Red Sails Research Articles

Temporal Separation of Red and Blue Photons Does Not Increase Photon Capture or Yield of Lettuce

Temporal separation of red (R) and blue (B) (alternating R/B) photons has been reported to increase leaf area, photon capture, and yield of lettuce compared with delivering both colors together (concurrent R+B). We grew three diverse lettuce cultivars (Grand Rapids, Rex, and Red Sails) under concurrent R+B photons (9/1 ratio) and alternating R/B photons (9/1 ratio) under an equal daily light integral (DLI) of either 8.6 or 23 mol⋅m−2⋅d−1. Contrary to five previous studies, we found no increase in either leaf area or fresh mass and dry mass in any of the alternating R/B photon treatments compared with concurrent R+B photons. In fact, at a DLI at 8.6 mol⋅m−2⋅d−1, alternating R/B photons decreased the dry mass of ‘Grand Rapids’ and ‘Rex’ lettuce by 38% and 17%, respectively. Two previous studies reported that photosynthetic rates increased with alternating R/B photons; however, we found that the net assimilation rate was generally decreased by alternating R/B photons. An analysis of images obtained from automated digital photography revealed that the relative expansion rate of leaves was 61% higher during intervals of pure B rather than intervals of pure R photons at the same photosynthetic photon flux density; however, this did not result in a higher leaf area compared with concurrent R+B photons. Overall, our studies do not indicate that alternating R/B photons increase lettuce leaf area or yield compared with concurrent R+B photons.

Combined application of zinc oxide and iron nanoparticles enhanced Red Sails lettuce growth and antioxidants enzymes activities while reducing the chromium uptake by plants grown in a Cr-contaminated soil

Soil contamination with chromium (Cr) is becoming a primary ecological and health concern, specifically in the Kasur and Sialkot regions of Pakistan. The main objective of the current study was to evaluate the impact of foliar application of zinc oxide nanoparticles (ZnO NPs) (0, 25, 50, 100 mg L−1) and Fe NPs (0, 5, 10, 20 mg L−1) in red sails lettuce plants grown in Cr-contaminated soil. Our results showed that both ZnO and Fe NPs improved plant growth, and photosynthetic attributes by minimizing oxidative stress in lettuce plants through the stimulation of antioxidant enzyme activities. At ZnO NPs (100 mgL−1), dry weights of shoots and roots and fresh weights of shoots and roots were improved by 53%, 58%, 34%, and 45%, respectively, as compared to the respective control plants. The Fe NPs treatment (20 mgL−1) increased the dry weight of shoots and the roots and fresh weights of shoots and roots by 53%, 76%, 42%, and 70%, respectively. Application of both NPs reduced the oxidative stress caused by Cr, as evident by the findings of the current study, i.e., at the ZnO NPs (100 mgL−1) and Fe NPs (20 mgL−1), the EL declined by 32% and 44%, respectively, in comparison with respective control plants. Moreover, Fe and ZnO NPs enhanced the Fe and Zn contents in red sails lettuce plants. Application of ZnO NPs at 100 mg L−1 and Fe NPs at 20 mg L−1, improved the Zn and Fe contents in plant leaves by 86%, and 68%, respectively, as compared to the control plants. This showed that the exogenous application of these NPs helped in Zn and Fe fortification in plants. At similar of concenteration ZnO NPs, CAT and APX activities were improved by 52% and 53%, respectively. Similarly, the POD contents were improved by 17% and 45% at 5 and 10 mg/L of Fe NPs. Furthermore, ZnO and Fe NPs limited the Cr uptake by plants, and the concentration of Cr in the leaves of lettuce was under the threshold limit. The exogenous application of ZnO NPs (100 mg L−1) and Fe NPs (20 mg L−1) reduced the Cr uptake in the leaves of red sails lettuce by 57% and 51%, respectively. In conclusion, ZnO and Fe NPs could be used for the improvement of plant growth and biomass as well as nutrient fortification in stressed environments. These findings not only underscore the efficacy of nanoparticle-assisted phytoremediation but also highlight its broader implications for sustainable agriculture and environmental health. However, future studies on other crops with molecular-level investigations are recommended for the validation of the results.

Impact of drought stress on vitamin C and anthocyanin content in cultivated lettuces (Lactuca sativa L.) and wild relatives (Lactuca spp.).

Lettuce production and quality could be seriously affected by the increasingly limited water resources. The effect of drought on the content of two antioxidant compounds, vitamin C and anthocyanins, in five cultivated lettuces and two wild relatives was assessed for 2 years. In leaf samples, Lactuca wild species generally had a higher content of total vitamin C than the cultivated lettuces. In contrast, the commercial varieties usually contained more total anthocyanins than the wild species. Total vitamin C decreased with the drought stress in all accessions, commercial varieties, and lettuce wild relatives, with this tendency being consistent and reproducible across the 2 years. These differences were significant in the case of the green commercial varieties 'Winter Crop' (in 2020/2021) and 'Dolomiti G12' (in 2021/2022) and very significant in the red commercial variety 'Red Sails' (in 2020/2021). However, the only group in which the effect of drought was either significant or very significant in both years was the wild species, Lactuca homblei and Lactuca dregeana, and in the latter also in both tissues (leaf and stem) analyzed. Water stress resulted in an increase of the total anthocyanin content in the leaves from all the accessions, both red commercial varieties and wild relatives, in both years. The most significant enrichment and the only one being either significant or very significant in both years was observed in one of the wild relatives assayed (L. homblei). Stems (L. dregeana) contained more anthocyanins than leaves under control conditions, and it was exactly the opposite under drought. Changes in anthocyanins in the two tissues in response to drought stress were in opposite directions, increasing in leaves and decreasing in stems. This could suggest a translocation of anthocyanins as a first quick mechanism to cope with a severe lack of water. In conclusion, anthocyanins (unlike vitamin C) could play a role in the mechanisms deployed by the plant to tolerate drought stress. The wild species with a robust significant enrichment in anthocyanins as a response to drought (L. homblei) is a promising plant material to breed more resilient lettuces.

Polystyrene particles combined with di-butyl phthalate cause significant decrease in photosynthesis and red lettuce quality.

Microplastics, an emerging pollutant in the environment, have attracted extensive attention in recent years for their possible negative impact on organisms. However, direct and indirect effects of polystyrene (PS) microplastics on vegetables are still not completely known. In this study, we used red lettuce (Lactuca sativa L. Red Sails) in a hydroponic system to investigate the effects of nano- and micro-sized PS and dibutyl phthalate (DBP) on the photosynthesis and red lettuce quality. The results clearly indicated that PS reduced the bioavailability of DBP while causing a decrease in the photosynthetic parameters as well as the total chorophyll content compared to DBP alone by affecting the crystalline structure of the water-soluble chlorophyll protein. Compared with DBP monotherapy, the presence of PS significantly increased hydrogen peroxide and malondialdehyde content in the lettuce treated with DBP, indicating serious oxidative damage. Furthermore, the soluble protein and sugar content in lettuce leaves decreased with higher PS concentration and smaller PS size. It may be due to PS inhibited lettuce root and ribulose-1,5-bisphosphate carboxylase/oxygenase activities. In contrast, nitrite content increased significantly with the induction of the glutathione-ascorbic acid cycle, indicating that the presence of PS reduced the quality of DBP-treated-red lettuce. Additionally, the nano-sized PS greatly inhibited lettuce growth and quality more than the micro-sized PS. This study described the interactions between microplastics and phthalates using molecular simulation and experimental validation to highlight the potential risks of microplastics on vegetable crop production.

Evaluation of Yield, Marketability, and Nitrate Levels of Lettuce Cultivars Produced in Southern Louisiana

Forty-five cultivars of lettuce (Lactuca sativa) were field-grown using best management practices at the Louisiana State University Agricultural Center (LSU AgCenter) Botanic Gardens in Baton Rouge during the Fall 2011 and Fall 2012 seasons. Recommended cultivars were selected for commercial production in Louisiana based on fresh weight and lettuce size (width and height). Nitrate (NO3–) concentration was analyzed for each cultivar, as lettuces are known to accumulate and concentrate NO3–, and were then compared with the U.S. Environmental Protection Agency’s (EPA) oral reference dose (RfD—the EPA’s maximum acceptable oral dose of a toxic substance) of 1.6 mg NO3-nitrogen (N) per kilogram body weight per day. Recommended butterhead cultivars were Caliente and Harmony (21.6 and 13.9 ppm NO3–, respectively); recommended green-leaf cultivars were Salad Bowl and Tango (10.6 and 4.6 ppm NO3–, respectively); recommended red-leaf cultivars were Red Salad Bowl, Red Sails, and New Red Fire (15.2, 15.4, and 24.0 ppm NO3–, respectively). The only recommended romaine cultivar was Green Towers (11.2 ppm NO3–), and recommended crisphead cultivars included Raider and Ithaca (17.6 and 14.9 ppm NO3–, respectively). Of the highest yielding cultivars, New Red Fire accumulated the greatest NO3– concentration: 24.0 ppm in both years 1 and 2. The NO3– concentration is less than the levels of concern for both men and women 20 to 74 years old, 3.9% of the RfD for men and 4.59% of the RfD for women.

From On High: after John Russell's Toul Rock (Guibel Rock) 1904–05

From On Highafter John Russell's Toul Rock (Guibel Rock) 1904–05 Kathryn Fry (bio) He sets his easel on the grassy sward by yellowgorse and wandering heath, above mudstonebattered into grey cliffs. On canvas, the broken headland becomes blue with brilliance,the aluminate to shine on the sea's mood. He grinds more pigment with oil, a little resin;he'll have each pure without loss, each to last(light-fast, weather-fast) so the sun's rays are always just so. There's Toul Rock withits window on the water, shimmering. Two decades he's known the bustle and calmof bays and inlets, red sails and fishermen;himself a sailor, a boat-builder. He brushes for an impression as rich as the real: the houseand garden for Marianna his love, their five sons and Jeanne. Each touch, each edge and spreadthis way and that, he'll square with his flat daband stroke into every nook: their simple lives on Belle-Île. Not Paris, nor Sydney, it's herehe can paint their everyday. Yesterday's ride with Marianna, the children at play, the flowersat Goulphar, the boats. He's here at the heightof his artistry en plein air. Like our best days of giving, he'll frame this and have us inthe high-key flow of an unfading summer. [End Page 396] Kathryn Fry Kathryn Fry has poems in various periodicals including Antipodes (2016) and the Newcastle Poetry Prize anthologies of 2014 and 2016. Her poems are also in Cordite Poetry Review (2016) and Not Very Quiet (2017, 2018). Her first collection is Green Point Bearings (Ginninderra Press, 2018). Copyright © 2021 Wayne State University Press

Internalization assessment of E. coli O157:H7 in hydroponically grown lettuce

Hydroponics and aquaponics have been gaining popularity to grow produce. Escherichia coli O157:H7 may internalize within edible produce. This study was to investigate E. coli O157:H7 internalization in red sails lettuce in a custom designed/constructed model hydroponic system under laboratory-controlled conditions. The objective was to determine not only the likelihood and level of internalization within hydroponically-grown lettuce but also potentially facilitated internalization with injured lettuce roots. The hydroponic tank was contaminated with Escherichia coli O157:H7 (E. coli) at 5-log CFU/mL. Roots of randomly selected plants were damaged by cutting either two- or three-times (two experimental treatment groups). Experimental control did not have root damage. Following lettuce harvest and surface decontamination, E. coli was enumerated on 3-M petrifilm™ EC. Internalized E. coli was detected at 2.4 ± 0.7, 4.0 ± 1.9, and 3.3 ± 1.3 log CFU/g in control, lettuce with two-, and three-cuts to their roots, respectively. Root injury showed a trend (p > 0.05) towards increasing E. coli internalization. Two-vs. three-cuts to roots did not (p > 0.05) affect E. coli internalization, although it showed 0.9-log CFU/g of a numerical difference. The highest level of internalized E. coli was detected at 4.7 log CFU/g in a lettuce plant that received two cuts to its root system.

Arriving at Corfu

Arriving at Corfu Constance Fenimore Woolson (bio) [End Page 194] The sea which I saw was of a miraculously blue tint; in the distance the cliffs of a mountainous island rose boldly from the water, their color that of a violet pansy; a fishing-boat with red sails was crossing the foreground; over all glittered an atmosphere so golden that it was like that of sunset in other lands, though the sky, at the same time, had unmistakably the purity of early morning. Later, on the deck, during the broadly practical time of after breakfast, this view, instead of diminishing in attraction, grew constantly more fair. The French novelist of today, Paul Bourget, describes Corfu as "so lovely that one wants to take it in one's arms!" Another Frenchman, who was not given to the making of phrases, no less a personage than Napoleon Bonaparte, has left upon record his belief that Corfu has "the most beautiful situation in the world." What, then, is this beauty? What is this situation? First, there is the long and charming approach, with the snow-capped mountains of Albania, in European Turkey, looming up against the sky at the end; then comes the landlocked harbor; then the picturesque old town, its high stone houses, all of creamy hue, crowded together on the hill-side above the sea-wall, with here and there a bell-tower shooting into the blue. Below is the busy, many-colored port. Above towers the dark double fortress on its rock. And, finally, the dense, grove-like vegetation of the island encircles all, and its own mountain-peaks rise behind, one of them attaining a height of three thousand feet. There are other islands of which all this, or almost all, can be said—Capri, for instance. But at Corfu there are two attributes peculiar to the region; these are: first, the color; second, the transparency. Although the voyage from Brindisi hardly occupies twelve hours, the atmosphere is utterly unlike that of Italy; there is no haze; all is clear. Some of us love the Italian haze (which is not in the least a mist), that soft veil which makes the mountains look as if they were covered with velvet. But a love of this softness need not, I hope, make us hate everything that is different. Greece (and Corfu is a Greek island) seemed to me all light—the lightest country in the world. In other lands, if we climb a high mountain and stand on its bald summit at noon, we feel as if we were taking a bath in light; in Greece we have this feeling everywhere, even in the valleys. Euripides described his countrymen as "forever delicately tripping through the pellucid air," and so their modern descendants trip to this day. This dry atmosphere has an exciting effect upon the nervous energy, and the faces of the people show it. It has also, I believe, the defect of this good quality—namely, an over-stimulation, which sometimes produces neuralgia. In some respects Americans recognize [End Page 195] this clearness of the atmosphere, and its influence, good and bad; the air of northern New England in the summer, and of California at the same season, is not unlike it. But in America the transparency is more white, more blank; we have little of the coloring that exists in Greece, tints whose intensity must be seen to be believed. The mountains, the hills, the fields, are sometimes bathed in lilac. Then comes violet for the plains, while the mountains are rose that deepens into crimson. At other times salmon, pink, and purple tinges are seen, and ochre, saffron, and cinnamon brown. This description applies to the whole of Greece, but among the Ionian Islands the effect of the color is doubled by the wonderful tint of the surrounding sea. I promise not to mention this hue again; hereafter it can be taken for granted, for it is always present; but for this once I must say that you may imagine the bluest blue you know—the sky, lapis lazuli, sapphires, the eyes of some children, the Bay of Naples—and the Ionian Sea is bluer than...

Evaluation of Lettuce Between Spring Water, Hydroponic, and Flow-through Aquaponic Systems

ABSTRACTLettuce (Lactuca sativa L.) is an important vegetable crop that can be grown in hydroponic and aquaponic systems. A comparative study to evaluate the efficacy of a cold water flow-through aquaponic system (FTS) to a hydroponic system is lacking. Twenty-seven lettuce cultivars with green or red leaves, in seven subtypes, belonging to four popular types in the Western diet, were grown in spring water or aquaponic or hydroponic treatments. Spring and aquaponic water flowed directly from a spring and a raceway growing rainbow trout, respectively. The hydroponic treatment had nutrients added to a recirculated system. Stand establishment, average yield, and productivity (yield/week) were determined for each subtype or cultivar and compared among water treatments. No comparison among lettuce types, subtypes, or cultivars was made due to inherent differences among genotypes. Total yield and productivity (402.5 g·m−2 and 4.9 kg/tray/week, respectively) in the FTS were lower than those in the hydroponic system (468.9 g·m−2 and 6.7 kg/tray/week, respectively). Average yields of butterhead and bibb subtypes in aquaponics were higher than in the hydroponic treatment. Bibb subtype lettuces performed better in the aquaponic treatment, and average yields of butterhead and romaine, one of the most popular and nutritious lettuce types, were similar to those in the hydroponic treatment. The cvs. Outredgeous in romaine, Winter Density in bibb, Red Sails in leaf, and Red Saladbowl in oakleaf subtypes were recommended for an FTS. Average yields of green lettuces were higher than red lettuces in the bibb subtype in all treatments. Lettuce yield, depending on cultivar, could be comparable to hydroponic or field production based upon yield per area.

Comparison of Two Harvest Methods for Lettuce Production in an Aquaponic System

<p>Aquaponics is an integrated food production technology of aquaculture and hydroponics. Lettuce (<em>Lactuca sativa </em>L.) is an economically important vegetable crop that can be grown aquaponically. In addition to selecting the right choice of lettuce cultivars, developing an optimal harvest strategy could increase lettuce production. Lettuce production using two harvest methods, Cut-and-Come-Again (CC) and Once-and-Done (OD), was evaluated using ‘Red Sails’ lettuce in a flow-through aquaponic system rearing trout. With the CC method continual harvesting was possible on a weekly basis after the initial harvest, while it took five weeks for each harvest using the OD method. The total yield of lettuce by the CC method was 6.7 kg from 9 trays, while 22.6 kg of lettuce was harvested by the OD method using 54 trays. In harvests by the OD method, 6 times as many seeds were sown compared to the CC method. The average yield per tray harvested by the CC method (744.4 g/tray) was 78% higher than that by the OD method (418.5 g/tray) because the CC method used 6 times less trays. Productivity, calculated by the average yield per growing week, of the two harvest methods at the first harvest was similar, but 4.8 times higher in the CC method than in the OD method at the second harvest due to the shorter harvest time. However, visual and decay ratings of lettuce harvested by the CC method began to decline afterwards. Together, the OD method after two consecutive harvests by the CC method would help growers to obtain increased yield of quality lettuce.</p>

Antioxidant phytochemicals in lettuce grown in high tunnels and open field

Genotype along with growing and management conditions can affect the content and the composition of phytochemicals in plants. Two lettuce (Lactuca sativa L.) cultivars, ‘Baronet’ and ‘Red Sails,’ were grown in an open field and high tunnels to examine the effect of growing conditions on their phytochemical content. The total phenolic concentration and antioxidant capacity of lettuce increased in response to transplanting from greenhouse to both open field and high tunnels. However, the increase was much greater when seedlings were transplanted to the open field and was more than 4 fold over the pre-transplant stage. The concentrations of two major phenolic compounds, chicoric acid and chlorogenic acid, were about 2.5–5.5 times higher in both cultivars when grown in open field than in high tunnels. Also, growing lettuce in open field resulted in a greater activation of key genes (phenylalanine ammonia-lyase, L-galactose dehydrogenase and γ-tocopherol methyl transferase) involved in the biosynthesis of phenolic compounds, ascorbic acid and α-tocopherol. ‘Red Sails’ accumulated caffeic acid 4 times as much in open field as it did in high tunnels and overall contained higher amount of phenolic compounds, especially in open field, than did Baronet. Although lettuce plants grown in open field were richer in phytochemicals, a significant reduction in biomass accumulation occurred when the lettuce plants were grown in open field compared to high tunnels regardless of cultivar. These results show that growing conditions, in addition to genotype, can significantly affect the content of many phenolic compounds in lettuce and that growing lettuce under open field can have a positive impact on its health-promoting qualities.

Hypobaria and hypoxia affects growth and phytochemical contents of lettuce

The primary objective of this research was to investigate how low pressure (hypobaria) and low oxygen (hypoxia) affect functional phytochemicals and the nutritional quality of ‘Red Sails’ lettuce ( Lactuca sativa L.). Plants were grown under two levels of total gas pressure (reduced or ambient (25 or 101 kPa, respectively)) at three levels of O 2 partial pressures (low, medium or ambient (6, 12 or 21 kPa, respectively)). Hypoxia effects on nutritional and functional phytochemicals were more pronounced than hypobaria effects. Regardless of the total pressure, hypoxia, in general, enhanced leaf anthocyanin levels, enhanced total phenolic compounds, enhanced carbohydrate concentration and enhanced free radical scavenging capacity of lettuce but reduced leaf mineral concentration. Hypoxia increased the ethylene production of plants but ethylene accumulation was not the sole reason for enhanced anthocyanin production in plants grown under hypoxia. Our results suggest that low oxygen stress induces the production of protective phytochemicals and the free radical scavenging potential in lettuce, which may in turn enhance the functional value. However, further human intervention studies are needed to confirm if enhanced phytochemicals in plants have significant impact in human body.

The Bitches of Barcelona Street

My Grandma Louisa always smelled of sherry wine. Whenever she minded us kids while Mama did work for one of the white families in the neighborhood, Grandma would herd us all out to her favorite spot in the backyard, and, with a heavy groan, plunk her bulk down in the used-to-be-green metal lawn chair that had been part of the landscape back there for as long as I can remember. We laughed when the paint-flaked old chair let out a groan almost as loud as Grandma did when she sat in it. Then we began our mad scramble for the most coveted seats: on her ample lap where we could rest our heads on the soft cushion of her equally ample bosom. When two of us had each claimed a knee, the others found a spot in the grass still warm from the day's heat. Whether standing or sitting, we began at once with our favor ite pastime: unplaiting and combing Grandma's two long, thick braids that age had turned first white then yellow. We'd drape the loosened hair over her shoulders like a shawl and style it, which she let us do until her head was too sore to take any more of our grooming. By then, her hair stuck up and out like chickens had been plucking in it. Grandma Louisa always sang to us, most often tunes that were popular in her day. She'd croon Red Sails in the Sunset, I'll Be Seeing You, and other love ballads. We were a rapt audience. While she sang, she sipped sherry from a fifth bottle stashed beneath her chair, and sometimes I got the feeling that she wasn't even aware she had an audience, rapt or not. Often in the middle of a song her voice would slowly fade, and her entire body would sag. She appeared to be spiraling down like my brother's spinning top, then her head slumped to her chest and the singing stopped. The forgotten bottle dangled from her hand, then dropped with a soft thud on the grass like a period at the end of a sentence. The quiet that hung upon the night then seemed to amplify the usual nocturnal chirr of crickets, cicadas, and whippoor wills. We kids looked at each other, but no one spoke. What was there to say? We all knew Grandma was drunk. But even though we

Influences of Organic Fertilization, High Tunnel Environment, and Postharvest Storage on Phenolic Compounds in Lettuce

As the largest group of phytochemicals, dietary phenolics play an important role in human health and disease prevention. Cultural practices have been shown to have the potential for affecting phenolic compounds in food crops. Spring and summer trials were conducted in 2003 to examine the effects of organic fertilization and high tunnel environments on phenolic constituents of lettuce (Lactuca sativa L.) cultivars Red Sails and Kalura. Effects of postharvest storage at 4 °C for 16 days on total phenolics of lettuce harvested from the summer trial were also evaluated. Total phenolics, excluding anthocyanins, were measured spectrophotometrically, and major phenolic constituents were identified and quantified by high-performance liquid chromatography. Chlorogenic acid and quercetin glycosides were found to be predominant in lettuce. ‘Red Sails’ consistently exhibited significantly higher phenolic concentrations than ‘Kalura’. Organic (compost + fish emulsion) and conventional (N–P–K + CaNO3) fertilization did not consistently differentially affect lettuce phenolics in our recently established organic and conventional plots. The high tunnel environment generally reduced phenolic levels in lettuce relative to the open field. However, differences between high tunnel and open field varied with cultivar and season. Effects of production factors on lettuce phenolics were maintained during cold storage. There was a substantial increase in total phenolics during storage, likely correlated with declining lettuce quality. Further studies are warranted to more fully assess the impact of cultivar and production management, including organic fertilization, on lettuce phenolics.

Growing Lettuce in Non-Aerated, Non-Circulated Hydroponic Systems

Abstract Low density, plant-holding trays conveniently float on nutrient solution in hydroponic systems, but they do not provide an air space to the plant root zone. Astudy was conducted to determine if an air space between the tank cover and the nutrient solution affected lettuce using three non-aerated hydroponic methods that were also non-circulated. ‘Red Sails’ leaf lettuce (Lactuca sativa L.) was grown in 5-cm net pots supported by expanded polystyrene bead board tank covers where the board was supported by the tank frame and remained fixed, the board floated on the nutrient solution, and the board initially floated on the nutrient solution and sank to a 5-cm depth as the solution was depleted. Tanks were 8.9-cm high and contained 7.6 cm (109 L) of non-circulating nutrient solution. No additional nutrient solution was added. Lettuce was harvested when only 1.3 cm of nutrient solution remained in the tank. When the board remained fixed, head fresh weights averaged 220 g during seven crops over a period of one year. Head weights were 19% lower when the boards floated on the nutrient solution for the duration of the crop. However, head weights were only 7% lower when the boards were initially floated on the nutrient solution and then rested on a 5-cm high support during the latter stage of growth. A greater growth rate was encouraged by an air space with high relative humidity between the nutrient solution and the expanded polystyrene bead board tank cover.

Total Phenolic and Flavonoid Contents of Organically and Conventionally Grown Lettuce, Collards and Chinese Cabbage

Organic vegetables have been suggested to produce higher levels of phytochmemicals, which play active roles in disease prevention. We measured total phenolic and aglycone flavonoid (apigenin, kaempferol, luteolin, and quercetin) contents in leaves of organically- and conventionally-grown lettuce (`Kalura' and `Red Sails'), collards (`Top Bunch') and Pak Choi (`Mei Qing') greens during spring and summer trials, using the Folin assay and HPLC, respectively. Postharvest changes in phenolic contents of organic and conventional lettuce were also investigated after 17-day storage at 4 °C. Production system did not cause a significant difference in total phenolic levels of lettuce and collards in either trial, but total phenolics were significantly higher in organic Pak Choi in the summer trial, possibly due to greater flea beetle damage in the organic plots. Organic production did not affect the aglycone flavonoid levels of lettuce and collards in the spring trial except that apigenin increased in organic samples. In the summer trial, however, concentrations of kaempferol, luteolin and quercetin tended to increase in organic lettuce and collards; only luteolin showed promising increase in Pak Choi. Species and cultivars both had significant effects on total phenolic and flavonoid contents. After 17-day storage, total phenolic content significantly increased in both organic and conventional lettuce although the concentrations of aglycone flavonoids remained relatively constant. Total phenolic content was higher in organic `Red Sails' at a marginal significance level after storage, while it did not differ between organic and conventional `Kalura'. We noted a dominant presence of glycoside flavonoids in lettuce before and after storage, which warrants further study.

SOMATIC EMBRYOGENESIS OF LETTUCE FROM MATURE TISSUES

The regeneration of somatic embryos (SEs) in tissue cultures derived from mature tissues of lettuce (Latuca sativa L.) is reported. We recently described the regeneration of somatic embryos on a wide range of genotypes, ploidy and tissues of potato (Solanum tuberosum L.) using a two-step protocol in vitro. Using the same protocols, SEs have been regenerated on seven cultivars (cvs.) of lettuce: Butter Crunch, Grand Rapids, Olga, Pluto, Queen Crown, Red sails and Summertime. Seeds from head-, leaf- and romaine-type lettuce plants were germinated, grown in a greenhouse, and axillary shoots from mature plants excised, disinfested and cultured in vitro. Once the shoots had grown into plantlets, the tissues were cultured on a medium lacking growth regulators. Leaf, stem and petiole tissue was excised and used to regenerate SEs. All cultures were grown at 1 °C under cool-white fluorescent lamps with an irradiance of 100 μmol.m -2 s -1 and a photoperiod of 16 h. Somatic embryos were also regenerated from seedling tissues of five lettuce cvs. Lettuce SEs germinated without difficulty and acclimatized to greenhouse conditions. Explants (leaf, stem-internode and petiole) from seedlings of all lettuce cvs. regenerated, although stem-internode sections were generally more productive. Regeneration from mature tissues of lettuce was most efficient using leaf and petiole explants.

GROWTH, NUTRIENT CONTENT, AND GROWTH MEDIUM ELECTRICAL CONDUCTIVITY OF POINSETTIA IRRIGATED BY SUBIRRIGATION OR FROM OVERHEAD

The effects of subirrigation versus conventional overhead irrigation on the growth and nutrition of containerized poinsettia (Euphorbia pulcherrima Willd. Ex Klotz) were studied by growing ‘Red Sails’ at different fertilizer levels. Plants were grown in 1.6-L pots of soilless growth medium and fertilized twice a week with 20N-4.3P-16.6K water-soluble fertilizer at 100, 175, 250, or 325 mg NL−1. Fertilizer solutions and extra irrigation water were applied by subirrigation from saucers placed below the pots or by conventional overhead watering. Regardless of irrigation method plants received 200–250mL of fertilize solution or tapwater at each irrigation. All treatments resulted in commercially acceptable plants at the end of the study, however overhead-irrigated plants were larger in diameter and had more shoot dry weight than subirrigated plants. There were no differences in plant height or bract diameter due to irrigation method and plant growth parameters were not affected by fertilizer level. The recently mature leaves of overhead-irrigated plants contained more nitrogen (N), phosphorus (P), boron (B), and molybdenum (Mo), but less magnesium (Mg) than subirrigated plants. Regardless of irrigation method or fertilizer level, there were no major differences in the nutrient content of plants in this study. At the end of the experiment the top one-third and bottom two-thirds and a composite sample of all of the growth medium were analyzed for electrical conductivity (EC). Overall there was no difference in EC between sample types with overhead irrigation, but the top and composite samples had higher EC than the bottom sample with subirrigation. Except at 100 mg NL−1 and all fertilizer levels in the case of the bottom sample, subirrigation resulted in greater salt accumulation than overhead irrigation. The highest EC levels were found in the top and composite samples of subirrigated growth medium; some of these ECs exceeded the satisfactory range for poinsettia but no visible symptoms of excess salinity were apparent. Results of this study indicate that there is little difference in the growth and nutrient status of subirrigated and overhead-irrigated poinsettias over a representative range of fertilizer levels and receiving about the same amount of water. Interpretation of EC analyses of subirrigated growth medium would be affected by sampling technique.

131 Effect of Blended Composts and N Rates on Growth Performance of Potted Poinsettia

Growth performance of potted `Peterstar Pink', `Top White', `Red Sails', and `Red Success' were evaluated in eight substrates and three fertilization rates. The substrates included Sunshine Mix 1 and Pro Gro 300S as control, and compost blends at 33%, 50%, and 67% of final substrate volumes mixed with peat and perlite (1:1). The blends included 2:1, 1:1, or 1:2 ratio of polymer dewatered biosolids (PDB):poultry litter (PL) and PDB: yard wastes (YW). Fertilization was applied twice weekly at 75, 100, and 150 mg/L N from 19N--2.2P-16.6K. Plants grown in Sunshine Mix 1 performed better than those grown in Pro Gro 300S. The growth parameters measured improved as the N rates increased for both controls. Plant diameter, grade, and dry weight of plants grown in 150 mg/L N treatment were usually similar to those in 100 mg/L N and were not 11% more than those at the lowest N treatment. The 1 PDB: 1 PL blend at the high N treatment produced premium-quality plants, and all remaining PDB:PL treatments produced good quality plants. The PDB:YW blends that received 100 and 150 mg/L N produced premium quality plants. The PDB:YW blends at the low N treatment produced slightly better quality plants than those grown in PDB:PL at the 75 mg/L N and were similar in quality as those grown in Sunshine Mix 1 at the 150 mg/L N treatment.

Effects of Compost Source and Timing of Fertigation Initiation on Growth of Potted Poinsettia

Treatment combinations of four poinsettia (Euphorbia pulcherrima) cultivars, 20 substrates, and three fertigation treatments were evaluated in a completely randomized block design. Poinsettia cultivars included ‘V-14 Glory’, ‘Red Sails’, ‘Lilo Pink’, and ‘Annette Hegg Top White’. The compost substrates were compost:peat:perlite blended (by vol.) at 2:3:3, 1:1:1, and 2:1:1 ratios. Sunshine Mix 1 and Pro Gro 300S were used as controls. Composts tested were those prepared from crab offal, lime and polymer-dewatered biosolids, municipal solid waste (MSW), yard waste, and poultry litter. Fertigation treatments were initiated on the week of potting, delayed one or two week after potting and applied once per week. Controls produced premium quality plants. Composts prepared from poultry litter, yard waste, polymer-dewatered biosolids, crab offal, and MSW produced good quality plants. Plant width in 25 percent compost treatments were greater than those in 50 percent compost treatments. Total number of branches, plant height, canopy diameter, and plant grade on plants treated with fertilizer on the first week were only three percent greater than in treatments where fertilizer application was delayed one or two weeks.