Cortical Cell Length Analysis During Gravitropic Root Growth.

The typical parameter used to evaluate the root growth response to gravity is the degree of root bending in time. This employs the quantification of the root tip angle toward gravity and, hence, does not directly assess the actual differential growth process. Here, we describe the cortical cell length as a parameter to quantify cell elongation during the gravitropic response, using median longitudinal confocal sections. This analysis depicts that root organ bending is a consequence of differential cellular elongation on the upper versus lower side of the gravistimulated root. Moreover, we introduce here a simple mounting setup that is suitable to gravistimulate and subsequently image seedlings on upright microscopes.