raw materials to redevelop leaf and shoot tissue ( Davidson and Mithorpe, 1966 ; Donaghy and Fulkerson, 1998 ; Morvan-Betrand et al., 1999 ). The primary reserve carbohydrate of creeping bentgrass ( Agrostis stolonifera L.) is fructan. Fructan is
Mark J. Howieson and Nick Edward Christians
Aneta K. Studzinska, David S. Gardner, James D. Metzger, David Shetlar, Robert Harriman, and T. Karl Danneberger
Creeping bentgrass ( Agrostis stolonifera L.) is a turfgrass species highly suitable for use on golf course tees, greens, and fairways. As a result of its ability to provide exceptional quality playing surfaces when mowed short, it is used
Edward J. Nangle, David S. Gardner, James D. Metzger, John R. Street, and T. Karl Danneberger
areas of ≈1500 m −2 each were then established in June 2006 with washed creeping bentgrass ‘Penncross’ ( Agrostis stolonifera L. cv. Penncross) sod (H&E Sod Nursery, Momence, IL) and allowed to acclimate for 3 weeks before initiation of routine
Eric M. Lyons, Robert H. Snyder, and Jonathan P. Lynch
Root distribution in turfgrass systems influences drought tolerance and resource competition with undesirable species. We hypothesized that spatial localization of phosphorus (P) supply would permit manipulation of turfgrass root distribution. To test this hypothesis, creeping bentgrass (Agrostis stolonifera L.) plants were exposed to localized P supply in two experiments. The first experiment split the root zone horizontally into two different growth tubes and the second used alumina-buffered P (Al-P) to localize P availability deeper within a continuous root zone. In the horizontally split root zones, heterogeneous P availability led to no difference in shoot growth compared with uniform P availability. Root proliferation was greatest in the growth tube with available P compared with the growth tube without P. The use of Al-P, regardless of its spatial distribution, doubled root-to-shoot ratios compared with soluble P. Much of the increase in the ratio was accounted for by reduced shoot growth. Use of Al-P increased rooting deeper in the root zone, especially when the Al-P was mixed only in the lower portion of the root zone. Our results are consistent with the hypothesis that root distribution of creeping bentgrass can be manipulated by spatial localization of P supply in the root zone and indicate that relative biomass allocation to roots and shoots may be manipulated with buffered P sources.
Gerald M. Henry and Stephen E. Hart
The tolerance of velvet bentgrass (Agrostis canina L.) to the herbicide fenoxaprop is not known. In greenhouse experiments velvet bentgrass cultivars SR7200 and Vesper had a much greater degree of tolerance to fenoxaprop at rates ranging from 0.01 to 0.30 kg·ha-1 relative to L-93 creeping bentgrass (Agrostis stolonifera L.). SR7200 and Vesper were tolerant to fenoxaprop at 0.15 kg·ha-1 or lower and growth reductions did not exceed 10% at the highest fenoxaprop rate of 0.30 kg·ha-1. In contrast, growth reduction of L-93 creeping bentgrass was evident at the lowest application of fenoxaprop at 0.01 kg·ha-1 and increased as fenoxaprop rates increased, reaching as high 58% at 0.30 kg·ha-1. Field experiments were conducted in 2002 and 2003 to compare the tolerance of established SR7200 velvet bentgrass and Penn A-4 creeping bentgrass maintained at 3.2 mm to three sequential applications at 21 day intervals of fenoxaprop at 0.02, 0.04, and 0.07 kg·ha-1. Turf quality of SR7200 was equal to the untreated following all fenoxaprop applications except the third sequential application at 0.07 kg·ha-1. Penn A-4 turf quality was consistently reduced compared to the untreated following fenoxaprop applications of 0.04 and 0.07 kg·ha-1. Turf density of SR7200 was not affected by three sequential applications of fenoxaprop at 0.02 and 0.04 kg·ha-1 but was reduced by 8% at 0.07 kg·ha-1. Penn A-4 turf density was reduced by 10 and 33% following three sequential applications of fenoxaprop at 0.04 and 0.07 kg·ha-1, respectively. Results from these studies showed that the velvet bentgrass cultivars were more tolerant to fenoxaprop, compared to the creeping bentgrass cultivars evaluated. Chemical names used: (+)-ethyl2-[4-[(6-chloro-2-benzoxazolyl)oxy]p henoxy] propanoate (fenoxaprop). 3,5-pyridinedicarbothioic acid, 2-(difluoromethyl)-4-(2-methylpropyl)-6-(trifluoromethyl)-S,S-dimethylester (dithiopyr).
Patricia Sweeney, Karl Danneberger, Daijun Wang, and Michael McBride
Limited information is available on the performance under temperate conditions in the United States of recently released cultivars of creeping bentgrass (Agrostis stolonifera L.) with high shoot density for use on golf course putting greens. Fifteen cultivars were established in Aug. 1996 on a greens mix with high sand content to compare their seasonal weights and total nonstructural carbohydrate (TNC) contents. The cultivars were maintained at 3.1 mm height of cut. Shoot density counts were taken during Apr., July, and Oct. 1998. Root weights and nonstructural carbohydrate levels were assessed monthly from June 1997 through Nov. 1998. A cultivar group contrast between the high shoot density cultivars (`Penn A1', `Penn A2', `Penn A4', `Penn G1', `Penn G2', and `Penn G6') and the standard cultivars (`Penncross', `Crenshaw', `Southshore', `DF-1', `Procup', `Lopez', `SR1020', and `Providence') revealed that the former averaged 342.9 and 216.1 more shoots/dm2 on two of the three sampling dates. Root dry weights did not vary significantly (P ≤ 0.05) among the cultivars. Performing a contrast between new high shoot density cultivars and standard cultivars revealed greater root dry weight in the former during Mar. and May 1998. Differences (P ≤ 0.05) in TNC were observed on two of the 18 sampling dates, but no trends were evident.
Chunhua Liu and R.J. Cooper
Growth and mineral nutrient content of creeping bentgrass [Agrostis stolonifera (L.) var. palustris (Huds.) Farw.] in response to salinity and humic acid (HA) application were investigated, and the effects of HA application on salinity tolerance was evaluated. Bentgrass plugs were grown hydroponically in one-quarter-strength Hoagland's nutrient solution containing HA at 0 or 400 mg·L-1 with salinity levels of 0, 8.0, or 16.0 dS·m-1. Clipping dry weight (DW), tissue water content, and net photosynthesis (PN) were measured weekly for 1 month. Maximum root length, and root DW from 0 to 10 cm and >10 cm root zones were determined 31 days after treatment (DAT). The turfgrass plugs were mowed three times weekly, with clippings collected and dried for mineral nutrient analysis. Salinity was inversely related to clipping DW, tissue water content, PN, and maximum root length. Salinity had less effect on root growth than top growth. HA treatment did not affect tissue water content, PN, or root growth of salt-stressed turf. Salinity decreased uptake of N, P, K, Ca, and S; increased uptake of Mg, Mn, Mo, B, Cl, and Na; and had no influence on uptake of Fe, Cu, and Zn. Application of HA at 400 mg·L-1 during salinity stress neither increased uptake of the mineral nutrients inhibited by salinity, nor decreased uptake of nutrients which were excessive and toxic in the salinity solution. In general, application of HA did not improve salinity tolerance of creeping bentgrass.
Chunhua Liu, R.J. Cooper, and D.C. Bowman
Humic acids (HA) reportedly enhance the growth of numerous crops; however, little information is available as to their effects on turfgrasses. Experiments were conducted to evaluate the effect of a commercial preparation of HA on the photosynthesis, chlorophyll concentration, rooting, and nutrient content of `Crenshaw' creeping bentgrass (Agrostis stolonifera L.). Bentgrass plugs were grown hydroponically in one-quarter-strength Hoagland's nutrient solution containing HA at 0, 100, 200, or 400 mg·L-1 with measurements made weekly for 1 month. The photosynthetic rates of plants growing in 100 or 200 mg·L-1 rarely differed from that of the control, but 400 mg·L-1 significantly enhanced net photosynthesis on all four observation dates. Chlorophyll content was unaffected by HA rate on all observation dates. Root dehydrogenase (DH) activity and root mass regrowth were significantly increased by HA at 400 mg·L-1 on all dates. The 100 and 200 mg·L-1 rates increased root DH activity on two of four observation dates, but root regrowth was unaffected. At one or more of the rates used, HA increased tissue concentrations of Mg, Mn, and S and decreased those of Ca, Cu, and N, but had no influence on the concentrations of P, K, Fe, Mo, and Zn.
D.S. Gardner, T.K. Danneberger, E. Nelson, W. Meyer, and K. Plumley
Genetically transformed cultivars of creeping bentgrass (Agrostis stolonifera L. syn. Agrostis palustris Huds.) that are resistant to glyphosate have been developed by a collaboration of the Scotts and Monsanto companies. Prior to commercial release, we desired to determine if the transformed plants behave similarly to traditional creeping bentgrass except for the effects expected from the inserted gene, i.e., resistance to glyphosate. Therefore, studies were initiated on 23 June 2000 in Marysville, Ohio; 14 July 2000 in Middleton, N.J.; and 20 June 2000 in Gervais, Ore., to examine the relative lateral spread and competitive ability of several transformed lines of creeping bentgrass, non-transformed controls, and reference cultivars. Vegetative plugs of creeping bentgrass were transplanted into a mature stand of Kentucky bluegrass (Poa pratensis L.) or a uniform mixture of Kentucky bluegrass with perennial ryegrass (Lolium perenne L.). The plots were watered as needed to prevent moisture stress. Competitive ability of the transformed plants and reference cultivars were determined monthly by measuring the average diameter of the creeping bentgrass patch. On all observation dates, the transgenic lines, as a group, were smaller in average diameter (5.1-7.6 cm) compared to the reference cultivars (5.4-14.2 cm) and non-transformed control lines (5.9-10.2 cm). At the end of the observation period (Aug. 2001), no differences (P = 0.05) in lateral spread were observed between individual lines of transgenic bentgrass. Three lines of interest, ASR365, ASR368, and ASR333, had lateral spread rates that are similar to, or less than, that of their non-transformed parent and the conventional creeping bentgrass cultivars tested. Chemical names used: N-(phosphonomethyl) glycine (glyphosate).
Qingzhang Xu, Bingru Huang, and Zhaolong Wang
Heat injury in creeping bentgrass (Agrostis stolonifera var. palustris Huds) has been associated with decreases in carbohydrate availability. Extending light duration may increase carbohydrate availability and thus improve growth of creeping bentgrass under heat stress. The objective of this study was to investigate whether turf performance and carbohydrate status could be improved by extending daily light duration for creeping bentgrass exposed to supraoptimal temperature conditions. `Penncross' plants were initially grown in growth chambers set at a day/night temperature of 20/15 °C and 14-hour photoperiod and then exposed to a day/night temperature of 33/28 °C (heat stress) and three different light durations: 14 (control), 18, and 22 hours (extended light duration) for 30 days. Turf quality and tiller density decreased with the duration of heat stress, as compared to the initial level at 20 °C, regardless of the light duration. However, both parameters increased with extended light duration from 14 to 18 or 22 hours. Extended light duration, particularly to 22 hours, also improved canopy net photosynthetic rate from -1.26 to 0.39 μmol·m-2·s-1 and daily total amount of carbon assimilation from -6.4 to 31.0 mmol·m-2·d-1, but reduced daily total amount of carbon loss or consumption to 50% through dark respiration compared to 14 hours treatment by the end of experiment. In addition, extending light duration from 14 to 22 hours increased water-soluble carbohydrate content in leaves both at the end of light duration and the dark period. These results demonstrated that extending light duration improved turf performance of creeping bentgrass under heat stress, as manifested by the increased tiller density and turf quality. This could be related to the increased carbohydrate production and accumulation. Supplemental lighting could be used to improve performance if creeping bentgrass is suffering from heat stress.