Anthocyanins are plant pigments that are in demand for medicinal and industrial uses. However, anthocyanin production is limited due to the harvest potential of the species currently used as anthocyanin sources. Rough bluegrass (Poa trivialis L.) is a perennial turfgrass known for accumulating anthocyanins, and may have the potential to serve as a source of anthocyanins through artificial light treatments. The objectives of this research were to determine optimal light conditions that favor anthocyanin synthesis in rough bluegrass, and to determine the suitability of rough bluegrass as a source of anthocyanins. When exposed to high-intensity white light, rough bluegrass increased anthocyanin content by 100-fold on average, and anthocyanin contents greater than 0.2% of dry tissue weight were observed in some samples. Blue light, at intensities between 150 and 250 μmol·m−2·s−1, was the only wavelength that increased anthocyanin content. However, when red light was applied with blue light at 30% or 50% of the total light intensity, anthocyanin content was increased compared with blue light alone. Further experiments demonstrated that these results may be potentially due to a combination of photosynthetic and photoreceptor-mediated regulation. Rough bluegrass is an attractive anthocyanin production system, since leaf tissue can be harvested while preserving meristematic tissues that allow new leaves to rapidly grow; thereby allowing multiple harvests in a single growing season and greater anthocyanin yields.
Dominic P. Petrella, James D. Metzger, Joshua J. Blakeslee, Edward J. Nangle, and David S. Gardner
Edward J. Nangle, David S. Gardner, James D. Metzger, John R. Street, and T. Karl Danneberger
Decreased light quantity or quality affects the growth of turfgrass plants. Shade causes thinning of turfgrass stands and loss in surface quality. Plant changes include increased chlorophyll levels, lower soluble sugars, and loss of canopy cover. The objective of this research was to investigate if applications of foliar nitrogen and trinexapac-ethyl [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (TE) would result in beneficial biochemical changes in creeping bentgrass (Agrostis stolonifera L. cv. Penncross) grown in different shaded environments. Foliar applications of three nitrogen treatments, (NH2)2CO, Ca(NO3)2, or (NH4)2SO4, were made weekly at 0.43 g N/m2. Growth regulator treatments consisted of an untreated control or TE applied biweekly at an a.i. rate of 0.057 kg·ha−1. Plots were established in full sun (FS), neutral shade (NS), and deciduous shade (DS). Chlorophyll content, soluble carbohydrates, flavonoids, clipping yield, and color were measured. Nitrogen treatments caused some variation in levels of soluble carbohydrates in shaded conditions. Chlorophyll (Chl) levels varied between TE treatments, with increased levels of chlorophyll b (Chl b) found in TE-treated plots under FS. Application of TE resulted in higher flavonoid concentrations in leaf tissue in shaded conditions. Repeated applications of (NH2)2CO significantly improved color (P = 0.05). Turfgrass managers maintaining creeping bentgrass in shade may benefit from applications of TE and (NH2)2CO.
Edward J. Nangle, David S. Gardner, James D. Metzger, Dominic P. Petrella, Tom K. Danneberger, Luis Rodriguez-Saona, and John L. Cisar
Ultraviolet (UV) radiation poses a potential stress for plant growth and development due to its effect on photosynthesis and plant productivity. In the northern hemisphere, peak UV radiation exposure is predicted to occur from 2010 to 2020, with reduced color from UV-related injury, a possibility for turfgrasses. The objective of this study was to investigate the effects of ultraviolet-B (UV-B) light on turfgrass growth and morphology in three cool-season grasses. Cultivars Barvado tall fescue [Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.], Penncross and L-93 creeping bentgrass (Agrostis stolonifera L.), and Barlenium perennial ryegrass (Lolium perenne L.), were selected because of limited information on their growth and development in elevated UV conditions at heights of cut above 10 cm. The impact of UV-B light treatment on color, relative growth rate, and tillering was measured over a 4-week period in repeated experiments. Ultraviolet-B radiation levels were measured at 16 kJ·m−2·d−1 biologically effective UV-B light in growth chambers programmed for a day/night regime of 14/10 hours. Chamber temperatures were maintained at 20 °C day/17 °C night. Ultraviolet-B light significantly inhibited tiller production in the first experiment in all grasses except PR, whereas no grasses were inhibited in the second experiment. Relative growth rates in all grasses were significantly lower in UV-B conditions 3 weeks after treatment initiation. Turfgrasses exposed to this level of UV-B light at typical lawn heights-of-cut had lower color ratings compared with the non-UV-B-treated control at 2 weeks after treatment initiation. The experiments demonstrated that exposure to UV-B resulted in a decline of growth rate and color in cool-season turfgrasses within a timeframe of 2 weeks. Coarse-textured turfgrasses [tall fescue (TF)/perennial ryegrass (PR)] may be more adapted to higher UV-B conditions due to morphological differences compared with the finer textured varieties [creeping bentgrass (CB)].