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CO₂ enrichment increases efficiency of light utilization and rate of growth, thereby reducing the need for supplemental lighting and potentially lowering cost of production. However, during warmer periods of the year, CO₂ enrichment is only possible intermittently due to the need to vent for temperature control. Previous research investigated the separate and combined effects of daily light integral and continuous CO₂ enrichment on biomass accumulation in lettuce. The current research was designed to look at the efficiency with which lettuce is able to utilize intermittent CO₂ enrichment, test the accuracy with which growth can be predicted and controlled, and examine effects of varying CO₂ enrichment and supplemental lighting on carbon assimilation and plant transpiration on a minute by minute basis. Experiments included application of various schedules of intermittent CO₂ enrichment and gas exchange analysis to elucidate underlying physiological processes. Same-day and day-to-day adjustments in daily light integrals were made in response to occasional CO₂ venting episodes, using an up-to-the-minute estimate of growth progress based on an integration of growth increments that were calculated from actual light levels and CO₂ concentrations experienced by the plants. Results indicated lettuce integrates periods of intermittent CO₂ enrichment well, achieving expected growth targets as measured by destructive sampling. The gas-exchange work quantified a pervasive impact of instantaneous light level and CO₂ concentration on conductance and CO₂ assimilation. Implications for when to apply supplemental lighting and CO₂ enrichment to best advantage and methods for predicting and controlling growth under intermittent CO₂ enrichment are discussed.

The pod cactus (Opuntia sp.), a tender stem, has been consumed by Mexican people for centuries either as a fresh or boiled vegetable. Traditionally, Southern Mexico people consume this tender pod cactus in several traditional Mexican dishes. During recent years, an increase in nopalitos consumption by Sonoran people has been observed. People interested in a disciplined diet or people troubled with high cholesterol desire this peculiar vegetable. In Hermosillo, Mexico, people buy nopalitos in small plastic bags packages a pound of small cutting of tender pods from local supermarkets and mobile sellers. Usually, a nopalitos bag pound price is a range of $1.00 to $1.2 U.S. dollars in Hermosillo. Nopalitos production in Sonora, Mexico, is a seasonal. Nopalitos harvesting starts in early April and runs through late October. Because low temperatures start in late October, and continue during the winter season, there is no nopalitos production in Sonora. Hense, Sonoran producers are considerig building high tunnels, to provide more temperature control and to produce nopalitos during the winter. Most growers are low-income people that produce nopalitos in home gardens. This activity allows low-income growers to have nopalitos during most of the year, except during the winter. The current growing area production of 240 acres (170 ha) of tender pod cactus was recorded during 2005 in Sonora, of which a half is cultivated in home gardens. A potential yield production of nopalitos in Sonora is about of 40 tons per acre of tender pod cactus. In comparison to other crops, nopalitos production is a good alternative for small growers.

Fresh strawberries (Fragaria ×ananassa Duch) are readily available throughout the year with several new cultivars being successfully grown in diverse environmental conditions (e.g., field and greenhouse). Consumption of strawberries with higher nutritive values and antioxidant activity may contribute to improved human wellness. Phytonutrient contents and antioxidant activity was measured as oxygen radical absorbance capacity (ORAC) were assayed in berries (`Camarosa', `Diamante', and `Gaviota') sampled in January, February to March, and April to May from fields in Plant City, Fla., and Oxnard, Calif., and from a greenhouse in Kearneysville, WV. Strawberry cultivars varied in skin color, soluble solids, total phenolics, and anthocyanins, ascorbic acid, folic acid, and ORAC activity. Response to environment was cultivar dependent. All phytonutrient constituents were lower in `Diamante' berries compared to `Camarosa' and `Gaviota'. For all cultivars, berry ORAC activity declined as TSS increased, and ORAC activity was coincident with phenolic content. ORAC activity in berries fruit harvested from plants grown in a temperature-controlled greenhouse did not change during the January to May sampling period. For `Gaviota', ORAC activity in greenhouse-produced berries was the same as that of field-produced berries. Whereas greenhouse vs. field-gown `Camarosa' and `Diamante' berries ORAC was higher and lower respectively. These findings demonstrate that the environmental conditions in greenhouses in Kearneysville, W.Va., from winter to spring are adequate for `Camarosa' and `Gaviota' color development, but not for `Diamante' strawberries. Of the three cultivars, only `Camarosa' was highly productive (1.2 kg berries per plant), even in the greenhouse. Berries were high in ascorbic acid, folic acid, phenolic acid, anthocyanins, and ORAC activity.

Olive cuttings root well using synthetic auxin indole-3-butyric acid (IBA). However, European and North American regulations do not allow the use of synthetic products to obtain organic vegetative propagation materials. In this work, we evaluated different products that could replace IBA in the propagation of olive cv. Cornicabra leafy-stem cuttings. In 2003, six products with a known auxin effect were assessed: IBA, algae extract, brewer's yeast, a bed of sunflower seed, seaweed dry extract (Sm-6 Organico™), and an extract of macerated seeds (Terrabal Organico™). The basal end of cuttings was treated with one of these products and placed on a mist bed with basal temperature control. After 2 months, rooting percentage, number of roots per cutting, number of cuttings with callus formation, and number of cuttings with basal thickening were determined. No significant differences were found in rooting percentage or number of roots per cutting between IBA and Terrabal Organico™ and Sm-6 Organico™. These last products had significantly higher percentage of rooted cuttings without callus formation than IBA. In 2004, a new trial was conducted in which seven treatments were evaluated: IBA applied for 7 s; Terrabal Organico™ applied for 1, 4, and 8 h; and Sm-6 Organico™ applied for 1, 4, and 8 h. No significant differences in rooting percentage or number of roots per cutting were observed between IBA and Terrabal Organico™ applied for 1 h, whereas all the Sm-6 Organico™ treatments had significantly lower rooting percentages than IBA. Both rooting percentage and the percentage of rooted cuttings without callus development decreased significantly as treatment duration with Terrabal Organico™ increased. Therefore, Terrabal Organico™ could produce a toxic effect on cuttings when treatment duration is increased. Thus, Terrabal Organico™ could be a valid alternative to IBA in the propagation of organic olive plants of cv. Cornicabra when applied to the basal end of cuttings for 1 h.

This research explored cool crop production in various climate zones using CEA facilities and hydroponics ponds to control growth rate and quality through root zone temperature control. The precise controls were used to vary air and water temperatures to study the temperature gradient between root and shoot zones. Effect of this gradient was measured by growth rates and final harvest dry weights. Lactuca sativa L. cv. Ostinata seedlings were germinated and grown 11 days in a growth chamber and moved to greenhouse ponds. Air temperatures chosen were 17, 24, and 31°C. These were constant for the 24 days that lettuce grew in the ponds with a 5°C decrease for 14 hours. during the night. Water temperatures of the three ponds in the greenhouse were set and maintained at 17, 24, and 31°C. Maximum final harvest weights were obtained at 24°C air/water 24°C. Final weights for the 17 and 31°C water setpoint were comparable at 24°C air. The 31 °C air /water inhibited quality and final dry weight, while 17 and 24°C water produced equivalent dry weights at 31°C air. At 31°C air heads were tighter at 17 than at 24°C, and loose at 31°C. At air 17 °C maximum weight was at 24°C water and minimum at 31°C water. At 17°C air, the 24°C water plants were of good quality, with thicker leaves but visibly smaller than the 31°C water crop. Significant differences in harvest dry weights were shown at each 7-day harvest beginning on day 14, due to both air and water setpoint factors and there was significant interaction between them.

Using greenhouse tomato (Solanum lycopersicum) as a model system to produce pharmaceutical proteins, electrical conductivity (EC) of hydroponic nutrient solution was examined as a possible factor that affects the protein concentration in fruit. Transgenic tomato plants, expressing F1-V protein, a plant-made candidate subunit vaccine against plague (Yersinia pestis), were grown hydroponically at high (5.4 dS·m⁻¹) or conventional EC [2.7 dS·m⁻¹ (control)] with a high-wire system in a temperature-controlled greenhouse. There was no significant difference in plant growth and development including final shoot dry weight (DW), leaf area, stem elongation rate, or leaf development rate between high EC and control. Net photosynthetic rate, transpiration rate, and stomatal conductance (g _S) of leaves were also not significantly different between EC treatments. For both EC treatments, immature green fruit accumulated DW at a similar rate, but dynamics observed in fruit total soluble protein (TSP) and F1-V during the fruit growth were different between the two ECs. Fruit TSP concentration per unit DW decreased while TSP content per whole fruit increased as fruit grew, regardless of EC. However, TSPs were significantly lower in high EC than in control. Fruit F1-V concentration per unit DW and F1-V content per whole fruit were also lower in high EC than in control. Our results found that increasing EC of nutrient solution decreased TSP including the vaccine protein in fruit, suggesting that adjusting nutrient solution EC at an appropriate level is necessary to avoid salinity stress in this transgenic tomato.

The genetic basis for heat tolerance during reproductive development in snap bean was investigated in a heat-tolerant × heat-sensitive common bean cross. Parental, F₁, F₂, and backcross generations of a cross between the heat-tolerant snap bean breeding line `Cornell 503' and the heat-sensitive wax bean cultivar Majestic were grown in a high-temperature controlled environment (32 °C day/28 °C night), initiated prior to anthesis and continued through plant senescence. During flowering, individual plants of all generations were visually rated and scored for extent of abscission of reproductive organs. The distribution of abscission scores in segregating generations (F<sub>2</sub> and backcrosses) indicated that a high rate of abscission in response to heat stress was controlled by a single recessive gene from `Majestic'. Abscission of reproductive organs is the primary determinant of yield under heat stress in many annual grain legumes; this is the first known report of single gene control of this reaction in common bean or similar legumes. Generation means analysis indicated that genetic variation among generations for pod number under heat stress was best explained by a six-parameter model that includes nonallelic interaction terms, perhaps the result of the hypothetical abscission gene interacting with other genes for pod number in the populations. A simple additive/dominance model accounted for genetic variance for seeds per pod. Dominance [h] and epistatic dominance × dominance [l] genetic parameters for yield components under high temperatures were the largest in magnitude. Results suggest `Cornell 503' can improve heat tolerance in sensitive cultivars, and heat tolerance in common bean may be influenced by major genes.

The effects of temperature and sowing date on the time to first flowering were investigated in Petunia ×hybrida Vilm `Express Blush Pink' sown on three separate dates (8 Feb., 1 Mar. and 22 Mar. 1993) and grown in glasshouse compartments set to provide six air temperature regimes (minimum temperatures of 4, 10, 14, 18, 22, and 26 °C). Flowering was hastened under high temperatures and sowing later in the season (22 Mar.). To determine the extent to which this seasonal effect was due to photoperiod, a second experiment was conducted where plants were grown under controlled daylengths (8, 11, 14, and 17 h·d^-1) within six temperature-controlled glasshouse compartments (set to provide minimum temperatures of 6, 10, 14, 18, 22, and 26 °C). The rate of progress to first flowering increased linearly with lengthening photoperiod up to a critical photoperiod of 14.4 h·d^-1, while further increases in daylength had no further affect in hastening flowering. The rate of progress to flowering increased linearly with increasing temperature, however, the optimum temperature, at which the rate of progress to flowering was maximal, was lower under short days compared to long days. Furthermore, the rate of progress to flowering increased linearly with increasing photosynthetic photon flux (PPF). Data from both experiments were analyzed to construct a model to predict the effects of temperature, photoperiod, and PPF on time of flowering in petunia. This model accurately (r ² = 0.88) predicted the flowering times of a different set of plants sown on three dates and grown under six temperature regimes (6, 10, 14, 18, 22, and 26 °C).

Sunburn can be caused either by heat stress or by UV-B radiation. Under natural conditions fruit sunburn is usually caused by the combination of both heat stress and UV-B radiation. To evaluate the use of reflectance spectroscopy in early detection of fruit sunburn, 5-year-old `Fuji' apple bearing trees growing in pot-in-pot system at the Lewis-Brown Horticulture Farm of Oregon State Univ. were used in the experiment. Fruit sunburn was monitored either under natural conditions or treated with UV-B, heat or both under controlled conditions after detached from the tree. Under natural conditions, the sun-exposed side of Fuji fruit has much higher anthocyanins than the shaded side. The increase in anthocyanins at the sun-exposed side is to protect the fruit from sunburn. When the temperature higher than 40 °C the sunburn symptom initiated first by change the color of the sun-exposed side from red to tan, then to yellow patches, and finally turn to brown and dark brown patches. The peel pigments analysis results indicated that anthocyanins decreased earlier than chlorophyll in the symptom development. The results of detached fruit exposure to 30,000μW/cm² UV-B lights or to 40 °C at control conditions for 2, 4, 6, 8, 10, and 12 hours indicated that high intensity UV-B lights or high temperature alone can cause sunburn respectively. The UV-B and temperature combination treatment enhanced the sunburn processes. The apples with sunburn caused under natural conditions or under UV-B and temperature controlled conditions were scanned by using reflectance spectroscopy of FOSS NIR system at different stage of the sunburn. The results indicted that Fuji apple sunburn can be efficiently detected at the early stage of sunburn in both natural and controlled conditions.

Fresh weight production of basil (Ocimum basilicum`Genovese') growing in a retractable roof greenhouse (RRGH) or outdoors was evaluated under different shade environments, cultural production systems, and roof control strategies in a semi-arid climate. Cultural production systems included raised beds and towers consisting of six pots arranged vertically and stacked on edge. The growing substrate in both systems was perlite. The three shade environments included a RRGH with either a clear woven roof (35% shade) or a white woven roof (50% shade), or outdoors in full sun (0% shade). Within the RRGH, three strategies of roof control were tested based on air temperature thresholds, quantum thresholds, and globe thermometer temperature thresholds. After establishment, plants were grown for 4 weeks, each under the three roof control strategies in each environment and in both cultural systems. New shoots were harvested weekly and fresh weights were determined. Overall, fresh weight per plant was significantly affected by cultural production system, and basil grown in raised beds produced twice the biomass compared to plants grown in vertical towers. Productivity of basil grown in raised beds was not affected by the three shade environments, but plants in vertical towers produced about 20% more when grown in full sun or under 35% shade compared to under 50% shade. Within the RRGH, roof control strategy significantly affected basil fresh weight per plant. Roof control, based on either a quantum sensor or globe thermometer, increased production by 31% compared to air temperature control. Greater productivity was related to higher cumulative light exposure of plants. Quality of basil grown in the RRGH was superior to that grown in full sun.