Lower Shoot Dry Weight Research Articles

Atividade residual e adsorção do tebuthiuron em diferentes solos

ABSTRACT Applications of tebuthiuron can increase the risks of environmental contamination and hinder the cultivation of sensitive species in succession. The objective of this work was to assess the residual activity and sorption of the herbicide tebuthiuron in soils with different physical and chemical attributes. The experiments were conducted in a completely randomized design with four replicates. The experiment for determining residual activity was conducted in a 2 × 7 factorial arrangement consisted of two herbicide doses (0.6 and 1.2 kg a.i. [active ingredient] ha-1) and seven sowing times (0, 60, 120, 180, 240, 300, and 360 days after herbicide application) in sandy loam and sandy clay loam soils. The experiment for evaluating sorption was conducted in a sandy loam soil and two clay loam soils with applications of increasing tebuthiuron doses (0.025, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30, 0.35, 0.40, 0.50, 0.60, 0.70, and 0.80 kg a.i. ha-1). Regarding residual activity, the herbicide’s effect of the decreased over time, with no toxicity detected 360 days after application (DAA), regardless of the soils and doses used. Sandy loam soils had lower sorption, resulting in lower shoot dry weight and plant height and in higher phytotoxicity 21 days after emergence. Residual activity was detected 360 DAA in the studied soils. Tebuthiuron sorption was higher in soils with higher organic carbon and clay contents.

Oryza glumaepatula: A wild relative to improve drought tolerance in cultivated rice.

Developing drought-resistant rice (Oryza sativa, L.) is essential for improving field productivity, especially in rain-fed areas affected by climate change. Wild relatives of rice are potential sources for drought-resistant traits. Therefore, we compared root growth and drought response among 22 wild Oryza species, from which Oryza glumaepatula was selected as a promising source for further exploration. A geographically diverse panel of 69 O. glumaepatula accessions was then screened for drought stress-related traits, and 6 of these accessions showed lower shoot dry weight (SDW) reduction, greater percentage of deep roots, and lower stomatal density (STO) under drought than the drought tolerant O. sativa variety, Sahbhagi dhan. Based on whole-genome resequencing of all 69 O. glumaepatula accessions and variant calling to a high-quality O. glumaepatula reference genome, we detected multiple genomic loci colocating for SDW, root dry weight at 30 to 45 cm depth, and STO in consecutive drought trials. Geo-referencing indicated that the potential drought donors originated in flood-prone locations, corroborating previous hypotheses about the coexistence of flood and drought tolerance within individual Oryza genomes. These findings present potential donor accessions, traits, and genomic loci from an AA genome wild relative of rice that, together with the recently developed reference genome, may be useful for further introgression of drought tolerance into the O. sativa backgrounds.

Genetic variation for terminal heat stress tolerance in winter wheat.

In many regions worldwide wheat (Triticum aestivum L.) plants experience terminal high temperature stress during the grain filling stage, which is a leading cause for single seed weight decrease and consequently for grain yield reduction. An approach to mitigate high temperature damage is to develop tolerant cultivars using the conventional breeding approach which involves identifying tolerant lines and then incorporating the tolerant traits in commercial varieties. In this study, we evaluated the terminal heat stress tolerance of 304 diverse elite winter wheat lines from wheat breeding programs in the US, Australia, and Serbia in controlled environmental conditions. Chlorophyll content and yield traits were measured and calculated as the percentage of non-stress control. The results showed that there was significant genetic variation for chlorophyll retention and seed weight under heat stress conditions. The positive correlation between the percent of chlorophyll content and the percent of single seed weight was significant. Two possible mechanisms of heat tolerance during grain filling were proposed. One represented by wheat line OK05723W might be mainly through the current photosynthesis since the high percentage of single seed weight was accompanied with high percentages of chlorophyll content and high shoot dry weight, and the other represented by wheat Line TX04M410164 might be mainly through the relocation of reserves since the high percentage of single seed weight was accompanied with low percentages of chlorophyll content and low shoot dry weight under heat stress. The tolerant genotypes identified in this study should be useful for breeding programs after further validation.

Growth and Quality Response of Four Container-grown Nursery Crop Species to Low-phosphorus Controlled-release Fertilizer

The amount of phosphorus (P) conventionally recommended and applied to container nursery crops commonly exceeds plant requirements, resulting in unused P leaching from containers and potentially contributing to surface water impairment. An experiment was replicated in the Middle Atlantic Coastal Plain (MACP) and Ridge and Valley ecoregions of Virginia to compare the effect of a low-P controlled-release fertilizer (CRF, 0.9% or 1.4% P depending on species) vs. a conventional CRF formulation (control, 1.7% P) on plant shoot growth, crop quality, and substrate nutrient concentrations of four species: ‘Natchez’ crape myrtle (Lagerstroemia indica × Lagerstroemia fauriei), ‘Roblec’ Encore azalea (Rhododendron hybrid), ‘Radrazz’ Knock Out rose (Rosa hybrid), and ‘Green Giant’ arborvitae (Thuja plicata × Thuja standishii). In both ecoregions, the low-P CRF resulted in 9% to 26% lower shoot dry weight in all four species compared with those given the conventional formulation, but quality ratings for two economically important species, ‘Radrazz’ Knock Out rose and ‘Green Giant’ arborvitae, were similar between treatments. When fertilized with the low-P CRF, ‘Roblec’ Encore azalea and ‘Natchez’ crape myrtle in both ecoregions, and ‘Green Giant’ arborvitae in the MACP ecoregion had ∼56% to 75% lower substrate pore-water P concentrations than those that received the control CRF. Nitrate-nitrogen (N) concentrations in substrate pore water at week 5 were more than six times greater in control-fertilized plants than in those that received a low-P CRF, which may have been a result of the greater urea-N content or the heterogeneous nature of the low-P CRFs. Lower water-extractable pore-water P and N indicate less environmental risk and potentially increased crop efficiency. Our results suggest low-P CRFs can be used to produce certain economically important ornamental nursery crops successfully without sacrificing quality; however, early adopters will need to evaluate the effect of low-P CRFs on crop quality of specific species before implementing on a large scale.

Bio-priming with a consortium of Streptomyces araujoniae strains modulates defense response in chickpea against Fusarium wilt.

Wilt caused by Fusarium oxysporum f. sp. ciceris (Foc) is one of the major diseases of chickpea affecting the potential yield significantly. Productivity and biotic stress resilience are both improved by the association and interaction of Streptomyces spp. with crop plants. In the present study, we evaluated two Streptomyces araujoniae strains (TN11 and TN19) for controlling the wilt of chickpea individually and as a consortium. The response of Foc challenged chickpea to inoculation with S. araujoniae TN11 and TN19 individually and as a consortium was recorded in terms of changes in physio-biochemical and expression of genes coding superoxide dismutase (SOD), peroxidase, and catalase. Priming with a consortium of TN11 and TN19 reduced the disease severity by 50–58% when challenged with Foc. Consortium primed-challenged plants recorded lower shoot dry weight to fresh weight ratio and root dry weight to fresh weight ratio as compared to challenged non-primed plants. The pathogen-challenged consortium primed plants recorded the highest accumulation of proline and electrolyte leakage. Similarly, total chlorophyll and carotenoids were recorded highest in the consortium treatment. Expression of genes coding SOD, peroxidase, and catalase was up-regulated which corroborated with higher activities of SOD, peroxidase, and catalase in consortium primed-challenged plants as compared to the challenged non-primed plants. Ethyl acetate extracts of TN11 and TN19 inhibited the growth of fungal pathogens viz., Fusarium oxysporum f. sp. ciceris. Macrophomina phaseolina, F. udum, and Sclerotinia sclerotiarum by 54–73%. LC–MS analyses of the extracts showed the presence of a variety of antifungal compounds like erucamide and valinomycin in TN11 and valinomycin and dinactin in TN19. These findings suggest that the consortium of two strains of S. araujoniae (TN11 and TN19) can modulate defense response in chickpea against wilt and can be explored as a biocontrol strategy.

PopW enhances drought stress tolerance of alfalfa via activating antioxidative enzymes, endogenous hormones, drought related genes and inhibiting senescence genes

Alfalfa (Medicago sativa L.) has the advantages of high yield and nutritional value as a perennial forage. However, one of the drawbacks of alfalfa is its susceptibility to drought conditions, which is a global problem in agriculture. The purpose of this study was to reveal the effects of exogenous PopW, a harpin protein from Ralstonia solanacearum, treatment on growth parameters, physiological and biochemical mechanism of alfalfa under drought-stress conditions. Growth parameters, relative water content, free proline, leaf area, total chlorophyll, antioxidative enzymes, endogenous hormones including ABA, CTK, GA, JA, SA and IAA were determined in response to exogenous PopW treatment under drought stress in alfalfa cultivar (Victoria). Moreover, relative gene expressions of drought-related and leaf senescence genes were determined. Under drought stress, alfalfa plants had lower shoot dry weight, shoot length, relative water content, leaf area, and total chlorophyll content, compared to control (non-stressed). However, Exogenous PopW treatment significantly increased growth values, relative water content, free proline, leaf area, total chlorophyll content, catalase, glutathione reductase and superoxide dismutase under drought conditions, compared to control and drought stress alone. Moreover, exogenous PopW treatment significantly increased ABA, GA, JA, SA, IAA contents, up-regulated auxin- and drought-responsive genes, down-regulated leaf senescence genes. Exogenous PopW treatment enhanced drought stress tolerance of alfalfa due to changes of endogenous hormone contents and expression levels of drought stress and leaf senescence genes. The results of the study show that PopW treatment could be used to increase the forage yield of alfalfa on areas having drought problem.

PERTUMBUHAN BAWANG MERAH (Allium cepa L.) YANG DIBERI PUPUK KOMPOS CAIR DAN JAMUR MIKORIZA ARBUSKULAR

The application of liquid compost and of beneficial soil microorganism such as arbsucular mycorrhizal fungi can be used to replace chemical fertilizer application. The aim of this study was to investigate the growth of red onion (Allium cepa L.) plant fertilized by liquid compost and inoculated by arbuscular mycorrhizal fungi. This study was conducted based on a completely randomized design with two factors. The first factor was an addition of liquid compost dosages (0, 50, 100 and 200 ml/polybag). The second factor was an addition of AM fungal inoculum (with and without addition). The results showed that the growth of red onion plant was not significantly affected by the addition of liquid compost and AM fungal inoculum. However, the red onion plant fertilized by 200 ml liquid compost per polybag had the lowest shoot dry weight. The addition of AM fungal inoculum was not increasing plant growth because the quality of used inoculum was not good.

Genetic Diversity of Purslane Populations of Iran Based on Some Morphological and Biochemical Traits

Portulaca oleracea L. is a medicinal plant belonging to Portulacaceae family, which exhibited a wide scope of pharmaceutical properties such as pain killer, antipyretic, anti-viral and anti-fungal. The aim of the present study was evaluation of morphological diversity 18 populations of P. oleracea. The seeds of 18 populations were cultivated based on a completely randomized design with three replicates in the research farm of Medicinal Plants Research Center, Shahed University, Tehran, Iran. The morphological traits, chlorophyll and protein contents were measured in the vegetative stage. The analysis of variance showed that there was a significant difference among populations of P. oleracea in terms of the most studied morphological and biochemical traits. The highest shoot dry weight (84.84±12.70 g per plant) belonged to the Zanjan population, while the lowest shoot dry weight (18.89±1.72 g per plant) belonged to the population of Lourdgan. The correlation between most of the studied traits was positively significant. The cluster analysis of the 18 P. oleracea populations based on morphological and biochemical traits produced three main clusters. Overall, the outcomes of the present study were indicated the presence of high genetic variability among the P. oleracea populations. Our findings suggested that collection of the plants from different regions can be used for hybridization to generate useful recombinants in the segregating generations and improve breeding varieties of P. oleracea and can be utilized for preservation and maintenance the germplasm of this medicinal plant.

Response of 25 Hybrid Maize Against Salinity Stress and Their Performance in Coastal Area

Plant stress due to NaCl compound will have an impact on the reduction of plant growth and yield. Tolerant varieties are required to increase plant production in coastal areas since these areas are closely related to salinity. This study aimed to (1) determine the appropriate NaCl concentration for saline tolerance in maize stress selection, (2) determine the response of maize plant to salinity stress in nutrient culture, and (3) determine the response of new hybrid maize having adaptibility in coastal area. Two experiments were run from November 2017 until May 2018. The first experiment was conducted in a greenhouse at the Laboratory of Agronomy, Faculty of Agriculture University of Bengkulu to determine the tolerance response of 25 new hybrid maize to salinity in nutrient culture. The second experiment was conducted on the coastal areas in Beringin Raya Village, Muarabangkahulu District, Bengkulu City to determine the response of new hybrid maize having adaptibility in a coastal areas. The concentration of NaCl at which level the LC50 was determined was found to be in 150 mM. This concentration was then used to test the tolerance of 25 new hybrid maize to NaCl stress. The hybrids of CT18, CT19, CT22, CT25, CT31, CT33, CT34, CT40, CT47, and CT50 showed good responses to the concentration treatment of 150 mM NaCl based on plant fresh weight and shoot dry weight. The hybrids of CT17,CT19, and CT20 showed good adaptibility on coastal area based on the length of cob, diameter of cob, seed weight per cob, and cob weight per plant. Among those three hybrids, CT17 and CT20 resulted low fresh weight and low shoot dry weight. The factors other than NaCl in coastal area maybe affect better response. However, CT19 proved as a hybrid which was consistently in a good response to salinity stress both in nutrient culture and in coastal growing area.

Relative Salt Tolerance of Seven Japanese Spirea Cultivars

Spirea (Spiraea sp.) plants are commonly used in landscapes in Utah and the intermountain western United States. The relative salt tolerance of seven japanese spirea (Spiraea japonica) cultivars (Galen, Minspi, NCSX1, NCSX2, SMNSJMFP, Tracy, and Yan) were evaluated in a greenhouse. Plants were irrigated with a nutrient solution with an electrical conductivity (EC) of 1.2 dS·m−1 (control) or saline solutions with an EC of 3.0 or 6.0 dS·m−1 once per week for 8 weeks. At 8 weeks after the initiation of treatment, all japanese spirea cultivars irrigated with saline solution with an EC of 3.0 dS·m−1 still exhibited good or excellent visual quality, with all plants having visual scores of 4 or 5 (0 = dead, 1 = severe foliar salt damage, 2 = moderate foliar salt damage, 3 = slight foliar salt damage, 4 = minimal foliar salt damage, 5 = excellent), except for Tracy and Yan, with only 29% and 64%, respectively, of plants with visual scores less than 3. When irrigated with saline solution with an EC of 6.0 dS·m−1, both ‘Tracy’ and ‘Yan’ plants died, and 75% of ‘NCSX2’ plants died. ‘Minspi’ showed severe foliar salt damage, with 32% of plants having a visual score of 1; 25% of plants died. ‘Galen’ and ‘NCSX1’ had slight-to-moderate foliar salt damage, with 25% and 21%, respectively, of plants with visual scores of 2 or less. However, 64% of ‘SMNSJMFP’ plants had good or excellent visual quality, with visual scores more than 4. Saline irrigation water with an EC of 3.0 dS·m−1 decreased the shoot dry weight of ‘Galen’, ‘Minspi’, ‘SMNSJMFP’, and ‘Yan’ by 27%, 22%, 28%, and 35%, respectively, compared with that of the control. All japanese spirea cultivars had 35% to 56% lower shoot dry weight than the control when they were irrigated with saline irrigation water with an EC of 6.0 dS·m−1. The japanese spirea were moderately sensitive to the salinity levels in this experiment. ‘Galen’ and ‘SMNSJMFP’ japanese spirea exhibited less foliar salt damage and reductions in shoot dry weight and were relatively more tolerant to the increased salinity levels tested in this study than the remaining five cultivars (Minspi, NCSX1, NCSX2, Tracy, and Yan).

Responses of Ornamental Grass and Grasslike Plants to Saline Water Irrigation

Ornamental grasses are popular in urban landscapes in Utah and the Intermountain West United States, one of the driest and fastest growing regions in the United States. This experiment evaluated the responses of five ornamental grass species [blue grama (Bouteloua gracilis), indian sea oats (Chasmanthium latifolium), ‘Blue Dune’ sand ryegrass (Leymus arenarius), pink muhly grass (Muhlenbergia capillaris), ‘Foxtrot’ fountain grass (Pennisetum alopecuroides)] and two ornamental grasslike species [fox sedge (Carex vulpinoidea), common rush (Juncus effusus)] to saline irrigation water in a greenhouse. Plants were irrigated weekly with a nutrient solution at an electrical conductivity (EC) of 1.2 dS·m–1 (control) or saline solutions at an EC of 5.0 or 10.0 dS·m–1. At the first harvest (9 weeks after the initiation of treatment), sand ryegrass, pink muhly grass, and fountain grass irrigated with solutions at an EC of 5.0 and 10 dS·m–1 had good visual quality with no or minimal foliar salt damage; however, the remaining species exhibited slight or moderate foliar salt damage. There were no significant differences in shoot dry weight (DW) among treatments within any species, except fox sedge and fountain grass. At the second harvest (18 weeks after the initiation of treatment), sand ryegrass, pink muhly grass, and fountain grass still had no or minimal foliar salt damage, and indian sea oats and fox sedge exhibited slight or moderate foliar salt damage. Compared with the control, all species irrigated with solutions at an EC of 10.0 dS·m–1 had reduced shoot DWs with the exception of blue grama. However, only common rush and pink muhly grass irrigated with solutions at an EC of 5.0 dS·m–1 had lower shoot DWs than the control. These results demonstrated that seven ornamental grass or grasslike species had a very strong tolerance to the salinity levels used in the 4-month experiment. Although plant growth was inhibited as a result of saline irrigation, plant visual quality of sand ryegrass, pink muhly grass, and fountain grass was still acceptable. These three species appear to be more suitable for landscapes in which saline irrigation water is used. Further research is needed to evaluate more ornamental grasses for landscapes in salt-prone areas and nearby coastal regions.

Plant Growth and Leachate Electrical Conductivity and pH as Influenced by Controlled-release Fertilizer Blends and Coating Technologies

Although controlled-release fertilizers (CRFs) have been used in container-grown ornamental plants for decades, new coating technologies and blends of fertilizers coated for specific release rates are being employed to customize fertility for specific environments and crops. A study was conducted in the transitional climate of Kentucky to determine the nutrient release rates of three controlled-release blends of 8- to 9-month release and growth response of ‘Double Play Pink’ japanese spirea (Spiraea japonica) and ‘Smaragd’ arbovitae (Thuja occidentalis). Fertilizer 1 (16N–3.5P–8.3K–1.8Mg + trace elements) and Fertilizer 2 (18N–3.1P–8.3K–1.8Mg + trace elements) were prototype blends with different experimental polymer coatings. Fertilizer 3 was a blend of 18N–2.2P–6.6K–1.1Ca–1.4Mg–5.8S + trace elements, which combined 100% resin-coated prills with a polymer coating. Fertilizer 4 was commercially available 15N–3.9P–10K–1.3Mg–6S + trace elements. Fertilizer 3 released its nutrients earlier in the 12-week study than the other three fertilizers and resulted in lower shoot dry weight in both species. The new polymer coating technologies show promise for delivering a predicted release rate and are appropriate for container production of these woody shrubs in Kentucky. An interesting side note of this experiment was that leachate pH measurements across treatments averaged 1.2 units lower for arbovitae (6.3) than for japanese spirea (7.5) at week 12. It was assumed that chemical and/or biological reactions at the root/substrate interface in arbovitae moderated pH increases over the study.

Hormonal and Nutritional Features in Contrasting Rootstock-mediated Tomato Growth under Low-phosphorus Nutrition.

Grafting provides a tool aimed to increase low-P stress tolerance of crops, however, little is known about the mechanism (s) by which rootstocks can confer resistance to P deprivation. In this study, 4 contrasting groups of rootstocks from different genetic backgrounds (Solanum lycopersicum var. cerasiforme and introgression and recombinant inbred lines derived from the wild relatives S. pennellii and S. pimpinellifolium) were grafted to a commercial F1 hybrid scion and cultivated under control (1 mM, c) and P deficient (0.1 mM, p) conditions for 30 days, to analyze rootstocks-mediated traits that impart low (L, low shoot dry weight, SDW) or high (H, high SDW) vigor. Xylem sap ionic and hormonal anlyses leaf nutritional status suggested that some physiological traits can explain rootstocks impacts on shoot growth. Although xylem P concentration increased with root biomass under both growing conditions, shoot biomass under low-P was explained by neither changes in root growth nor P transport and assimilation. Indeed, decreased root P export only explained the sensitivity of the HcLp rootstocks, while leaf P status was similarly affected in all graft combinations. Interestingly, most of the nutrients analyzed in the xylem sap correlated with root biomass under standard fertilization but only Ca was consistently related to shoot biomass under both control and low-P, suggesting an important role for this nutrient in rootstock-mediated vigor. Moreover, foliar Ca, S, and Mn concentrations were (i) specifically correlated with shoot growth under low-P and (ii) positively and negatively associated to the root-to-shoot transport of the cytokinin trans-zeatin (t-Z) and the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC), respectively. Indeed, those hormones seem to play an antagonistic positive (t-Z) and negative (ACC) role in the rootstock-mediated regulation of shoot growth in response to P nutrition. The use of Hp-type rootstocks seems to enhance P use efficiency of a commercial scion variety, therefore could potentially be used for increasing yield and agronomic stability under low P availability.

Evaluating Calibrachoa (Calibrachoa ×hybrida Cerv.) Genotype Sensitivity to Iron Deficiency at High Substrate pH

Floriculture crop species that are inefficient at iron uptake are susceptible to developing iron deficiency symptoms in container production at high substrate pH. The objective of this study was to compare genotypes of iron-inefficient calibrachoa (Calibrachoa ×hybrid Cerv.) in terms of their susceptibility to showing iron deficiency symptoms when grown at high vs. low substrate pH. In a greenhouse factorial experiment, 24 genotypes of calibrachoa were grown in peat:perlite substrate at low pH (5.4) and high pH (7.1). Shoot dry weight, leaf SPAD chlorophyll index, flower index value, and shoot iron concentration were measured after 13 weeks at each substrate pH level. Of the 24 genotypes, analysis of variance (ANOVA) found that 19 genotypes had lower SPAD and 18 genotypes had reduced shoot dry weight at high substrate pH compared with SPAD and dry weight at low substrate pH. High substrate pH had less effect on flower index and shoot iron concentration than the pH effect on SPAD or shoot dry weight. No visual symptoms of iron deficiency were observed at low substrate pH. Genotypes were separated into three groups using k-means cluster analysis, based on the four measured variables (SPAD, dry weight, flower index, and iron concentration in shoot tissue). These four variables were each expressed as the percent reduction in measured responses at high vs. low substrate pH. Greater percent reduction values indicated increased sensitivity of genotypes to high substrate pH. The three clusters, which about represented high, medium, or low sensitivity to high substrate pH, averaged 59.7%, 42.8%, and 25.2% reduction in SPAD, 47.7%, 51.0%, and 39.5% reduction in shoot dry weight, and 32.2%, 9.2%, and 27.7% reduction in shoot iron, respectively. Flowering was not different between clusters when tested with ANOVA. The least pH-sensitive cluster included all four genotypes in the breeding series ‘Calipetite’. ‘Calipetite’ also had low shoot dry weight at low substrate pH, indicating low overall vigor. There were no differences between clusters in terms of their effect on substrate pH, which is one potential plant iron-efficiency mechanism in response to low iron availability. This experiment demonstrated an experimental and statistical approach for plant breeders to test sensitivity to substrate pH for iron-inefficient floriculture species.

Nitric oxide protects carbon assimilation process of watermelon from boron-induced oxidative injury

Nitric oxide (NO) mediates plant response to a variety of abiotic stresses; however, limited information is available on its effect on boron (B)-stressed watermelon plants. The present study investigates the mechanism through which NO protects watermelon seedlings from B deficiency and toxicity stresses. Five days old watermelon seedlings were exposed to B (0, 0.5 and 10 mg L−1) alone or with 75 μmole of NO donor sodium nitroprusside (SNP) for 30 days. Both low and high B concentrations in the media altered nutrient accumulation and impaired various physiological processes of watermelon seedlings, leading to a significant reduction in biomass production. The plants exposed to B deficient or toxic concentrations had 66 and 69% lower shoot dry weight, respectively compared with optimum B levels. B toxicity-induced growth inhibition of watermelon seedlings was associated with high B translocation to shoot tissues, which caused lipid membrane peroxidation (12% increase) and chlorophyll destruction (25% reduction). In contrast, B deficiency accelerated generation of reactive oxygen species (ROS), specifically OH−1 and induced cellular oxidative injury. Exogenously applied SNP promoted leaf chlorophyll, photosynthesis and consequently biomass production in B-stressed watermelon seedlings by reducing B accumulation, lipid membrane peroxidation and ROS generation. It also activated antioxidant enzymes such as SOD, POD and APX, and protected the seedlings from ROS-induced cellular burst.

Micronutrient Availability from Steel Slag Amendment in Pine Bark Substrates

Steel slag is a byproduct of the steel industry that can be used as a liming agent, but also has a high mineral nutrient content. While micronutrients are present in steel slag, it is not known if the mineral form of the micronutrients would render them available for plant uptake. The objective of this research was to determine if steel slag could be used as the sole micronutrient source for container-grown nursery crops. Butterfly bush (Buddleja davidii ‘Pink Delight’) and rose (Rosa ‘Radrazz’) were grown in #3 (3 gal) containers in a base substrate composed of pine bark and peatmoss (80:20, by vol). The base substrate was amended with the following treatments: with a complete controlled release fertilizer (CRF) including micronutrients (C-control), a substrate amended with a different CRF containing only N, P, and K along with a granular micronutrient package (M-control), and three additional treatments amended with the CRF (N, P, and K only) and either 1.2, 2.4, or 4.8 kg·m−3 (2, 4, and 8 lb·yd−3) of steel slag. Plants were harvested at 2 and 4 months after potting (MAP). None of the plants displayed any sign of nutrient deficiency or toxicity throughout the experiment. However, plants grown in the substrate amended with the highest slag rate [4.8 kg·m−3 (8 lb·yd−3)] had lower shoot dry weight (SDW) than both control groups. Substrate pH increased with increasing slag rate, which may have affected micronutrient availability in those substrates. Among the micronutrients analyzed, only Copper (Cu) was consistently deficient in both the substrate and foliar tissue of slag-amended treatments. Steel slag either does not provide a sufficient quantity of Cu or the concomitant increase in pH with increasing rates of steel slag renders Cu unavailable for plant uptake. Steel slag should not be used as the sole source of micronutrients for shrubs grown in pine bark-based substrates.

Numerical and graphical assessment of relationships between traits of the Iranian Coriandrum sativum L. core collection by considering genotype × irrigation interaction

Drought is a worldwide problem seriously influencing production of agricultural plants such as coriander, but development of tolerant genotypes is inhibited by a lack of effective selection criteria. The objective of this study was to interpret the relationship between fruit yield and related traits in coriander to evaluate genotype by trait interaction by considering genotype×irrigation interaction. According to this aim, 16 Iranian endemic coriander genotypes were grown in a glasshouse under well watered (WW) and water stressed (WS) conditions. Structural equation modeling (SEM) was used, based on genotypic correlation coefficients and genotypic variance estimates obtained from combined analysis of WW and WS conditions and genotype-trait (GT) biplot analysis. Applying both types of analyze to the multiple trait data revealed that SEM and DC+YPr data based GT biplot results are similar. The GT biplot graphically displayed the interrelationships among traits and facilitated visual comparison of genotypes for selection. Predictors in the causal diagram could explain 70.8%, 80.9%, 100% and 41.7% of the total variation in fruit weight per plant (FWPP), fruit number per plant (FNPP), day to end of flowering (DTEOF) and umbel number per plant (UNPP), respectively. Also, the GT biplots explained 81.2% for WW data, 74% for WS data and 79.7% for DC+YPr data. It was found that selection for high SPAD chlorophyll content in the grain filling stage (SCCIGFS), UNPP, FNPP and branch number per plant (BNPP), and low shoot dry weight per plant (SDWPP) and DTEOF should be considered as priorities in breeding programs for coriander aiming for more productive and drought tolerant genotypes. Furthermore, G13 (TN-59-353) can be used as a drought tolerance donor in breeding programs.

Nutrients Limiting Soybean (glycine max l) Growth in Acrisols and Ferralsols of Western Kenya

Low soybean yields in western Kenya have been attributed to low soil fertility despite much work done on nitrogen (N) and phosphorus (P) nutrition leading to suspicion of other nutrient limitations. To investigate this, a nutrient omission trial was set up in the greenhouse at the University of Eldoret-Kenya to diagnose the nutrients limiting soybean production in Acrisols from Masaba central and Butere sub-Counties, and Ferralsols from Kakamega (Shikhulu and Khwisero sub-locations) and Butula sub-Counties and to assess the effect of liming on soil pH and soybean growth. The experiment was laid out in a completely randomized design with ten treatments viz; positive control (complete), negative control (distilled water), complete with lime, complete with N, minus macronutrients P, potassium (K), calcium (Ca), magnesium (Mg) and sulphur (S) and with, micro-nutrients boron (B), molybdenum (Mo), manganese (Mn), copper (Cu) and zinc (Zn) omitted. Visual deficiency symptoms observed included interveinal leaf yellowing in Mg omission and N addition and dark green leaves in P omission. Nutrients omission resulted in their significantly low concentration in plant tissues than the complete treatment. Significantly (P≤ 0.05) lower shoot dry weights (SDWs) than the complete treatment were obtained in different treatments; omission of K and Mg in Masaba and Shikhulu, Mg in Khwisero, K in Butere and, P, Mg and K in Butula. Nitrogen significantly improved SDWs in soils from Kakamega and Butula. Liming significantly raised soil pH by 9, 13 and 11% from 4.65, 4.91 and 4.99 in soils from Masaba, Butere and Butula respectively and soybean SDWs in soils from Butere. The results show that, poor soybean growth was due to K, Mg and P limitation and low pH in some soils. The results also signify necessity of application of small quantities of N for initial soybean use.

Optimizing Irrigation and Fertilization of Gardenia jasminoides for Good Growth and Minimal Leaching

Excessive irrigation and leaching are of increasing concern in container plant production. It can also necessitate multiple fertilizer applications, which is costly for growers. Our objective was to determine whether fertilizer and irrigation water can be applied more efficiently to reduce leachate volume and nutrient content without negatively impacting aboveground growth of Gardenia jasminoides ‘MAGDA I’. Plants were fertilized with one of three rates of a controlled-release fertilizer (subplots) (Florikan 18–6–8, 9–10 month release; 18.0N–2.6P–6.6K) [100 (40 g/plant), 50 (20 g/plant), and 25% of bag rate (10 g/plant)] and grown in 5.4-L containers outside for 137 days. Soil moisture sensor-controlled, automated irrigation was used to provide plants with one of four irrigation volumes (whole plots) (66, 100, 132, or 165 mL) at each irrigation event. All plants were irrigated when the control treatment (66 mL irrigation volume, 100% fertilizer treatment) reached a volumetric water content (VWC) of 0.35 m3·m−3. Plants in the different irrigation treatments were irrigated for 2, 3, 4, or 5 minutes, thus applying 66, 100, 132, or 165 mL/plant in the different irrigation treatments. Fertilizer rate had a greater effect on aboveground growth than irrigation volume with the 25% fertilizer rate resulting in significantly lower shoot dry weight (18.7 g/plant) than the 50% and 100% rates (25.3 and 27.3 g/plant respectively). Growth index was also lowest in the 25% fertilizer rate. Leachate volume varied greatly during the growing season due to rainfall and irrigation volume effects on leachate were most evident during the third, eighth, and ninth biweekly leachate collections, during which there was minimal or no rainfall. For these collections the control treatment of 66 mL resulted in minimal leachate (less than 130 mL over the 2-week leachate collection period), whereas leachate volume increased with increasing irrigation volumes. Pore water electrical conductivity (EC), leachate EC, NO3-N content, and PO4-P content were all highest with the 100% fertilizer rate, with the 66 mL irrigation treatment having the highest leachate EC for all fertilizer treatments. Cumulative leachate volumes for the 66 and 100 mL irrigation treatments were unaffected by fertilizer rate, whereas the 132 and 165 mL had greater leaching at the 25% fertilizer rate. Lower irrigation volumes resulted in reduced water and nutrient leaching and higher leachate EC. The higher leachate EC was the result of higher concentration of nutrients in less volume of leachate. The results of this study suggest that a combination of reduced fertilizer rates (up to 50%) and more efficient irrigation can be used to produce salable plants with reduced leaching and thus less environmental impact.

Response of bread-wheat seedlings to waterlogging stress

Waterlogging is a widespread problem and one of the major yield-limiting factors of wheat in some parts of the coastal plains of Turkey. The object of this study was to identify waterlogging-tolerant cultivars in bread wheat. Twenty-four bread-wheat genotypes were tested under aerobic and anaerobic conditions to determine shoot dry weight gain, root dry weight gain, total dry weight gain, dry leaf weight, specific dry leaf weight, chlorophyll content, carotenoid content, transpiration and photosynthesis rates, and their tolerance indices. A complete randomized block design with three replications was conducted for both aerobic and anaerobic conditions. The current study clearly demonstrated that wheat seedlings growing under anaerobic conditions had significantly lower shoot dry weight, root dry weight, total dry biomass weight, leaf dry weight, specific leaf dry weight, chlorophyll a, chlorophyll b, chlorophyll a + b, and carotenoid content, and photosynthesis and transpiration rates. There were significant correlations between total dry weight gain and shoot dry weight gain and between chlorophyll a and specific leaf dry weight. Wheat cultivars had different tolerance indices for the investigated plant parameters. Further studies are needed to confirm which tolerance index is significantly correlated with seed yield and which one could be used as a selection criterion under field conditions.