André Gosselin

Characterization and use of essential oil from Thymus vulgaris against Botrytis cinerea and Rhizopus stolonifer in strawberry fruits

Abstract The essential oils from two clonal types of Thymus vulgaris (Laval-1 and Laval-2) were characterized and tested for antifungal activity. Contents were high in p -cymene, linalool, terpinen-4-ol and thymol which constituted 53.5% and 66.2% of Laval-1 and Laval-2 essential oils respectively. The essential oil volatiles from two clonal types exhibited antifungal activity against Botrytis cinerea and Rhizopus stolonifer , two common storage pathogens of strawberries ( Fragaria ananassa ). The inhibition of B. cinerea and R. stolonifer ranged from 26.5 to 63.5% and 5.5 to 50.5% respectively by oil from Laval-1, when exposed to concentrations of 50 to 200 ppm, while values of 36.9 to 90.5% and 11.5 to 65.8% were observed from oil from Laval-2. The decay of strawberry fruits caused by B. cinerea and R. stolonifer was controlled up to 73.6 and 73.0% respectively by volatiles from maximin concentration of Laval-1, and up to 75.8 and 74.8% from Laval-2. No visual phytotoxic symptoms were noticed for the observed period. Essential oil from Laval-2 exhibited higher antifungal activity which was related to its relatively higher content of antimicrobial compounds.

Variations in photosynthesis and essential oil in thyme

Summary Plants of two clonal thymol-type thyme selections were grown under natural light and natural light supplemented by a PPF of 200 μmol m-2s-1, provided by HPS lamps at 50%, 70% and 90% soil water amount (SWA) of field capacity in a greenhouse. We investigated the variations in net CO2 assimilation rates (Pn), dry matter and volatile oil accumulation and their relationships during different development periods. Pn varied between 5.88 to 15.80 μmol CO2 m-2s-1 under natural light and from 11.93 to 28.04 μmol CO2 m-2s-1 under supplemental light. The highest Pn, 28.04 μmol CO2 m-2s-1, was obtained from ≪Laval-1≫, after 120 days of growth under supplemental light at 70% SWA. The lowest Pn, 5,88 μmol CO2 m-2s-1, was obtained from ≪Laval-2≫, after 40 days of growth under natural light at 50 % SWA. Volatile oil accumulation steadily increased from 0.38 % to 1.35 % under natural light and 0.68 % to 2.18 % under supplemental light, with further development of the plants. Similarly, the dry matter shoot yield grew from 1.31 to 18.20g/plant under natural light and 2.87 to 50.30g/plant under supplemental light, depending on SWA and the time of harvest. We discovered, that mean shoot yield and essential oil accumulation over the growing period were fairly associated with Pn. There were significantly positive correlations between Pn and essential oil accumulation (r2 = 0.64), shoot yield and essential oil content (r2 = 0.58) and Pn and shoot yield (r2 = 0.55).

Photosynthesis and transpiration of in vitro cultured asparagus plantlets

Abstract Nodal sections of asparagus ( Asparagus officinalis L.) were cultured and rooted on a modified Murashige and Skoog (MS) medium for 10 weeks. These plants were then acclimatized for 5 weeks. Photosynthesis and transpiration of in vitro plantlets, acclimatized plantlets and control seedlings were measured with an open gas exchange system. Rates of photosynthesis of in vitro-cultured plantlets were as high as those of seedlings grown in a greenhouse, while their rates of transpiration were much higher. Photosynthetic capacity of in vitro-cultured asparagus plantlets was sufficiently high to support autotrophic growth during the period of acclimatization. Photosynthesis of acclimatized plantlets was always considerably lower than that of in vitro plantlets except at high concentrations of CO 2 . Evaportranspiration of acclimatized plantlets was comparable to that of seedlings. These results suggest that high water loss incurred by in vitro shoots imposes severe limitations on newly formed shoots in acclimatization thus reducing whole plant photosynthesis. Protecting in vitro plantlets from water stress is the most important factor to consider in order to ensure their survival during the acclimatization period.

Examination of environmental quality of raw and composting de-inking paper sludge

Paper sludges were traditionally landfilled or burned. Over the years, the use of paper sludges on soils has increased, as well as the concerns about their environmental effects. Therefore, the chemical characterization of paper sludges and their young (immature) compost needed to be investigated, and over 150 inorganic and organic chemicals were analyzed in de-inking paper sludge (DPS). In general, nitrogen, phosphorus and potassium contents were low but variable in raw DPS and its young compost. The contents of arsenic, boron, cadmium, cobalt, chromium, manganese, mercury, molybdenum, nickel, lead, selenium, and zinc were also low and showed low variability. However, the copper contents were above the Canadian compost regulation for unrestricted use and required a follow-up. The fatty- and resin acids, and polycyclic aromatic hydrocarbons were the organic chemicals measured at the highest concentrations. For resinic acids, care should be taken to avoid that leachates reach aquatic life. For polycyclic aromatic hydrocarbons, naphthalene should be followed until soil content reaches 0.1 microg g(-1), the maximum allowed for soil use for agricultural purposes according to Canadian Environmental Quality Guidelines. In young compost, the concentration of these chemical families decreased over time and most compounds were below the detection limits after 24 weeks of composting. In raw DPS, among the phenol, halogenated and monoaromatic hydrocarbons, dioxin and furan, and polychlorinated biphenyl families, most compounds were below the detection limits. The raw DPS and its young compost do not represent a major threat for the environment but can require an environmental follow-up.

Understory light and root ginsenosides in forest-grown Panax quinquefolius

The objective of this study was to determine the relationship between light levels in the understory of a broadleaf forest and the content of six ginsenosides (Rg(1), Re, Rb(1), Rc, Rb(2,) and Rd) in 1- and 2-year-old American ginseng (Panax quinquefolius L.) roots. Our results revealed that ginsenoside contents in 1- and 2 year-old roots collected in September were significantly related to direct and total light levels, and duration of sunflecks. At this time, the effect of light levels accounted for up to 48 and 62% of the variation in ginsenoside contents of 1- and 2-year-old American ginseng roots. Also, red (R) and far red (FR) light, and the R:FR ratio significantly affected Rd, Rc, and Rg(1) contents in 2-year-old roots, accounting for up to 40% of the variation in ginsenoside contents.

Effect of covering materials on energy consumption and greenhouse microclimate

Abstract The objective of the study was to conduct an extensive energy and microclimatic assessment of different greenhouse covering materials. Single glass (GL) and three types of double polyethylene (PE) claddings were compared. The double polyethylene cladding consisting of an anti-fog thermal film for the inner layer and a standard PE film for the outer layer was the most energy efficient. It had an average measured heat transfer coefficient ( U value) of 2.9 W m −2 K −1 . The average U value for the other PE cladding was 3.4 W m −2 K −1 . The use of thermal screens in the PE houses during the night reduced heat loss rates by 23–24%. The differences in climates under different claddings is presented in terms of PAR transmission and humidity levels. The measured average PAR transmission during the winter months (November–March) were 0.68, 0.62, 0.65 and 0.60 for glass, anti-fog 1-year, anti-fog 3-year and anti-fog thermal claddings, respectively. In the summer months (April–October) the values were higher. The average vapour pressure deficit in the double PE houses was found to be 0.2 kPa lower than under single glass during the winter season, but no significant difference was observed between various anti-fog films. The use of a thermal screen in a double PE houses caused only a slight increase in greenhouse humidity. The contribution of supplementary lighting to greenhouse heating demand is also presented and discussed.

Influence of extended photoperiod on photosynthate partitioning and export in tomato and pepper plants

Abstract Changes in photosynthetic efficiency and carbon partitioning under extended photoperiods (from 8 to 24 h) was studied using a photoperiod‐sensitive species (tomato—Lycopersicon esculentum Mill.) and a non‐photoperiod‐sensitive species (sweet pepper—Capsicum annuum L.). Extending photoperiod by supplemental lighting resulted in an increase in total carbohydrates (CH2O) produced in both species. In tomato, extended photoperiod principally favored shoot development. Dry weight of tomato plants increased by c. 30% when light periods were increased from 12 to 18 h, although no significant differences were observed in fruit yields. In contrast, extended photoperiod did not increase shoot dry weight of pepper plants but significantly increased its fruit yields. Furthermore, studies on CH2O translocation supported these data. In pepper plants, translocation efficiency varied from 71 to 90%, whereas it varied from 54 to 69% in tomato plants. On a daily basis, tomato plants exposed to extended light period...

Effects of fertigation management on growth and photosynthesis of tomato plants grown in peat, rockwool and NFT

A greenhouse experiment was conducted to determine the effects of substrate, irrigation scheduling and nutrient solution electrical conductivity (EC) on plant growth and photosynthesis of tomato plants. The plants grown in peat-bags were irrigated by a potential evapotranspiration (PET) dependent irrigation system. The first peat-bag treatment (control) was irrigated when the soil water potential reached −5 kPa. EC was fixed at 2.5 dS m−1. EC of other two peat-bag treatments was varied between 1 and 4 dS m−1 with a soil water potential setpoint (SWPS) of either −5 or −9 kPa. Plants grown in rockwool and by the nutrient film technique (NFT) were treated with EC levels of 2.5, 4.0 and 5.5 dS m−1. EC variation resulted in higher photosynthetic capacity (Pc), quantum use efficiency (QUE) and dry matter production (DMP) under high SWPS compared with the control. The increase in DMP resulted mainly from fruit yield increase. In the treatment of EC variation with low SWPS, Pc and DMP were lower than in treatment of EC variation with high SWPS, but not different from that in the treatment of fixed EC. The high EC treatment of 4.0 dS m−1 decreased DMP in NFT, but did not in rockwool. EC of 5.5 dS m−1 decreased fruit yield but did not affect shoot DMP. However, high EC treatments, especially EC of 4 dS m−1, increased Pc as well as QUE in rockwool and in NFT. DMP and Pc was not positively correlated with each other for EC treatment. However, it is concluded that PET-dependent EC variation increases photosynthetic capacity, plant growth and fruit yield of greenhouse tomato plants.

Effects of varying sulphate concentrations on growth, physiology and yield of the greenhouse tomato

Abstract In soilless culture systems, recycling the nutrient solution causes an accumulation of sulphate ions, which can generate nutrient imbalances affecting crop yield. This study determined the effects of four sulphate concentrations in the nutrient solution on growth, foliar mineral composition, physiology and yield of greenhouse tomatoes. Ten days after transplanting, young tomato plants (Lycopersicon esculentum Mill, cultivar ‘Trust’) grown in rockwool were subjected to four sulphate concentrations (S0 = 0, S1 = 5.2 (control), S2 = 10.4 and S4 = 20.8 mmol L−1) in the nutrient solution. The S0 reduced plant dry weight, photosynthetic rate, chlorophyll content, and the total number of fruits. The S0 treatment was associated with high concentrations of P, Ca and Mg, but low levels of S in the leaves. The highest concentration of sulphates in the nutrient solution did not reduce shoot dry weight, photosynthesis, crop yield and fruit quality, although it decreased Mg, Ca and P content in the leaves. Consequently, tomato plants appeared prone to sulphate deficiency but tolerated sulphate concentrations up to 20.8 mmol l−1 in the nutrient solution with no apparent detrimental effects on yield and fruit quality over a short cropping period.

Effect of light intensity and CO2 enrichment during in vitro rooting on subsequent growth of plantlets of strawberry, raspberry and asparagus in acclimatization

Abstract Growth of plantlets of asparagus (Asparagus officinalis L.), raspberry (Rubus idaeus L.) and strawberry (Fragaria × ananassa Duch.), treated during the in vitro rooting stage under three photosynthetic photon flux densities (PPFD) (80, 125 and 250 μmol s−1 m−2) (17.5, 26.9 and 53.8 W m−2 (PAR), respectively) and three CO2 enrichment levels (CDE) (330, 1650 and 3000 μmol mol−1), was monitored during the acclimatization stage. For the three species, generic differences were observed in the plant response to treatments. A significant residual growth enhancement was caused by CDE. High PPFD in vitro increased the dry weight of strawberry and fresh weight of asparagus in acclimatization. Raspberry leaf dry weight was increased by 262% in acclimatization after in vitro treatment with high CDE. This enhanced the performance of micropropagated plantlets in acclimatization and reduced by 2 weeks the acclimatization period with raspberry. Our results suggest that in vitro leaves may be a source of nutritional reserves for leaves initiated ex vitro, but do not exclude a morphogenetic effect of CO2 during the in vitro rooting stage.