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Phototropism and Gravitropism: Quantifying Stem Curvature in Plants Introduction

Author(s): Lou Gross1, Monica Beals1, Susan Harrell1

University of Tennessee Knoxville

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This module introduces phototropism and gravitropism in the context of understanding how to quantify stem curvature of plants. It is intended for an introductory biology audience.

Licensed under CC Attribution-ShareAlike 4.0 International according to these terms

Version 1.0 - published on 15 Feb 2019 doi:10.25334/Q4C44N - cite this


Student Introduction: Plants adjust to the conditions of their environment through growth responses. For example, plant stems generally bend toward light sources while roots grow away from light sources. This process is called phototropism. Substances called auxins play a strong role in controlling various plant responses. Auxin increases the plasticity of plant cell walls causing them to stretch more during active plant growth. During phototropism, the auxin concentration in stem cells is usually higher on the side of the stem away from light. These cells will stretch more during active growth, causing the plant to move toward the light source. In gravitropism, plants respond to gravity, generally causing shoots to grow up and roots to grow down.

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