how is the force of gravity perceived in the apical region of shoots?explain with the help of a diagram.

Asked by mrinalchatterjee | 21st Sep, 2010, 12:48: PM

Expert Answer:

 Shoots are negatively geotropic, that is, they will bend and grow upwards, or away, from the earth's  surface. This behaviour can be easily demonstrated with a potted plant. When laid onto its side, the growing parts of the stem begin to display negative gravitropism, bending upwards.
 
In both roots and stems auxin accumulates towards the gravity vector on the lower side. In roots, this results in the inhibition of cell expansion on the lower side and the concomitant curvature of the roots towards gravity (positive gravitropism). In stems, the auxin also accumulates on the lower side, however in this tissue it increases cell expansion and results in the shoot curving up (statolithic gravitropism).

Answered by  | 21st Sep, 2010, 03:48: PM

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