One of the first things we found is that some root growth strategies, which we believed required gravity, do not require it at all. In the search for water and nutrients, plants grow roots, sending them to places nearby. On Earth, gravity is an important “indicator” trend growth, but plants also use touch (think root tip as a sensitive finger) to navigate around obstacles.
In 1880, Charles Darwin showed that when you grow plants along the inclined surface, the roots grow from the seeds, not directly, but rather are deflected in the same direction. This growth strategy is called a “skew.” Darwin suggested that the reason for this – a combination of gravity and the touch of the roots – and 130 years, all the others also thought so.
But the roots grew with a skew and without gravity. In 2010, we saw that the roots of plants grown on the ISS, overcame all the way across the surface of a Petri dish with the perfect tilting roots – without any gravity. It was a surprise. Obviously, not gravity is behind the pattern of root growth.
Plants on the ISS have a second potential source of information, from which they could be repelled: light. We have assumed in the absence of gravity, which could indicate the roots grow in the direction “away” from the leaves, light plays an important role in the orientation of the roots.
It turned out that, yes, light is very important, but not just light – must be the light intensity gradient, then it will act as a valuable guide. Imagine it as a good smell: you can with closed eyes to find the source of the smell in the kitchen, if the oven is only opened with cookies, but if the house is equally drowned in the scent of chocolate chip cookies, you can hardly find it.