English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Calcium-rich vegetables in the diet could ameliorate the potential for calcium (Ca) deficiency in human nutrition. This study investigated the prospect of increasing Ca density of lettuce (Lactuca sativa L.) through cultivar selection and nutrient management in a greenhouse. Eighteen lettuce cultivars including butterhead, romaine, and loose-leaf phenotypes of heritage and modern genetics were tested. Organic fertilizer (3N–0.7P– 3.3K) and commercial conventional fertilizer (20N–4.4P–16.6K) factored with three Ca levels (50, 100, 200 mg·L as CaCl2) were the fertilizer regimes. Calcium in whole shoots was analyzed by atomic absorption spectrometry of oven-ashed samples. Heritage cultivars had a significantly higher Ca concentration (1.93% dry weight) than modern cultivars (1.54%). Loose-leaf phenotypes had the highest Ca concentration (2.06%) followed by butterhead (1.66%) and romaine (1.49%). Accumulation of Ca was higher with the conventional fertilizer (1.90%) than with the organic fertilizer (1.58%). Elevated Ca level in the fertility regimes raised the Ca concentration in lettuce from 1.56% at 50 mg·L to a mean of 1.82% at 100 mg·L and 200 mg·L. Large differences in Ca concentration occurred among individual cultivars with ranges from 1.27% to 3.05%. ‘Salad Bowl’, ‘Red Deer Tongue’, ‘Buttercrunch’, and ‘Bronze Mignonette’ were the top in cultivar ranking with mean Ca concentration of 2.50%, whereas ‘Adriana’, ‘Australe’, ‘Coastal Star’, and ‘Forellenschluss’ were low accumulators with a mean of 1.33%. Head size of cultivars had no correlation with Ca concentration. This experiment indicates that selection of nutrient regimes and cultivars can be used to increase Ca accumulation in lettuce. Critical functions in the human body require mineral nutrients that are obtained through consumption of food. Calcium is required for constructing and maintaining bones, clotting of blood, and for function of hormones and enzymes (Department of Health & Human Services, 2000; Ervin et al., 2004; Karll, 2000; Krause and Mahan, 1984; National Research Council, 1989). Diets rich in Ca minimize Ca deficiency and maximize good health and well-being (Greenwald et al., 2001). The recommended daily intake of Ca for most men and women is 1000 mg·d (Meacham et al., 2008); however, for elderly individuals, the required Ca intake should total 1300 to 1700 mg·d (Heaney, 2001). A study suggested that it is possible to improve dietary Ca intake by increasing consumption of fruits, vegetables, and Ca-rich foods (Bernstein et al., 2002). However, fresh fruits are high in vitamins but are often low in minerals (Ashmead, 1982); on the other hand, fresh leafy vegetables are major sources of minerals (Kamchan et al., 2004). Vegetables such as kale, celery, collard, Chinese cabbage, and soybean sprouts contain high levels of Ca (Kamchan et al., 2004). Lettuce (Lactuca sativa L.) is an important vegetable crop with high market value, and its nutritional characteristics have been studied throughout the world (Ashkar and Ries, 1970; Keat et al., 1999). The Ca content of lettuce is affected by relative humidity, which affects Ca distribution in the shoots, thereby resulting in the deficiency disorder of tipburn (Collier and Tibbitts, 1984; Schlagnhaufer et al., 1987). Degree Brix, a measure of sucrose, is used commonly for expressing the quality of juices, fruits, and vegetables (Hale et al., 2005; Ikeda et al., 2013; Widodo et al., 1996). This use has been expanded to include the concept that foods with high Brix readings also are high in mineral nutrients and that Brix readings are a general indicator of nutritional qualities of foods (Anderson, 2009; Frank, 2013; Sullivan, 2012). This study was conducted to determine whether the nutrient concentration of lettuce varied among cultivars and if nutritional regimes could be managed to increase the Ca contents in the produce. Brix was measured in this investigation to assess whether a correlation occurred between this reading and Ca concentration in lettuce. Materials and Methods Plant materials. Eighteen lettuce cultivars of heritage and modern genetics with butterhead, romaine, and loose-leaf phenotypes were studied. Seeds were obtained from Seeds of Change (Rancho Dominguez, CA) and Johnny’s Seeds (Winslow, ME). All seeds were planted in peatmoss-based medium (Fafard Growing Mix 1-PV; Conrad Fafard Inc, Agawam, MA). Seedlings at the threeleaf stage were transplanted to 15-cm round standard pots filled with the same peatmoss medium. Temperatures generally ranged from 23 to 30 C during day and 18 to 24 C at night. Light conditions in the greenhouse, at the University of Massachusetts, Amherst (lat. 42.37 N, long. 72.53 W), were from sunlight during the season of production in June and July 2010 with 13 h of daylight and 11 h of night. Treatments. Two fertilizers factored with three elevated Ca concentrations were fertility regimes for this study. One regime was conventional, peatlite professional fertilizer (20N–4.4P–16.6K with micronutrients reported; Peters Fertilizer Products, J.R. Peters, Inc., Allentown, PA). The conventional fertilizer solution was prepared at 1 g·L and 4 mL 0.5 M MgSO4 was added per liter. The second fertilizer regime was a commercial organic fertilizer (3N–0.7P–3.3K with micronutrients not reported; Pure Blend Pro Grow; Pure Blend Pro Fertilizer Products, Chandler, AZ). The organic fertilizer solution was prepared at 6.7 mL·L to approximate the supply from the conventional fertilizer. The factorial design consisted of three concentrations of Ca (50, 100, 200 mg·L as CaCl2) with three replicates in randomized complete blocks. The two fertilizers solutions were applied at 100 mL/plant for the first week and then 200 mL/plant until harvest 3 weeks later. The nutrient solution drained through the medium during application to avoid salt accumulation in the medium and to ensure a constant supply of nutrients. Measurements. At harvest, fresh weights of plants were recorded, and the samples were washed once in tap water and twice in deionized water and oven-dried to a constant weight at 70 C with dry weights being recorded. For tissue analysis of Ca, 0.5 g of ground samples was ashed at 500 C for 8 h in a furnace, and the ash was dissolved in 10% (v/v) HCl prepared with distilled H2O and concentrated HCl. The solutions were analyzed for Ca by atomic absorption spectrometry (Kalra, 1998). Brix. Two leaves were selected from each head, one leaf from the center of the head and one from the outside. Juice was squeezed by hand into a plastic cup, mixed, and measured Received for publication 2 Aug. 2013. Accepted for publication 10 Oct. 2013. This material is based on work supported by the National Institute of Food and Agriculture, U.S. Department of Agriculture, the Massachusetts Agricultural Experiment Station, and the Stockbridge School of Agriculture under Projects number MAS00963 and MAS00981. Paper number 3497 in the Experiment Station journal series. To whom reprint requests should be addressed; e-mail barker@umass.edu. 1502 HORTSCIENCE VOL. 48(12) DECEMBER 2013 by a refractometer in sunlight (Pocket Refractometer PAL-1; ATAGO, Tokyo, Japan). One degree Brix is equivalent to 1 g of sucrose in 100 mL water. No correlation of Brix with Ca or other nutrient contents in plants is available. Tipburn. Tipburn was assessed just before harvest by examination of each head of lettuce and ranking the severity of tipburn with an index of 0, no tipburn; 1, slight tipburn; 2, moderate tipburn; and 3, severe tipburn based on judgment of the investigators. Statistical analysis. The statistical analyses of data were performed by analysis of variance or regression analysis (Steel and Torrie, 1980) with data processing by SAS software (SAS Version 9.2; Cary, NC). Means were separated by Duncan’s new multiple range test for main effects of treatments and by least significant difference for interactions of treatments (Steel and Torrie, 1980).

Nutrient Density in Lettuce Cultivars Grown with Organic or Conventional Fertilization with Elevated Calcium Concentrations