Field observations show that velvet bentgrass (Agrostis canina L.) (VB) an alternative species to creeping bentgrass (Agrostis stoloniera L.) (CB) exhibits chlorosis in the leaves at high nitrogen rates. Growth chamber experiments were conducted that compared VB and CB using a hydroponic system. The experiments tested 5%NH4+-N, 45%NH4+-N, 95%NH4+-N and urea N-sources. Chlorosis only occurred in VB at the 95% NH4+-N and 100% urea-N source. Nitrate, nitrite, and ammonium levels in leaves showed ammonium accumulation was positively correlated to chlorosis in VB. Enzyme analysis showed initial glutamine synthetase (GS) activity in roots compared to leaves is higher in CB than in VB, explaining low ammonium levels in leaves of CB. The GS activity in the roots of VB increased after 24 hours of treatment. The results showed that the chlorosis in the leaves of VB is the correlated to ammonium accumulation associated with nitrogen form supplied and GS activity.

Creeping bentgrass (Agrostis stolonifera L.) and velvet bentgrass (Agrostis canina L.) are the principal grass species for golf course putting greens in northern latitudes. Wear injury is a major physical stress that limits the function and quality of turfgrass. Wear evaluations in Agrostis species are limited and no studies have been conducted to evaluate recovery from wear and associated wear mechanisms. To that end, Agrostis species and genotypes were evaluated for wear tolerance and recovery on a golf green built according to USGA specifications. Equal numbers of creeping bentgrass and velvet bentgrass genotypes were tested. Wear was applied using a grooming brush over a 3-year period and plots were visually rated for wear and recovery. As much as 90% of the total variation in Agrostis wear tolerance was due to interspecific variation. Velvet entries provided significantly better wear tolerance than creeping bentgrass. Velvet bentgrass genotypes provided acceptable wear tolerance and full recovery in most years with the exception of SR-7200. None of the creeping bentgrass entries evaluated exhibited acceptable wear tolerance or achieved full recovery. Fourteen Agrostis genotypes, which included equal numbers of creeping and velvet species were selected for further evaluation of anatomical, morphological and physiological characterstics associated with wear tolerance. Eleven characteristics were measured comparing greenhouse grown spaced-plants established from field plots and seed. Characteristics included tiller density, shoot dry weight, shoot water content, relative water content (RWC), leaf width, leaf strength, leaf angle, crown type and leaf cell wall constituents. Siginificant interspecific difference in charactersitics were found. Little difference at the intraspecific level was obserevd especially within creeping bentgrass. Wear tolerant velvet genotypes were associated with a more vertical tiller and leaf angle, greater cell wall content and greater shoot density. Lignocellulose content accounted for as much as 62.8 to 72.3% of the variation in Agrostis wear tolerance while tiller density accounted for as much as 65.9 to 75.8%. Wear tolerance in Agrostis can be improved by giving priority to breeding for greater density and cell wall content with secondary emphasis to breeding for a more upright growth habit (tiller and leaf).