In this study,we used hydroponics to cultivate the root hemiparasites,Pedicularis tricolor and P.rex,in the absence of their host plants.The direct effects of nitrogen( N) and phosphorus( P) levels and different nitrogen forms on root architecture of the two species were tested in two experiments using nutrient solutions modified from the standard Long Ashton formula.In Experiment 1,solutions were used which either lacked N or P,or contained double the standard concentrations of N or P.In Experiment 2,diffe...