Hey there! Sign in to join this conversationNew here? Join for free

Control in plants-hormones GCSE AQA Biology Unit 1 Watch

Announcements
    • Thread Starter
    Offline

    2
    ReputationRep:
    Can someone please tell me what the auxin does in phototropism and gravitropism please?
    Offline

    0
    ReputationRep:
    Photo tropism means a part of the plant grows towards the light, and gravitropism means part of the plant (the root) grows with gravity. if thats what your asking....
    Online

    15
    ReputationRep:
    (Original post by tkrv)
    Can someone please tell me what the auxin does in phototropism and gravitropism please?
    I did this last year not really fresh in my head..

    I believe the cells on the tip of shoot detects light stimulus and causes auxin to be produced. The auxin moves to the shaded region of the stem causing that side of the stem to elongate faster compared to the non-shaded side. This is the reason the shoot bends towards the light. (Phototropism)

    For gravitropism, all I know is that the root bends towards water and minerals/ions. I don't really know why.

    Correct me if im wrong
    Offline

    1
    ReputationRep:
    Phototropism
    This means that the shoots in a plant towards the light. In shoots, auxin stimulates growth. Auxin accumulates on the side with the least light. This means that the side with the auxin on grows faster compared to the side with more light. As there's an unequal rate of growth in the sides, it causes the shoot to bend towards the light.

    Gravitropism
    This means that the roots grow towards gravity. In the roots, auxin inhibits growth. Due to the natural nature of gravity, auxin accumulates on the lower side of the root. This means that there, again, is an unequal rate of growth on both sides of the root. The top (side with no auxin) grows faster, while the side with auxin in grows slower. This means that the root bends downwards, towards the gravity and in the opposite direction of the shoots.

    If you need any more help, feel free to ask
    • Thread Starter
    Offline

    2
    ReputationRep:
    (Original post by MersennePrime)
    Phototropism
    This means that the shoots in a plant towards the light. In shoots, auxin stimulates growth. Auxin accumulates on the side with the least light. This means that the side with the auxin on grows faster compared to the side with more light. As there's an unequal rate of growth in the sides, it causes the shoot to bend towards the light.

    Gravitropism
    This means that the roots grow towards gravity. In the roots, auxin inhibits growth. Due to the natural nature of gravity, auxin accumulates on the lower side of the root. This means that there, again, is an unequal rate of growth on both sides of the root. The top (side with no auxin) grows faster, while the side with auxin in grows slower. This means that the root bends downwards, towards the gravity and in the opposite direction of the shoots.

    If you need any more help, feel free to ask
    thanks so much!! really helps!!
    but can you explain gravitropism as negative and positive please. i'm quite confused with gravitropism ://
    Offline

    0
    ReputationRep:
    (Original post by tkrv)
    thanks so much!! really helps!!
    but can you explain gravitropism as negative and positive please. i'm quite confused with gravitropism ://
    Positive tropism is where part of the plant grows TOWARDS the stimulus.

    Negative tropism is where part of the plant grows AWAY FROM the stimulus.

    So in terms of gravitropism, the roots show POSITIVE GRAVITROPISM because the roots of a plant grow towards (in the direction of) gravity, and the shoots show NEGATIVE GRAVITROPISM because they grow away from (against) gravity.

    Hope this helps
 
 
 
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • Poll
    Should Spain allow Catalonia to declare independence?
    Useful resources

    Study tools

    Rosette

    Essay expert

    Learn to write like a pro with our ultimate essay guide.

    Thinking about uni already?

    Thinking about uni already?

    See where you can apply with our uni match tool

    Student chat

    Ask a question

    Chat to other GCSE students and get your study questions answered.

    Creating

    Make study resources

    Create all the resources you need to get the grades.

    Planner

    Create your own Study Plan

    Organise all your homework and exams so you never miss another deadline.

    Resources by subject

    From flashcards to mind maps; there's everything you need for all of your GCSE subjects.

    Papers

    Find past papers

    100s of GCSE past papers for all your subjects at your fingertips.

    Help out other students

    Can you help? Study help unanswered threads

    Groups associated with this forum:

    View associated groups
  • See more of what you like on The Student Room

    You can personalise what you see on TSR. Tell us a little about yourself to get started.

  • The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

    Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

    Quick reply
    Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.