Plant Growth Room Research Articles

Microbial Populations and Enzyme Activities in Soil In Situ under Transgenic Corn Expressing Cry Proteins fromBacillus thuringiensis

Transgenic Bt crops produce insecticidal Cry proteins that are released to soil in plant residues, root exudates, and pollen and that may affect soil microorganisms. As a continuation of studies in the laboratory and a plant-growth room, a field study was conducted at the Rosemount Experiment Station of the University of Minnesota. Three Bt corn varieties that express the Cry1Ab protein, which is toxic to the European corn borer (Ostrinia nubilalis Hübner), and one Bt corn variety that expresses the Cry3Bb1 protein, which is toxic to the corn rootworm complex (Diabrotica spp.), and their near-isogenic non-Bt varieties were evaluated for their effects on microbial diversity by classical dilution plating and molecular (polymerase chain reaction-denaturing gradient gel electrophoresis) techniques and for the activities of some enzymes (arylsulfatases, acid and alkaline phosphatases, dehydrogenases, and proteases) involved in the degradation of plant biomass. After 4 consecutive years of corn cultivation (2003-2006), there were, in general, no consistent statistically significant differences in the numbers of different groups of microorganisms, the activities of the enzymes, and the pH between soils planted with Bt and non-Bt corn. Numbers and types of microorganisms and enzyme activities differed with season and with the varieties of corn, but these differences were not related to the presence of the Cry proteins in soil. The Cry1Ab protein of Bt corn (events Bt11 and MON810) was detected in most soils during the 4 yr, whereas the Cry3Bb1 protein was not detected in soils of Bt corn (event MON863) expressing the cry3Bb1 gene.

Efficient in vitro regeneration of fireweed, a medicinal plant

Epilobium angustifolium L. (fireweed) is a medicinal plant that has been used to treat diarrhea, mucous colitis, irritable-bowel syndrome, skin problems, prostate problems, menstrual disorders, asthma, whooping cough, and hiccups. A highly efficient and rapid regeneration system via multiple shoot formation was developed for fireweed. Explants (leaf, petiole, root, and stem segments) excised from sterile seedlings were cultured on medium supplemented with different concentrations and combinations of various plant growth regulators. Explant browning, a major problem for regeneration, was overcome by adding 100 mg/l ascorbic acid to all prepared media containing growth regulator combinations. Root explants formed more shoots than other explants. Best shoot proliferation was obtained from root explants cultured on media with 0.1 mg/l BA and 0.5 mg/l IAA. Regenerated shoots were transferred to rooting media containing different concentrations of IAA, IBA, NAA or 2,4-D. Most shoots developed roots on medium with 0.5 mg/l IAA. Rooted explants were transferred to vermiculate in Magenta containers for acclimatization and after 3 weeks they were planted in to plastic pots containing potting soil and maintained in the plant growth room.

Compensatory effects of elevated CO<sub>2</sub> concentration on the inhibitory effects of high temperature and irradiance on photosynthetic gas exchange in carrots

We determined the interactive effects of irradiance, elevated CO2 concentration (EC), and temperature in carrot (Daucus carota var. sativus). Plants of the cv. Red Core Chantenay (RCC) were grown in a controlled environmental plant growth room and exposed to 3 levels of photosynthetically active radiation (PAR) (400, 800, 1 200 µmol m-2 s-1), 3 leaf chamber temperatures (15, 20, 30 °C), and 2 external CO2 concentrations (C a), AC and EC (350 and 750 µmol mol-1, respectively). Rates of net photosynthesis (P N) and transpiration (E) and stomatal conductance (g s ) were measured, along with water use efficiency (WUE) and ratio of internal and external CO2 concentrations (C i/C a). P N revealed an interactive effect between PAR and C a. As PAR increased so did P N under both C a regimes. The g s showed no interactive effects between the three parameters but had singular effects of temperature and PAR. E was strongly influenced by the combination of PAR and temperature. WUE was interactively affected by all three parameters. Maximum WUE occurred at 15 °C and 1 200 µmol m-2 s- 1 PAR under EC. The C i /C a was influenced independently by temperature and C a. Hence photosynthetic responses are interactively affected by changes in irradiance, external CO2 concentration, and temperature. EC significantly compensates the inhibitory effects of high temperature and irradiance on P N and WUE.

Effects of fertilizer, fungal endophytes and plant cultivar on the performance of insect herbivores and their natural enemies

1 Endophytic fungi are associates of most species of plants and may modify insect community structures through the production of toxic alkaloids. Fertilization is known to increase food plant quality for herbivores, but it is also conceivable that additional nitrogen could increase the production of the insect toxic alkaloid, peramine, in endophyte-infected plants. 2 The relative importance of soil fertility and endophyte infection on herbivores and their natural enemies is unknown. As performance of the host plant is often affected by an interaction between endophyte infection and genetic background, four different plant cultivars were tested. The main questions addressed in this study were whether plant cultivar and fertilizer addition to endophyte-infected and endophyte-free Lolium perenne affect alkaloid concentrations, plant life-history traits and the abundances of aphid species and their parasitoids. 3 In a full factorial outdoor experiment we found a strong positive effect of fertilizer on plant biomass and on the abundance of aphids and parasitoids. While plant traits differed between cultivars, there was little effect of cultivar on either aphid or parasitoid abundance. Only endophyte-infected plants contained alkaloids, and the concentration of peramine was enhanced in fertilized plants. However, endophyte infection had no negative effect on aphid or parasitoid abundances. Plant traits were only weakly influenced by endophyte infection in the field, which contrasts with plant growth room studies, where both germination rate and plant height were influenced by endophyte–cultivar interactions. 4 The generally weak effects of endophytes in the outdoor experiment could be explained by various additional constraints under field conditions and the relatively low peramine concentration that we observed.

Plasticity in the Composition of the Light Harvesting Antenna of Higher Plants Preserves Structural Integrity and Biological Function

Arabidopsis plants in which the major trimeric light harvesting complex (LHCIIb) is eliminated by antisense expression still exhibit the typical macrostructure of photosystem II in the granal membranes. Here the detailed analysis of the composition and the functional state of the light harvesting antennae of both photosystem I and II of these plants is presented. Two new populations of trimers were found, both functional in energy transfer to the PSII reaction center, a homotrimer of CP26 and a heterotrimer of CP26 and Lhcb3. These trimers possess characteristic features thought to be specific for the native LHCIIb trimers they are replacing: the long wavelength form of lutein and at least one extra chlorophyll b, but they were less stable. A new population of loosely bound LHCI was also found, contributing to an increased antenna size for photosystem I, which may in part compensate for the loss of the phosphorylated LHCIIb that can associate with this photosystem. Thus, the loss of LHCIIb has triggered concerted compensatory responses in the composition of antennae of both photosystems. These responses clearly show the importance of LHCIIb in the structure and assembly of the photosynthetic membrane and illustrate the extreme plasticity at the level of the composition of the light harvesting system.

(295) Measuring and Reporting Growing Conditions in Controlled Environments

Do you accurately measure and report the growing conditions of your controlled environment experiments? Conditions in controlled environment plant growth rooms and chambers should be reported in detail. This is important to allow replication of experiments on plants, to compare results among facilities, and to avoid artefacts due to uncontrolled variables. The International Committee for Controlled Environment Guidelines, with representatives from the U.K. Controlled Environment Users' Group, the North American Committee on Controlled Environment Technology and Use (NCR-101), and Australasian Controlled Environment Working Group (ACEWG), has developed guidlines to report environmental conditions in controlled environment experiments. These guidelines include measurements of light, temperature, humidity, CO2, air speed, and fertility. A brochure with these guidelines and a sample paragraph on how to include this information in a manuscript will be available.

Bt corn has a higher lignin content than non‐Bt corn

Bt corn has been genetically modified to express the Cry1Ab protein of Bacillus thuringiensis to kill lepidopteran pests. Fluorescence microscopy and staining with toluidine blue indicated a higher content of lignin in the vascular bundle sheaths and in the sclerenchyma cells surrounding the vascular bundle in all ten Bt corn hybrids, representing three different transformation events, studied than of their respective non-Bt isolines. Chemical analysis confirmed that the lignin content of all hybrids of Bt corn, whether grown in a plant growth room or in the field, was significantly higher (33-97% higher) than that of their respective non-Bt isolines. As lignin is a major structural component of plant cells, modifications in lignin content may have ecological implications.

Interactions of aphid herbivory and nitrogen availability on the total foliar glycoalkaloid content of potato plants.

In plant growth room (PGR) and open-air pot (OAP) experiments, potato cvs King Edward and Maris Piper were grown under two nitrogen levels or two different nitrogen release patterns. Plants were subjected to infestation by peach potato aphids Myzus persicae (Homoptera: Aphididae). Total glycoalkaloid (GA) levels were measured in the foliage of both infested and non-infested plants, before, during and after aphid infestation. In the PGR experiment, aphid infestation reduced the amounts of total GAs in both cultivars. This reduction is attributed to the sugar deficiency induced in the plants owing to the dense aphid colonization. Results from the OAP experiment showed a temporal increase of GAs produced by potato cv. King Edward plants subjected to aphid infestation. Elevated amounts of nitrogen in the nutrient solutions (PGR experiment) reduced total GAs, while no differences were observed between manure and fertilizer treated plants (OAP experiment). It is concluded that the source of available nitrogen does not affect foliar GA synthesis in potatoes, and as a consequence, does not affect its endogenous chemical defense against insect herbivory. The case for insect-induced chemical defense mechanisms as triggered by low rates of aphid infestation is discussed.

Insecticidal toxin from Bacillus thuringiensis is released from roots of transgenic Bt corn in vitro and in situ.

The insecticidal toxin encoded by the cry1Ab gene from Bacillus thuringiensis was released in root exudates from transgenic Bt corn during 40 days of growth in soil amended to 0, 3, 6, 9, or 12% (v/v) with montmorillonite or kaolinite in a plant growth room and from plants grown to maturity in the field. The presence of the toxin in rhizosphere soil was determined by immunological and larvicidal assays. No toxin was detected in any soils from isogenic non-Bt corn or without plants. Persistence of the toxin was apparently the result of its binding on surface-active particles in the soils, which reduced the biodegradation of the toxin. The release of the toxin could enhance the control of insect pests or constitute a hazard to nontarget organisms, including the microbiota of soil, and increase the selection of toxin-resistant target insects.

Insecticidal toxin from Bacillus thuringiensis is released from roots of transgenic Bt corn in vitro and in situ

The insecticidal toxin encoded by the cry1Ab gene from Bacillus thuringiensis was released in root exudates from transgenic Bt corn during 40 days of growth in soil amended to 0, 3, 6, 9, or 12% (v/v) with montmorillonite or kaolinite in a plant growth room and from plants grown to maturity in the field. The presence of the toxin in rhizosphere soil was determined by immunological and larvicidal assays. No toxin was detected in any soils from isogenic non- Bt corn or without plants. Persistence of the toxin was apparently the result of its binding on surface-active particles in the soils, which reduced the biodegradation of the toxin. The release of the toxin could enhance the control of insect pests or constitute a hazard to nontarget organisms, including the microbiota of soil, and increase the selection of toxin-resistant target insects.

Screening for Ascochyta Blight Resistance in Chickpea Under Controlled Environment and Field Conditions

The occurrence and severity of Ascochyta blight of chickpea is influenced by environmental factors, which can complicate field screening. A controlled-environment plant growth room was developed at ICRISAT Asia Center to rapidly screen chickpea genotypes within 15 days for resistance to Ascochyta blight caused by Ascochyta rabiei. A positive correlation was observed between results from controlled-environment and field screenings in an area where the pathogen is endemic.

Fungal transmission of a potyvirus: uredospores of Puccinia sorghi transmit maize dwarf mosaic virus.

Maize dwarf mosaic virus (MDMV) and maize rust, Puccinia sorghi Schw., occur as natural infections on cultivated maize in South Africa. P. sorghi often occurs as a secondary late infection on maize plants which have already been infected with MDMV earlier in the season, either seed or aphid transmitted. When MDMV isolates from maize plants naturally infected by both virus and fungus were propagated by sap inoculation in plant growth rooms, residual uredospores in the sap gave rise to the development of uredia under conditions of high humidity. When uredospores developing on MDMV-B-infected plants were germinated on virus free maize seedlings, these plants became infected with MDMV-B. Similarly, when uredospores, originating from maize plants infected with MDMV-A, were scattered onto virus free maize seedlings, these plants became infected with MDMV-A. The presence of virus on uredospores in infected plant tissue was visualized by indirect immunofluorescence. Identification of virus infection was by DAS-ELISA and immunoelectro-blotting utilizing strain-specific antisera. Virus transmission occurred between closely situated plants which had no actual contact (unaided transmission). MDMV-B transmission by uredospores, to new maize seedlings, has been maintained for three successive years (1988-1991) in a plant growth room. The MDMV-B isolate remained sap and non-persistently aphid transmissible.

Fungal Interference withAspergillus flavusInfection and Aflatoxin Contamination of Maize Grown in a Controlled Environment

The ability of 'competing fungi' in preharvested maize to interfere with Aspergillus flavus infection and aflatoxin contamination of developing kernels was examined. Experiments were conducted in a plant growth room to eliminate insect damage of the ear, contaminating fungi, and unpredictable climatic events. Silk inoculation of uninjured ears resulted in fewer than 2% A. flavus-infected kernels and no detectable aflatoxin. Sterile toothpick-wounding of several kernels on ears that were similarly silk-inoculated promoted substantial A. flavus infestation and aflatoxin contamination of the wounded kernels. Many of the uninjured kernels also became infected with A. flavus. Kernel wounding by toothpick also promoted ear infection by Fusarium moniliforme, Acremonium strictum, and Aspergillus niger. When kernels were directly wound-inoculated with A. flavus and competing fungi, high levels of aflatoxins were detected in both the wounded kernel tissues and the first surrounding circle of uninjured kernels. However, the competing fungi, particularly F. moniliforme, inhibited A. flavus from further infecting and contaminating the other uninjured kernels on the same ear with aflatoxin.

Sclerotium Production by Aspergillus flavus on Corn Kernels

Sclerotia of Aspergillus flavus were produced during the moist chamber incubation of kernels from corn that was either naturally infested in the field or artificially inoculated in a plant growth room. Initial inspection of the kernels used in these experiments revealed no sclerotia. Sclerotia of A. flavus formed on autoclaved inoculated kernels that were incubated (21 da, 25 C) on sterile washed sand, sterilized (autoclaved) soil, or non-sterile garden soil. Treatments incorporating exposure to light or incubation on non-sterile soil resulted in a reduction in the numbers of sclerotia produced. Because A. flavus-infested kernels commonly reach the soil surface in the form of downed ears or through spillage at harvest, sclerotia may represent an important source of A. fiavus inoculum in field soils where corn is grown. Sclerotia of Aspergillusfiavus Link have not been reported to occur in nature even though the large mcllority of strains isolated from natup:uly occurring sub­ strates produce sclerotia when cultured in the laboratory (Wicklow and Cole, 1982). The importance of A. fiavus as a colonist of preharvest cereals and other agricultural produce makes it imperative that we understand the role of the sclero­ tium in the life cycle of A. fiavus. Sclerotia could represent a principal source of overwintering inoculum in cereal agroecosystems. Some plant pathogenic fungi (e.g., Ciaviceps spp.) produce sclerotia on plant parts above ground, whereas others develop sclerotia or other resistant resting propagules, such as chlamydospores, after the plant parts they colonize reach the soil surface. In the latter situation, the activities of litter-inhabiting fungal colo­ nists or soil bacteria may either promote or inhibit the production of such resting propagules (Wilhelm, 1954; Das and Western, 1959; Wilhelm and Taylor, 1965; Evans et ai., 1966; Alexander et ai., 1966; Ford et ai., 1970; Linderman, 1973). Our research was concerned with sclerotium development by A. fiavus in (1) naturally infested com grown near Tifton, Georgia, (2) corn produced in a plant growth room (Biotron, University of Wisconsin) and inoculated at silk with scle­ rotium-forming strains of A. fiavus, and (3) sterile (autoclaved) com kernels in­ oculated with A. fiavus. In the latter situation we investigated the response of A. fiavus to soil biotic factors and the presence of light.

Sclerotium Production byAspergillus Flavuson Corn Kernels

Sclerotia of Aspergillus flavus were produced during the moist chamber incubation of kernels from corn that was either naturally infested in the field or artificially inoculated in a plant growth room. Initial inspection of the kernels used in these experiments revealed no sclerotia. Sclerotia of A. flavus formed on autoclaved inoculated kernels that were incubated (21 da, 25 C) on sterile washed sand, sterilized (autoclaved) soil, or non-sterile garden soil. Treatments incorporating exposure to light or incubation on non-sterile soil resulted in a reduction in the numbers of sclerotia produced. Because A. flavus-infested kernels commonly reach the soil surface in the form of downed ears or through spillage at harvest, sclerotia may represent an important source of A. flavus inoculum in field soils where corn is grown. Sclerotia of Aspergillus flavus Link have not been reported to occur in nature even though the large majority of strains isolated from naturally occurring substrates produce sclerotia when cultured in the laboratory (Wicklow and Cole, 1982). The importance of A. flavus as a colonist of preharvest cereals and other agricultural produce makes it imperative that we understand the role of the sclerotium in the life cycle of A. flavus. Sclerotia could represent a principal source of overwintering inoculum in cereal agroecosystems. Some plant pathogenic fungi (e.g., Claviceps spp.) produce sclerotia on plant parts above ground, whereas others develop sclerotia or other resistant resting

A Versatile Plant Growth System With Wide Range Environmental Control

ABSTRACT A controlled-environment facility is described that can be used as a general purpose plant growth room (9.3 m3 total volume) or a dual chamber unit (0.97 m3 each) for studying photosynthesis, respiration and transpira-tion. Temperature for either application can be main-tained with average fluctuations of less than 1.5 C for the range of 15 to 35 C. Humidity and carbon dioxide control is possible over ranges of 30 to 95 percent relative humidity and 300 to 1400 ppm C02 with maximum fluc-tuations of 8.2 percent RH and 10 percent of full operational scale, respectively. Continuous measurement of evapotranspiration and carbon dioxide exchange is provided. Photosynthetically active radiation (400 - 700 nm) up to 1150 JLIE nr2 s'1 (81 klux illuminance) is pro-vided by a combination of fluorescent and high pressure sodium lamps. The internally located chambers are detachable and mobile and assembled of structural subunits for simple interchange of cultivation type and/or separation of aerial and root environments.

An Interface, Allowing a Commercial Paper-Tape Reader to be used in the Continuous Programming of Growth-Room Temperatures

A circuit is described which forms a link between a commercially available tape reader and the temperature-control circuit of a plant growth-room. Successive temperature adjustments are at 5 min intervals and the resulting programming system, subject to the limitations of the room control circuit, has a possible temperature span of 49·5 °C with a resolution of 0·5 °C. The paper tapes used may be (i) derived from existing data for the simulation of field conditions, (ii) output from a computer program to produce a temperature curve which obeys a mathematical law, or (iii) manually punched. The tapes may provide a continuously changing regime for a succession of days or, for diurnal repetition, may be spliced to form a loop. The system provides the means of studying plant response to fluctuating regimes of temperature and other environmental factors.

Pure culture synthesis of ectomycorrhizae by Thelephora terrestris and Pisolithus tinctorius on different conifer hosts

In a special plant-growth room, isolates of Thelephora terrestris produced basidiocarps and formed typical ectomycorrhizae with seedlings of bristlecone, jack, sand, lodgepole, shortleaf, slash, sugar, Austrian, longleaf, cluster, ponderosa, red, pitch, eastern white, Scots, loblolly, and Virginia pines and Douglas fir. Atypical mycorrhizae (lacking mantle) were formed on seedlings of Norway spruce and jack, Japanese red, and Himalayan pines. The formation of atypical mycorrhizae was considered a result of differences in the symbiotic–parasitic nature of the fungal symbionts on different hosts. Pisolithus tinctorius formed typical mycorrhizae with seedlings of jack, sand, Japanese red, shortleaf, slash, Austrian, longleaf, cluster, red, pitch, eastern white, Scots, loblolly, and Virginia pines. Reisolation of specific fungal symbionts from mycorrhizae of several pine hosts was successful.Mycorrhizae formed by T. terrestris were macroscopically and microscopically different from those of P. tinctorius, but mycorrhizae formed by different isolates of T. terrestris were indistinguishable from each other, regardless of host. These results suggest that the fungal symbiont determines color and morphology of ectomycorrhizae.

MOVEMENT OF PHOSPHORUS TO BARLEY ROOTS GROWING IN SOIL

A plant growth room experiment was conducted using seven soils of Alberta with a treatment of 300 ppm of P on four of the soils. The contributions to the movement of P to the roots were calculated according to the method of Barber and co-workers, with some modifications. Results of the experiment showed clearly that movement by mass flow was the most important process of P transport to roots in soils treated with 300 ppm of P. Apparent diffusion was found to be the major process of P movement to roots in untreated soils, which included two soils with naturally high levels of available P. Root interception was found to be of least importance in P movement to roots. Since the concentration of P in soil solution affected the amounts of P reaching the roots by diffusion, mass flow or root interception, the importance of the determination of soil solution P is emphasized. A correlation of 0.86 was obtained between the yield and soil solution P concentration of the untreated soils.

Studies on ectomycorrhizae of pine in an electronically air-filtered, air-conditioned, plant-growth room

An air-filtered, air-conditioned, plant-growth room is described and results of initial studies on ectomycorrhizae of pine in the room are presented. The room was fumigated with methyl bromide and maintained free of airborne spores of ectomycorrhizal fungi for 5 months.In the room, loblolly pine seedlings in pots of soil infested with forest humus developed ectomycorrhizae, whereas several hundred control loblolly pine seedlings did not form ectomycorrhizae. Eleven pine species grown in flats of soil infested with either of two isolates of Thelephora terrestris formed morphologically indistinguishable ectomycorrhizae. Noninoculated seedlings of the same pine species did not form ectomycorrhizae but developed dichotomously branched short roots and root hairs.Outside the room, 90% of loblolly pine seedlings grown in pots developed four different ectomycorrhizal forms, regardless of treatment. The 11 species of pine in flats of initially uninfested soil formed abundant ectomycorrhizae with at least two airborne symbionts, one of which was T. terrestris.Large numbers of pine seedlings with and without specific ectomycorrhizal associations can be studied in other than aseptic culture in the room. In this manner, natural forest conditions can be more closely duplicated for studies on ectomycorrhizal versus nonmycorrhizal relationships.