Adjacent Greenhouses Research Articles

A spatio-temporal methodology for greenhouse microclimatic mapping

Greenhouse internal microclimate has been proven to be non-homogeneous in many aspects. However, this variability is only sometimes considered by greenhouse models, which often calculate climatic variables without any spatial reference. Farmers, on the other hand, may wish to have these differences highlighted as they could lead to aimed actions only for a specific area of the greenhouse, while at the same time, they are not willing to invest in sensors to be installed everywhere. This paper presents a data-driven methodology to generate a virtual 2D map of a greenhouse, which allows farmers to control any critical parameter they desire with minimum investment, as monitoring is done via soft sensing with only a few actual sensors. The proposed flow starts with a set of temporary sensors placed in the points of interest; then, a model for each of them is developed via linear regression and, finally, a map of the entire area can be derived by interpolating values from these models. This allows the generation of accurate models at a reduced cost as temporary sensors can be reused at other locations. The methodology has been tested on adjacent greenhouses and in two farms, where temperature and other climatic variables have been monitored. Experimental results show that the proposed methodology can reach an adjusted R2 value of 98% for predicting values in different greenhouse locations.

Effect of horizontal and radial airflow fans on the microclimate of single-span greenhouses and their yield

The present study evaluated and compared the distribution patterns of microclimatic parameters within greenhouses to provide insights into optimizing growing conditions and maximizing crop productivity. Experiments were conducted from January to March 2023 at Sangju Smart Farm Innovation Valley, Sangju-si, South Korea, in two adjacent greenhouses covered with two polyolefin layers and a thermal screen layer. The distinctive design of the radial airflow fan connecting to the external environment and ability to uniformly blend air, demonstrated superior performance than the horizontal air flow fan. The adoption of radial airflow fans could greatly influence commercial production by enhancing the distribution of microclimate variables, resulting in improved greenhouse efficiency and ultimately leading to increased crop yields.

Anaerobic Soil Disinfestation Promotes Soil Microbial Stability and Antagonistic Bacteria Abundance in Greenhouse Vegetable Production Systems

Excessive water and fertiliser inputs, as well as long-term monocropping, not only cause resource waste and environmental pollution but also drive soil degradation and the occurrence of soil-borne diseases. Anaerobic soil disinfestation (ASD) is a widely used technique in greenhouse vegetable production to replace the use of agrochemicals in disinfestation and improve product quality. While the short-term effects of ASD on the soil microbial community have been well documented in the past 15 years, only a few studies have investigated the multiseason effects of ASD, particularly on the soil microbial community composition and stability, as well as on pathogens and antagonistic microorganisms. Field experiments were conducted in three adjacent greenhouses used for tomato production for at least 20 years. Three treatments were included: CK (control: no irrigation, no plastic film covering, incorporation of chicken manure), ASD (irrigation, plastic film covering, and incorporation of rice husks), and ASD+M (ASD plus incorporation of chicken manure). Results showed that (1) ASD significantly reduced the diversity of soil bacteria and fungi and improved the complexity and stability of the soil bacterial community at the end of the ASD, but the soil microbial diversity recovered to the level before the experiment after 1.5 years. (2) Compared with CK, ASD significantly increased the relative abundance of antagonistic bacteria Bacillus, Paenibacillus and Streptomyces, decreased the relative abundance of pathogens Fusarium and the quantity of nematodes and could still effectively eliminate soil pathogens after 1.5 years. (3) Chicken manure application did not increase the pathogenic microorganisms Fusarium and nematodes, but it significantly decreased the relative abundance of antagonistic bacteria. Our results highlight that ASD not only showed an inhibitory effect on soil-borne diseases after 1.5 years but also significantly increased the relative abundance of antagonistic bacteria. However, the additional incorporation of chicken manure for ASD should be avoided due to its negative effects on the abundance of antagonistic bacteria and its contribution to environmental pollution due to N leaching and increased emissions of GHG N2O.

Numerical Simulation of Ventilation Performance in Mushroom Solar Greenhouse Design

Numerical simulation is an effective tool for the thermal management of propulsion systems. Moreover, it contributes to the design and performance assessment of solar greenhouses for mushroom ventilation. Because the planning and design of the clustered solar greenhouse are still undiscovered, this study has developed a 3-D mathematical model suitable for a large-scale park of mushroom solar greenhouses based on computational fluid dynamics (CFD) theory. The effects of the orientation arrangement, horizontal spacing, vertical spacing of the cultivation racks, and the building distance between adjacent greenhouses on the ventilation performance were analyzed. The numerical simulation showed good agreement with the experimental measurement. The CFD results indicated that the reasonable layout of cultivation racks in mushroom solar greenhouses is a north-south arrangement. The horizontal spacing of cultivation racks has a significant influence on the wind speed and cooling rate, and the optimal spacing is 0.8 m. The overall height of the cultivation racks has little effect on the ventilation performance. Nevertheless, the vertical spacing between cultivation rack layers has a remarkable effect, and the optimal vertical spacing is 0.29 m. Reducing the building distance between the two adjacent greenhouses within a certain range helps increase the ventilation efficiency, leading to an increase in land utilization in the greenhouse park. The optimal building distance between the adjacent greenhouses is 10 m. The research results can provide theoretical guidance for improving the production quality and land utilization of mushroom facilities.

Predicting net radiation in naturally ventilated greenhouses based on outside global solar radiation for reference evapotranspiration estimation

A reliable prediction of net radiation (Rn) inside naturally ventilated greenhouses is critical for accurate evapotranspiration evaluation and thus for water saving, considering that previous studies have indicated that evapotranspiration in such relatively decoupled greenhouses is predominantly controlled by greenhouse Rn (Rn-GH). We hypothesized here that Rn-GH in naturally ventilated greenhouses can be accurately predicted using global solar radiation in the vicinity of the greenhouse (Rs-out) as the only measured parameter, together with the calculated position of the sun, defined by the solar elevation angle and solar azimuth. To test this hypothesis, we performed experiments in two adjacent greenhouses in the Southern Negev, Israel (30.96° N, 34.69° E) under arid climate. In one of the greenhouses, tomato was grown during winter 2017–2018, while in the other, melon was grown during winter and spring 2018–2019. Our analyses demonstrated that Rn-GH can be accurately predicted (r2 = 0.982) using Rs-out as the only measured parameter, while the global solar radiation inside the greenhouse (Rs-GH), and the ratio between Rn-GH and Rs-GH are predominantly dependent on solar elevation angle and solar azimuth, as well as the greenhouse structure and cloud cover. This paper shows that the impact of these properties on the association between Rs-out and Rn-GH can be accurately resolved using multivariate regression by the k-nearest neighbors approach. This suggests that computerized modeling of the greenhouse structure and light transmission can potentially enable precise evaluation of Rn-GH and therefore also reference evapotranspiration in naturally ventilated greenhouses, using Rs-out as the only measured parameter. A calculation-based factor for the cloud effect on Rs-out transmittance into the greenhouse significantly improved the Rn-GH prediction under cloudy conditions.

Temperate-zone cultivation of Oedogonium in municipal wastewater effluent to produce cellulose and oxygen.

Cultivation of the filamentous chlorophyte Oedogonium in municipal wastewater effluent is known to improve water quality and yield lipid- and protein-rich biomass for industrial applications. Chlorophyte celluloses, whose molecular organization and physical traits differ from those of plants, represent yet another valuable extractive, and algal oxygen production is of economic value in wastewater treatment. Consequently, we explored cellulose and oxygen production from Oedogonium biomass batch-cultivated in treated secondary municipal wastewater effluent. We compared biomass, cellulose, and oxygen production outside and within an adjacent greenhouse, under differing dissolved CO2 and pH conditions, and during temperate-zone seasonal change from summer through fall. Overall production did not differ within or outside the greenhouse, but outside production was higher in summer and lower in fall as air temperatures declined. Batch cultivation offered advantages, but high levels of mixing and CO2 were essential to maintain neutral pH for optimal algal growth and oxygen production.

The effect of dynamic solar heat load on the greenhouse microclimate using CFD simulation

Indoor greenhouse temperature exceeds tolerable range for plants growth mostly during the summer in Ahvaz-Iran. Attempts for improving ventilation in summer was not adequate despite a huge energy consumption. Computational fluid dynamic models of a full scaled gable greenhouse covered by semitransparent materials among several adjacent greenhouses inside a greenhouse paradise for predicting the dynamics of its microclimate during a day as well as a year 2017–2018 were developed. The accuracy of the models was approved by comparing to the physical experiments and meteorological reports. The results approved the capability of the model for predicting variable solar heat load and higher indoor temperature than ambient in several hours of a day as well as surface heat transfer coefficient of the walls as affected by regional dominant wind profile. This study enhanced the understanding of required solar heat load removal during the hot months while the average temperature exceeds 40 °C for more than 11 h a day. This finding also indicates the critical periods in which the fan assisted natural ventilation system can be applied to cool down the greenhouse from more than 40 °C to 25–35 °C.

Reducing the excessive evaporative demand improved photosynthesis capacity at low costs of irrigation via regulating water driving force and moderating plant water stress of two tomato cultivars

Although atmospheric evaporative demand is increasingly recognized as significant roles in coupling water transport and carbon acquisition, potentials to reduce irrigation demand and improve photosynthesis performance via regulating evaporative demands is highly uncertain. To bridge this gap, plant water status in combination with photosynthetic carbon acquisition under contrasting evaporative demand was examined in two cultivars of tomato (Solanum lycopersicum L.). Experiments were conducted from May to August in 2016. Evaporative demand gradients were achieved via regulating vapor pressure deficit (VPD) at two adjacent greenhouses of similar characteristics: High VPD was maintained in natural greenhouse condition without environmental regulation (Control); Moderate VPD was achieved by artificially humidification when evaporative demand exceeded optimal ranges (Humidification). VPD regulation by humidification reduced the excessive driving force for water flow, which efficiently prevented the declines in plant water potential and alleviated hydraulic limitation. Transpiration rate and irrigation demand over experimental period were substantially reduced via reducing evaporative driving force in humidification treatment. Moderation in plant water stress sustained stomatal openness for CO2 acquisition and utilization. Photosynthetic capacity was significantly improved by humidification, as indicated by the substantial increases in photosynthesis rate(Pn), rubisco carboxylation capacity(Vcmax), maximum electron transport capacity (Jmax) and net assimilate rate (NAR). At long-term scales, fruit yield was increased by 14.6% and 16.7% for two cultivars. Whole plant biomass was increased by 22.6% and 16.9% for two cultivars. Plants irrigation amount in humidification treatment over the experimental period was significantly saved by 16.9% and 17.4% for two cultivars. Taken together, VPD regulation had great potentials to reduce irrigation demand and improve photosynthetic capacity via reducing water driving force and sustaining stomatal function. The present study provided novel information to improve photosynthetic and reduce irrigation demand for sustainable crop production.

Determinación de los patrones de flujo de aire en un invernadero multitúnel mediante anemometría sónica

En este trabajo se ha desarrollado una metodología para estudiar la ventilación natural en invernaderos mediterráneos mediante anemometría sónica. Los ensayos se han realizado en un invernadero multitúnel de tres módulos situado en el Campo de Prácticas de la Universidad de Almería. Esta metodología nos ha permitido obtener los patrones de ventilación natural del invernadero experimental para los vientos más comunes de la región. También nos ha permitido describir la interacción entre el efecto eólico y térmico, así como detectar deficiencias en la ventilación natural del invernadero debidas al efecto barrera de otro invernadero adyacente (provocando una reducción media en la velocidad del aire en el exterior de la ventana de barlovento de hasta el 98% para u, 63% para uy y, más importante, 88% para ux, la componente de la velocidad del aire que es perpendicular a la superficie de ventilación lateral). Los conocimientos adquiridos en este trabajo nos permitirán mejorar los algoritmos de control del sistema de ventilación. En este trabajo se realizan una serie de propuestas que podrían mejorar sustancialmente la ventilación natural del invernadero. Por ejemplo, se proponen algunas posibles modificaciones de la configuración de las ventanas laterales, buscando una mayor captación del aire exterior: se podría optar por ventanas dotadas de alerones exteriores que dirijan al aire hacia el interior o ventanas en las que la malla no se coloque directamente sobre la superficie lateral del invernadero, diseñando una antesala donde el aire pueda entrar sin la oposición de la malla. Otra propuesta sería prolongar la apertura de las ventanas laterales hasta el suelo, para favorecer así la entrada de aire a nivel del cultivo.

Soil organic carbon and total nitrogen in intensively managed arable soils

The conversion from cereal fields to vegetable production in the last three decades represents a significant shift in land use in China. Here, we studied the effects of conversion form cereal fields to vegetable production in north China on soil organic carbon (SOC) and total nitrogen (TN) in both bulk soil and soil aggregates. We used two approaches: (1) measurements of paired soil samples from wheat (Triticum aestivum L.) – maize (Zea mays L.) fields and adjacent greenhouses vegetable fields in three vegetable production areas representing various management intensities in terms of C and N inputs and frequency of tillage; (2) fractionating soil to distinguish intra-aggregate particulate organic matter (iPOM) and organo-mineral complexes (silt+clay). Our results indicated that converting cereal fields to greenhouse vegetable production with intermediate and high management intensity led to increases in SOC and TN and decreases in C:N ratios in the top soil. The accumulation rates of C and N in the surface soil (0–30cm) were estimated to be 1.37MgCha−1yr−1 and 0.21MgNha−1yr−1 over an average period of 8 years after cereal fields to greenhouse vegetable production conversion. At the soil aggregate level, only the coarse (>250μm) and fine (53–250μm) iPOM fraction contributed to the increases in soil C (e.g., 49% and 51% of total C increases, respectively), while the coarse and fine iPOM, and silt+clay fraction accounted for 22%, 30% and 48%, respectively, of total N increases. This illustrates how the addition of readily available C (manure) and N (manure and inorganic N) leads to a temporary stabilization of C in relatively labile SOM fractions, but to a preferential stabilization of N in organo-mineral SOM fractions. In conclusion, the conversion to highly intensive vegetable systems in China leads to marked differences in C and N stabilization dynamics.

First Report of Tomato chlorosis virus Infecting Tomato in Sudan.

In March 2011, interveinal yellowing and necrosis symptoms on middle and lower leaves were observed in tomato (Solanum lycopersicum L., cv. Castle Rock) plants grown in three adjacent greenhouses of the Agricultural Research Corporation at Wad Medani (Gezira State, Sudan). These symptoms resembled those caused by Tomato chlorosis virus (ToCV) and Tomato infectious chlorosis virus (TICV) (4) (genus Crinivirus, family Closteroviridae). Whitefly (Bemisia tabaci) infestation was also observed in these greenhouses. Total RNA was extracted by TRIzol Reagent (Invitrogen, Carlsbad, CA) from symptomatic leaves and analyzed by dot-blot hybridization with digoxigenin-labelled RNA probes to the coat protein (CP) gene of ToCV and to the minor coat protein (CPm) gene of TICV. Positive signal was obtained only with the ToCV probe. Reverse transcription (RT)-PCR reactions were performed with two pairs of primers specific for the detection of ToCV, MA380(+) (5'-GTGAGACCCCGATGACAGAT-3') and MA381(-) (5'-TACAGTTCCTTGCCCTCGTT-3'), specific to the CP gene (ToCV RNA 2) (3), and MA396(+) (5'-TGGTCGAACAGTTTGAGAGC-3') and MA397(-) (5'-TGAACTCGAATTGGGACAGA-3'), specific to the RNA-dependent RNA polymerase (RdRp) gene (ToCV RNA 1) (1). DNA fragments of the expected sizes (436 and 763 bp, respectively) were obtained, thus supporting the presence of ToCV in the symptomatic samples. Amplified DNA fragments were cloned in pGEM-T Easy vector (Promega, Madison, WI) and one clone per amplicon was sequenced (Macrogen Inc., Seoul, South Korea). The highest nucleotide sequence identity of the CP gene fragment obtained (GenBank Accession No. JN411685) was 99.2% related with North American ToCV isolates from Florida (DQ234674), Colorado (DQ234675), and Georgia (HQ879842), while the RdRp gene fragment (JN411686) was more closely related (99.0%) to the Spanish AT80/99 isolate (DQ983480). Although yellowing symptoms similar to those reported here have been observed sporadically during the last few years in open-field tomato crops in the state of Gezira, additional studies are needed to determine the prevalence and economic impact of ToCV infections in tomato cultivation in Sudan. To our knowledge, ToCV has been found in continental Africa only in Morocco and South Africa, in the Mediterranean climate areas in the northern and southern edges of the continent, respectively (2). The finding of ToCV infecting tomato in Sudan raises the question of whether this virus is emerging also in other tropical areas of the continent and illustrates the need to monitor whitefly-infested areas within Africa for the presence of ToCV.

The air spora of an orchid greenhouse

The orchid collection of the ELTE Botanical Garden, Budapest, Hungary was monitored for airborne fungi using viable and non-viable air-sampling methods (Hirst-type and a 3-stage Andersen sampler) with three different culture media. A new culture method was also applied to identify fungal spores from Hirst-type samples. The aim of this study was to determine the diversity, human- and phytopathological potential of the air spora. To find out sources of airborne fungi, samples were collected from the air in an adjacent greenhouse and outdoors, and from necrotic plants. A total of 58 genera were found in the air samples. Cladosporium and Penicillium spp. were common members of the airborne biota. A high proportion (27.5%) of identified genera may be presented as a member of microbial consortium associated with the orchids. Airborne fungi potentially pathogenic to humans were also detected. One species, Zygosporium masonii, was new to Hungary. Statistical analysis indicated that conditions of sampling had significant effects. The principal component analysis elucidated the three principal components representing 75.34% of the total variance; the clusters of variables were related to the three types of culture media. Relative abundance of small-sized spores was high, presumably because of the fungal species composition and accelerated sedimentation of large spores in still air. Apparently, in the studied orchid greenhouse, a specific mycobiota developed due to the climate and hosts (Orchideaceae) grown there.

Genotype × Environment Effects on Single‐Plant Selection at Low Density for Yield and Stability in Climbing Dry Bean Populations

Breeders ought to consider the confounding effects of the environment and genotype × environment (G × E) interaction on response to early generation selection. To meet this requirement, honeycomb breeding was performed at a low density within two dry bean populations (Phaseolus vulgaris L.) under typical open‐field conditions and in an adjacent greenhouse. Nineteen progeny lines were formed through selection of nine and ten of the highest‐yielding plants in the greenhouse and the field, respectively. Honeycomb progeny testing at the low density in the two distinct environments showed up to 75% improvement in plant‐yield potential. Under farming‐density conditions in five environments, six of the lines outyielded the respective original population by 12 to 38% and exhibited the greatest stability according to the genotype and genotype × environment (GGE) biplot model. At low density, the greenhouse evaluation demonstrated less acquired variance than the field evaluation and was especially useful for selection and progeny evaluation. Three of the six outstanding lines originated from the greenhouse. Honeycomb progeny estimation on a single‐plant yield basis in the greenhouse, rather than in the field, gave a better prediction of yield potential on an area basis. The results showed that honeycomb breeding performed in two environments to address the G × E interaction may be successful for developing varieties that exhibit both high and stable productivity.

Interactive Effects of Drought Stresses and Elevated CO2 Concentration on Photochemistry Efficiency of Cucumber Seedlings

To reveal and quantify the interactive effects of drought stresses and elevated CO2 concentration [CO2] on photochemistry efficiency of cucumber seedlings, the portable chlorophyll meter was used to measure the chlorophyll content, and the Imaging-PAM was used to image the chlorophyll fluorescence parameters and rapid light response curves (RLC) of leaves in two adjacent greenhouses. The results showed that chlorophyll content of leaves was reduced significantly with drought stress aggravated. Minimal fluorescence (Fo) was increased while maximal quantum yield of PSII (Fv/Fm) decreased significantly by severe drought stress. The significant decrease of effective quantum yield of PSII (Y(II)) accompanied by the significant increase of quantum yield of regulated energy dissipation (Y(NPQ)) was observed under severe drought stress condition, but there was no change of quantum yield of nonregulated energy dissipation (Y(NO)). We detected that the coefficient of photochemical quenching (qP) decreased, and non-photochemical quenching (NPQ) increased significantly under severe drought stress. Furthermore, we found that maximum apparent electron transport rate (ETR(max)) and saturating photosynthetically active radiation (PPFD(sat)) decreased significantly with drought stress aggravated. However, elevated [CO2] significantly increased Fv/Fm, qP and PPFD(sat), and decreased NPQ under all water conditions, although there were no significant effects on chlorophyll content, Fo, Y(II), Y(NPQ), Y(NO) and ETR(max). Therefore, it is concluded that CO2-fertilized greenhouses or elevated atmospheric [CO2] in the future could be favorable for cucumber growth and development, and beneficial to alleviate the negative effects of drought stresses to a certain extent.

Performance of underground heat storage system in a double-film-covered greenhouse

An underground heat storage system in a double-film-covered greenhouse and an adjacent greenhouse without the heat storage system were designed on the basis of plant physiology to reduce the energy consumption in greenhouses. The results indicated that the floor temperature was respectively 5.2 degrees C, 4.6 degrees C and 2.0 degrees C higher than that of the soil in the adjacent reference greenhouse after heat storage in a clear, cloudy and overcast sky in winter. Results showed that the temperature and humidity were feasible for plant growth in the heat saving greenhouse.

Occurrence of Leaf Blight on Petunia Caused by Phytophthora infestans in Maryland.

In April 2001, late blight was detected on petunia (Petunia × hybrida Hort.) in a glasshouse in central Maryland. Symptomatic plants had extensive light gray, irregularly shaped, slightly sunken lesions up to 3 cm long on upper leaves and branches. Stems were distorted or dead above points where lesions had coalesced to cause stem girdling. Disease initially occurred as scattered foci but rapidly spread through the crop causing significant loss. The disease reappeared in the same and adjacent greenhouses in 2002. Phytophthora infestans Mont deBary was observed sporulating on leaves and stems of plants in both years. Isolates PE-01, PE-02, and PE-03 were isolated on rye medium from symptomatic stem and leaf tissue (1). To confirm pathogenicity, leaves and stems of 6-wk-old petunia (cv. White Madness) were sprayed with water or with aqueous suspensions of 105 sporangia per ml. Plants were placed in plastic bags in a growth chamber at 20 to 22°C. Bags were removed after 3 days. Five to seven days after spraying, necrotic leaf lesions similar to those on naturally infected plants developed on inoculated plants only. Lesions occurred at leaf margins or near midribs and were 1 to 6 mm, irregular in shape, slightly sunken, grayish, and accompanied by white, fluffy mycelial and sporangial growth. P. infestans was reisolated onto rye agar from lesions from all inoculated plants, completing Koch's postulates. Lesions contained abundant, nonseptate sporangia on obvious sporangiophore structures whose morphology matched that of P. infestans (2). Sporangia from these lesions were 39 to 50 μm (average 45 μm) long × 26 to 28 μm (average 27 μm) wide with a length/breadth ratio of 1.66. Sporangia were caducous and limoniform to ovoid in shape. Oospores were not observed. The fungus grew more slowly on potato dextrose agar (PDA) than on rye medium at 18°C (2.7 versus 9.8 mm per day) and 25°C (1.6 versus 3.0 mm per day). All three isolates mated with an A1 type isolate of P. infestans forming oogonia (36.14 μm in diameter), amphigynous antheridia (22.39 μm × 17.00 μm wide), and aplerotic oospores (16.91 μm in diameter), indicating that the petunia isolates were the A2 mating type. These characteristics were consistent with a heterothallic species such as P. infestans (3). Tomato and potato plants were susceptible to PE-01. The three petunia isolates were US-8 multilocus genotype, resistant to Ridomil and mitochondrial haplotype Ia, characteristics typical of P. infestans from potato in North America. All isolates were monomorphic and homozygous for glucose-6-phosphate isomerase and peptidase (Gpi 100/100; Pep 100/100). Restriction fragment length polymorphism (RG-57) analysis confirmed the close similarity of the petunia and potato isolates. Greenhouse growers who cultivate more than one Solanaceous species should be aware that petunia transplants may have incipient Phytophthora spp. infections serving as reservoirs of inoculum, and that some strains are resistant to metalaxyl-based fungicides. P. infestans has been reported to cause leaf blight on petunia in the northeastern United States (2,4). To our knowledge, this is the first report of natural infection of P. infestans on petunia in Maryland.

Plastome from high-altitude Lycopersicon hirsutum does not improve low-temperature tolerance of cold-sensitive Lycopersicon esculentum

The role of the chloroplast in suboptimal-temperature tolerance was studied by comparing growth and photosynthesis of an alloplasmic tomato cybrid of L. esculentum c.v. LRC with chloroplasts from a more cold-tolerant L. hirsutum accession (LA 1777) with the performace of both euplasmic parents. Plants were grown in two adjacent greenhouses with an optimal (25/20°C) and suboptimal (16/14°C) temperature regime, under a minimum PPFD of 225 µmol m-2 s-1 during a 12-h photoperiod. Irrespective of the temperature regime, shoot biomass production was similar in L. esculentum and the cybrid. Shoot biomass production of the plastome donor L. hirsutum was less inhibited by suboptimal growth temperature than in LRC and the cybrid. Photosynthetic rates of the cybrid and LRC at both growth conditions were similar but lower than the values of L. hirsutum. Leaves of LRC, the cybrid and L. hirsutum grown at 25/20°C demonstrated comparable temperature dependencies of maximum photosynthetic capacity (Pmax). In contrast to LRC and the cybrid, Pmax was significantly increased at all temperatures in leaves of L. hirsutum acclimated to 16/14°C. The alloplasmic tomato was more susceptible to chilling-induced photoinhibition than its parents. It is concluded that combining the L. esculentum genome with a L. hirsutum plastome did not improve growth and photosynthetic performance of the domestic tomato at suboptimal temperature and that low-temperature acclimation of chloroplast functioning in tomato is not controled by the plastome.

022 Manipulation of the Greenhouse Microclimate to Improve the Efficacy of Entomopathogens for Control of Greenhouse Pests

Application of entomopathogenic fungi by inundative releases has been attempted for control of a wide range of insect pests, with generally poor results. This is largely because entomopathogens are often treated as direct substitutes for chemical insecticides and applied without an adequate knowledge of their interactions with the local environment. Humidity of greater than 90% RH has long been regarded as the a critical condition for germination and infection by the spores. With both temperature and humidity controlled, greenhouse crops offer an excellent potential for pest control using entomopathogens. The long-term maintenance of >90% RH, however, is not standard practice in greenhouse production. This study explored the possibility of improving the efficacy of the fungi by temporarily changing greenhouse humidity without adversely affecting crop growth. The study included laboratory and greenhouse trials. In laboratory trials, four humidity levels of 75%, 80%, 89%, and 97.5% RH were evaluated over a 48-h period. Three commercial products of Beauveria bassiana were evaluated (Naturalis-O, Botanigard 22 WP, and Botanigard ES). Greenhouse pests of green peach aphid, melon aphid, western flower thrips, whitefly, and two-spotted spider mite were used as target insects. The infection rate of B. bassiana was found to increase when the sprayed adult insects were exposed to higher humidity levels with the maximum infection obtained at 97.5% RH. Percent infection and difference between humidity levels, however, were formulation- and host-dependent. The highest overall control efficacy was obtained by using Botanigard ES. Botanigard ES was highly effective to adult green peach aphid, melon aphid, and greenhouse whitefly at high humidities. Effects of B. bassiana against biological control agents for greenhouse vegetable crops were also evaluated. Greenhouse trials were conducted in two adjacent greenhouse compartment with high and low humidity conditions for 48 h, respectively, for selected pest insects to valid laboratory results.

Focus on Rays

It's summer. You are sitting outside, enjoying the sights, sounds, and hot sun. You begin to wonder why the sun's rays seem to be focused on you. As you sit up straight and look around, the bright reflection off a nearby metal sculpture blinds you, the adjacent greenhouse glares at you, and you catch a flash from a high-flying jet. Now you're bothered enough to shift to a different location, but oddly enough you still seem to be at a focal point. Now you realize that you are really sweating, so you decide to go inside where you can more safely contemplate the dazzling effects of focusing. While cooling down, why not write some fun educational software or problem sets and send it to us at EduQuakes! One of my favorite seismological programs is Seismic Waves, written by Alan Jones at SUNY Binghamton and made available for download through his...

Effect of Night Temperature on Pollen Characteristics, Growth, and Fruit Set in Tomato

Lycopersicon esculentum Mill. `Laura' plants were grown in the North Carolina State Univ. phytotron at 26C day temperature and 18, 22, 24, or 26C night temperatures to determine the effects of night temperature on pollen characteristics, growth, fruit set, and early fruit growth. Total and percentage normal pollen grains were higher in plants grown at night temperatures of 18 and 22C than at 24 and 26C, but germination was highest in pollen produced at 26C. Seed content was rated higher on the plants grown at 18C night temperatures than in any of the other treatments. Numbers of flowers and fruit on the first cluster were lower in the 26C night treatment than in the other night temperature treatments. Plant height was greatest but total shoot dry mass was lowest in the 22C night temperature treatments. Fruit fresh mass increased with night temperature, reflecting more rapid development, but the experiment was not continued to fruit maturity, so the effect of night temperature on final fruit size and total plant production could not be determined. Night temperatures of 26C reduced fruit number and percentage fruit set only slightly at a day temperature of 26C, even though these temperatures were above optimal for pollen production and seed formation. To separate temperature effects on pollen from direct or developmental effects on female reproductive structures, pollen was collected from plants in the four night temperature treatments and applied to stigmas of a male-sterile cultivar kept at 24-18C minimum temperatures in adjacent greenhouses. In the greenhouse-grown male sterile plants, no consistent effects of night temperature treatment given the pollen could be seen in fruit set, fruit mass, seed content (either on a rating or seed count basis), seedling germination, or seedling dry mass.