In an effort to view root growth, most turf managers use a cup cutter or profile indicator, and take a slice to view the roots. Root biomass may or may not correlate to rooting depth. Total root biomass is a better indication of root growth than root depth. Any positive or negative effects on root growth affect the stress tolerance of bentgrass and other turf species. It is well documented that Primo is a foliar absorbed product that suppresses gibberellin biosynthesis in plants.
Gibberellins have several effects in green plants, such as cell and stem elongation.
Previous studies have also shown that a vast majority of Primo remains in aboveground plant parts. Therefore, the argument goes that Primo only slows aboveground shoot growth and therefore photosynthates are redirected down into root systems, thereby increasing root growth. A hydroponics study was initiated at North Carolina State University to evaluate the effects of Primo on root growth of Penncross creeping bentgrass. Because it took place in a soilless medium, root biomass could easily be quantified with a high level of accuracy and precision. Primo had a significant positive effect on bentgrass root growth at five of the seven temperatures.