A water bath providing accurate and reliable temperature control for many types of biological studies can be made with materials available to all laboratories. The low cost permits assembling multiple units for short-term experiments, yet the equipment is durable enough for continued or repeated use.
A simple temperature control system constructed from a $10 homemade, precise, solid-state, proportional thermoregulator, resistive heating element, and insulated enclosure is described. It is intended as one of a series of small heated units, each set to a different temperature and placed in a single, large, refrigerated area, such as a large cooler or air-conditioned room, but can be modified for cooling in a heated area. Its demonstrated temperature control precision over 24 hr was ± 0.02°C at the thermal sensor at a set point of 25° and ambient of 19° ± 2.5°. Control temperature precision, range, and span are determined by thermoregulator components, enclosure construction, and ambient conditions. This or similar systems have been used successfully in seed germination, postharvest, cell culture, and nutrient release studies.
), the growing point was removed to stop vertical plant growth. Table 1. Amount of fertilizer supplied (g·L −1 ) by different fertigation treatments at different stages of tomato plant development. Fig. 1. ( A ) Temperature-controlled tunnel. ( B ) Non-temperature-controlled
predictor of N release from individual CRFs and CRF grouped by release duration in tomato production in south Florida. Material and Methods Accelerated temperature-controlled incubation method. Fourteen CRFs from Florikan ESA L.L.C. (Sarasota, FL), Agrium
A system for greenhouse soil temperature control was designed which combines a moderately wide range of soil temperature above and below air temperature, whole-plot replication, and relatively high numbers of plants per treatment The apparatus was developed for studies involving Cyclamen persicum Mill., but also should be useful for studies of other crops or plant diseases.
High-temperature, controlled-atmosphere treatments were explored for disinfestation of codling moths from `Bartlett' pear fruit. Fruit were freshly harvested in 1996 and 1997 and sorted for uniformity and absence of defects. Fruit were exposed to forced-heating at 46 °C for 1, 2 and 3 h in either air or a controlled atmosphere of 1% oxygen and 15% carbon dioxide. Fruit were evaluated during ripening at 20 °C immediately after treatment (1997 only) and after 3 weeks of cold storage at -1 °C. Fruit were ripened with and without an exogenous ethylene treatment in 1997. Heat treatments, and particularly heat plus CA treatments, slowed fruit ripening, even after fruit had been stored for 3 weeks. The longer the treatment, the greater the inhibition. Fruit from longer treatments were firmer than untreated fruit after 4 days of ripening, but treatment with exogenous ethylene did not overcome the inhibition in the rate of ripening, although fruit from all treatments softened faster. The mortality of codling moths following exposure to the same treatments was also determined. With the heat plus controlled-atmosphere treatments, 100% mortality was achieved in 2.5 h with the faster heating rate used in our 1996 experiment, while it took 3 h to achieve 100% mortality with the slower heating rate.
storage at 0 °C in air, fruit were exposed to a break in temperature control (e.g., to simulate repacking or loading onto a ship) and then followed by a small cool storage and shelf life period ( Table 1 ; Fig. 1 ). This simulated break (B = break) was 3
Tree-ripe `Tommy Atkins' mangoes were not injured during storage in controlled atmospheres (CA) for 21 days at 8°C, and the fruit resumed ripening after transfer to air at 20°C (Bender et al., 1995). In our study, tree-ripe `Keitt' mangoes were stored at 5 and 8°C in either 10% or 25% CO2 combined with 5% O2 with control fruit maintained in air. Control fruit had higher percentages of electrolyte leakage than CO2-treated fruit at transfer from the CA and after 3 days in air at 20°C. Fruit stored in 25% CO2 at 5°C had significantly higher concentrations of 1-aminocyclopropane-1-carboxylic acid (ACC), over 0.5 nmol ACC/g fresh weight in mesocarp tissue. All the other treatments had similar ACC levels (<0.3 nmol/g fresh weight) after 21 days in CA. Ethylene production rates at both temperatures were significantly lower in the 10% CO2 treatment than in control fruit and were not detectable in 25% CO2. Ethylene production was similar in all treatments after transfer to air. Fruit from the 25% CO2 treatment at 5°C developed dull, green-grayish spots on the epidermis, but otherwise epidermal color, as determined by chroma and hue angles, did not differ among the treatments. There also were no differences in flesh color and flesh firmness.
An inexpensive system for maintaining desired water potentials throughout seed germination was developed. During hydration, a water reservoir at the base of inclined petri dishes allowed continual saturation of filter paper on which seeds were placed. During dehydration, seeds were exposed to equilibrium vapor pressures above saturated salt solutions. Constant temperature, necessary to prevent condensation of water vapor, was achieved via a small (0.2 A) fan that furnished and circulated heat throughout an insulated chamber in which salt solutions were placed. By operating the chamber above ambient laboratory temperature, interior cooling was not required. The system allowed manipulation of the rate, degree, and frequency of dehydration episodes to which germinating seeds were exposed.
The objective of this research was to investigate whether a controlled atmosphere established inside a high temperature forced air chamber could enhance the mortality of the most heat-resistant life stage of Mexican fruit fly larvae (Anastrepha ludens Loew) and thereby reduce the amount of time grapefruit (Citrus paradisi Macf.) harvested from Mexican fruit fly-infested regions must be exposed to high-temperature forced air to achieve quarantine security. The mortality of third instar larvae treated on diet was significantly higher after exposure to 1% oxygen or 1% oxygen enriched with 20% carbon dioxide than it was in either air or air enriched with 20% oxygen. Reducing the amount of oxygen in air from 21% to 1% during forced air heating at 46°C, reduced the exposure time required for 100% kill of larvae inside artificially infested grapefruit from 5 hours to 3.5 hours. Inconsistent fruit quality results warrant further study to optimize controlled atmosphere conditions during heating. Based upon relative levels of carbon dioxide inside the grapefruit during heating, fruit respiration during heating in 1% oxygen was lower than during heating in air. Results from this research suggest that reducing the amount of oxygen in a high temperature forced air chamber during heating can reduce the amount of time fruit must be exposed to heat for quarantine security against Mexican fruit fly.