Name three tropisms and explain why they are important to plants.?

Question

Name three tropisms and explain why they are important to plants.?

Answer 1

The tropisms can go into two directions:

A positive response is when the plant moves toward or in the direction of the stimulus. A negative response is when a plant moves away from the stimulus.

Phototropism: plant stems grow towards light ( positive ), important for photosynthesis.

Photoperiodism: response of a sunflower f.e. to naturally occurring changes in light during a 24-hour period and to have always best wavelength to photosynthesize ( positive )

Gravitropism/geotropism: a plant will grow so that it stays oriented relative to the source of gravity (the earth).If a plant is knocked down the shoot will grow faster on the lower side until the shoot is more-or-less standing up again ( negatively to gravity by growing up toward the sky ).

The root grows down into soil ( direction of gravity > positive ); that`s important for stability and uptaking nutrients.

Hydrotropism: plant grows or bends in response to water, roots grow down in search of water ( positive ). Every plant needs water to transport nutrients and to photosynthesize.

Thigmotropism: plants ( fungi, bacteria ) grow or bend in response to touch.

http://cat.inist.fr/?aModele=afficheN&cp...

When mistletoe-seeds geminate, a root-like structure, called a radicle, emerges from the germinated seed and grows along the branch surface by a process known as thigmotropism.

http://www.apsnet.org/online/feature/mis...

Here you find some more tropisms:

http://en.wikipedia.org/wiki/Tropism