plant gravitropism

As we move away from Earth, gravity changes. While in space or on other planets, plants will experience microgravity, hypergravity, and everything in-between. This is important because plants sense gravity. Their response to gravity is called gravitropism and it is a critical aspect of astrobotany research.

Plant gravitropism may be more intuitive than it seems. Let’s break it down. You can think of plants as simple systems of roots and shoots. Roots take up water and nutrients, and shoots transport them. Roots grow down and shoots grow up. The question on our minds? How do plants know where up and down is?

Plants must sense the influence of gravity to maximize their growth. The key to plant gravity sensing lies in the plants root tips, specifically in organelles called amyloplasts. Amyloplasts contain starch and are the main player in gravity response.

A gravitropic assay is a common experiment performed by astrobotanists.  Using a 2-d or 3-d clinostat, a plant (typically arabidopsis thaliana) is stressed in a way that mimics components of gravity by rotation.  Analysis is performed using RootTrace software.  Usually gravitropic assays cause abnormalities in root growth, typically resulting in a skewing of roots.

QTL Analysis

Arabidopsis thaliana has 5 chromosomes each of which contains genes that allow the plant to adapt to its environment. Quantitive Trait Loci (QTL) analysis performed in the Spalding Lab at the University of Wisconsin-Madison identified regions that are likely to contain genes that are involved in plant response to a gravitropic assay. The use of time-lapse photography and high-throughput computing the researchers to identify chromosomal regions linked to different stages of the gravitropic response.  Check out the data visualization tool here.