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W. Letchamo and A. Gosselin

Camomile (Chamomilla recutita Rauschert) is an annual plant from the Asteraceae. Camomile is one of the most frequently used medicinal plants, and has a commanding place in the world market. The flower heads are used in pharmaceutical preparations, and the cosmetic and beverage industries. The extracts from camomile flowers, to mention some, are known to have the most-effective sedative (3.29× compared to papaverin), antidepressive, tumor -protective, antiinflammatory, and accelerative properties in the regeneration of skin tissues. It is considered a panecia, due to its strong effects among many others, in the treatment of gastric ulcers, stomatology, respiratory complications, nephritis and nephrolithiasis (dilution of the kidney stones), and urinary bladder stones (cystolithiasis). Recently, successful research programs have been carried out to develop new camomile varieties with higher flower yield and better content of the active substances, suitable for mechanical harvesting under conventional cultivation. Apart from growing consumer demand for organically grown herbal products, the use of some herbicides and insecticides has resulted in the shifts of the content of active substances. The yield stability, content, and composition of the active substances under organic cultivation, particularly in areas with extreme climatic conditions, such as northern North America, should be investigated. We identified and introduced new camomile varieties and studied their suitability for organic field cultivation in Quebec, Canada. We studied over-wintering ability, yield potentials, and the content and composition of essential oil, flavonoids, and coumarins under field conditions. The physiology of the new varieties, particularly the relationship between photosynthesis and yield formation, and the accumulation of the active substances under different cultivation conditions remain to be studied.

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J. Norrie and A. Gosselin

The behavior of turfgrass grown on paper-sludge-amended soils was evaluated over 2 years. Two experiments were performed, one with deinked sludge and another with primary sludge. Four paper sludge, sand, and organic soil substrate mixtures with proportions ranging from 0% to 50% paper sludge were incorporated into existing soils. Two fertilization levels were applied in strip plots across sludge treatments and three turfgrasses of seeded Kentucky bluegrass (Poa pratensis L. `Georgetown'), Kentucky bluegrass sod, and an 80 Kentucky bluegrass: 20 perennial ryegrass (Lolium perenne L. `Prelude') seed mix were arranged within split plots. Effects of deinked and primary sludge experiments were similar. Supplemental N and, to a lesser degree, P and K fertilization with N at ≈4.5 to 5.5 t·ha–1, P at 1.18 to 1.26 t·ha–1, and K at 1.34 to 1.46 t·ha–1 improved ground cover, turf color, and stand quality. Despite differences in visual evaluations, leaf mineral nutrition was only slightly affected by fertilization treatments. Soil in nonfertilized plots was several times lower in N-NO3 when compared to fertilized plots, regardless of sludge rate. Soil in fertilized plots had higher concentrations of inorganic N regardless of sludge amendment. The soil C: N ratio was ≈13:1 in nonamended plots and more than 15:1 under the highest sludge rate. Deinked and primary paper sludges can be used effectively as soil amendments if turfgrass receives adequate supplemental N, P, and K.

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A. Gagnon, S. Yelle, and A. Gosselin

The objective of this experiment was to examine the influence of continuous and intermittent carbon dioxide enrichment on the growth of greenhouse tomato plants. Tomato plants were grown under four CO2 regimes: Control at 330 ppm, continuous supply at 1000 ppm, and intermittent supply (1h supply/2 hours) at 1000 ppm and 2000 ppm. Carbon enrichment produced an increase in photosynthetic rate and plant dry weight, a decrease in leaf nitrate level, and leaf accumulation of reducing sugars and starch. A loss in efficiency was observed over time in plants grown under high atmospheric C02 concentration. However, intermittent carbon enrichment reduced the plant acclimation. Even with 32% less C02, intermittent enrichment at 1000 ppm produced yields 6% greater than continuous enrichment. The superior yield may be explained by preferential allocation of photosynthates to the fruit under intermittent supply.

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W. Letchamo, C. Mengle, and A. Gosselin

The content of essential oil, thymol, and carvacrol in a thymol-type of clonally selected thyme plants during different developmental stages were investigated under greenhouse and field conditions. Plants in the greenhouse were grown from July to November, under natural light and natural light supplemented by a PPF of 200 μmol·m–2·s–1, provided by HPS lamps, while plants in the field were studied from June to November. Shoot yield and the accumulation of the active principles from greenhouse-grown plants were determined by harvesting the plants at 40-, 60-, and 120-day intervals, while field-grown plants were harvested in August, September, October, and November. Essential oil content, qualitative and quantitative changes in the oil were determined by subjecting the samples to steam distillation and subsequent gas chromatographic analysis. There were important changes in shoot yield, essential oil, thymol, and carvacrol content in the course of plant development. After 120 days of growth under greenhouse conditions, the essential oil content increased by >150%, while thymol content increased by ≈200% compared with the 40-day-old plants. We found some differences in oil content, thymol, and carvacrol accumulation between field- and greenhouse-grown plants. The pattern of crop yield and the accumulation of the major active substances under field and greenhouse conditions are presented and discussed.

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O. Ayari, M. Dorais, and A. Gosselin

Daily and seasonal variations of photosynthetic activity, chlorophyll a (Chl-a) fluorescence and foliar carbohydrate content were studied in situ on greenhouse tomato (Lycopersicon esculentum Mill. `Trust') plants grown under CO2 enrichment and supplemental lighting. The objective of this study was to assess the effect of seasonal variation of the photosynthetic photon flux (PPF) on photosynthetic efficiency of tomato plants and to determine the presence or absence of photosynthetic down-regulation under greenhouse growing conditions prevailing in northern latitudes. During winter, the fifth and the tenth leaves of tomato plants showed low, constant daily photosynthetic activity suggesting a source limitation under low PPF. In winter, the ratio of variable to maximum Chl-a fluorescence in dark adapted state (Fv/Fm) remained constant during the day indicating no photoinhibition occurred. In February, an increase in photosynthetic activity was followed by a decline during March, April, and May accompanied by an increase in sucrose and daily starch concentrations and constant but high hexose level. This accumulation was a long-term response to high PPF and CO2 enrichment which would be caused by a sink limitation. Thus, in spring we observed an in situ downregulation of photosynthesis. The ratio Fv/Fm decreased in spring compared to winter in response to increasing PPF. The daily decline of Fv/Fm was observed particularly as a midday depression followed by a recovery towards the end of the day. This indicated that tomato leaves were subject to a reversible inhibition in spring. Fv/Fm was lower in March than in April and May even though PPF was higher in April and May than in March. These results suggest that tomato plants develop an adaptive and protective strategy as PPF increases in spring.

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H. Zekki, L. Gauthier, and A. Gosselin

Tomato plants (Lycopersicon esculentum Mill. cv. Capello) were grown in the three most promising and used hydroponic cultivation systems using rockwool and peatmoss substrates and nutrient film technique (NFT), either with or without recovery and recycling of the drainage solutions. Prolonged recycling of nutrient solutions in NFT caused a reduction in fresh weight, dry weight, and yield compared to plants grown in NFT with regular renewal of the nutrient solution. There were no differences in growth, productivity, and leaf mineral composition between plants grown in rockwool and peatmoss systems, with or without recycling, and in the NFT system without recycling. These results suggest that recycling drainage solutions is an economically and environmentally sound horticultural practice that when used correctly does not cause a reduction in yield of tomatoes cultivated in rockwool or peatmoss. However, prolonged use of the same solution in the NFT cultivation system can negatively affect growth and yield. This is most likely due to an accumulation of sulfate ions in the fertigation solutions.

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Mohamed Badrane Erhioui, M. Dorais, A. Gosselin, and A.P. Papadopulos

Most experiments on the effects of cover materials on greenhouse crops have provided no real statistical replication for the cover materials. This study was conducted in Winter 1996 at the Harrow Research Centre (Ontario) in nine minihouses covered with glass (single-glass), D-poly (double inflated polyethylene film), and acrylic (rigid twin acrylic panel) offering a 3 × 3 latin square experimental design. Tomato plants (Lycopersicon esculentum L.) were grown in CO2-enriched atmosphere (1000 ppm) under three covering materials, and two light treatments (natural light, and supplemental light at 65 μmol·m–2·s–1) in order to determine the effects of supplemental light on growth, photosynthesis, reproductive carbon allocation, and evolution of carbohydrates synthesis in the diurnal cycles. Overall, the application of supplemental light increased photosynthesis rate, yields, harvest index, total chlorophyll content, and starch accumulation in all treatments, regardless of the type of cover materials. Early marketable yield in acrylic and D-poly houses was higher than in glasshouses. Plants grown under enhanced light intensity flowered earlier and produced 12% more marketable fruits than those grown under natural light. The photosynthetic rate of plants grown in acrylic houses was higher than that of plants grown in glasshouses and those grown in D-poly. The leaves of plants grown in acrylic and D-poly houses had higher dry mass contents and much higher specific leaf weight (>10%) than plants in glasshouses. The net photosynthesis dropped after 3 months of treatment, accompanied by a high accumulation of carbohydrates in the leaves. These results indicate that a photosynthetic acclimation occurs earlier during the growth period suggesting a limitations in carbon metabolism.

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A. Fierro, J. Norrie, A. Gosselin, and C.J. Beauchamp

Paper recycling generates large quantities of de-inking sludge, which is disposed of mainly by landfilling. More ecological disposal alternatives include land application and use as a container nursery medium. In this study, raw de-inking sludge was evaluated as a medium component supplemented with applications of four N fertilization regimes for the growth of three grass species (Festuca ovina duriuscula, Agropyron elongatum, Alopecurus pratensis), and four regimes of P fertilization for the growth of three Rhizobium-inoculated legumes (Medicago lupulina, Galega orientalis, Melillotus officinalis). Fertilizer was applied on the basis of sludge rate to maintain a uniform C: N ratio across sludge treatments. In one experiment, sand was mixed with 0, 10%, 20%, and 30% sludge by volume and 20% perlite, while in a second experiment, mineral soil was mixed with 0, 27%, 53%, and 80 % sludge and 20% perlite. Results indicate that shoot dry weight of all species increased with the amount of sludge in the mixture in tests with sand. In the soil mixture experiment, grasses showed the best response to treatments of 53% sludge mixture at the two highest N treatments. In general, shoot dry weight was more directly related to the total amount of N applied than to the C: N ratio of the substrate. The nutritional status (foliar N and P) also was investigated for one grass and one legume species.

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H. Wang, S. Parent, A. Gosselin, and Y. Desjardins

Micropropagated plantlets of Gerbera jamesonii H. Bolus ex Hook. F. `Terra Mix', Nephrolepis exaltata (L.) Schott `Florida Ruffles', and Syngonium podophyllum Schott `White Butterfly' were inoculated with two vesicular-arbuscular mycorrhizal (VAM) fungi, Glomus intraradices Schenck and Smith and G. vesiculiferum Gerderman and Trappe. They were potted in three peat-based media to determine the effects of mycorrhizal peat substrate on acclimatization and subsequent growth of micropropagated plantlets under greenhouse conditions. Symbiosis was established between the three ornamental species and VAM fungi within 4 to 8 weeks of culture in the greenhouse, but not during acclimatization. Mortality of Gerbera and Nephrolepis mycorrhizal plantlets was reduced at week 8 compared to the noninoculated control. A peat-based substrate low in P and with good aeration improved VAM fungi spread and efficiency. Mycorrhizal substrates had a long-term benefit of increasing leaf and root dry weight of Gerbera and Nephrolepis. Mycorrhizal Gerbera plants flowered significantly faster than non-mycorrhizal plants.

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J. Lopez, L.E. Parent, N. Tremblay, and A. Gosselin

In hydroponic recirculating systems, sulfate ions can accumulate to excessive levels and interfere with other nutrient ions. The objective of this research was to determine the effects of four sulfate concentrations on growth and mineral nutrition of greenhouse tomato plants (Lycopersicon esculentum Mill. cv. Trust). Tomato seeds were sown in flats and subsequently transplanted into rockwool slabs. Ten days after transplanting, plants were given four sulfate concentrations in nutrient solutions (S0 = 0.1, S1 = 5.2, S2 = 10.4, and S4 = 20.8 mM). The plots were arranged in a randomized complete-block design with four replications. Treatment S0 reduced dry weight of the top portion of the plant. A sulfate shortage in the nutrient solution decreased S concentrations in the leaf and decreased fruit number. Activities and concentrations of major ions in solutions expressed in mM or as row-centered logratios were correlated with corresponding foliar concentrations expressed in grams of nutrient per kilogram of dry matter or as row-centered logratios. Data were presented in this manner in order to explore interactive models describing relationships between mineral composition of both nutrient solutions and plant tissues. High concentrations of sulfate ions in the nutrient solution up to 20.8 mM did not affect tomato growth or yield. Tomato plants appeared prone to sulfate deficiency, but tolerant to sulfate concentrations up to 20.8 mM in the nutrient solution.