Source Texts
Text
Auxins are a class of hormones that influence plant growth, including leaf orientation (the tendency of leaves to be larger on one side of their long central axis than the other). University of California, Berkeley biologist Ciera Martinez and colleagues noted that in certain plants in which leaves grow in pairs, auxins will typically be concentrated in opposite sides of each leaf in the pair (e.g., on the left side of one leaf in the pair and the right side of the other). Accordingly, they hypothesized that paired leaves should tend to show opposite side orientation, and they tested their hypothesis by examining paired leaves from several species of grapevines.