Seedling Leaf Research Articles

Diploid True Potato Seed: Relationships among Seed Weight, Germination, and Seedling Vigor

The use of true potato seed (TPS) offers many advantages over the tuber pieces used in current potato cropping systems. Hybrid TPS based on diploid inbred lines has the potential to revolutionize the potato industry. In preparation for the transition to TPS, seed productivity traits must be characterized. The present study aims to provide data on seed germination rates and seedling vigor of diploid potatoes. The germplasm for this study consisted of families from a cross between DM1-3 and M6 that have been inbred to varying degrees. Seedling leaf area and percent germination were evaluated on 51 populations across six dates. Positive Pearson correlations were found between seed weight, percent germination, and seedling leaf area. Significant levels of variation were detected between lineages, generations, and lineage by generation interactions using ANOVA for leaf area and percent germination. Families that exhibited vigorous growth by 14-18 days post sowing continued to sustain high growth rates while families that did not exhibit vigorous growth at this time did not experience a drastic increase in growth rate. This timeframe will be an important stage in which to ensure a seedlings health in order to maximize its potential.

The effects of Solidago canadensis water extracts on maize seedling growth in association with the biomass allocation pattern.

BackgroundSolidago canadensis L. is an aggressive exotic plant species in China that has potential allelopathic effects on competing plant species. Effects of hormesis are frequently observed in studies of allelopathy; however, the mechanisms of such effects need to be elucidated. Allelopathic compounds may affect the growth of recipient plants via alteration of biomass allocation patterns or photosynthetic capacity. The aim of this study was to determine how water extracts from S. canadensis affected the shoot and root growth of recipient plants and whether the underlying mechanism was related to the biomass allocation pattern or photosynthetic gas exchange capacity.MethodsThe water extracts from S. canadensis shoots at 12 different concentrations in the range of 0–0.25 g/ml were applied thrice in 9 days to maize seedlings cultivated in silica sand. The growth (shoot height, leaf length and area and root length) and biomass accumulation and allocation (specific leaf area (SLA), leaf area ratio (LAR) and leaf mass ratio (LMR)) were compared among maize seedlings exposed to different treatment concentrations. Gas exchange (photosynthetic light response curve) was measured and compared among maize seedlings exposed to three concentrations of water extract (0, 0.0125 and 0.2 g/ml) before and after the first application, and seedling growth was measured after the third and final application.ResultsThe growth of seedlings (shoot height, leaf length and area and root length) was promoted at concentrations below 0.125 g/ml and inhibited at concentrations above this level (P < 0.05). The pattern of change in biomass accumulation and allocation was similar to that of shoot growth, but biomass accumulation and allocation was not significantly affected by the water extract treatments (P > 0.05). The water extract treatments did not significantly affect the photosynthetic capacity (P > 0.05), but the dark respiration rate was higher in the low-dose treatment than that in the high-dose treatment. Shoot height was positively correlated with the biomass allocation indicators SLA and LAR (P < 0.05) but not with LMR (P > 0.05).ConclusionsThe results suggested that the effects of the water extracts from S. canadensis were highly dependent on the concentration, with the growth of maize seedlings promoted at low concentrations of water extracts. The effects of the water extracts on the growth of maize seedlings were mainly due to the effects on the LAR, the allocation to leaf area growth, whereas the effects of the water extracts on leaf gas exchange capacity cannot explain variation of seedling growth. Thus, the stimulation of plant growth was very likely due to increased biomass allocation towards the shoot.

Fourier Descriptors Based Expert Decision Classification of Plug Seedlings

To enable automatic transplantation of plug seedlings and improve identification accuracy, an algorithm to identify ideal seedling leaf sets based on Fourier descriptors is developed, and a classification method based on expert system is adopted to improve the identification rate of the plug seedlings. First, the image of the plug seedlings is captured by image acquisition system, followed by application of K-means clustering for image segmentation and binary processing and identification of the ideal seedling leaf set by Fourier descriptors. Then we obtain feature vectors, such as gray scale (R+B+G)/3, hue H, and rectangularity. After that the knowledge model of the plug seedlings is defined, and the inference engine based on knowledge is designed. Finally, the recognizing test is carried out. The success rate of the identification of 10 varieties of plug seedlings from 190 plates is 98.5%. For the same sample, the recognizing rate of support vector machine (SVM) is 85%, the recognizing rate of particle-swarm optimization SVM (PSOSVM) is 87%, the recognizing rate of back propagation neural network (BP) is 63%, and the recognizing rate of Fourier descriptors SVM (FDSVM) is 87%. These results show that our recognition method based on an expert system satisfies the requirements of automatic transplanting.

Short-Term Nitrogen Addition Does Not Significantly Alter the Effects of Seasonal Drought on Leaf Functional Traits in Machilus pauhoi Kanehira Seedlings

Research Highlights: Short-term nitrogen (N) addition did not significantly alter the effects of seasonal drought on the leaf functional traits in Machilus pauhoi Kanehira seedlings in N-rich subtropical China. Background and Objectives: Seasonal drought and N deposition are major drivers of global environmental change that affect plant growth and ecosystem function in subtropical China. However, no consensus has been reached on the interactive effects of these two drivers. Materials and Methods: We conducted a full-factorial experiment to analyze the single and combined effects of seasonal drought and short-term N addition on chemical, morphological and physiological traits of M. pauhoi seedlings. Results: Seasonal drought (40% of soil field capacity) had significant negative effects on the leaf N concentrations (LNC), phosphorus (P) concentrations (LPC), leaf thickness (LT), net photosynthetic rate (A), transpiration rate (E), stomatal conductance (Gs), and predawn leaf water potential (ψPD), and significant positive effects on the carbon:N (C:N) ratio and specific leaf area (SLA). Short-term N addition (50 kg N·hm−2·year−1 and 100 kg N·hm−2·year−1) tended to decrease the C:N ratio and enhance leaf nutrient, growth, and photosynthetic performance because of increased LNC, LPC, LT, leaf area (LA), SLA, A, E, and ψPD; however, it only had significant effects on LT and Gs. No significant interactive effects on leaf traits were detected. Seasonal drought, short-term N addition, and their interactions had significant effects on soil properties. The soil total C (STC), nitrate N (NO3−-N) and soil total N (STN) concentrations were the main factors that affected the leaf traits. Conclusions: Seasonal drought had a stronger effect on M. pauhoi seedling leaf traits than short-term N deposition, indicating that the interaction between seasonal drought and short-term N deposition may have an additive effecton M. pauhoi seedling growth in N-rich subtropical China.

Evaluation of sorghum genotypes for their resistance to shoot fly Atherigona soccata

An experiment with sixteen sorghum genotypes including two checks was conducted to evaluate their reaction against shoot fly at Akola, during kharif 2016–17. Observations were made on the eggs, deadhearts, seedling vigour, leaf glossiness, trichome density, chlorophyll content and Bricks index. The results revealed that the seedling leaf glossiness score (SLGS) of 1.67 to 4.67 and these were significantly positively corelated with oviposition and deadhearts. Seedling vigour score (SVS) also was observed with a positive significant association with eggs and deadhearts on 14th and 28th days after emergence. The trichomes on abaxial (lower) surface was observed to be maximum with the resistant check IS-18551, and this showed a significant negative association with oviposition and deadhearts. Chlorophyll index had highly significant positive impact on the oviposition and deadhearts. Low Bricks indices were observed in the resistant lines.

Impact of irrigation with saline water on morphology of sea buckthorn seedlings in nursery

The experiment for evaluate the effect of salinity stress on the morphological behaviors of Elaeagnus rhamnoides (L.) A. Nelson seedlings were done in Torogh nursery in Iran country. This species were conducted based on completely randomized design in summer season. Non-stress (EC 0.8 dSm-1) and salt treatment (EC 12.03dS m-1) were used every two days. Several morphological traits of seedlings stressed-including height, diameter, leaf number, leaf area, shoot and root length, freshly and number of root, fresh and dry weight of stem, root and leaf and ratio of root to shoot, leaf to shoot, leaf area, specific leaf area, leaf weight and slenderness index were determined analyzed. Results indicated that diameter growth, end of period height, height mean and leaf area growth were significantly different at p&lt;0.05 level and height growth and number of leaves reduced significantly at p&lt;0.01 in comparison with control treatment. Analysis of variance for nonlinear regression in salinity stress indicated in the height and diameter significant differences of p&lt;0.01 and leaf number not significant differences. Principal component analysis showed that in first axis (PC1) in salinity treatment dry weights leaf, stem and root, leaf area, root to shoot ratio, freshly, leaf area ratio decrease and were the most correlated with first axis. Thus, not recommend that to be done irrigation with EC 12.03 dS m-1.

Effects of Intercropping with Post-Grafting Generation of Cosmos sulphureus on Total Potassium Content in Grape Seedling under Cadmium Stress

The effects of intercropping with post-grafting generation of Cosmos sulphureus on total potassium content of grape seedling were investigated through pot experiment under cadmium stress. The results showed that the intercropping treatments had significant effect on soil available potassium content and total potassium content in root, stem and leaf of grape seedling, while intercropping with ungrafted and post-grafting generation of C. sulphureus all decreased the potassium content of grape seedling and soil compared with grape monoculture. The potassium content of grape seedling and soil were all ranked as: grape monoculture (MG) > intercropping with the ungrafted generation of C. sulphureus (UG) > intercropping with the post-grafting generation of C. sulphureus of self-rooted grafting by the same one seedling (PSG) > intercropping with the post-grafting generation of C. sulphureus of self-rooted grafting by two different sizes seedlings (PSDG) > intercropping with the post-grafting generation of C. sulphureus of self-rooted grafting by two same sizes seedlings (PSSG). Therefore, intercropping with post-grafting generation of C. sulphureus could not increase but reduce the potassium content, which is one of essential minerals that contributes to plant growth and development.

IMPACT OF FERTILIZERS APPLICATION ON SEED GERMINATION AND SEEDLING GROWTH OF VIGNA RADIATA

Currently, a real challenge for the workers in the agricultural research field is to stop or reduce the use of expensive agrochemicals/ chemical fertilizers which are hazardous to the environment as well as human health. Present study was aimed to improve the growth and obtain optimum yield of Vigna crop with eco-friendly, non-toxic way and to reduce the use of agrochemical/chemical fertilizer application in agricultural activities. A pot experiment was conducted to study the effect of chemical fertilizer (DAP) and biofertilizer ( Rhizobium strain) separately and in combination on seed germination and seedling growth (at 30 days) based on morphological parameters such as seedling length (cm), fresh weight (g), dry weight (g) and leaf area (cm)2 of Vigna radiata (L.) Wilczek. After one month (30 Days) observations, it was found that seedling length, fresh and dry weights and leaf area were maximum in T4 and minimum in T15, T7 and T8 favored improved seedling length and leaf area whereas T7, T8, and T9 favored improved fresh and dry weights as compared to control.

Molecular Evidence for the Fitness of Cotton Aphid, Aphis gossypii in Response to Elevated CO2 From the Perspective of Feeding Behavior Analysis.

Rising atmospheric carbon dioxide (CO2) concentration is likely to influence insect–plant interactions. Aphid, as a typical phloem-feeding herbivorous insect, has shown consistently more positive responses in fitness to elevated CO2 concentrations than those seen in leaf-chewing insects. But, little is known about the mechanism of this performance. In this study, the foliar soluble constituents of cotton and the life history of the cotton aphid Aphis gossypii and its mean relative growth rate (MRGR) and feeding behavior were measured, as well as the relative transcript levels of target genes related appetite, salivary proteins, molting hormone (MH), and juvenile hormone, to investigate the fitness of A. gossypii in response to elevated CO2 (800 ppm vs. 400 ppm). The results indicated that elevated CO2 significantly stimulated the increase in concentrations of soluble proteins in the leaf and sucrose in seedlings. Significant increases in adult longevity, lifespan, fecundity, and MRGR of A. gossypii were found under elevated CO2 in contrast to ambient CO2. Furthermore, the feeding behavior of A. gossypii was significantly affected by elevated CO2, including significant shortening of the time of stylet penetration to phloem position and significant decrease in the mean frequency of xylem phase. It is presumed that the fitness of A. gossypii can be enhanced, resulting from the increases in nutrient sources and potential increase in the duration of phloem ingestion under elevated CO2 in contrast to ambient CO2. In addition, the qPCR results also demonstrated that the genes related to appetite and salivary proteins were significantly upregulated, whereas, the genes related to MH were significantly downregulated under elevated CO2 in contrast to ambient CO2, this is in accordance with the performance of A. gossypii in response to elevated CO2. In conclusion, rise in atmospheric CO2 concentration can enhance the fitness of A. gossypii by increasing their ingestion of higher quantity and higher quality of host plant tissues and by simultaneously upregulating the transcript expression of the genes related to appetite and salivary proteins, and then this may increase the control risk of A. gossypii under conditions of climate change in the future.

Quantitative Trait Loci Conferring Leaf Rust Resistance in Hexaploid Wheat.

Leaf rust, caused by the fungal pathogen Puccinia triticina, is a major threat to wheat production in many wheat-growing regions of the world. The introduction of leaf rust resistance genes into elite wheat germplasm is the preferred method of disease control, being environmentally friendly and crucial to sustained wheat production. Consequently, there is considerable value in identifying and characterizing new sources of leaf rust resistance. While many major, qualitative leaf rust resistance genes have been identified in wheat, a growing number of valuable sources of quantitative resistance have been reported. Here we review the progress made in the genetic identification of quantitative trait loci (QTL) for leaf rust resistance detected primarily in field analyses, i.e., adult plant resistance. Over the past 50 years, leaf rust resistance loci have been assigned to genomic locations through chromosome analyses and genetic mapping in biparental mapping populations, studies that represent 79 different wheat leaf rust resistance donor lines. In addition, seven association mapping studies have identified adult plant and seedling leaf rust resistance marker trait associations in over 4,000 wheat genotypes. Adult plant leaf rust resistance QTL have been found on all 21 chromosomes of hexaploid wheat, with the B genome carrying the greatest number of QTL. The group 2 chromosomes are also particularly rich in leaf rust resistance QTL. The A genome has the lowest number of QTL for leaf rust resistance. Copyright © 2018 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .

5-Aminolevulinic Acid Improves Nutrient Uptake and Endogenous Hormone Accumulation, Enhancing Low-Temperature Stress Tolerance in Cucumbers.

5-aminolevulinic acid (ALA) increases plant tolerance to low-temperature stress, but the physiological and biochemical mechanisms that underlie its effects are not fully understood. To investigate them, cucumber seedlings were treated with different ALA concentrations (0, 15, 30 and 45 mg/L ALA) and subjected to low temperatures (12/8 °C day/night temperature). The another group (RT; regular temperature) was exposed to normal temperature (28/18 °C day/night temperature). Low-temperature stress decreased plant height, root length, leaf area, dry mass accumulation and the strong seedling index (SSI), chlorophyll contents, photosynthesis, leaf and root nutrient contents, antioxidant enzymatic activities, and hormone accumulation. Exogenous ALA application significantly alleviated the inhibition of seedling growth and increased plant height, root length, hypocotyl diameter, leaf area, and dry mass accumulation under low-temperature stress. Moreover, ALA increased chlorophyll content (Chl a, Chl b, Chl a+b, and Carotenoids) and photosynthetic capacity, net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), and transpiration rate (Tr), as well as the activities of superoxide dismutase (SOD), peroxidase (POD, catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) enzymes, while decreasing hydrogen peroxide (H2O2), superoxide (O2•−), and malondialdehyde (MDA) contents under low-temperature stress. In addition, nutrient contents (N, P, K, Mg, Ca, Cu, Fe, Mn, and Zn) and endogenous hormones (JA, IAA, BR, iPA, and ZR) were enhanced in roots and leaves, and GA4 and ABA were decreased. Our results suggest the up-regulation of antioxidant enzyme activities, nutrient contents, and hormone accumulation with the application of ALA increases tolerance to low-temperature stress, leading to improved cucumber seedling performance.

Identification of known leaf rust resistance genes in common wheat cultivars from Sichuan province in China

Leaf rust, caused by Puccinia triticina (Pt), is one of the most important wheat diseases of common wheat (Triticum aestivum L.). Using resistant cultivars is the most economical and efficient way to control the disease. A total of 86 wheat cultivars from Sichuan province in China were inoculated with 14 Pt races for postulating seedling leaf rust resistance (Lr) gene(s) in the greenhouse. Meanwhile, these cultivars were also planted in Baoding and Zhoukou trial fields for identifying slow leaf rusting genes during the 2014–2015 and 2015–2016 cropping seasons. Twelve specific markers for ten known Lr genes (Lr1, Lr9, Lr10, Lr19, Lr20, Lr24, Lr26, Lr34, Lr37 and Lr46) were also used for molecular marker detection. Based on the results from the gene postulation and molecular marker detection, nine Lr genes (Lr1, Lr2a, Lr26, Lr3ka, Lr30, Lr36, Lr15, Lr37, and Lr46) were identified in 45 cultivars either singly or in combination. Most frequently identified Lr genes were Lr26 in 25 cultivars and Lr37 in 21 cultivars. Less frequently detected genes were Lr1 and Lr46 each in nine cultivars, Lr3ka in five cultivars, Lr30 in three cultivars and Lr36 in two cultivars. Lr2a and Lr15 were found in Chuannong 16 and Chuanmai 1, respectively. Twenty-nine cultivars were found to have slow rusting resistance during the two growing seasons. The results should be useful for selecting cultivars with combinations of genes for effective resistance to grow and in breeding new cultivars with improved resistance to leaf rust.

Moisture Content Quantization of Masson Pine Seedling Leaf Based on Stacked Autoencoder with Near-Infrared Spectroscopy

Masson pine is widely planted in southern China, and moisture content of the pine seedling leaves is an important index for evaluating the vigor of seedlings. For precisely predicting leaf moisture content, near-infrared spectroscopy analysis is applied in the experiment, which is a cost-effective, high-speed, and noninvasive material content prediction tool. To further improve the spectroscopy analysis accuracy, in this study, a new analysis model is proposed which integrates a stacked autoencoder for extracting hierarchical output-related features layer by layer and a support vector regression model to leverage these features for precisely predicting moisture contents. Compared with traditional spectroscopy analysis method like partial least squares regression and basic support vector regression, the proposed model shows great superiority for leaf moisture content prediction, with R2 value 0.9946 and root-mean squared error (RMSE) value 0.1636 in calibration set and R2 value 0.9621 and RMSE 0.4249 in prediction set.

Seedling emergence and early growth of Chinese fir under different light levels and seed positions: implications for natural regeneration

Chinese fir, Cunninghamia lanceolata (Lamb.) Hook. (Taxodiaceae), is an evergreen conifer primarily distributed in southern China. This species exhibits very poor natural regeneration, possibly due to low light and a thick litter layer. To improve the understanding of the natural regeneration capacity of Chinese fir, in this study, we conducted a shade house experiment to determine the optimum light requirements and seed positions for seedling emergence and early growth. The experiment involved five light levels (100%, 60%, 40%, 15%, 5% of full sunlight) and four seed positions (1 cm beneath the soil surface without litter, on the soil surface without soil–seed contact, on the soil surface and covered with litter, and 1 cm beneath the soil surface and covered with litter). Seedling emergence was highest at 5%–15% sunlight, whereas seedling height, root length, root mass, stem mass, leaf mass, and total mass were highest at 60% sunlight. For each light level, seed position significantly affected emergence and growth. The above-litter position inhibited seedling emergence and survival, while the below-litter position favored seedling emergence and early growth, particularly under high light levels. Based on these results, to enhance natural regeneration of Chinese fir, we recommend periodical thinning to increase light into the understory after successful seedling emergence. We also recommend sowing seeds deeper into the litter to improve soil contact and moisture conditions.

Abiotic stress and tissue-specific reference genes for quantitative reverse transcription PCR analysis in Korean native watermelons, Citrullus lanatus ‘Black-King’ and ‘Speed-Plus-Honey’

A wide variety of research on watermelon has been conducted, and such studies have been motivated by the published genome sequence database of watermelon. Screening of proper reference genes is the primary step for normalization in gene expression analysis. Based on previous studies conducted on Arabidopsis and cucumber, we selected eight candidate reference genes of ClACT, ClEF1α, ClGAPDH, ClIDH, ClLUG, ClPTB, ClUBC2, and Cl18SrRNA, respectively, encoding β-Actin, elongation factor 1-α, glyceraldehyde-3-phosphate-dehydrogenase, NADP-isocitrate dehydrogenase, leunig, polypyrimidine tract-binding protein1, ubiquitin-conjugating enzyme E2, and 18S ribosomal RNA from watermelon (Citrullus lanatus). The expression levels of these eight genes were evaluated by RT-qPCR under plant hormone-treatment (100 μM ABA) and abiotic stresses such as drought, cold (4 °C), and high salt concentration (250 mM NaCl). The expression patterns of these eight genes were further compared across different types of watermelon tissues such as flower, leaf, tendril, stem, root, and whole seedling. Our results showed that expressions of ClACT and ClEF1α, respectively in the Korean native watermelon cultivars Citrullus lanatus ‘Black-King’ and ‘Speed-Plus-Honey’ were least affected by the environmental stresses regardless of tissue types. Here, we suggest two ideal reference genes for watermelon RT-qPCR-based gene expression study.

ASSESSMENT OF SEEDLING ABUNDANCE, SURVIVAL AND GROWTH OF TWO DIPTEROCARP SPECIES IN PEAT SWAMP FORESTS OF BRUNEI DARUSSALAM

Dryobalanops rappa Becc. and Shorea albida Sym. are Bornean endemics of high conservation value and increasingly threatened by anthropogenic disturbances. In-situ study of seedling abundance and growth performance of these Dipterocarp species was conducted in two selected peat swamp forests of Brunei Darussalam, following a mast fruiting event in March–May 2014. Within six 6 x 6 m plots at each forest site, D. rappa seedlings at the Anduki peat swamp forest and S. albida seedlings at the Badas peat swamp forest were measured for abundance at the initial census in September 2014, as well as survival and relative growth rates (RGR) after a period of 5 months, with the final census in February 2015. We found significantly higher seedling abundance for D. rappa (1885 ± 208) than S. albida (160 ± 71). Significantly higher percentage survival was recorded for D. rappa seedlings (90.8 ± 2.2%) in comparison to S. albida seedlings (81.7 ± 2.2%). S. albida seedlings (0.24 ± 0.02 mm mm-1 month-1) showed significantly greater RGR in stem diameter than D. rappa seedlings (0.18 ± 0.02 mm mm-1 month-1), however, there were no significant differences in the RGRs based on seedling height, leaf number and biomass between D. rappa and S. albida seedlings. In terms of seedling abundance and percentage survival, D. rappa seedlings appeared to be more successful in regeneration and may potentially be used for rehabilitation of degraded tropical peat swamps and other forest types. Our results suggested that greater conservation efforts of peat swamps must be made to protect the Bornean endemic plant species, in particular S. albida.

High Light Acclimated Developing Primary Leaves of Wheat Seedlings Generate Signal for Stress Adaptation through Super Oxide Dismutase

Wheat seedlings grown in petri dishes were acclimated to high light during their development and subsequently were subjected to osmotic stress by application of polyethylene glycol (PEG). The photochemical efficiency of photosystem II (PS II) of the acclimated seedlings was found to be higher than that of non-acclimated ones under osmotic stress during senescence. The damage of the photosynthetic apparatus seems to be mediated by reactive oxygen species. The higher level of lutein (Lut) and superoxide dismutase (SOD) activity in acclimated seedlings suggest their involvement in the protective mechanism. The senescing leaves, although in a deteriorating phase, exhibit tolerance to osmotic stress due to the adaptation potential acquired earlier during high light (HL) acclimation.

The effects of micropropagation, acclimatisation substrate and physiological age on the growth and Ca and Fe content of selected Solanum nigrum genotypes

The aims and objectives of the current study were to investigate the level of genotypic variation in the leaf calcium (Ca) and iron (Fe) contents within a relatively small population of Solanum nigrum, to select high and low Ca- and Fe-producing genotypes and clonally propagate them in vitro and to test the resulting clonal progeny ex vitro for their Ca and Fe content and growth, based on their physiological age and on the use of different substrates. Firstly, chilled and fresh S. nigrum seeds were acid-scarified and sown onto potting soil in a greenhouse. Optimal germination (95%) was achieved in seeds chilled for 3 weeks and scarified with 0.01 M HCl for 10 min. Thereafter, fifty 6-week old seedlings were screened using Inductively Coupled Plasma-Optical Emission Spectrometry resulting in ranges of leaf calcium (Ca) and iron (Fe) of 331.0–916.3 mg 100 g−1 dry mass (DM) and 0.64–14.95 mg 100 g−1 DM, respectively. When a micropropagation protocol using seedling nodal and leaf explants was investigated, direct organogenesis using leaves on shoot multiplication medium containing 3 mg l−1 benzylaminopurine (BAP) and rooting on hormone-free MS medium was most successful resulting in 80% explants producing shoots, 50 shoots/explant and 80% rooted shoots. After acclimatisation in nutrient-rich potting soil, the yield was 25 plants/explant. Subsequently, genotypes for high Ca (G20), high Fe (G15), low Ca (G43) and low Fe (G35) were micropropagated using the established protocol. At certain physiological ages, G43 was the only genotype whose clones had better shoot and root growth on the nutrient-poor substrate than on the nutrient-rich one while G35 was the only genotype whose clones had better root growth on the nutrient-rich substrate than on the nutrient-poor one. The clones of G20 produced high numbers of leaves and shoot and root fresh and dry masses on both substrate types but the overall growth was better on soil. For the G15 clones, shoot and root growth increased with age with no overall difference in growth between the substrates. The levels of phenotypic plasticity for the selected genotypes were found to be G43 > G35 > G20 > G15 and in cases where phenotypic plasticity was observed, more clones with higher overall biomass were found on the nutrient-poor substrate. When compared to their respective parents, the G20 clones produced the same amount of Ca on both tested substrates while G43 exhibited higher Ca production on the nutrient-rich substrate. The Fe levels in the clones of G15 decreased with physiological age, and were lower than that of the parent plant, on both the nutrient-rich and poor substrates while the Fe levels of the G35 clones were higher than that of the parent plant on nutrient-rich soil at all ages.

Foliar application of selenium for protection against the first stages of mycotoxin infection of crop plant leaves.

The aim of this study was to investigate whether the application of selenium (Se) ions directly to the leaf surface can protect plants against infection by the fungal toxin zearalenone (ZEA). The experiments were performed for the most common and agronomically important crops such as wheat, oat, and barley (both tolerant and sensitive varieties) because mycotoxin accumulation in plants is the cause of many diseases in animals and people. ZEA at a concentration of 10 µmol L-1 either alone or in combination with Se (5 µmol L-1 Na2 SeO4 ) was applied to the second leaf of seedlings. Visualization of leaf temperature profiles by infrared thermography demonstrated a decrease in temperature at the location of ZEA infection that was more noticeable in sensitive genotypes. The presence of Se significantly suppressed changes at the site of ZEA application in all tested plants, especially the tolerant genotypes. Microscopic observations confirmed that foliar administration of ZEA resulted in its penetration to deeper localized cells and that damage induced by ZEA (mainly to chloroplasts) decreased after Se application. Analyses of antioxidant enzymes demonstrated the involvement of Se in antioxidation mechanisms, in particular by activating SOD and CAT under ZEA-induced stress conditions. The foliar application of Se to seedling leaves may be a non-invasive method of protecting crops against the first steps of ZEA infection. © 2018 Society of Chemical Industry.

Influence of iron plaque on the uptake and accumulation of chromium by rice (Oryza sativa L.) seedlings: Insights from hydroponic and soil cultivation

The effects of iron plaque formation on chromium (Cr) uptake and accumulation by rice seedlings (Oryza sativa L.) were assessed using hydroponic and soil experiments, where each 3 levels of Fe supplementation were added to Hoagland solution (0, 30, and 100 mg Fe2+ L−1) and a typical paddy soil (0, 1, and 2 g Fe2+ kg−1). For each treatment, rice seedlings were exposed to different levels of Cr as chromate at 0, 0.5, 2, 5, 10, and 20 mg L−1 in solution or 300 mg kg−1 in soil. Low levels of Cr supply (0.5, 2, and 5 mg L−1) promoted root biomass, while high levels (10 and 20 mg L−1) decreased root and shoot biomass and undermined the density and integrity of iron plaque. Iron supply significantly increased the proportion of Cr in iron plaque, but decreased that in rice plants. The results of hydroponic experiment showed that iron plaque formed with Fe supply at 100 mg L−1 markedly reduced Cr accumulation in shoots of rice seedlings when exposure to 10 and 20 mg L−1 Cr. The soil culture experiment also demonstrated that exogenous Fe addition significantly decreased Cr concentration in leaf and stem of rice seedlings. These results suggested that iron plaque with appropriate amount was effective to reduce the uptake and accumulation of Cr in rice plants, which have strong implication for taking measures to regulate Cr accumulation in rice grains.