Simple stereological procedure to estimate the number and dimensions of root hairs

We demonstrate a simple procedure for systematic, uniformly random sampling of a root system of known length to obtain practically unbiased estimates of the total number and dimensions of root hairs. Irrespective of the length of the root system, only 100 root hairs need to be counted to estimate the total number with sufficient precision. Numbers and dimensions of root hairs were estimated for five crested wheatgrass (Agropyron cristatum L.) root systems that had been grown for one month in a gel. Less than one hour was required to obtain estimates of root hair parameters for a single plant. There was low variability of spatial density of root hairs within a given branching order (CV < 15%); however, because of large variation in the total length of laterals, the total number of root hairs varied greatly (CV similar to 70%). On average, root hairs provided half of the total surface area of a root system and a total length 20 times that of the roots.