Dean A. Kopsell

Nitrogen Concentration Affects Nutrient and Carotenoid Accumulation in Parsley

ABSTRACT Previous research has suggested that the herbal crop parsley (Petroselinum crispum Nym.) has a relatively high concentration of nutritionally important carotenoid phytonutrients, such as lutein-zeaxanthin and β -carotene. Nitrogen (N) has the most direct impact on plant growth, but influence of N on phytonutritional quality is contradictory. Therefore, the objectives of this study were to measure the effects of different concentrations of N on growth, elemental accumulation, and carotenoid production in parsley. ‘Dark Green Italian’ parsley was greenhouse-grown in a nutrient solution with 6.0, 13.1, 26.3, 52.5, or 105.0 mg N L−1. After 8 weeks, plants were harvested and analyzed for biomass production, micro- and macronutrient concentrations, and lutein-zeaxanthin and β -carotene levels. Increasing N in the nutrient solution increased plant biomass, leaf tissue N, phosphorus (P), potassium (K), lutein-zeaxanthin, β -carotene, and chlorophyll. Leaf iron (Fe), manganese (Mn), and molybdenum (Mo) decreased with increases in N in nutrient solutions. Quadratic increases in response to increasing solution N occurred for leaf calcium (Ca), magnesium (Mg), sulfur (S), boron (B), copper (Cu), and zinc (Zn). Increasing the elemental and carotenoid concentrations in parsley through N fertility modification would be expected to increase the nutritional value of this culinary herbal crop.

Nitrogen Levels Influence Biomass, Elemental Accumulations, and Pigment Concentrations in Spinach

ABSTRACT Spinach (Spinacia oleracea L.) has one of the highest United States per capita consumption rates among leafy vegetable crops, and also ranks second for lutein and β-carotene carotenoid concentration. The objectives of this study were to determine the effects of nitrogen (N) concentration on elemental and pigment accumulation in spinach. Two spinach cultivars (‘Melody’ and ‘Springer F1’) were greenhouse grown in nutrient solution culture under N treatments of 13, 26, 52, and 105 mg L− 1. Leaf tissue biomass increased from 45.6 to 273.2 g plant− 1 and from 127.0 to 438.6 g plant− 1 as N increased from 13 to 105 mg L− 1 for ‘Springer F1’ and ‘Melody’, respectively. Leaf tissue N, phosphorus (P), calcium (Ca), magnesium (Mg), copper (Cu), and zinc (Zn) responded to N treatments. Lutein accumulations, expressed on a fresh weight basis, responded quadratically to increasing N treatments for ‘Springer F1’. Maximum lutein values were 110 and 76 μ g g− 1 on a fresh weight basis, and maximum β-carotene values were 85 and 57 μ g g− 1 on a fresh weight basis for ‘Springer F1’ and ‘Melody’, respectively. Interestingly, N levels had a significant effect on carotenoid accumulation in both ‘Springer F1’ and ‘Melody’ when the pigments were expressed on a dry weight basis. Leaf tissue lutein increased from 0.59 to 1.06 mg g− 1 and from 0.59 to 0.90 mg g− 1 on a dry weight basis with increasing N treatments for ‘Springer F1’ and ‘Melody’, respectively. Reporting lutein and β-carotene on both a fresh and dry weight basis may be the most accurate way to express the carotenoid values of spinach.

Effects of Mesotrione on Perennial Ryegrass (Lolium perenne L.) Carotenoid Concentrations under Varying Environmental Conditions

Mesotrione is a carotenoid biosynthesis inhibiting herbicide, which is being evaluated for use in turfgrass. Carotenoids are important light harvesting and photoprotecting pigments that dissipate and quench excess light energy. The effects of mesotrione on carotenoid concentrations in turf and weed species, such as perennial ryegrass (Lolium perenne L.), are poorly understood. Mesotrione injury to perennial ryegrass has been reported, and symptomology may differ due to postapplication environmental factors such as irradiance and temperature. Research was conducted to investigate the effects of mesotrione on perennial ryegrass under varying irradiance (600, 1100, or 1600 micromol/m (2)/s) at three different temperatures (18, 26, and 34 degrees C). Postapplication irradiance and temperature levels did not affect visual injury symptoms in perennial ryegrass. Bleaching of treated plants was highest 7 days after treatment (DAT; 8%) and recovered to nontreated levels by 21 DAT. Mesotrione applications did not decrease perennial ryegrass foliar biomass accumulations. Carotenoid concentrations of nontreated plants were similar to those reported in creeping bentgrass and many green leafy vegetable crops. However, chlorophyll a and b, beta-carotene, lutein, and violaxanthin concentrations decreased due to mesotrione applications, while phytoene and zeaxanthin, a photoprotecting carotenoid, increased. The photochemical efficiency (F v/ F m) of treated plants was lower than nontreated plants at 3 and 7 DAT; however, treated plants recovered to nontreated levels 21 DAT. Results indicate that postapplication irradiance and temperature levels may not affect mesotrione efficacy in perennial ryegrass. Preferential accumulation of zeaxanthin following mesotrione applications may be a stress-related response, which may reduce light harvesting complex size and directly quench excess light energy.

Selenium Influences Glucosinolate and Isothiocyanates and Increases Sulfur Uptake in Arabidopsis thaliana and Rapid-Cycling Brassica oleracea

This study investigated the impact of Se on glucosinolates (GSs) and isothiocyanates (ITCs). Plants of Arabidopsis thaliana cv. Columbia and a rapid-cycling base population of Brassica oleracea were grown hydroponically under different Se and S concentrations. The objective was to determine the effects of increasing Se and S concentrations on the GSs and ITCs. The results indicate that S and Se concentrations increased in A. thaliana and B. oleracea leaf tissue in response to increasing Se treatments. Aliphatic and total GSs decreased significantly (P ≤ 0.001) from 0.0 to 3.2 mg Se L(-1) in B. oleracea and A. thaliana leaf tissues. Consequently, aliphatic and total ITCs decreased significantly (P ≤ 0.001) from 0.0 to 3.2 mg Se L(-1) in B. oleracea and A. thaliana leaf tissues. Data demonstrate that high levels of anticarcinogenic GSs can be maintained as the Se concentration is increased to 0.8 mg L(-1). Thus, it is feasible to increase Se to beneficial dietary levels without compromising GS concentrations.

Mesotrione plus Prodiamine for Smooth Crabgrass (Digitaria ischaemum) Control in Established Bermudagrass Turf

Crabgrass species are problematic weeds in bermudagrass turf that can be controlled by PRE herbicide applications. Because of the difficulty in predicting crabgrass emergence and other prevailing management constraints, PRE herbicide applications are not always properly timed. Mesotrione controls crabgrass both PRE and POST; however, relatively short soil-residual activity limits its use as a PRE herbicide. Two experiments were conducted to evaluate smooth crabgrass control with PRE applications of mesotrione plus prodiamine. The first experiment evaluated the influence of application timing on the efficacy of mesotrione-plus-prodiamine combinations. Applications were made every 2 wk from March 15 to May 24. Mesotrione plus prodiamine controlled smooth crabgrass more consistently across all application dates than either mesotrione or prodiamine applied alone. The second experiment evaluated mesotrione along with current PRE and early POST herbicide treatments used for control of crabgrass. When applied at one to two tillers growth stage, mesotrione plus prodiamine controlled smooth crabgrass 99% when rated on August 31. Bermudagrass injury from mesotrione ranged from 9 to 44%, but did not result in any reduction in turf plant density. Mesotrione plus prodiamine is an effective tank mixture when prodiamine alone is not applied in a timely fashion; however, variable and excessive turf injury is a potential impediment to mesotrione use on bermudagrass turf. Nomenclature: Mesotrione, prodiamine, smooth crabgrass, Digitaria ischaemum (Schreb) Schreb. ex Muhl Schreb. DIGIS, bermudagrass, Cynodon dactylon L. CYNDA

Increase in Nutritionally Important Sweet Corn Kernel Carotenoids following Mesotrione and Atrazine Applications

The herbicide mesotrione inhibits a critical enzyme, phytoene desaturase, in plant carotenoid biosynthesis. Mesotrione is currently labeled for selective weed control in sweet corn ( Zea mays var. rugosa). Mesotrione applied alone, or in mixtures with the photosystem II inhibitor atrazine, acted to increase concentrations of kernel antheraxanthin, lutein, and zeaxanthin carotenoids in several sweet corn genotypes. Kernel lutein and zeaxanthin levels significantly increased 15.6% after mesotrione + atrazine early postemergence applications, as compared to the control treatment. It appears that mesotrione applications resulted in greater pools of kernel carotenoids once the sweet corn genotypes expressing moderate injury overcame the initial herbicidal photo-oxidative stress. This is the first report of herbicides directly up-regulating the carotenoid biosynthetic pathway in corn kernels, which is associated with the nutritional quality of sweet corn. Enhanced accumulation of lutein and zeaxanthin is important because dietary carotenoids function in suppressing aging eye diseases such as macular degeneration, now affecting 1.75 million older Americans.

Mesotrione control and pigment concentration of large crabgrass (Digitaria sanguinalis) under varying environmental conditions

BACKGROUND Mesotrione is a carotenoid biosynthesis-inhibiting herbicide currently labeled for crabgrass (Digitaria spp.) control. Mesotrione control of large crabgrass has been reported to vary with temperature and relative humidity; however, the effect of irradiance on mesotrione efficacy has not previously been reported. Likewise, little is known about pigment concentrations of Digitaria spp. The present research investigated the effects of mesotrione on large crabgrass, Digitaria sanguinalis (L.) Scop., control and pigment concentrations under varying irradiance at three temperatures. RESULTS Mesotrione (0.28 kg ha(-1)) control of large crabgrass did not differ between temperature levels (18, 26 and 32 degrees C). Control was similar at tested irradiance levels (600, 1100 and 1600 micromol m(-2) s(-1)). Mesotrione reduced large crabgrass chlorophyll a, chlorophyll b and total carotenoid concentrations, as well as chlorophyll a to b ratios. Treated plant bleaching was highest 7 days after treatment (DAT) but decreased by 21 DAT. Treated plants were less than 10% necrotic 3 and 7 DAT but nearly 35% necrotic 21 DAT. Treated large crabgrass bleaching was highest and photochemical efficiency was lowest 7 DAT. These results indicate that some plant recovery occurs prior to 21 DAT. CONCLUSION Although mesotrione efficacy has previously been reported to vary according to environmental factors, mesotrione control of large crabgrass did not vary with measured temperature and irradiance levels in this study. On account of crabgrass convalescence, secondary applications of mesotrione may control large crabgrass more effectively when applied prior to 21 DAT.

Effect of Reed-Sedge Peat Moss on Hybrid Bermudagrass Injury with Indaziflam and Prodiamine in Sand-Based Root Zones

Abstract PRE herbicides have been reported to injure both the foliage and roots of hybrid bermudagrass turf established in sand culture. Research was conducted to evaluate the influence of reed-sedge peat moss (RSPM) on hybrid bermudagrass injury following PRE herbicide applications to plants established in sand culture. Washed sod plugs were established in mini-rhizotrons constructed with sand root-zones varying in organic carbon content (0.000, 0.003, 0.007, and 0.012 kg kg−1). Herbicide treatments included indaziflam (35 and 52.5 g ai ha−1) and prodiamine (840 g ai ha−1). Significant foliar injury was only observed with indaziflam at 52.5 g ha−1. When applied to plants in sand with no detectable (0.000 kg kg−1) organic carbon, foliar injury measured 61% by 6 wk after treatment. Comparatively, injury with indaziflam at 52.5 g ha−1 was reduced by 40% with applications to plants established in sand with 0.007 kg kg−1 organic carbon. Root length, root length density, and root surface area were greatest in sand-based root zones with ≥ 0.007 kg kg−1 organic carbon regardless of herbicide treatment; however, only indaziflam (52.5 g ha−1) and prodiamine-treated plants exhibited diminished root parameters relative to the nontreated check. Data in the current study illustrate that RSPM can affect above- and belowground injury following PRE herbicide applications to hybrid bermudagrass in sand root-zones. Nomenclature: Indaziflam; prodiamine; hybrid bermudagrass; Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davey. Resumen Los herbicidas PRE han sido reportados como causantes del daño en el follaje y las raíces del césped bermuda híbrido en cultivo en arena. Se realizó una investigación para evaluar la influencia del musgo Sphagnum (RSPM) sobre el daño del césped bermuda híbrido después de aplicaciones de herbicidas PRE a plantas establecidas en cultivo en arena. Fragmentos lavados de estolones enraizados fueron establecidos en mini-rizotrones construidos con zonas de crecimiento radical de arena con un contenido variable de carbono orgánico (0.000, 0.003, 0.007, y 0.012 kg kg−1). Los tratamientos con herbicidas incluyeron (indaziflam 35 y 52.5 g ai ha−1) y prodiamine (840 g ai ha−1). Se observó un daño foliar significativo con indaziflam a 52.5 g ha−1. Cuando se aplicó a plantas en arena con carbono orgánico no detectable (0.000 kg kg−1), el daño foliar fue 61% a 6 semanas después del tratamiento. Comparativamente, el daño con indaziflam a 52.5 g ha−1 fue reducido en 40% con aplicaciones a plantas establecidas en arena con 0.007 kg kg−1 carbono orgánico. Las máximas longitud, longitud-densidad y área superficial de las raíces se observaron en zonas de crecimiento radical de arena con ≥0.007 kg kg−1 carbono orgánico sin importar el tratamiento del herbicida. Sin embargo, solamente plantas tratadas con indaziflam (52.5 g ha−1) y prodiamine exhibieron disminuciones en los parámetros de raíz en relación con el testigo no tratado. Los datos del presente estudio ilustran cómo RSPM puede afectar el daño del tejido aéreo y subterráneo en el césped bermuda híbrido posterior a aplicaciones de herbicidas PRE en las zonas de crecimiento radical en arena.

Nitrogen-Enhanced Efficacy of Mesotrione and Topramezone for Smooth Crabgrass (Digitaria ischaemum) Control

Abstract The herbicides mesotrione and topramezone inhibit 4-hydroxyphenylpyruvate dioxygenase (HPPD) and have efficacy against smooth crabgrass. Research was conducted to determine the impacts of soil-applied nitrogen (N) fertilizer on the effectiveness of single applications of mesotrione and topramezone for postemergence smooth crabgrass control. Field experiments in 2010 and 2011 evaluated the efficacy of mesotrione (280 g a.i. ha−1) and topramezone (9 g a.i. ha−1) for control of multitiller smooth crabgrass subjected to five N fertility treatments (0, 12, 25, 37, or 49 kg N ha−1). Greenhouse experiments evaluated the response of smooth crabgrass to mesotrione (0, 70, 140, 280, 560, and 1,120 g ha−1) and topramezone (0, 4.5, 9, 18, 36, and 72 g ha−1) with 0 or 49 kg N ha−1. Further research evaluated changes in smooth crabgrass leaf tissue pigment concentrations following treatment with mesotrione (280 g ha−1) and topramezone (18 g ha−1) with 0 or 49 kg N ha−1. In field experiments, N increased smooth crabgrass control with mesotrione and topramezone for 8 wk; however, increasing N rate above 25 kg ha−1 did not improve control on any rating date. In dose-response experiments, N application reduced I50 values for mesotrione and topramezone by 67 and 53%, respectively, 21 d after treatment (DAT). Reductions in aboveground biomass with both herbicides were greater when applied following N treatment as well. In leaf-response experiments, N decreased new leaf chlorophyll and carotenoid concentrations and new leaf production after treatment with topramezone. Future research should investigate whether increased translocation of these herbicides to meristimatic regions contribute to N-enhanced efficacy. Nomenclature: Mesotrione, smooth crabgrass (Digitaria ischaemum Schreb. ex Muhl.); topramezone.

Physiological role of carotenoids and other antioxidants in plants and application to turfgrass stress management

Abstract Reactive oxygen species (ROS) are highly destructive chemicals within plant systems. Antioxidants are important photoprotective chemicals that guard plants from oxidative stress. Antioxidants can be classified into two groups: enzymatic and non-enzymatic. Of the non-enzymatic antioxidants, carotenoids have received relatively little attention in turfgrass research. However, carotenoids are vital antioxidants for buffering of singlet oxygen, dissipation of excess light energy through non-photochemical quenching, and harvesting light energy and channeling to the photosystem. Greater emphasis on carotenoids in turfgrass research could provide several benefits. For example, new cultivars could be selected that have improved high light tolerance owing to greater zeaxanthin production. Additionally, xenobiotics could potentially increase carotenoid production, thereby increasing turfgrass survivability under oxidative stress. Previous research indicates turfgrass species have robust carotenoid pool levels comparable to vegetables and herbs consumed for their phytonutrient benefits.