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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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Abstract

Celery transplants (Apium graveolens L. cv. Florida 683) were fertilized with complete nutrient solutions at three N concentrations and three concentrations of P in a factorial combination, both with or without atmospheric CO2 enrichment. They then were planted on a muck soil and harvested at the end of July. Carbon dioxide enrichment increased the transplant leaf area as well as shoot and root dry weight and decreased the leaf area ratio (LAR), but had no significant effect on growth parameters at harvest. Nitrogen affected leaf area, dry weight, leaf area ratio, and dry matter content of transplant shoots together with root: shoot dry weight ratio. Total, marketable, and side shoot weights at harvest were significantly increased by the intermediate N concentration (400 ppm N) provided during transplant raising. Phosphorus had no effect on transplant growth but interacted with N on the weight of marketable shoots harvested.

Open Access

Abstract

The effect of CO2 enrichment (CE) and supplemental lighting (SL) on the growth of ex vitro strawberry (Fragaria × ananassa Duch.) plantlets was studied during acclimatization. Three different concentrations of CO2 [330, 900, and 1500 ppm (v/v)] and two SL treatments (0 and 150 μmol·s–1·m–2) were applied. There was no significant interaction between light and CO2 for root and leaf dry weight and leaf area. CE had no effect on these parameters in the early period following transfer but resulted in significant increases at days 20 and 30. CE had no significant influence on leaf and root relative growth rate (RGR) over the three sampling periods, but had a significant effect on net assimilation rate at a 20- to 30-day period. At the end of the experiment, 900- and 1500-ppm treatments had a significantly higher root and shoot dry weight than the 300-ppm treatment. SL resulted in increased dry weight at 10 days and even greater increases at days 20 and 30. CE was more effective than SL in stimulating root growth, whereas SL increased shoot growth significantly. There was a synergistic effect between CE and SL. The period needed to obtain plants of a similar size to an acclimatized plantlet was shortened by 15 days with 900 ppm CO2 and SL. At the end of the experiment, SL and CE at 1500 and 900 ppm increased leaf and root dry weight by a factor of 3 and 5 for ‘Honeyoye’ and ‘Kent’, respectively. These increases were less important for SL or CE used alone.

Open Access

The potential impact of propane flamers on the development and release of ascosporic inoculum of Venturia inaequalis (Cke.) Wint. from infected dead apple (Malus domestica Borkh.) leaves that overwintered on the soil of an experimental orchard was assessed. Thermal reduction of scab primary inoculum was first conducted under controlled conditions using an indoor testing facility. At the time of ascospore maturation, heavily infected leaves were submitted to temperature rises ranging from 150 to 200 °C with open-flame burners, thus reducing the number of ascospores subsequently released by 76% and 87%, respectively. During Spring 1995, thermal treatments of overwintered dead leaves were performed directly on the ground of an apple orchard with an experimental propane flamer design to generate uniform heat at ground level. Four thermal treatment strategies, involving two dates of flaming and two heat intensities, were tested. Flaming orchard ground, when performed in early May, before significant development of ground cover, reduced the number of ascopores released from infected dead leaves by half. A significant residual effect of the treatments on ascospore ejection was still observed 2 and 4 weeks after the treatments, thus indicating that ascospore maturation inside the leaves may be reduced by heat treatment. These results indicate potential for propane flamers to reduce apple scab primary inoculum in orchards.

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