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Abstract
The yield of 2 crops of tomatoes (Lycopersicon esculentum Mill. cv. Tropic) was determined in CO2 enriched, unventilated and conventionally ventilated greenhouses. The “ventilated” control house was cooled at 26.5°C with conventional ventilation fans and wetted pads. The “unventilated” houses were cooled at 26.5° by recirculating the greenhouse air through direct-contact heat exchanger pads sprayed with water from evaporative cooling towers and also under severely humid conditions by ventilating at 29.5°. For the first spring crop, the ventilated control house at ambient CO2 yielded 8.58 kg/plant (0.35 m2/plant). Unventilated houses enriched with 650 and 1000 μl CO2/liter air had 17 and 48% greater yields than the control. An unventilated, unenriched house suffered a 13% yield decrease. For the second winter crop, the control house yielded 8.48 and 9.70 kg/plant at standard and high nutrient levels, respectively. At the standard nutrient level, unventilated houses yielded 64 and 63% greater than the control at 1000 and 1350 μl CO2/liter, respectively. At the high nutrient level, they yielded 35 and 37% greater. A ventilated house enriched to 1000 μl/liter whenever cooling was not required yielded 8 and 10% greater than the control at the standard and high nutrient levels, respectively.
Abstract
The flavor and consumer acceptability of tomatoes (Lycopersicon esculentum Mill. cv. Tropic) grown in 4 greenhouses with different CO2-enrichment-ventilation environments and 2 nutrient concentrations (standard and 1.5 × standard) were tested with sensory panels. Enriching conventional ventilated greenhouses to 1000 μl CO2/liter had no significant effect on acceptability. Lack of ventilation caused a decrease in acceptability while the higher nutrient concentration significantly improved it. Vitamin A content of ‘N-65’ and ‘Tropic’ tomatoes was increased with CO2 enrichment and lack of ventilation, but nutrient concentration had no effect. None of the treatments consistently affected Vitamin C content.
Abstract
A conductimetric CO2 analyzer was designed, built, and tested. The principle of operation is based on measuring the increase in electrical conductivity of recirculated, deionized water when a sample air stream is bubbled through the water. An improvement over previous models was the addition of temperature compensation so the instrument could be used in greenhouses to reliably measure CO2 concentration in the 0-3000 ppm range at 1/9th the cost of an infrared CO2 analyzer.
Hydrolyzed casein (HC) and retail products that contain HC are evaluated as repellents to minimize deer damage to trees and shrubs. Three different experiments demonstrate that HC is an effective deer repellent. Technical-grade HC completely eliminated browse damage to evergreen shrubs (Gaultheria shallon Pursh.) and conifers (Thuja plicata Donn.) during the test periods. Retail sources of HC (concentrated baby formula powders) are not as effective as pure hydrolyzed protein, but do offer browse protection when alternative sources of browse are available. For nursery, orchard, and reforestation applications, HC is a promising deer repellent to minimize losses due to browse. For the private homeowner, a simple repellent formulated with glue and a HC-containing baby formula may offer considerable browse protection when alternative forage is available.
Growth and topological indices of `Eureka' lemon were measured after 6 months in well-watered and well-fertilized conditions and factorial combinations of moderate (29/21C day/night) or high (42/32C day/night) temperatures and ambient (350 to 380 μmol·mol) or elevated (constant 680 μmol·mol-1) CO2. In high temperatures, plants were smaller and had higher levels of leaf chlorophyll a than in moderate temperatures. Moreover, plants in high temperatures and elevated CO2 had about 15 % higher levels of leaf chlorophyll a than those in high temperatures and ambient CO2. In high temperatures, plant growth in elevated CO2 was about 87% more than in ambient CO2. Thus, high CO2 reduced the negative effect of high temperature on shoot growth. In moderate temperatures, plant growth in elevated CO2 was only about 21% more than in ambient CO2. Irrespective of temperature treatments, shoot branch architecture in elevated CO2 was more hierarchical than those in ambient CO2. Specific shoot extension, a topological measure of branch frequency, was not affected by elevated CO2 in moderate temperatures, but was increased by elevated CO2 enrichment in high temperatures-an indication of decreased branch frequency and increased apical dominance. In moderate temperatures, plants in elevated CO2 had fibrous root branch patterns that were less hierarchical than at ambient CO2. The lengths of exterior and interior fibrous roots between branch points and the length of second-degree adventitious lateral branches were increased >50% by high temperatures compared with moderate temperatures. Root length between branch points was not affected by CO2 levels.