As sessile organisms, plants rely on their roots to acquire sufficient water and nutrients from the soil. Making the right choice about where to deploy new roots can determine survival, especially when soil resources are scarce and unevenly distributed. Recently, it was discovered that plant roots can respond to gradients of soil moisture by favoring the formation of lateral roots toward sites with available water (1). On page 1407 of this issue, Orosa-Puente et al. (2) show how growth along an air-water interface in the soil triggers asymmetric activation of a signaling module coordinated by the plant hormone auxin that biases lateral root initiation to the side in contact with water. These findings demonstrate how spatial environmental cues determine organ formation in higher plants.
http://science.sciencemag.org/content/362/6421/1358
http://science.sciencemag.org/content/362/6421/1358