Night Air Temperature Research Articles

Performance of a Solar Heat Collection and Release System for Improving Night Temperature in a Chinese Solar Greenhouse

<abstract> <b><i>Abstract. </i></b> To increase the year-round greenhouse production in North China, a sustainable heating method should be developed to increase the night air temperature during the winter in Chinese Solar Greenhouses (CSGs). Solar heating is an inexpensive and effective way to heat greenhouses, and has been investigated by several previous studies. For the present study, a heat collection-heat release (HCHR) system that was attached to the north wall was developed for CSG night temperature improvement. Two experimental greenhouses were located in Beijing, China, with a floor area of 392 m² each. Environmental parameters (temperature, humidity, heat flux) inside and outside the greenhouse were investigated, including the average solar collection efficiency of the heating system and the pump energy consumption rates. The results showed that the average solar collection efficiency of the system was 52%, which was 1.3 times greater than the reported value of a HCHR system installed in a small CSG. The effective collector absorptivity was 0.59 and heat transfer proved to be by natural convection. The night air temperature in the experimental CSG was increased by 5°C on average compared to the reference CSG. To meet the heating demand of the CSG during cold winter nights the release capacity must be increased by 40%. Pump capacity to circulate the water proved to be crucial for energy efficiency.

Parametric analysis of environmentally responsive strategies for building envelopes specific for hot hyperarid regions

Abstract The deep hot hyper-arid valley between Israel and Jordan presents unique design and construction challenges for energy conservation and thermal comfort. Winters are relatively mild, summers extremely hot during the day, with night air temperature remaining above 25 °C. Such conditions present real challenges in this sparsely populated yet rapidly developing region. Development depends on the ability to provide acceptable indoor environments at a low energy investment. Potential solutions were investigated through a parametric analysis including physical and operational elements aiming at establishing benchmarks for free running, low energy buildings under extreme conditions. First, building performance was simulated for a limited number of parameters. Additional operational and physical parameters were introduced and results compared. Data were analyzed to determine the best performing options for building assemblies. Permutations investigated confirmed that conventional building systems did not allow for free running operation and that mechanical systems for heating and cooling were needed. This research concluded that it is imperative to extensively insulate building envelopes in order for them to be free running in winter. Extensive shading is needed in the transition seasons to allow for free running operation and avoid overheating. Completely shaded buildings, high efficiency window systems and levels of insulation above those currently employed when simulated with summer climate conditions had significantly lower energy consumption requirements than other building designs. The research showed that energy efficiency in this region depends on a combination of extensive insulation, full shade, high performance windows, air tightness and seasonal operation of window shutters utilized together.

Responses of carbon and oxygen stable isotopes in rice grain (Oryza sativa L.) to an increase in air temperature during grain filling in the Japanese archipelago

AbstractStable isotopic compositions of carbon (δ13C) and oxygen (δ18O) in plants reflect growth conditions. Therefore, these isotopes might be good indicators of changes in environmental factors, such as variations in air temperature caused by climate change. It is predicted that climate change will lead to a greater increase in minimum air temperatures (primarily during the night) than in maximum air temperatures (primarily during the day) in many parts of Japan. In the present study, we investigated whether the δ13C and δ18O of the rice grain Koshihikari (Oryza sativa L.) from the northern latitudes (30.49°–37.14°) of Japan reflect variations in air temperature during grain filling and are related to the yield and proportion of first‐grade rice (&lt;15 % transparency, roundness, and cracking) as an indicator of quality. We revealed that rice δ13C was not correlated with mean maximum or minimum air temperatures for each prefecture. By contrast, rice δ18O was positively correlated with mean minimum air temperature, suggesting that rice δ18O reflects changes in night air temperature. We further showed that an increase in the mean minimum air temperature during grain filling had a negative effect on rice yield and quality. Our findings indicate that the δ18O of rice grain may be a good indicator of physiological changes in response to minimum air temperatures during grain filling.

Interaction of environment conditions and genotypes on expression of genetic background in micro-phenophases of strawberry mixed flower bud

The aim of this research is differentiation or micro-phenophases of reproductive organs on two junebearing strawberry (Fragaria x anannassa) varieties senga sengana and pocahontas, depending on climate conditions, rosettes ordering and cultivate manner (orchard mulched on black foil and orchard on bare soil). The beginning of differentiation of flower buds is genetic characteristic depending on climate conditions (insulations, day length, higher midday and night air temperatures from 1.05 till the beginning of differentiation, the sum of rainfalls from the beginning of May until the end of July), order of rosettes and cultivate manner The sum of effective temperatures over 10?C from 1st of May till the beginning of differentiation has no influence on beginning of flower buds differentiation. First morphological changes of the apical meristem were started in the first decade of August that has coincided with the day length of 14 hours and day insulations of 9.3 hours. Micro-phenophases were undergoing almost at the same time in both varieties, only the beginning at pocahontas was 2-3 days earlier. Primary rosettes differ 10-15 days earlier than the secondary rosettes. Plants that grown on black foil had 7-10 days earlier flower bud differentiation compared to those grown on bare soil.

EFFECT OF OVERNIGHT SUPPLEMENTAL LIGHTING WITH DIFFERENT SPECTRAL LEDS ON THE GROWTH OF SOME LEAFY VEGETABLES

The use of light emitting diodes (LEDs) for supplemental lighting in greenhouses is a major interest. Overnight lighting with LEDs is expected to increase the crop yield and quality with less cost. Growth chamber experiments were carried out to investigate the effect of overnight supplemental lighting by LEDs with four different spectral qualities (blue, green, red, and far-red light) on the growth of three cultivars each of lettuce, garland chrysanthemum, Chinese mustard, and Welsh onion. Plants transplanted in 7.5 cm plastic pots were placed in the growth chambers at the 4-6 true-leaf stage and were grown under different spectral light treatments for three to five weeks. The originally installed cool white fluorescent lamps were used during the day (10 h) period. The photosynthetic photon flux (PPF, 400-700 nm) at the top of plants was adjusted to 100 µmol m-2 s-1. During the night (14 h) period, overnight lighting by LEDs was provided at a PPF level of 50 µmol m-2 s-1. The day and night air temperatures were maintained at 25 and 20°C, respectively. The relative humidity was maintained at 70% throughout the two periods. The results showed that the growth of most plant species was affected by the light quality of the overnight lighting. Particularly, the shoot fresh weights of lettuce under blue and red light were 22 and 38% greater, respectively than in the control without overnight lighting. Blue and red light showed a similar effect on the shoot fresh weight of garland chrysanthemum. Blue light promoted the elongation of stem and leaves of both crops.

PERFORMANCE OF A DAY/NIGHT WATER HEAT STORAGE SYSTEM FOR HEATING AND COOLING OF SEMI-CLOSED GREENHOUSES IN MILD WINTER CLIMATE

A novel system for heating/cooling greenhouses based on air/water heat exchangers connected to a thermally stratified water storage tank was tested in a small greenhouse compartment at the Experimental Station of the Cajamar Foundation in Almeria, Spain. The system maintained a closed greenhouse (no natural ventilation) throughout the winter and spring during which a truss tomato crop was grown. Atmospheric CO2 concentration could be maintained during the daytime allowing for greater net photosynthesis in relation to a reference greenhouse in which traditional natural ventilation was used to control temperature and humidity. Three fine wire heat exchangers (Fiwihex®) were installed 1 m above the crop when at full development. The heat exchangers allowed for a very efficient transfer of the sensible and latent heat accumulated in the compartment. During the winter, the daytime temperatures were maintained below the ventilation set point (30°C). During the night, the system was able to maintain temperatures above the heating set point (12°C), with stored warm water temperatures between 15 and 17°C after clear days. After cloudy days, with water temperatures between 11 and 13°C, the system could always keep a temperature gradient with the exterior of 4-6°C, enough to maintain greenhouse air temperatures above 8°C the entire night. When seasonal night air temperatures exceeded the heating set point, the hot water at the top of the tank was cooled to the wet bulb temperature by means of an open cooling tower. The cooled water was used for cooling the greenhouse, which allowed for closing the greenhouse for a longer period. The water condensate during the cooling mode, allowed for a high water saving and maintained the relative humidity very constant during the day (around 80%). During the night, humidity was kept at 90% without ever reaching saturation.

A Method For Estimating Solar Radiation From Air Temperature Data In Samaru, Northern Guinea Savanna Of Nigeria

A major limitation to the application of weather data in engineering designs and agricultural engineering is the lack of solar radiation data, while temperature and rainfall data are relatively available. Four empirical model methods (Bristow-Campbell (BC model), Campbell- Donatelli (CD model), Donatelli- Bellocchi (DB model) and Donatelli-Campbell-Bristow-Bellocchi (Modular DCBB)) were tested by comparing their estimated global radiation values with measured solar radiation data obtained for several years from the meteorological station at Samaru, northern Nigeria with the aim of determining which model estimate correlates more with measured values. The CD model had the best slope of the regression estimated vs measured of 0.87 with the DB and BC models having a slope of 0.65. The CD model also had the lowest RMSE of 2.7 while the DB model had the highest value of 4.5. From the coefficient of residual mass (CRM), BC, CD, and DB models overestimates the global solar radiation while the DCBB model gave underestimated values. The CD model which accounts for situations in which the night air temperature cooling is less than the corresponding clear day and also accounts for the date by using the average air temperature proved to be a reasonably accurate method for estimating global solar radiation for Samaru. Keywords: Solar radiation, air temperature, model, northern NigeriaGlobal Journal of Engineering Research Vol. 7 (1) 2008: pp. 21-28

Symptoms, complaints, ocular and nasal physiological signs in university staff in relation to indoor environment – temperature and gender interactions

Symptoms, signs, perceptions, and objective measures were studied in university buildings. Two problem buildings with a history of dampness and complaints were compared with two control buildings. Health investigations among university staff were performed at the workplace (n = 173) including tear film stability [non-invasive break-up time (NIBUT) and self-reported break-up time (SBUT)], nasal patency (acoustic rhinometry), nasal lavage fluid analysis [NAL: eosinophil cationic protein (ECP), myeloperoxidase (MPO), lysozyme and albumin] and atopy by total serum IgE and IgE antibodies (Phadiatop). Exposure assessment included inspections, thermal and atmospheric climate at 56 points modelled for all work sites. Multiple regressions were applied, controlling for age and gender. Exposure differences between problem buildings and controls were small, and variations between rooms were greater. Workers in the problem buildings had more general and dermal symptoms, but not more objective signs than the others. Adjusted day NIBUT and SBUT increased at higher night air temperatures, with B (95% CI) 0.6 (0.04-1.2) and 1.3 (-0.02 to 2.5), respectively. Higher relative humidity at mean day air temperature <22.1 degrees C was associated with adjusted NIBUT and SBUT, with B (95% CI) 0.16 (0.03-0.29) and 0.37 (-0.01 to 0.75), respectively. Air velocity below recommended winter values and reduced relative humidity in the range of 15-30% were associated with dry air and too low temperature. Thermal climate in university buildings may be associated with both perceptions and physiological signs. Reduced night time air temperature, increased difference in air temperature between day and night, and fast changes in air temperature might impair indoor environment. This may have implication for energy-saving policies. It might be difficult to identify the exposure behind, and find the reason why, some buildings are defined as 'problem buildings'.

Root-zone heating at a night air temperature of 8°C does not decrease starch accumulation in Chrysanthemum morifolium

SummaryTo study whether root-zone heating during cold nights could increase root growth and nutrient uptake, plants of Chrysanthemum morifolium were grown in nutrient solution cultures at a day temperature (DT) of 20°C, and four combinations of night air temperatures (NAT) and night root-zone temperatures (NRT) in a controlled climate chamber experiment. The NAT/NRT temperatures of the four treatments were 8°/8°C, 8°/20°C, 20°/8°C and 20°/20ºC, respectively. Plants grown at 8°C NAT had increased starch accumulation in the leaves, which explained the increase in leaf dry matter (DM), and which occurred at the expense of stem and root DM. Furthermore, plants grown at 8°C NAT had fewer leaves, reduced leaf area, and shorter stems. Root-zone heating of plants grown at 8°C NAT, did not affect total leaf number, or leaf area, but the root length increased. However, this had no effect on NO3- uptake. Furthermore, root-zone heating did not reduce leaf starch accumulation and the increase in leaf DM. The present results do not support the hypothesis that root-zone heating in chrysanthemum can be used to increase root demand for carbohydrates, and increase the export of carbohydrates from leaves at night, when the night air temperature is 8ºC.

Projection of global warming onto night air temperature over Kyushu by PGWM (Pseudo Global Warming Method)

Projection of global warming onto night air temperature over Kyushu by PGWM (Pseudo Global Warming Method)

Short communication. Paclobutrazol for height control of two Lilium L.A. hybrids grown in pots

Height control is often required in order to obtain bulb plants that are proportional to their pot size and to reduce post-harvest stem elongation. Plant growth regulators afford an effective means of controlling plant height. In this study, paclobutrazol (Pbz) was studied for use in the chemical dwarfing of potted Lilium plants -the hybrids "Ercolano" and "Royal Respect"- for marketing. Their bulbs were dipped in the growth regulator (0, 50, 100, and 150 ppm) for 10 min before planting. Plant height (measured at 7 day intervals), the duration of the different stages of the growth cycle, the number of flower buds formed, and the number of open and aborted flowers were recorded. The average day and night air temperatures were 25 and 13 deg C, respectively. Increasing Pbz dose progressively reduced the height of the "Ercolano" hybrid by between 29% (46.2 cm; 50 ppm) and 45% (35.3 cm; 150 ppm) compared to control plants (64.4 cm), however, neither the duration of flowering nor the number of flowers was modified. The "Royal Respect" hybrid responded with a marked shortening - by 45% (20.8 cm; 50 ppm) to 59% (28.2 cm; 150 ppm) in comparison with the average control height (51.1 cm), but in this case both the duration of flowering and the number of open flowers was reduced at the highest concentration. The feasibility of cultivating these Lilium hybrids for marketing in pots is demonstrated. However, the concentration of paclobutrazol should be adjusted according to the hybrid grown.

Modelling the effects of climate change on the potential feeding activity of Thaumetopoea pityocampa (Den. &amp; Schiff.) (Lep., Notodontidae) in France

ABSTRACTAim We investigated whether climate change has affected the potential feeding activity of a winter active larva, the pine processionary moth (PPM), Thaumetopoea pityocampa L., and whether it may explain its range expansion.Location The study area is France and, at a smaller scale, the Paris Basin.Methods We used a statistical model derived from Huchon and Démolin [1970 Revue Forestière Française (special issue: La lutte biologique en forêt), 220–234] to test whether their model, updated with climate change, could explain the observed range expansion. Since Battisti and colleagues have recently shown that climate could affect survival of the PPM through its effect on feeding activity, we also developed a mechanistic model based on larval feeding requirements (night air temperature above 0 °C and temperature inside the nest above 9 °C on the preceding day). We reconstructed the geographical distribution of feeding activity and we compared the resulting change with the PPM range expansion.Results The statistical model did not successfully predict the observed expansion but the mechanistic model showed considerable change in the feeding activity of the PPM. In the Paris Basin, the PPM border coincided with a zone unfavourable for feeding activity in the period 1992–96. Feeding conditions became more favourable in the period 2001–04, and the PPM succeeded in crossing this zone. Over larger temporal and spatial scales improved feeding conditions in the north‐western part of France were forecast by the mechanistic model.Main conclusions (1) The range distribution of the PPM in the Paris Basin is no longer limited by unfavourable feeding conditions. (2) The pattern of range expansion of the PPM is now governed mainly by its dispersal capabilities and host tree distribution. (3) At the country scale, this approach gives an approximate prediction of the potential distribution of the PPM, though the model may not be reliable in mountainous regions.

Temperature responses of growth and wood anatomy in European beech saplings grown in different carbon dioxide concentrations

Effects of temperature on growth and wood anatomy were studied in young European beech (Fagus sylvatica L.) grown in 7-l pots for 2.5 years in field-phytotron chambers supplied with an ambient (approximately 400 micromol mol-1) or elevated (approximately 700 micromol mol-1) carbon dioxide concentration ([CO2]). Temperatures in the chambers ranged in increments of 2 degrees C from -4 degrees C to +4 degrees C relative to the long-term mean monthly (day and night) air temperature in Berlin-Dahlem. Soil was not fertilized and soil water and air humidity were kept constant. Data were evaluated by regression analysis. At final harvest, stem diameter was significantly greater at increased temperature (Delta1 degrees C: 2.4%), stems were taller (Delta1 degrees C: 8.5%) and stem mass tree-1 (Delta1 degrees C: 10.9%) and leaf area tree-1(Delta1 degrees C: 6.5%) were greater. Allocation pattern was slightly influenced by temperature: leaf mass ratio and leaf area ratio decreased with increasing temperature (Delta1 degrees C: 2.3% and 2.2% respectively), whereas stem mass/total mass increased (Delta1 degrees C: 2.1%). Elevated [CO2] enhanced height growth by 8.8% and decreased coarse root mass/total mass by 10.3% and root/shoot ratio by 11.7%. Additional carbon was mainly invested in aboveground growth. At final harvest a synergistic interaction between elevated [CO2] and temperature yielded trees that were 3.2% taller at -4 degrees C and 12.7% taller at +4 degrees C than trees in ambient [CO2]. After 2.5 seasons, cross-sectional area of the oldest stem part was approximately 32% greater in the +4 degrees C treatment than in the -4 degrees C treatment, and in the last year approximately 67% more leaf area/unit tree ring area was produced in the highest temperature regime compared with the lowest. Elevated [CO2] decreased mean vessel area of the 120 largest vessels per mm2 by 5.8%, causing a decrease in water conducting capacity. There was a positive interaction between temperature and elevated [CO2] for relative vessel area, which was approximately 38% higher at +4 degrees C than at -4 degrees C in elevated [CO2] compared with ambient [CO2]. Overall, temperature had a greater effect on growth than [CO2], but elevated [CO2] caused quantitative changes in wood anatomy.

Temperature as a predictor of survival of the pine processionary moth in the Italian Alps

Abstract1 The pine processionary moth Thaumetopoea pityocampa is expanding its geographical range in Europe, as a consequence of enhanced winter survival under a warmer climate. A combination of daytime nest temperatures and night air temperatures determines the number of hours larvae are able to feed (hours above realized feeding threshold, RFT).2 We tested the RFT‐based model for survival across multiple areas of the insect’s range in the Italian Alps over a 2‐year period. In a series of translocation experiments using natural temperature gradients as spatial analogues for global warming, we transferred colonies of T. pityocampa larvae to sites within zones of historical distribution, recent distribution, and outside the present range. The sites included traditional (Pinus nigra, Pinus sylvestris) as well as novel (Pinus mugo, Pinus uncinata, Pinus cembra) hosts.3 Survival during precold (August to November), cold (December to February) and postcold (March to May) periods were analysed against climatic variables (temperature and rainfall) and predictors developed by the model.4 Host species did not significantly affect final survival, with the exception of slower larval development, and resulting lower cold tolerance, on P. cembra than on P. mugo at the same site.5 Across all the sites and hosts, final survival of colonies depended on the number of feeding hours during the cold period (RFT), which explained 82% of the variance in a regression model. We recommend using RFT, or its surrogate daily mean minimum temperature when nest temperature is not available, in predictive models of range expansion of T. pityocampa under climate change scenarios.

Influence of vegetation cover on thermal regime of mountainous catchments

Air temperature at heights of 5 and 200 cm above soil surface, as well as soil temperature at depths of 15, 30 and 60 cm were studied in the cold climatic zone at three localities (catchments) under different plant cover during the growing season of 2002. The catchments Kout (dead forest), Doupě (clearing) and Stolec (mature spruce forest) are situated in the National Park of the Sumava Mts. (Czech Republic) in elevation of 1105–1330 m a.s.l., in which Kout and Doupě form some small “islands” inside an extensive spruce forest. Plant transpiration was not limited by water shortage in all the three localities. It was found that both soil and air temperatures were influenced with plant cover. In hot and dry days, the extremes in daily and night air temperatures were a function of transpiring vegetation height, with higher daily maximum and lower night minimum for smaller vegetation. For the whole growing season (from 29 July to 10 October 2002), the mean values of air temperature were independent upon the plant cover, but the magnitude of the dispersion variance followed the sequence in ascending order: mature forest-clearing-dead forest.

Microclimatic characterization and productivity of coffee plants grown under shade of pigeon pea in Southern Brazil

Recent studies on coffee (Coffea arabica L.) cultivation in agroforestry systems in Southern Brazil have shown the potential of partial shading to improve management of this crop. The objective of this work was to evaluate microclimatic conditions and their effects on coffee production of plants shaded with pigeon pea (Cajanus cajan) in comparison to unshaded ones, from May 2001 to August 2002 in Londrina, State of Paraná, Brazil. The appraised microclimatic characteristics were: global radiation, photosynthetic and radiation balance; air, leaf and soil temperatures; and soil humidity. Shading caused significant reduction in incident global solar radiation, photosynthetically active radiation and net radiation, and attenuated maximum leaf, air and soil temperatures, during the day. Shade also reduced the rate of cooling of night air and leaf temperatures, especially during nights with radiative frost. Soil moisture at 0-10 cm depth was higher under shade. The shaded coffee plants produced larger cherries due to slower maturation, resulting in larger bean size. Nevertheless, plants under shade emitted less plagiotropic branches, with smaller number of nodes per branch, and fewer nodes with fruits, resulting in a large reduction in coffee production. These results show the need to find an optimal tree density and management that do not compromise coffee production and protect against extreme temperatures.

EXPANSION OF GEOGRAPHIC RANGE IN THE PINE PROCESSIONARY MOTH CAUSED BY INCREASED WINTER TEMPERATURES

Global warming is predicted to cause distributional changes in organisms whose geographic ranges are controlled by temperature. We report a recent latitudinal and altitudinal expansion of the pine processionary moth, Thaumetopoea pityocampa, whose larvae build silk nests and feed on pine foliage in the winter. In north-central France (Paris Basin), its range boundary has shifted by 87 km northwards between 1972 and 2004; in northern Italy (Alps), an altitudinal shift of 110–230 m upwards occurred between 1975 and 2004. By experimentally linking winter temperature, feeding activity, and survival of T. pityocampa larvae, we attribute the expansions to increased winter survival due to a warming trend over the past three decades. In the laboratory we determined the minimum nest and night air temperatures required for larval feeding and developed a mechanistic model based on these temperature thresholds. We tested the model in a translocation experiment that employed natural temperature gradients as spatial an...

Simulation of Greenhouse Management in the Subtropics, Part I: Model Validation and Scenario Study for the Winter Season

Adaptation of greenhouse climate management strategy to local climatic conditions is very important for the improvement of resource use efficiency of greenhouse crop production. The objective of this study was to explore alternatives to the existing Venlo-type greenhouse climate control policy under Chinese subtropical climate conditions, through simulation analysis using the Greenhouse Process (KASPRO) model. Experiments were carried out in a Dutch Venlo-type glasshouse on a farm in Shanghai (31·3 °N, 121·4 °E), to collect climate and crop data to validate the model. The results show that using outside hourly weather data as inputs, the KASPRO model generally gives satisfactory predictions of greenhouse air temperature and humidity, and of canopy transpiration rate under both summer and winter climate conditions for subtropical China. After the model validation, scenario studies were carried out to investigate the possible responses of crop biomass production and energy consumption to different nighttime and daytime air temperature set points and canopy size based on leaf area index (LAI), under the winter climate conditions typical of subtropical China. The scenario analysis shows that, during winter, the highest biomass production is achieved when the daily mean air temperature in the greenhouse is 19·7 °C, which is realised when day and night air temperature set points are 23 and 18 °C, respectively. The highest energy use efficiency for biomass production is achieved when daily mean air temperature in the greenhouse is 18 °C, which is realised by setting the set points of air temperature at 19 and 15 °C, respectively. During winter, crop biomass production reaches the maximum at a LAI of 3. The energy consumption increases with the canopy LAI. It is concluded that both from the biomass production and energy saving point of view, an air temperature set point of 19 °C for daytime and 15 °C for nighttime and a canopy LAI of 2–3 provides the most energy-efficient conditions for greenhouse cucumber crop production under the winter climate conditions in subtropical China.

Yield responses of southern US rice cultivars to CO 2 and temperature

Previous studies on the effects and interactions of atmospheric carbon dioxide concentration ([CO 2]) and air temperatures have shown large differences in growth and yield responses among Asian rice ( Oryza sativa L.) cultivars. Far less attention has been focused on rice cultivars commonly grown in the Southern US. This 2-year study was conducted to determine the effects of [CO 2] and air temperature on four Southern US rice cultivars. In 2000, ‘Cocodrie’, ‘Cypress’, and ‘Jefferson’ were grown season-long in five outdoor, naturally sunlit, controlled-environment chambers in constant day–night air temperature regimes of 24, 28, 32, 36, and 40 °C under an elevated [CO 2] of 700 μmol mol −1. In 2000, an additional chamber containing all three cultivars was maintained at 28 °C and an ambient [CO 2] treatment of 350 μmol mol −1. In 2002, a more detailed study examining both main crop (MC) and ratoon crop (RC) yields was conducted with the rice cultivar ‘Lamont’ in these same chambers with day–night air temperature treatments of 19/15, 23/19, 27/23, 31/27, and 35/31 °C under an elevated [CO 2] of 700 μmol mol −1. In 2002, an additional chamber was maintained at 27/23 °C and an ambient [CO 2] treatment of 350 μmol mol −1. In the 2000 experiment, all the plants of all three cultivars in the 40 °C treatment died during early vegetative growth. In the constant 36 °C air temperature treatment, all three cultivars survived to produce panicles but failed to produce any seed yield. At the 28 °C temperature treatment, CO 2 enrichment increased grain yield by 46–71% among the three cultivars with the cultivar Cypress being the most responsive to CO 2 enrichment. In the 2002 experiment with the cultivar Lamont, plants in the 35/31 and 19/15 °C treatments survived to produce panicles but failed to produce any seed yield. In the 27/23 °C treatment, CO 2 enrichment resulted in a non-significant increase in seed yield for the MC but more than doubled RC yields. Comparisons of these results with findings from prior studies on Asian indica and japonica cultivars indicate that these Southern US rice cultivars may be more sensitive to high temperature stresses during reproductive development than previously studied Asian cultivars. These results also point to the possibility of selecting or breeding rice cultivars with enhanced capability to take advantage of future global increases in [CO 2].

Effects of day and night air temperature in early season on growth, productivity and energy use of spring tomato

Effects of air temperature on tomato (Lycopersicon esculentum Mill) growth, yield and heating energy consumption were investigated in spring of 1993 and 1994. Tomato plants were grown under nine day/night air temperature regimes formed by factorial combination of three day (19, 20 and 21°C) and three night (16, 17 and 18°C) heating temperature set points. Early (until 30 April) fruit yield increased but early fruit size decreased with increasing daily average air temperature (MT, 24-h mean). The plants grown under high daily average air temperature early in the season had lower fruit yield late in the season. Plants grown under high night air temperature (NT) and low day air temperature (DT) during the early production period achieved high fruit yield in early season and avoided the negative effects of high MT on early fruit size; these plants also had high yield and large fruit size late in the season. The different day and night heating temperature regimes studied caused no more than 10% in heating energy use variation. Therefore, for greenhouse tomato production under Great Lakes conditions (approx. 42°N), the optimal day/night air temperature (from January to April) is 20.8–21.0/18.5–19.0°C (actual air temperatures). Key words: Lycopersicon esculentum, tomato, yield, quality, fruit size, daily average air temperature (MT), day-night air temperature difference (DIF), day air temperature (DT), night air temperature (NT)