As v animals, plants additionally use a variety of hormones to regulate their growth and development. A family members of hormones referred to as auxins are frequently found in plants, and promote (and occasionally inhibit) growth.

You are watching: What do phototropism and geotropism enable plants to do


Auxins are produced in the meristems of plants (meristems are described on successive pages).

Auxins space responsible for promoting cell elongation, a procedure that is required prior to the differentiation of a cell. It is able come this by cultivating the entry of water, boosting the elasticity the the cell to cope v the increase of water taken in by the cell.

One the the most typical auxins is indole acetic acid.

Indole Acetic mountain (IAA)

Indole Acetic mountain affects the root and also shoot advice of the plant, as explained below.

Shoot Tip – No issue what the concentration, IAA promotes growth in the shoot area that a tree (though higher concentrations promote growth more). Root Tip – High concentration of auxininhibitgrowth while little amounts are sufficient topromotegrowth in the root v indole acetic acid.


Auxins likewise play a component in phototropism, an incident that entails plants bending or moving away indigenous light. The shoot pointer is responsible for directional movement by the plant in an answer to sunlight, together this is the area where auxins can be found.

Sunlight eradicates auxin, meaning that the part of the shoot pointer of the plant which is receiving direct sunlight will have the the very least amount that auxin.

The extra auxin existing on the shaded side promotes an ext cell department and elongation, resulting in the tree to bend towards the sunshine after this lop-sided growth.

Credit: science Sauce


Geotropism is a similar occurrence come phototropism where the tree exhibits directional development in response to gravity. The shoot tip illustrates an adverse geotropism (grows against the force of gravity) if the root tip exhibits confident geotropism (grows in the very same direction as gravity).

Apical Dominance

The visibility of auxins in the lateral areas of the tree (in between the root and shoot tip) stop lateral growth. If you cut off the shoot pointer of a plant, the absence of ‘diffusable’ auxins way that they can not inhibit growth in these lateral areas. This is well-known as apical dominance.

Leaf Abscission

The visibility of auxins in the lateral areas additionally prevents sheet abscission. In the colder months, auxin concentrations and also the price of photosynthesis drops.

This lack of auxin in the lateral areas results in the creating of anabscissionlayer at the stalk the the leaf, i m sorry weakens its connection with the plant and also soon falls off it.

The next tutorial look at at an additional family of growth hormones, the gibberellin family, with proceeding pages looking at the meristems, the website of tree growth.


Select true if the declare is correct and also false if incorrect.

1. Plants create auxins in your meristematic tissues.
2. Auxins promote cell elongation by fostering water intake and increasing cabinet elasticity
3. Indole acetic acid is a rare type of auxin.
4. Phototropism refers to the propensity of plants to move towards or away from gravity.
5. The tendency of roots to relocate away indigenous the source of light is an example of phototropism.

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biology Tutorials > regulate of growth & development > plant Auxins – Phototropism & Geotropism

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