Controlled Environment Greenhouse Research Articles

First report of citrus-associated rhabdovirus in Australia in citrus.

Citrus-associated rhabdovirus (CiaRV), putatively classified in the Cytorhabdovirus genus as a strain of Cytorhabdovirus caricae, was first reported in China in 2021. Budwood from an asymptomatic kumquat (Citrus japonica Thunb.) collected in the Northern Territory, Australia in November 2021 a daughter tree was propagated from this budwood onto Carrizo citrange (Citrus ×insitorum Mabb.) rootstock and grown in a controlled environment greenhouse at the Elizabeth Macarthur Agricultural Institute (EMAI). Green bark tissue (100 mg) was sampled from the daughter plant and total RNA was extracted using Invitrogen Trizol TM Reagent (ThermoFisher Scientific, Australia), with DNA removed using DNaseI (Bioline, Australia). The Ramaciotti Centre for Genomics (Sydney, Australia) completed library preparation using a Truseq Stranded Total RNA with Ribo-Zero Plant kit (Illumina, California, United States) and high throughput sequencing using an Illumina NovaSeq6000 sequencing system resulting in 128,234,594 raw reads (2x150bp). The data was trimmed using BBduk (Bushnell 2017) and de novo assembled using rnaSPAdes (v3.15.5) (Bushmanova et al. 2019). The resulting contigs were analysed using a local NCBI ref_viruses_rep_genomes BLAST database (downloaded 15 December 2023). There were eight contigs showing 95-99% identity to citrus leaf blotch virus (CLBV), family Betaflexiviridae (NC_003877), and three contigs (length - 6646, 6044, 1144 nucleotides; coverage - 2043, 174, 214x, respectively) generated showed 80.6, 78.6 and 83% identity to C. caricae (NC_055504). These contigs were analysed using the NCBI BLASTn database online and were 94.5% (MT302546), 90.7% (MT302546) and 94.7% (MT302545) identical to CiaRV isolates from China. Mapping of reads to MT302546 using Geneious Prime (Biomatters, New Zealand) resulted in a consensus sequence (PP998055) of a CiaRV genome with 92.8% identity to both MT302545 and MT302546 isolates. To confirm the presence of CiaRV in the sample, two primer sets, LF117/LR120 (Zhang et al. 2021) and CiaRV-F/CiaRV-R (Huang et al. 2023), were engaged to amplify regions of the L gene or nucleocapsid protein gene respectively. Bidirectional amplicon sequencing was followed by alignment using Geneious Prime (Biomatters) to the consensus sequence obtained by HTS, resulting in 100% identity. A further 176 citrus samples from Australia were tested by RT-PCR using the CiaRV-F/CiaRV-R primers that partially amplify the nucleoprotein (N) gene. Four trees (3 × kumquat, 1 × lemon (Citrus ×limon (L.) Osbeck)) were found to contain CiaRV including a kumquat which was held at EMAI as a living control for CLBV for over 20 years. Bidirectional Sanger sequencing was completed for each of the four positive samples with >99% similarity of each to the original sample. CiaRV was first detected in citrus (Citrus spp.), passionfruit (Passiflora edulis Sims) and paper bush (Edgeworthia chrysantha Lindl.) trees (Zhang et al. 2021) with no symptoms in infected citrus and foliar symptoms observed in the latter two hosts. The papaya virus E strain of C. caricae causes mild leaf vein clearing in Macroptilium lathyroides. When co-infected with cowpea severe mosaic virus (CPSMV), severe leaf mosaic is observed (Cornejo-Franco et al. 2022), noting that CPSMV causes mild leaf mottling in single infection of the host. The likely transmission of CiaRV by whitefly (Zhang et al. 2021), may result in the transmission of CiaRV to other hosts and possible mixed infections, increasing symptom severity. To our knowledge, this is the first report of CiaRV outside of China and it likely has been present in Australia for decades, possibly imported in budwood.

Active heating of greenhouse integrated semitransparent photovoltaic thermal system with series connected semitransparent photovoltaic thermal air collectors

In order to fulfill the demand for energy and food security, an active heating of a controlled environment greenhouse integrated semitransparent photovoltaic thermal (GiSPVT) system with N-semitransparent photovoltaic thermal (SPVT) air collector for cold climatic conditions has been analyzed in this paper. The proposed SPVT air collectors are connected in series and integrated with GiSPVT. It is used to generate thermal as well as electrical energy to meet the daily requirements of users. Based on the energy balance equation which is a function of design and climatic parameters, an analytical expression for various variable parameters namely plant, room air, and solar cell temperatures have been derived. Numerical computation has been made in Matlab for computing the thermal, electrical, and overall exergy of the proposed system. Based on numerical computation, the following observations have been made: (i) From a thermal point of view, the packing factor (0.5, 0.8) of the semitransparent PV module plays an important role and it must be optimized for maximum thermal heating. (ii) The selection of a number of collector N is an important parameter to generate electrical energy as well as thermal heating of GiSPVT room air in an optimum way.

A high daily light integral can influence photoperiodic flowering responses in long day herbaceous ornamentals

Commercial producers of herbaceous ornamentals have reported that long-day plants sometimes flower under short-day conditions when the photosynthetic daily light integral (DLI) is high, but little research-based information is available to support the phenomenon. We grew seedlings of tickseed (Coreopsis grandiflora), echinacea (Echinacea × hybrida), lavender (Lavandula angustifolia), lobelia (Lobelia × speciosa), and salvia (Salvia longispicata × farinacea) in a controlled-environment greenhouse. They were then transplanted and grown under photoperiods of 10, 11, 12, 13, 14, or 15 h under an average DLI of 5.3 or 13.4 mol·m−2·d−1 and at an air temperature setpoint of 20 °C. Based on flowering percentage, the DLI influenced the photoperiodic responses in four species. Flowering percentages of tickseed, echinacea, lavender, and lobelia were lower under the low DLI compared with the high DLI under photoperiods <11, <12, <12, or <13 h, respectively. Time to flower for all species generally decreased as photoperiod increased. In addition, most species had more inflorescences and were more compact under the higher DLI. Under the high DLI, all echinacea and lobelia plants flowered under all photoperiods tested. Salvia flowered in all treatments, and formed fewer leaves before flowering under photoperiods ≥14 h compared to other photoperiods. However, under the higher DLI, salvia plants took slightly longer to flower under 15 h than 14 h. To clarify its photoperiodic response, we performed an additional experiment with salvia the following year. At germination, seedlings were placed under photoperiods of 14, 15, or 16 h, or a 9 h day with a 4-h night interruption and received an average DLI of 9.2 mol·m−2·d−1. Flowering was delayed under the 16 h and night-interruption treatments compared to under 14 and 15 h. We conclude that photoperiod and DLI interact to influence flowering of at least some long-day plants and that salvia has an intermediate photoperiodic flowering response.

Cultivation of Organics in Controlled Environment Greenhouse

A greenhouse is essentially an enclosed structure, which traps the short wavelength solar radiation and stores the long wavelength thermal radiation to create a favourable microclimate for higher productivity. The sun’s radiation incident on the greenhouse has two parts: direct radiation and an associated diffuse sky radiation. The diffuse part is not focused by the lenses and goes right through Frensel lenses onto the surface of the absorbers. This energy is absorbed and transformed into heat, which is then transported via the liquid medium in copper pipes to the water (heat) storage tanks or, if used, open fish tanks. In this way, an optimal temperature for both plant cultivation and fish production can be maintained. Stable plant growth conditions are light, temperature and air humidity. Light for the photosynthesis of plants comes from the diffuse radiation, which is without substantial fluctuations and variation throughout most of the day. The air temperature inside the greenhouse is one of the factors that have an influence on the precocity of production. The selective collector acts in a more perceptible way on extreme air temperatures inside the greenhouse. Hence, the system makes it possible to avoid the excessive deviation of the temperature inside the greenhouse and provides a favourable microclimate for the precocity of the culture. Sediment and some associated water from the sediment traps are used as organic fertiliser for the plant cultivation. The present trend in greenhouse cultivation is to extend the crop production season in order to maximise use of the equipment and increase annual productivity and profitability. However, in many Mediterranean greenhouses, such practices are limited because the improper cooling methods (mainly natural or forced ventilation) used do not provide the desired micro-climatic condition during the summer of a composite climate. Also, some of these greenhouses have been built where the meteorological conditions require some heating during the winter, particularly at night. The worst scenario is during the winter months when relatively large difference in temperature between day and night occurs. However, overheating of the greenhouse during the day is common, even in winter, requiring ventilation of the structure. Hence, several techniques have been proposed for the storage of the solar energy received by the greenhouse during the day and its use to heat the structure at night. Reviews of such techniques are presented in this article. Air or water can be used for heat transport. The circulating water is heated during the day via two processes. The water absorbs part of the infrared radiation of the solar spectrum. Since the water is transparent in the visible region, they do not compete with the plants that need it. Alternatively, the water exchanges heat with the greenhouse air through the walls. At night, if the greenhouse temperature goes down below a specified value, the water begins to circulate acting as heat transfer surfaces heating the air in the greenhouse.

An adult plant stripe rust resistance gene maps on chromosome 7A of Australian wheat cultivar Axe.

An adult plant stripe rust resistance gene Yr75 was located on the long arm of chromosome 7A. Fine mapping of the region identified markers closely linked with Yr75. Australian wheat cultivar Axe produced resistant to moderately resistant stripe rust responses under field conditions and was exhibiting seedling responses varying from 33C to 3+ under greenhouse conditions. Experiments covering tests at different growth stages (2nd, 3rd and 4th leaf stages) demonstrated the clear expression of resistance at the 4th leaf stage under controlled-environment greenhouse conditions. A recombinant inbred line (RIL) population was developed from the Axe/Nyabing-3 (Nyb) cross. Genetic analysis of Axe/Nyb RIL population in the greenhouse at the 4th leaf stage showed monogenic inheritance of stripe rust resistance. Selective genotyping using the iSelect 90K Infinium SNP genotyping array was performed, and the resistance locus was mapped to the long arm of chromosome 7A and named Yr75. The Axe/Nyb RIL population was genotyped using a targeted genotype-by-sequencing assay, and the resistance-linked SNPs were converted into kompetitive allele-specific PCR (KASP) markers. These markers were tested on the entire Axe/Nyb RIL population, and markers sunKASP_430 and sunKASP_427 showed close association with Yr75 in the Axe/Nyb RIL population. A high-resolution mapping family of 1032 F2 plants from the Axe/Nyb cross was developed and genotyped with sunKASP_430 and sunKASP_427, and these markers flanked Yr75 at 0.3cM and 0.4cM, respectively. These markers cover 1.24Mb of the physical map of Chinese Spring, and this information will be useful for map-based cloning of Yr75.

Studies on environmental control of greenhouse for crop production

The design of a greenhouse mainly depends on the type of plants to be grown in the greenhouse, the light and heat requirements of plants, season of crop cultivation, desired degree of automation, topography, climate and mode of business. Environmental control can be achieved if greenhouse is designed accordingly by considering the optimum responses of the crop. Since the natural environment and the input availability may not be optimum as a place for proper growth, the controlled environment greenhouse is the right approach for maximising productivity. This paper elucidates the number of structural and operational design as well as the optimum level of environmental parameters for enhancing productivity in an energy efficient and economically viable solar greenhouse.

Performance Assessment of Chlorophyll Meter to Determine When to Irrigate Wheat under Different Soil Moisture Deficit Conditions: An Initial Study

ABSTRACTProper irrigation timing can minimize the negative impacts that reduce crop yields. Therefore, in an initial pot experimental study, we assessed the SPAD (Soil–Plant Analysis Development)-chlorophyll meter as a tool to determine proper irrigation timing of wheat under different soil water deficit conditions in a controlled-environment greenhouse. The treatments were controlled irrigation at 100% (T1), 70% (T2), 50% (T3) and 30% (T4) of soil water content at field capacity; and the growth stages were development, mid-season and late-season. SPAD readings were measured pre-irrigation events. The results indicated that the T3 and T2 achieved maximum grain yield per accumulated crop evapotranspiration, i.e. water productivity (0.82 and 0.76 kg m−3), and were at par with T1. Moreover, the SPAD readings had a high Pearson’s correlation coefficient with crop evapotranspiration (r = 0.95; P ≤ 0.001) and wheat grain yield (r = 0.90; P ≤ 0.001), indicating that SPAD reading could be used to reliably estimate when to irrigate wheat. Therefore, T3 and T2 SPAD readings were averaged to estimate a target limit at which irrigation should be applied. Accordingly, the target limit was defined as >44.76 for the development stage, >50.72 for the mid-season stage, and >37.64 for the late-season stage; readings below this target limit indicate that it is time to irrigate.

Moderate-intensity blue radiation can regulate flowering, but not extension growth, of several photoperiodic ornamental crops

Lighting that creates an effective phytochrome photoequilibrium at the end of the day (day extension) or during the middle of the night (night interruption) can regulate flowering of photoperiodic ornamentals grown under short days. In addition to phytochrome regulation, blue (B) radiation can elicit cryptochrome-mediated photoperiodic responses, such as flowering and stem growth. Although B radiation at a low intensity does not influence plant development, we postulated that it could regulate flowering at a higher intensity while acting as a plant growth regulator. We grew five long-day plants [calibrachoa (Calibrachoa×hybrida), coreopsis (Coreopsis grandiflora), petunia (Petunia×hybrida), rudbeckia (Rudbeckia hirta), and snapdragon (Antirrhinum majus)] and two short-day plants [chrysanthemum (Chrysanthemum×morifolium) and marigold (Tagetes erecta)] in a controlled-environment greenhouse under a 9-h short day with or without 5.5-h day-extension or 4-h night-interruption lighting from light-emitting diodes. B radiation was delivered at 0, 1 (low), 15, or 30 (moderate) μmolm−2s−1, with or without low red (R)+white+far-red (FR) radiation. Moderate B radiation created long days in all crops as effectively as low R+white+FR radiation. Flowering of calibrachoa and petunia, but not other crops, was 2–4d earlier when moderate B radiation was added to low R+white+FR radiation. At a sufficiently high intensity, B radiation possibly mediated these flowering responses through interactions of signaling molecules and multiple photoreceptors besides phytochromes. There were few or no morphological differences among flower-inducing treatments in most crops. We conclude that night-interruption lighting with moderate B radiation, alone and when added to low R and FR radiation, can regulate flowering, but does not inhibit extension growth, of a wide range of photoperiodic crops.

Green roof substrates: Effect of recycled crushed porcelain and foamed glass on plant growth and water retention

A study was conducted in a controlled environment greenhouse to examine the potential of recycled crushed porcelain and foamed glass for use as a component of green roof substrates. Porcelain and foamed glass substrates were compared to heat-expanded shale which served as the control. Each finished substrate was analyzed per German FLL guidelines to determine granulometric distribution, bulk density, total porosity, water-holding capacity, saturated hydraulic conductivity, pH, soluble salts, organic matter content, and cation exchange capacity. Both substrates met FLL Guidelines except the porcelain substrate contained a greater percentage of larger particles and its maximum water holding capacity was lower than recommended. Two plant species were used in the study, Sedum album (stonecrop) and Ocinum x citriodolum (lemon basil). Data collected included substrate volumetric moisture content (VMC), plant growth, biomass accumulation, and plant stress as measured by chlorophyll fluorescence. Substrate VMC was generally greater in shale than in foamed glass or porcelain. At the end of the study plant growth index was greatest for stonecrop growing in shale, but there was no difference among the substrates for basil. However, plants of both basil and stonecrop accumulated the most total biomass when grown in shale. It is probable that water retention could be improved for both recycled crushed porcelain and foamed glass if more attention was paid to reducing particle size during processing. If so, then they may perform equal to heat expanded shale when incorporated into green roof substrates. In the case of porcelain, its use could divert some waste from landfills and greatly reduce the embodied energy required to construct a green roof.

Potassium fertilization enhances pepper fruit quality

ABSTRACTThe effect of potassium (K+) concentration on the nutritional quality and yield of pepper fruits was evaluated. Pepper plants were grown in a controlled-environment greenhouse under hydroponic conditions with different nutrient solutions obtained by modifying the Hoagland solution to achieve different K+ concentrations. Potassium nutrition affected fruit yield parameters more than vegetative biomass in pepper plants. The maximum fruit yield was obtained with 7 mM K+ in the nutrient solution. However, it is possible to improve the bioactive compounds of pepper fruits with a higher application of K+ without reducing yield. The increase of K+ in the nutrient solution improved pepper fruit quality by increasing fruit firmness, TSS content, soluble sugars and ascorbic acid concentration. Therefore, the fruit quality improvements obtained with adequate K+ nutrition resulted in nutritionally enriched fruits, which, at little or no extra cost, benefits the consumer.

Evidence for Compensatory Photosynthetic and Yield Response of Soybeans to Aphid Herbivory.

The soybean aphid, Aphis glycines Matsumura, an exotic species in North America that has been detected in 21 U.S. states and Canada, is a major pest for soybean that can reduce maximum photosynthetic capacity and yields. Our existing knowledge is based on relatively few studies that do not span a wide variety of environmental conditions, and often focus on relatively high and damaging population pressure. We examined the effects of varied populations and duration of soybean aphids on soybean photosynthetic rates and yield in two experiments. In a 2011 field study, we found that plants with low cumulative aphid days (CAD, less than 2,300) had higher yields than plants not experiencing significant aphid pressure, suggesting a compensatory growth response to low aphid pressure. This response did not hold at higher CAD, and yields declined. In a 2013 controlled-environment greenhouse study, soybean plants were well-watered and fertilized with nitrogen (N), and aphid populations were manipulated to reach moderate to high levels (8,000-50,000 CAD). Plants tolerated these population levels when aphids were introduced during the vegetative or reproductive phenological stages of the plant, showing no significant reduction in yield. Leaf N concentration and CAD were positively and significantly correlated with increasing ambient photosynthetic rates. Our findings suggest that, given the right environmental conditions, modern soybean plants can withstand higher aphid pressure than previously assumed. Moreover, soybean plants also responded positively through a compensatory photosynthetic effect to moderate population pressure, contributing to stable or increased yield.

Increasing green roof plant drought tolerance through substrate modification and the use of water retention gels

The optimal provision of green roof services is largely dependent on the health of the vegetation on the green roof, which is often affected by water availability.We assessed the impact of two substrate components, brick particle size and a polyacrylamide gel additive, and a living mulch (companion planting of Sedum spp.) on the growth, physiological and visual health of newly established plugs of Festuca ovina and Linaria vulgaris during an extreme drought (25 days) in a controlled environment greenhouse. Polyacrylamide gel and large brick substrates increased both plant species' drought tolerance whilst a Sedum living mulch had no effect. Polyacrylamide gel increased the reservoir of water that plants could access during the drought, whilst large brick promoted slower and therefore more drought resistant plant growth. Overall this study shows that polyacrylamide gel and coarser particle size substrates can significantly improve the drought tolerance of green roof plants.

Replacing incandescent lamps with compact fluorescent lamps may delay flowering

The natural photoperiod is often modified in the commercial production of floriculture crops to promote or inhibit flowering. In addition, low-intensity lighting is sometimes provided in growth chambers to influence flowering of photoperiodic plants. Incandescent (INC) lamps have been commonly used to provide photoperiodic lighting, but they are being phased out of production because of their energy inefficiency. Here, we compared flowering and morphological responses of two short-day chrysanthemum (Chrysanthemum×grandiflorum) potted varieties and four long-day (LD) plants grown in a controlled environment greenhouse at 20°C with a truncated 9-h day and a 2- or 4-h night interruption (NI) or 6-h day extension (DE) lighting with INC lamps, compact fluorescent lamps (CFLs), or a combination of the two (INC+CFLs). Bulb type had no effect on flowering percentage of campanula (Campanula carpatica ‘Pearl Deep Blue’), coreopsis (Coreopsis grandiflora ‘Early Sunrise’), petunia (Petunia×hybrida ‘Wave Purple Classic’), and rudbeckia (Rudbeckia hirta ‘Becky Cinnamon Bicolor’). Within bulb type, the LD lighting regimen had no effect on flowering percentage, with the exception of chrysanthemum ‘Bianca’, in which the 4-h NI inhibited flowering more than the 2-h NI or 6-h DE treatments. However, petunia that received a 4-h NI or 6-h DE from CFLs flowered 2–3 weeks later than when the lighting treatments were provided by INC lamps. Therefore, complete replacement of INCs with CFLs can delay flowering in some crops such as petunia, whereas a hybrid approach (INC+CFL) or use of lamps that emit far-red light can alleviate this potential problem.

Modeling and Simulation of Evaporative Cooling System in Controlled Environment Greenhouse

Greenhouses are used for the main purpose of improving the environmental conditions in which plants are grown. There are many parameters can affect the growing of plants inside greenhouse, such as air temperature and relative humidity. The adjustment of these parameters is achieved by selecting appropriate control actions. This work proposes a controlling technique for greenhouse indoor temperature and relative humidity. The proposed greenhouse cooling system temperature controller is designed to adjust the air volume flow rate in pad-fan cooling system to fix the greenhouse indoor temperature at 20?C and 70% relative humidity. The designed control technique is realized to ensure the required and continuous operation of the greenhouse. Moreover, this work present, a complete mathematical modeling and simulation of cooling system is introduced. In addition, a computer model based on MATLAB SIMULINK software has been used to predict the temperature and relative humidity profiles inside the greenhouse. The results are realized the requirements of the greenhouse cooling system environment.

Salinity Tolerance of Ryegrass Turf Cultivars

Relative salinity tolerance of 32 perennial (Lolium perenne L.) and three intermediate (Lolium ×hybridum Hausskn.) ryegrass turf cultivars was determined by measuring turf leaf clipping dry weight, root weight, rooting depth, and percent green leaf canopy area relative to control (non-salinized) plants. After gradual acclimation, grasses were exposed to moderate salinity stress (6 dS·m−1) for 6 weeks through solution culture in a controlled environment greenhouse. Shoot parameters were highly correlated, being mutually effective predictors of salinity tolerance. After 6 weeks of salinity stress, percent green leaf canopy area (GL) was correlated with relative (to control) final week leaf clipping weight (LWREL) (r = 0.90) and with linear slope of decline of weekly leaf clipping weight over the 6-week exposure to salinity (LWSLOPE) (r = 0.66). Rooting parameters root dry weight (RW) and rooting depth (RD), although significantly correlated with all shoot parameters, were only moderately effective in predicting relative salinity tolerance. ‘Paragon’ was the most salt-tolerant as indicated by all parameters. Other salt-tolerant cultivars included Divine and Williamsburg. Intermediate ryegrass cultivars (Froghair, Midway, and Transist) were invariably found within the most salt-sensitive category for all parameters.

Changes in Nutritional Value of Cyanogenic Trifolium repens Grown at Elevated Atmospheric CO2

Global food security in a changing climate depends on both the nutritive value of staple crops as well as their yields. Here, we examined the direct effect of atmospheric carbon dioxide on the toxicity of the important pasture crop, Trifolium repens L. (clover). Shoots of T. repens contain cyanogenic glycosides that break down to release toxic hydrogen cyanide when damaged. The ability of animals to tolerate cyanogenic compounds is dependent, in part, on their overall protein intake. We grew T. repens communities at ambient and approximately twice-ambient CO(2) in a controlled environment greenhouse experiment. We found that the ratio of total cyanogenic glycosides to total protein ratio was nearly two times higher in leaves of T. repens grown at elevated CO(2). This study highlights the importance of assessing the nutritive value of this and other plants in response to rising CO(2) so that steps can be taken to address any adverse consequences for herbivores.

Yield, blossom-end rot incidence, and fruit quality in pepper plants under moderate salinity are affected by K + and Ca 2+ fertilization

One of the most important factors limiting agricultural expansion and production is the restricted supply of good quality water. The present study examines the effects of K + and Ca 2+ fertilization on sweet pepper production, blossom-end rot (BER) incidence and fruit quality of pepper plants ( Capsicum annuum L.) grown under moderate saline conditions. Pepper plants were grown in a controlled-environment greenhouse under hydroponic conditions with different nutrient solutions obtained by modifying the Hoagland solution. The experiment consisted on four K + treatments (0.2, 2, 7 and 14 mM) +30 mM NaCl, and four Ca 2+ treatments (0.2, 2, 4 and 8 mM) +30 mM NaCl, having in common a control without salt with 7 mM K +/4 mM Ca 2+. Salinity decreased total fruit yield and marketable fruit yield by 23% and 37%, respectively. The marketable fruit yield reduction by salt treatment was mainly due to the increase in the number of fruit affected by BER. This typical physiopathy of the pepper fruits occurred between 18 and 25 days after anthesis (DAA), when the highest fruit growth rate was reached. Fruit quality parameters were also affected by salt treatment where the fruit pulp thickness and firmness were decreased, and fructose, glucose and myo-inositol fruit concentrations increased with salinity relative to fruits from control treatment. Under saline conditions an increased supply of K + reduced the fruit fresh weight, the percentage of BER and the marketable yield although promoted the vegetative growth. However, increasing Ca 2+ concentration in the nutrient solution increased the fruit production, and the marketable yield as consequence of decreasing the percentage of fruit affected with BER. Fruit quality parameters also were affected by the K + and Ca 2+ treatments.

ATTRACTION OF MEXICAN FRUIT FLIES (DIPTERA: TEPHRITIDAE) TO TWO SYNTHETIC LURES: EFFECTS OF WATER AND THERMAL STRESS

Experiments were conducted in a flight chamber in a controlled-environment greenhouse to determine if thermal and water stress differentially affects attraction of Mexican fruit flies, Anastrepha ludens (Loew), to BioLure MFF 2-component lures and AFF lures. For most combinations of air temperature, water vs. no water in traps, and non-thirsty vs. thirsty flies, responses to traps with BioLures or AFF lures were equal. Generally, higher temperatures, water deprivation of flies, and especially presence of water in traps, increased attraction to both lures. Results indicate that observed greater attractiveness of BioLures compared with AFF lures in Multi-Lure traps in the field is not due to water in traps or thermal stress. Results are consistent with observed greater attractiveness of Multi-Lure traps containing water compared with sticky traps under hot, dry field conditions.

(242) Callus Induction and Regeneration in Hydrangea macrophylla (Thunb.) Ser.

Development of a reliable method for Hydrangea macrophylla (Thunb.) Ser. organogenesis is critical for developing an in-vitro mutagenesis protocol. Container-grown (11.8 L) H. macrophylla `Nikko Blue' plants were maintained in a controlled environment greenhouse, with supplemental lighting (1600 hr to 2400 hr mercury vapor lamp), fertilized with 65 g Nutricote total (18N–2.6P–6.6K, Agrivert, Inc., New York, N.Y.) and hand-watered. To reduce fungal contamination, stock plants were sprayed to run-off biweekly with Alliette WDG (375 mg·L-1, aluminum tris), Bayleton (250 mg·L-1, triadimefon), and Heritage (25 mg·L-1, azoxystrobin). Leaf explants were sterilized with 0%, 10%, 15%, or 20% bleach (5.25% sodium hypochlorite) (by volume) for 10 or 15 min, and stem explants were sterilized with 0%, 10%, 25%, or 50% bleach (5.25% sodium hypochlorite) for 10 or 15 min. About 97% of fungal contaminates were eliminated from leaf and stem explants when treated with 10% bleach for either 10 or 15 min. Leaves were plated on Gamborg B5 media at pH 5.7 containing 0, 2.5, 5, or 10 μM 2,4-D and 0, 0.25, 0.5, or 1.0 μM BAP and placed in a controlled environment growth room under a 14-h photoperiod or in a dark growth chamber. Callogenesis followed by root organogenesis was observed on explants treated with a variety of concentrations and combinations of 2,4-D and BAP. Strongest callogenesis was observed on media supplemented with 10 μM 2,4-D. A greater callus concentration was observed along the edges of dark cultured leaf discs. Indirect root induction was greatest on 10 μM 2,4-D.

Plant species and temperature effects on the k– C* first-order model for COD removal in batch-loaded SSF wetlands

The modified k– C * first-order degradation model proposed by Kadlec and Knight [Kadlec, R.H., Knight, R.L., 1996. Treatment Wetlands. Lewis Publishers, Boca Raton, FL] was fit to 192 data sets of COD concentration versus time measured in batch-loaded wetland microcosms. The time series sets were divided into four replicates of four plant species treatments; Carex utriculata (sedge), Schoenoplectus acutus (bulrush), Typha latifolia (cattail) and unplanted controls housed in a controlled-environment greenhouse in which temperature was cycled in 4 °C increments from 24 to 4 °C and back to 24 °C over a yearlong period. One 20-day batch incubation was conducted at each temperature setting during which seven chemical oxygen demand (COD) samples were drawn from each of 16 wetland columns. Non-linear mixed effects regression was used to fit parameters of the model. Best-fit values of the rate parameter k and the background concentration C * varied significantly by plant species and greenhouse temperature setting. An Arrhenius relationship was used to assess the effect of temperature on these parameters. Species greatly influenced the value of volumetric rate parameter at 20 °C ( k 20) and ranked Carex > Schoenoplectus > Typha > unplanted control (0.925, 0.743, 0.612 and 0.366 day −1, respectively). All displayed decreasing values for increasing temperature but species variation was much less ( θ k = 0.945, 0.957, 0.953 and 0.936, respectively). Background COD concentration values at 20 °C ( C 20 * ) ranked Carex < Schoenoplectus < Typha < unplanted control (42, 46, 66, 67 mg L −1, respectively) but seasonal variation was mixed ( θ C * = 1.029 , 0.999, 0.958 and 0.935, respectively). The results indicate that (1) seasonal variation of performance is plant-species specific; (2) singly, the rate constant k cannot capture the variation in performance due to temperature as much of the variation is reflected in the C * and (3) there are strong interactions between values of k and C *.