Nimo

Study smarter with Nimo

Personalised revision that adapts to you. Ace your revision with unlimited practice questions that are designed to help you learn faster. We're slowly rolling out to more and more students.

Try Nimo

Plant hormones and tropisms explained

Homeostasis and response • Plant hormones (biology only)

Key concepts

What you'll likely be quizzed about

  • Plant hormones are chemical substances produced in specific tissues that control growth and development at distant sites.
  • Hormones travel within plant tissues by diffusion and cell-to-cell transport, creating concentration gradients that change cell behaviour.
  • Hormones coordinate responses across organs to match environmental cues and internal programmes.

Flashcards

Test your knowledge with interactive flashcards

Why do shoots generally grow toward light?

Click to reveal answer

Shoots align with light to maximize photosynthesis, as auxin redistribution produces the bending that orients shoots toward available light.

Key notes

Important points to keep in mind

Auxin is synthesised in shoot and root tips; directional transport creates concentration gradients.

Phototropism: auxin accumulates on the shaded side, leading to greater cell elongation and bending toward light.

Gravitropism: after reorientation, auxin distribution causes roots to curve down and shoots to curve up due to tissue-specific sensitivity.

Tip removal or blocking diffusion prevents tropic bending, confirming the tip as the hormone source and showing hormone mobility.

Hydrotropism can override gravitropism in roots when water gradients present a stronger stimulus.

Hormone concentration ranges affect responses: too little auxin produces no effect; too much can inhibit growth or cause abnormal development.

Agricultural uses exploit hormone effects: rooting powders (auxins), selective weedkillers (synthetic auxins), gibberellins (germination/fruit size), ethene (ripening).

Built with v0