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. Gravitropism is also sometimes also referred to as geotropism.

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.

Plant Gravitropism in Microgravity

So how does this affect plants grown in space microgravity?

Here are some takeaways from research that’s been performed:

  • plants grown in microgravity have roots that are shorter (shown statistically)
  • plants grown in microgravity have shorter root hairs
  • microgravity can weaken cell walls, affecting root systems (Kwon et al. 2015)
  • root systems in space experience more skewing and waving (Ferl et al. 2015)
  • the literature suggests directional light can direct root growth in a microgravity environment (Ferl et al. 2015)