Differential Root Growth of FourSetariaTaxa

Abstract

We studied the early root growth of fourSetariataxa: giant foxtail (Setaria faberiHerrm.), giant green foxtail [Setaria viridisvar.major(Gaud.) Posp.], robust white foxtail (Setaria viridisvar.robusta-albaSchreiber), robust purple foxtail (Setaria viridisvar.robusta-purpureaSchreiber). Growth studies in controlled environments showed significant differences in root elongation among the taxa at three photoperiods. Seminal root lengths after 4 days followed the order presented for selectivity and metabolism of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] and propazine [2-chloro-4,6-bis(isopropylamino)-s-triazine] (robust white foxtail > giant green foxtail = robust purple foxtail > giant foxtail). Giant foxtail had the greatest root diameter, resulting in the greatest surface area and volume when lengths were equated. The order of seminal root lengths or diameters changed little after 7 days. Robust white foxtail had the most and longest first order lateral roots. Diameter of first order laterals showed giant foxtail > giant green foxtail = robust purple foxtail > robust white foxtail.