concentration of auxin the stronger the apical dominance
• Photoperiodism is when plants respond to changes in day length
• lateral buds are suppressed by auxins produced by apical meristem
• Gibberellins can be used for germination or stem elongation
• Gibberellins cause enzymes to be released that can break down food stores in the seed so that embryo plants can respire and make ATP
• Starts to germinate when it absorbs water and this activates the production of gibberellins
• Gibberellins are collection of hormones that help plants grow by stimulating elongation in the stem
• The higher the concentration of Jerrell, the more elongated the stem becomes
• Plant hormones could also be used for commercial use
• ethene Can be used to control the ripening of fruits, therefore unripe fruits can be picked whilst still firm and then sprayed with ethene before sold
• Rooting powders can be used to encourage the growth of new roots from plant cutting auxin can also be used in rooting powders
• auxin can be used as weed killers spraying auxin over weeds causes them to grow too quickly and their stems give away and the weed dies
• Auxin causes cells at the tip of the shoot to divide rapidly which leads to an increase in length
• Auxin is produced at the shoot tip and moves downwards through the xylem vessels towards the base of the plant where it causes cells to divide and differentiate into root hair cells which absorb nutrients from soil
• If there is no apical meristem present (e.g. if the top has been cut off) then the plant will not produce any more leaves or stems as there is no source of auxin