Autoclaving is a standard procedure for sterilizing nutrient media for plant tissue cultures. Most tissue cultures are grown at pH 5.2 to 5.8 with pH adjustments being made prior to autoclaving. This paper reports that there are significant differences between initial pH levels and pH levels following autoclaving, particularly in the pH range of 5.7 to 8.5. This effect is noted with and without agar. In addition, we report that with time the pH of the medium drifts into the acid range. When Cucumis callus was added to the medium, the pH was changed significantly within 48 hours. The amount and direction (increase or decrease of pH) was significantly correlated with the original pH. This suggests that researchers should be wary of the true pH situation in their medium. In addition, in publications authors should specify whether their medium pH value was determined before or after autoclaving.

The goal of the professional lawn care industry is to provide the homeowner with a dark green weed-free lawn. Members of this industry are interested in techniques to enhance the color of a turfgrass stand in lieu of excessive N fertilization. The purpose ohbis research was to evaluate tbe use of foliar applications of Fe alone or in com· bination with N on the color response of Kentucky bluegrass (Poa pratensis L.). Iron sulfate or an iron chelate was applied at the rate of 1.1, 2.2, or 4.5 kg Fe ha-I in combination with either 0, 25, or 49 kg N ha-1 to a mixed 'Columbia'I'Touchdown' Kentucky bluegrass turf growing on a Catlin silt loam (fine-silty, mixed, mesic Typic Argiudoll). Color ratings and clipping weights were determined on a weekly basis until treatment effects were no longer significant. In a separate experiment, both sources of Fe were applied at rates of 1.1 to 72.4 kg Fe ha-I to Kentucky bluegrass to evaluate phytotoxicity. The color enhancement due to Fe applications without N lasted from several weeks to several months depending on the weather following application. Use of Fe during cool wet periods enhanced turf color for only 2 to 3 weeks and therefore, was considered of limited value. Iron applications during cool dry periods enhanced turf color for several months. The treatment of 2.2 kg ha-I of Fe from iron chelate was judged to be the most effective Fe treatment because the color enhancement was usually equal to that provided by a 4.5 kg rate of either source but it did not result in any discoloration as was found with the 4.5 kg rate. Combining Fe with tbe 25 kg ha-I rate of N resulted in color enhancement equal to that caused by applying 49 kg ba-I of N alone. The results of the study indicate that combining Fe with N can result in acceptable turfgrass color with lower rates of N. No permanent damage was caused to turfs receiving Fe at rates up to 72.2 kg ha-I although foliar phytotoxicity was observed.

Plant growth regulators are becoming important tools for managing high-quality turf. However, long-term suppression of growth might affect the potential of the turf to recuperate from summer stresses. This study was initiated to determine the impact of popular commercial turfgrass growth regulators (TGR) on the accumulation of total nonstructural carbohydrates (TNC), and their effect on turf quality. Three experiments, one each year from 1994 through 1996, were conducted on creeping bentgrass (Agrostis stolonifera Huds. `Penncross') in a greenhouse. Growth retardants evaluated included trinexapac-ethyl at 0.28 kg·ha-1, flurprimidol at 0.56 kg·ha-1, and paclobutrazol at 0.28 kg·ha-1. Each retardant was applied at three different intervals: a single initial application or multiple applications every 2 or 4 weeks, for the first 8 weeks of each experiment. The verdure and roots were harvested and analyzed for TNC. Trinexapac-ethyl, flurprimidol, and paclobutrazol significantly increased the TNC of creeping bentgrass 2 weeks after their initial application, but TNC levels began to decrease at week 4. The TNC content was strongly influenced by TGR application rate but not application intervals. A single trinexapac-ethyl application at 0.28 kg·ha-1 reduced TNC content more than did split applications, each at lower rates. Accordingly, TNC levels recovered more rapidly with lower, more frequent application rates; however, the retardation effect on vegetative growth diminished as the concentration was lowered. On the other hand, repeated low application rates of trinexapac-ethyl may have minimal effect on TNC accumulation. Chemical names used: [4(cyclopropyl-α-hydroxy-methylene)-3,5-dioxocyclohexanecarboxylic acid ethyl ester] (trinexapac-ethyl); {α-[1-methylethyl]-α-[4-(trifluoro-methoxy)phenyl]-5-pyrimidine-m ethanol}(flurprimidol);[(2RS,3RS)-1-(4-chlorophenyl)-4,4-dimethyl-2-1,2,4,-t riazole-1-yl)penta-n-3--ol] (paclobutrazol).

bohydrate content, which represents an energy source (White, 1973). The major TNC found in turfgrass shoots Any future precision turfgrass management system will benefit consist of the monosaccharides, glucose and fructose, from the evaluation of turfgrass stress through indirect measurements the disaccharide sucrose, various oligosaccharides of the of plant components. One such component might be the accumulation ␤-(2→6)-linked polyfructosylsucrose type, starch, and dynamics of total nonstructural carbohydrates (TNC). The effects of mowing height (MH) on TNC concentrations were measured in a field long-chain fructans (Hull, 1992). Some C-3 grasses accuexperiment. Clippings were collected from eight creeping bentgrass mulate starch (Bender and Smith, 1973) or sucrose (Borcultivars {Agrostis palustris Huds. [ϭ A. stolonifera var. palustris land and Farrar, 1985) in their stem bases, but most (Huds.) Farw.]} mowed at three different heights (0.64, 1.27, 1.90 cm) cool-season turfgrasses concentrate fructans in their from 1998 through 2001. Clippings were evaluated 29 times by samvegetative tissues (Chatterton et al., 1989). pling early in the photoperiod before 1200 h. Collected clippings The quantification of TNC in turfgrasses has proven were instantly frozen in liquid nitrogen and freeze-dried before TNC valuable in investigations of assimilate translocation in analyses. The TNC levels were predicted with near infrared reflectance perennial grasses (Hull and Smith, 1974) and the physiospectroscopy (NIRS) after building a predictive equation for each logical response of turf to environmental and cultural carbohydrate fraction with conventional laboratory values. Seasonal factors ( Watschke et al., 1970;Cooper et al., 1988). The trends in TNC concentrations and differences in TNC accumulation among creeping bentgrass cultivars were also evaluated. Mowing

Solution and suspension N sources have been developed as substitutes for urea in spray solutions used by lawn‐care professionals. A field study was conducted to evaluate the response of Kentucky bluegrass (Poa pratensis L.) growing on a Catlin silt loam (Typic Argiudoll), to applications of the new solution and suspension N sources, alone or combined with urea, by comparison to turf response from application of the traditional fertilizer materials ammonium nitrate (AN), Nitroform (ureaform), sulfur‐coated urea (SCU), ammonium sulfate (AS), granular urea, spray‐applied urea (US), and urea‐ammonium nitrate (UAN) solution. Also, urea and AS treated with dicyandiamide (DCD) were compared to the untreated sources. Fertilization rate was 195 kg N ha−1 yr−1 split into four applications except SCU which was applied twice. Turfgrass color and clipping production were monitored along with thatch accumulation and soil pH. In a second field experiment, foliar burn potentials of the new N sources were evaluated by comparison to burn potentials from US, UAN, and a liquid 12‐1.8‐3.3 fertilizer. Turf response to Formolene (solution N source) paralleled that due to US. Turf treated with US received higher color ratings than did that treated with Nitroform or FLUF (suspension N source) during the early growing season but this trend was reversed by late summer. Turf fertilized with FLUF resembled turf fertilized with Nitroform but was inferior to turf fertilized with SCU. There was no benefit from the inclusion of DCD with either AS or urea. Soil pH after 2 yr ranged from 5.3 to 6.4 and was lowest with AS treatment; thatch depth ranged from 7.0 to 19.3 mm and was greatest with AS treatment. Formolene and FLUF caused less foliar injury than did US, UAN, or the 12‐1.8‐3.3 fertilizer. Results from the two experiments indicated that the major advantage of using Formolene or FLUF was the reduced potential for foliar fertilizer burn.