Plant Top Dry Weight Research Articles

Reflectance spectroscopy to characterize the response of Corymbia calophylla to Phytophthora root rot and waterlogging stress

Abstract The health of Corymbia calophylla (marri), a keystone tree species in the native forests of southwest Western Australia, has been in decline for the past few decades. Phytophthora root disease and waterlogging have often been cited as contributing to this decline. Traditional methods (i.e., field surveys and sampling) of mapping Phytophthora root infection in the field are time-consuming and expensive; thus, the potential of reflectance spectroscopy to characterize marri response to Phytophthora and waterlogging stress was investigated. Twelve-month old marri plants were infected with either P. cinnamomi or P. multivora in two glasshouse trials and waterlogged for 24 h each fortnight. Spectral measurements with a portable high-resolution spectroradiometer were taken weekly. Plant biophysical measurements were taken at harvest time. Normalized difference spectral index (NDSI) was calculated for every combination of reflectance values between 400 and 2500 nm for all time points, correlated with the treatment effects and displayed as heat maps. Narrowband vegetation indices (VIs), utilizing different wavelengths of the electromagnetic spectrum, were also calculated from the spectral data. The Phytophthora treatments did not cause significant differences with the biophysical measurements in both trials. In the second trial, the waterlogging treatment significantly lowered plant top dry weight (P = 0.016) and diameter (P = 0.044). Reflectance values plotted against wavelength displayed differences between treatments as well as a seasonal trend. The NDSI heat maps indicated that the Phytophthora and waterlogging treatment effects were strongest correlated with bandwidths in the visible and near-infrared portions of the electromagnetic spectrum (538–558 nm and 701–709 nm). Six of the VIs (normalized difference nitrogen index 2, anthocyanin reflectance index 1, photochemical reflectance index, Carter index 1, Vogelman index 3 and water band index) were able to track the biochemical changes in the leaves over the 10 weeks, confirming the seasonal trend. The interaction effect between P. cinnamomi, waterlogging and elapsed time in the first trial was significant for water band index (P = 0.010). This study demonstrates that reflectance spectroscopy holds promise for characterizing marri response but more work needs to be done to identify the optimum wavelengths for identifying Phytophthora and waterlogging stress with marri.

Pertumbuhan Cabai Merah (Capsicum annuum L.) pada Tanah Masam yang Diinokulasi Mikoriza Vesikula Arbuskula (MVA) Campuran dan Pupuk Fosfat

This research aimed to find out the interaction effect between mixed Vesicular Arbuscular Mycorrhiza (VAM) and phosphate fertilizer to the growth of red chili (C. annuum) in acid soil, and to fnd out the best combination of mixed VAM and phosphate fertilizer to the growth of red chili (C. annuum) in acid soil. This research used an experimental method with Completely Randomized Design (CRD) in a factorial pattern with two factors. The first factor was mixed VAM dosages consisted of four levels: 0; 10; 15; 20 g/plant. The second factor was phosphate fertilizer dosages consisted of four levels: 0; 0,2; 0,4; 0,6 g/plant. Each combination treatment had three replication. The parameters were observed in the form of plant height, stem diameter, plant top dry weight, degree of VAM infection, and P content of plant tissue. Data obtained from the observation was analyzed with Analysis of Variance (ANOVA) at an error rate of 5% and 1%, treatment that showed significant or very significant result, then followed with Honestly Significant Difference (HSD) test. The result showed that interaction between mixed Vesicular Arbuscular Mycorrhiza (VAM) and phosphate fertilizer did not increase the plant height, stem diameter, and plant top dry weight, but each factor increased the plant height, stem diameter, and plant top dry weight. VAM dosage inoculation of 20 g/plant without phosphate fertilizer is the most effective combination in increasing the degree of VAM infection.

Survey of Vesicular-Arbuscular Mycorrhizal Fungi in the Faculty of Agriculture Farm, Al-Azhar University, Assiut Governorate

The growth and yield response of a greenhouse experiments were conducted to investigate soybean plants to colonization by 20 isolates (including G. glomus and 3 Gigaspora species) of vesicular-arbuscular mycorrhizal fungi. Each isolate was evaluated in a high (71kg/fed. Bray-1 P2O5) and a low (21kg/fed. Bray-1 P2O5) fertility soil. Colonization by most Glomus isolates significantly increased plant top dry weight and seed yields. These isolates produced a high increases in dry weigh in the low of soil fertility . Colonization by five of the Gigaspora isolates did not significantly affect top dry weight and seed yield in the high or low fertility soil. The value of comparative testing of species is discussed.

First Report of a Ceratobasidium sp. Causing Root Rot on Canola in Washington State.

Rhizoctonia root rot occurs commonly on canola (Brassica napus L.) in Washington State. Recently, isolates of an additional pathogen were found to be involved in this disease complex. Isolates of an AG-I-like Ceratobasidium sp. were collected from roots and root zone soil in central Washington near Ritzville. Identity of selected isolates was verified by sequencing the internal transcribed spacer (ITS) region of the rDNA (GenBank Accession Nos. JQ247570, JQ247571, and JQ247572), with a 90 to 93% identity to AG-I. All isolates also amplified with AG-I-like specific primers (1). Six isolates were included in pathogenicity assays conducted in the greenhouse. There were five replicates of three plants for each treatment and the experiment was conducted twice. Pasteurized soil was infested with ground oat inoculum (1%) and placed into containers (3.8 × 21 cm). Infested soils were seeded with canola, chickpea (Cicer arietinum L.), lentil (Lens culinaris Medik.), pea (Pisum sativum L.), barley (Hordeum vulgare L.), or wheat (Triticum aestivum L.). After 3 weeks of incubation at 15°C, the plants were destructively harvested. The emergence of canola was consistently reduced in soil infested with a Ceratobasidium sp., with reductions of 0 to 23% (average 11%). There was no postemergence damping-off, a symptom commonly associated with AG-2-1 (2). Plant height and top dry weights were significantly reduced for canola seeded into infested soil. Heights of plants growing in infested soil was reduced by 25 to 53% (average 42%) and top dry weight was reduced by 37 to 81% (average 61%) compared with the noninfested control. The legume hosts tested in this study were also affected by this Ceratobasidium sp., but to a lesser extent. Compared with the noninfested controls, there was evidence of preemergence damping-off in chickpea (0 to 27%, average 13%) and pea plants were consistently stunted (5 to 23%, average 12%). Chickpea and pea plants grown in infested soil also had reduced top dry weights of 9 to 28% (average 17%) and 13 to 35% (average 21%), respectively. The roots of all infected hosts had a characteristic brown discoloration with tapered, rotted root tips (spear tips). There was no reduction in emergence or plant height of wheat and barley; there was inconsistent reduction in dry weight of these plants. To our knowledge, this is the first report of a Ceratobasidium sp. causing disease on canola in Washington State.

EFFECTS OF SHEEP MANURE ON VEGETATIVE AND REPRODUCTIVE GROWTH AND NUTRIENT CONCENTRATIONS OF SOYBEAN PLANTS UNDER LEACHING AND NON-LEACHING CONDITIONS

Lack of adequate organic matter (OM) is responsible for the poor physico-chemical condition in the agricultural soils of Iran. Thus, increasing soil OM has an important role in improving soil fertility and structure. The main purpose of this greenhouse study was to evaluate the impact of sheep manure and its leaching status on growth, nutrient concentration of soybean plants and some physico-chemical properties of the soil. Treatments consisted of four levels of sheep manure (0, 1, 2, and 4% based on dry weight), each with both leaching and non-leaching statuses. To reduce salinity, leaching of manure was done with 1:10 manure-water ratio. Results indicated that sheep manure employment significantly increased plant top dry weight. Plant nutrient concentrations increased as manure content increased, which were shown under non-leaching status. However, soybean has moderate tolerance to salinity; thus, application of essential amount of manure to this plant is proposed.

Biological management of gray mold in pot roses by co-inoculation of the biocontrol agent Ulocladium atrum and the mycorrhizal fungus Glomus mosseae

In pursuit of a biological disease and stress management strategy for ornamentals, a three-factorial experiment was performed to examine the effects of plant darkness stress, Ulocladium atrum and Glomus mosseae on gray mold caused by Botrytis cinerea and plant vigour in potted roses. While darkness stress significantly enhanced gray mold, U. atrum negated the stress effect, reducing disease incidence to comparable levels in both stressed and non-stressed plants. G. mosseae interacted positively with U. atrum under non-stress conditions and negatively in darkness. G. mosseae significantly reduced non-specific leaf wilt incidence. Darkness significantly reduced the number of leaves formed above the pruning stub; U. atrum efficiently counteracted this effect, but had no effect under non-stress conditions. G. mosseae and U. atrum additively increased the total number of leaves per plant, and increased plant top dry weight. However, G. mosseae had no effect on dry weight under stress conditions. G. mosseae root colonization increased significantly when U. atrum was applied, but only under normal light conditions. In conclusion, a biological approach combining a foliar biocontrol agent and an arbuscular mycorrhizal fungus for gray mold protection seems promising.

Growth, Chlorophyll, and Cation Concentration of Tetraploid Wheat on a Solution High in Sodium Chloride Salt: Hulled Versus Free-Threshing Genotypes

ABSTRACT Based on the literature, under-utilized hulled wheats could be tolerant to some harsh environmental conditions. The effect of salt stress on chlorophyll content, leaf area, dry weight, and ion concentrations in eight genotypes of tetraploid wheat (Triticum turgidum) using a three-replicate completely random design indoor experiment was studied. These genotypes included six hulled wheat (HW), T. turgidum subspp. Dicoccum, and two free-threshing wheat (FTW), T. turgidum subspp. durum. Salt stress was induced by adding sodium chloride (NaCl) to a hydroponic medium to 40, 80, and 120 mM, in addition to control. Salinity reduced leaf content of chlorophyll a (chl-a) at 120 mM but had not significant effect on chlorophyll b (chl-b) content. Salt stress decreased plant leaf area by nearly 63%. Plant top dry weight declined by 52% with increasing salinity to 120 mM level. Plant top calcium (Ca2+) content was not affected, whereas plant top sodium (Na+) concentration increased and potassium (K+) and magnesium (Mg+) concentration decreased with increasing salinity, averaged over genotypes. No significant interaction of genotype × salinity was detected for traits studied in this experiment. When contrasted as two groups of genotypes, i.e., HW vs. FTW, the former group suffered more severe decreases in terms of chl-a, chl-b, leaf area, dry weight, and Mg2+ concentration and a more pronounced increase in Na+ compared to the FTW. Overall, no evidence of salt tolerance was found for hulled tetraploid wheats of central Iran.

Role of Fermented Bio-extracts Produced by Farmers on Growth, Yield and Nutrient Contents in Cowpea (Vigna unguiculata (L.) Walp.) in Northeast Thailand

ABSTRACT Many small farmers in Northeast Thailand have adopted the on-farm production of fermented bio-extracts as a supplement to, or replacement for, chemical fertilizers. They use bio-extracts either singly or in combination with other organic amendments in crop production. The aim of this study was to investigate the benefit of bio-extract combined with organic fertilizers and alone as a nutrient source for crop biomass and yield. In a pot trial, addition of bio-extract alone at the local farmers' rate and frequency did not increase either biomass or yield of cowpea as its nutrient contents were much lower than those in the chemical fertilizer and all organic fertilizer treatments, and did not supply sufficient amounts of nutrients for crop growth on the low fertility sandy soil. However, in field and pot experiments, addition of bio-extract with organic fertilizers significantly increased plant top dry weight and yield above that obtained with organic fertilizer alone. Animal-based bio-extract gave larger and more consistent yield response than plant-based extract. The lack of response of yield to plant-based bio-extract with organic fertilizer was evident on the higher fertility alluvial soil. It may be concluded that bio-extract enhances the effect of organic fertilizers on cowpea growth. However, it is not clear whether bio-extract enhances crop growth by supplying a significant source of microorganisms or by supplying soluble C and/or N substrate for microbial activity to accelerate decomposition rate of organic fertilizers and release nutrients for the crop production.

PHYSICAL PROPERTIES OF MEDIA COMPOSED OF GROUND WHOLE PINE TREES AND THEIR EFFECTS ON VINCA (CATHARANTHUS ROSEUS) GROWTH

The objective of this study was to evaluate the potential use of container substrates composed of whole pine trees. Three species [loblolly pine (Pinus taeda), slash pine (Pinus elliottii) and longleaf pine (Pinus palustris)] of 8–10 year old pine trees were harvested at ground level and the entire tree was chipped with a tree chipper. The chips from each tree species were then further processed with a hammer mill to pass a ½-inch screen. On 29 June 2005 these three substrates along with 100% pinebark were mixed with the addition per cubic yard of 9.49 kg·m–3 Polyon 18–6–12 (18N–2.6P–10K), 2.97 kg·m–3 dolomitic lime and 0.89 kg·m–3 Micromax. One gallon (3.8 L) containers were then filled and placed into full sun under overhead irrigation. Into these containers were planted 72 cell plugs of Catharanthus roseus`Little Blanche'. Data collected were pre-plant chemical and physical properties of substrates, as well as plant growth index (GI), plant top dry weight, root ratings, and plant tissue (leaves) nutrient analysis at 60 days after planting (DAP). The test was repeated on 27 Aug. 2005 with C. roseus Raspberry Red Cooler. Top dry weights were on average 15% greater for the 100% pinebark substrate over all others at 60 DAP. However there were non differences in plant GI for any substrate at 60 DAP. There were no differences in plant tissue macro nutrient content for any substrate. Tissue micronutrient content was similar and within ranges reported by Mills and Jones (1996, Plant Analysis Handbook II) with the exception of Manganese. Manganese was highest for slash and loblolly pine and well over reported ranges. There were no differences in root ratings. There were no differences in substrate physical properties between the three whole tree substrates. However the 100% pinebark substrate had on average 50% less air space and 25% greater water holding capacity than the other substrates. Physical properties of all substrates were within recommended ranges. Based on the results of this study substrates composed of whole pine trees have potential as an alternative sustainable source for a substrate used in producing short term nursery crops.

Soils of the Chinese Hubei Province Show a Very High Diversity of Sinorhizobium fredii Strains

Biodiversity studies of native soybean-nodulating rhizobia in soils from the Chinese Hubei province (Honghu county; pH 8, alluvial soil) have been carried out. Inoculation of an American (Williams) and an Asiatic (Peking) soybean cultivar with eleven soil samples led to the isolation of 167 rhizobia strains. The ratio (%) of slow-/fast-growing isolates was different depending on the trap plant used. All isolates were able to nodulate both cultivars, although the N2-fixation efficiency (measured as plant-top dry weight) was different among them. A total of thirty-three isolates were selected for further characterisation on the basis of physiological parameters, PCR-RFLP of symbiotic genes and Low Molecular Weight RNA, lipopolysaccharide, protein and plasmid profiles. Low Molecular Weight RNA profiling indicates that all the isolates belong to species Sinorhizobium fredii. The dendrogram obtained with the physiological parameters has been useful to classify the isolates at strain level, although plasmid profiling was the most discriminating technique to detect differences among the analysed soybean-rhizobia isolates, showing there is not two isolates identical each other. Plasmid profile analyses also revealed that some of the investigated strains contain low molecular weight plasmids (7-8-kb). They are, to our knowledge, the smallest ever found in rhizobia and they could be the starting point for the construction of the first group of vectors based on a native rhizobia replicon.

Effect of seed size and phosphorus fertilization on growth of selected legumes

A screenhouse experiment was conducted to assess the effects of seed size and phosphorus (P) fertilization on growth of 12 herbaceous and shrub legumes [Arachis hypogaea, Cajanus cajan, Centrosema pascuorum, Centrosema brasilianum, Crotolaria ochroleuca, Glycine max, Lablab purpureus, Mucuna cochinchinensis, Mucuna pruriens var. utilis (black seed), Mucunapruriens (white seed), Pueraria phaseoloides and Vigna unguiculata] grown on a P‐deficient Plinthustalf. Species with large seed size showed higher biomass accumulation, nodulation and higher plant nutrient element content. However, response to P fertilization was higher in small size seeded species. Plant top dry weight was highly correlated with seed weight and seed nutrient element contents. Although P application significantly increased nitrogen (N), P, potassium (K), calcium (Ca), and magnesium (Mg) contents of plant tops, high rate of P fertilization appeared not to be beneficial to the early growth of the species tested on this P‐deficient soil. The use of large seed size with high seed nutrient element contents is highly recommended for fast establish ment of fallow legume species intended for use in production systems on P‐deficient soils.

A Rhizobium strain that nodulates and fixes nitrogen in association with alfalfa and soybean plants.

A Rhizobium meliloti strain that forms effective nodules on soybean (Glycine max) and alfalfa (Medicago sativa) is described. The strain, 042B, was isolated from root nodules of alfalfa in Xinjiang Autonomous Region of China. Experiments showed that strain 042B was able to nodulate soybean as effectively as Bradyrhizobium japonicum USDA110, a widely used inoculant strain. Under hydroponic conditions, both strains performed similarly in many respects such as time required for the appearance of nodules, total nitrogenase activity, plant top dry weight and total plant nitrogen. In soil pot experiments, total nitrogen, seed weight and seed nitrogen of soybean plants inoculated with strains 042B or USDA110 were much higher than those of the uninoculated control, but there were no differences between plants with strain 042B relative to strain USDA110. However, when strain 042B was the inoculant, the number of nodules was greater, but the nodules were smaller than those of strain USDA110. Results from ELISA showed that nodule occupancy of strain 042B in soybean ranged from 82-90% and that of strain USDA110 ranged from 78-86%. Strain 042B can grow in the presence of 5% (w/v) NaCl, at 42 °C, and at pH 10·7. Strain 042B was shown to have two large plasmids (molecular sizes 200 kb and > 1000 kb, respectively). The DNA G + C mol% of strain 042B was 63·6. The DNA level of homology between strain 042B and type-strain R. meliloti USDA1002 was 76%, while DNA homologies of strain 042B were 10% and 12% with R. fredii USDA205 and B. japonicum USDA6, respectively.

162 GROWTH AND FLOWERING RESPONSES OF `DARK RED HEGG' POINSETTIAS IN COAL ASH-AMENDED ROOT MEDIA TO 3 NUTRIENT SOLUTIONS IN A CLOSED-LOOP NUTRICULTURE SYSTEM

Rooted cuttings of `Dark Red Hegg' poinsettia were potted in root media containing 0, 50, or 100 percent by volume of coal bottom ash in peat::vermiculite (50:50, v/v), one cutting per 1 liter pot. The plants were placed in a closed loop nutriculture system and irrigated with 200 mg N.liter-1 of (N-P-K) 20-8.8-17.8. 15-2.2-22.25. or 20-4.8-21.6 (commercial Hydrosol + Ca(NO3)2). each with soluble trace elements. Fertilizer solutions were maintained at pH=6.0-6.5 and E.C.=1.6-2.5 dS.m-1. Media pH and E.C. tended to increase with amount of ash in the media. The 20-8.8-17.8 fertilizer reduced pH values 0.6-0.8 in all media. Plants were of equal height in all media. Average bract cluster diameters of plants in 100 percent coal ash were reduced compared to those in 0 and 50 percent coal ash by the 15-2.2-22.25 fertilizer. but not by the other two fertilizers. Plant top dry weights in 100 percent ash were reduced below those in 0 and 50 percent ash by the 20-8.8-17.8 and the 15-2.2-22.25 fertilizers.

Comparison between two controlled-release fertilizers on selected foliage plants in an artificial potting mix

A series of trials compared Osmocote® and a recently available controlled-release fertilizer (CRF) product, Nutricote®, at the same rates of N per container. Comparable formulations (e.i. 3–4 months) were compared on a variety of tropical foliage plants including:Impatiens, palms (Chamaedorea seifrizii, Chrysalidocarpus lutescens, Phoenix roebelinii, Rhapis excelsa andChamaedorea elegans) andSpathiphyllum; at 10 rates of N from 0 to 2–3 times the manufacture's recommended rate in a 1:1 (v:v) peat:perlite mix amended with dolomitic lime and a commercial micronutrient mixture. The plants were grown in a shade house, watered with overhead spray stakes and pest control measures used as required. Growth parameters used were plant height, growth index and top dry weight, along with tissue analysis and NO3- concentrations. Overall plant height of the majority of plants tested was found to be comparable for the two CRF sources. However, there were some differences in top dry weight and leaf green color which were species specific. These results suggest that the release rate and availability of specific nutrients during the various plant growth phases may be more important for optimum plant growth and quality than the fertilizer formulation used. In general, both CRF products resulted in satisfactory plant growth and quality under the conditions of these trials.

INFLUENCE DE LA TEMPÉRATURE NOCTURNE ET D’UN APPOINT DE LUMIÈRE SUR LA CROISSANCE ET LE DÉVELOPPEMENT DU Gerbera ET DU Calendula

During fall-winter and spring conditions, Gerbera jamesonii H. Bolus ex Hook. ’Happipot’ and Calendula officinalis L. ’Fiesta Gitanas’ plants were subjected to night temperatures of 9, 13, 17 and 20 °C (1700–0800 h) during the first year of experiment and were grown under supplementary lighting treatments (control, 75 and 150 μmol m−2 s−1) for 7 h per day at a temperature of 13 °C during the second year. The plant top dry weight of gerbera increased with a rise in night temperature and supplementary lighting, but the reverse tendency was noted with calendula under the night temperature treatment; increases in plant top dry weight under supplementary lighting were observed only during the fall-winter period. For both species, root dry weight showed less variation than plant top dry weight under night temperature and supplementary lighting treatments. The percentage of gerbera plants having shoots increased with a reduction of the night temperature and supplementary lighting during the fall-winter experiments. The lowering of night temperature and supplementary lighting reduced calendula flower bud abortion only during the fall-winter period. For both species, flower number was not significantly different among die night temperature treatments. Supplementary lighting enhanced flower number of calendula only. Flowering of gerbera was accelerated with a reduction of night temperature and with supplementary lighting.Key words: Calendula officinalis, Gerbera jamesonii, night temperature, supplementary lighting

Effects of Curing Time on Physical and Chemical Properties of Composted Sewage Sludge Bind on the Growth of Selected Bedding Plants

Raw sewage sludge treated with lime and ferric chloride was composted by the Beltsville Aerated Pile Method, screened and piled outdoors (cured) for 4, 6, 8, or 10 months. As curing time increased there was a decrease in CO2 and temperature, and an increase in O2 within the piles. The NH4 concentrations and electrical conductivity (EC) of the compost decreased while pH, NO3 + NO2, and extractable P increased with time. Curing time did not influence extractable K while bulk density (BD) and particle size distribution (PSD) exhibited only moderate changes. Marketable seedlings of Impatiens hybrida ‘Super Elfin Scarlet’ and Tagetes patula L. ‘Yellow Boy’ were produced in peat:vermiculite (v/v) amended with 10 or 20% compost, regardless of compost curing time. Seedlings of Coleus x hybridus Voss. ‘Saber Golden’ were stunted and unmarketable in all compost amended media. Increasing compost curing time decreased EC, pH, and extractable N and K of the media at transplant time, and resulted in increased dry weight of I. hybrida and T. patula. Increasing compost concentrations in the media decreased plant top dry weight and visual ratings, and increased EC, pH, and NH4, NO3 + NO2, and extractable N, P, and K.

Response ofBromus inermis inoculated withGlomus fasciculatum to potassium fertilization and drought stress

Bromus inermis Leyss. was grown in a 2×2×2 factorial design using different levels of mycorrhizal inoculation (inoculated and noninoculated), soil water stress (Ψ1 or −0.8 MPa) and potassium (K) fertilization (0 or 150 ppm) as factors. Soil water stress and mycorrhizal inoculation significantly reduced plant top dry weight during the 18 week study. Chlamydospore production by the mycorrhizal symbiontGlomus fasciculatum (Thaxter sensu. Gerd.) Gerd. and Trappe was significantly reduced by soil water stress of −0.8 MPa. Potassium (K) fertilization did not significantly influence plant top growth or mycorrhizal colonization. However, foliar Ca and Mg were significantly lower in plants fertilized with K. Foliar Ca and Mg concentrations of P, K, N, Mn, Zn and Cu were significantly greater in drought stressed plants whereas Ca and Mg concentrations were significantly greater in well-watered plants.

GROWTH, NUTRITION AND GAS EXCHANGE OF BROMUS INERMIS INOCULATED WITH GLOMUS FASCICULA TUM

SUMMARYPlants of Bromus inermis Leyss. inoculated or not with the mycorrhizal fungus Glomus fasciculatum (Thaxter sensu. Gerd.) Gerd. and Trappe, were pre‐conditioned at two soil moisture levels (Φs− 0.03 or − 0.8 MPa) for 17 weeks, then subjected to a drying cycle. Stomatal conductance (g1), soil‐plant liquid flow resistance (Rs−p), and photosynthesis rates (Ps) were measured before, during, and after the drying cycle. Soil water stress and mycorrhizal inoculation significantly reduced plant top dry weight during the 18 week study. Chlamydospore production by the mycorrhizal symbiont G. fasciculatum was significantly increased by soil water stress of −0.8 MPa. Foliar Ca and Mg concentrations were significantly greater in mycorrhizal plants. Foliar concentrations of P, K, N, Mn, Zn and Cu were significantly greater in drought stressed plants whereas Ca and Mg concentrations were significantly greater in well‐watered plants.Mycorrhizal plants pre‐conditioned at Φs−0.8 MPa had 36 and 34% lower Rs−p values than nonmycorrhizal plants at pre and peak drought sampling times, respectively. Following re‐irrigation, g1 was 64% greater in mycorrhizal plants when compared to nonmycorrhizal plants. Inoculation with G. fasciculatum increased photosynthesis rates by 20, 52, and 22 % over the noninoculated plants before, during, and after the drying cycle respectively. Despite increased rates of photosynthesis, top dry weight of mycorrhizal plants was 15 % less than that of noninoculated plants.Regardless of inoculation treatment, plants pre‐conditioned at ΦS−0.8 MPa exhibited greater g1 and Ps values during and after the drying cycle. Bromus inermis demonstrated the ability to adapt to water deficits. Mycorrhizal symbiosis may play a role in the adaptation of B. inermis to dry sites.

Relative Effect of Vesicular‐Arbuscular Mycorrhizal Fungi on the Growth and Yield of Soybeans

AbstractThe growth and yield response of greenhouse‐grown soybean plants to colonization by 19 isolates (including 6 Glomus and 3 Gigaspora species) of vesicular‐arbuscular mycorrhizal fungi is reported. Each isolate was evaluated in a high (169 kg/ha Bray‐I P2O5) and a low (50 kg/ha Bray‐I P2O5) fertility soil. Colonization by most Glomus isolates significantly increased plant top dry weight and seed yields, and of these isolates most produced larger increases in dry weight in the low fertility soil. Colonization by five of the Gigaspora isolates did not significantly affect top dry weight and seed yield in the high or Iow fertility soil. The value of comparative testing of species is discussed.

Título en español.

Con aplicaciones de los nematicidas Fensulfothion granulado, D-D y Vorlex (líquido) a razón de 20 lb., 40 y 40 galones por acre, respectivamente, a plantas de sorgo sembradas en invernadero, se logró sobrepasar en peso seco de las raíces, los de las plantas testigo y los de las que recibieron aplicaciones insecticidas y fungicidas. En las sembradas a la intemperie, la aplicación de bromuro metílico, a razón de 1 lb./100 p2 fue muy eficaz en uno de dos experimentos. En todos los experimentos las plantas se sembraron en un suelo Coto arcilloso (Oxisol). Cuando el bromuro metílico, Fensulfothion (30 lb./acre) y D-D (40 lb./acre) se aplicaron antes de la siembra, el peso seco de las plantas aumentó 132, 106 y 66%, respectivamente sobre los de las plantas testigo. Vorlex y D-D (ambos a razón de 40 galones por acre) también los aumentaron sobre el de éstas y sobre los de las plantas sembradas en suelo tratado con Oxamyl y Phenamiphos. De tres dosis evaluadas, las de 20 lb. de Fensulfoth ion y 60 lb. de D-D, aumentaron el peso seco un 40% sobre el de las plantas testigo. Tanto en el invernadero como en el campo, las aplicaciones insecticidas y fungicidas fueron ineficaces. El pH del suelo era más bajo y la población de nematodos fitoparasíticos menos densa en el suelo de la rizosfera en plantas de poco crecimiento en comparación con las de crecimiento normal. En las primeras, la concentración de aluminio en el suelo era mucho más elevada.