Control in plants

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Plants & hormones

Even if you plant seeds upside down, the shoot will grow up & the root will grow down

Hormones used to grow plants:

  • Cuttings can be dipped in rooting powder ( plant hormone) to encourage growth

Hormones used as weed killer:

  • Hormones make the plants use up all of their energy to grow fast
  • The plants aren't strong enough to stand, so fall & die
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Where the plant stem bends TOWARDS the light

Auxin is a plant homone that controls cell growth. 

The auxin is usually spread out in the stem.

When light hits the auxin, it is destroyed, meaning that                                                           there is no auxin on that side of the shoot.

The side with more auxin elongates more than the side                                                             with no auxin

The plant bends towards the light

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Geotropism / Gravitropism

The plant is growing HORIZONTALLY, so the auxin makes the root grow down & the shoot grow up

  • Auxin in the shoot make the cells elongate
  • Auxin in the root makes the cells shorten

Gravity makes the auxin fall to the bottom of the plant

The auxin elongates the side of the shoot so it grows up

The auxin shortened the side of the root so it grow down

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