Rape Seedlings Research Articles

Effect of Copper Oxide Nanoparticles on the Physiology, Bioactive Molecules, and Transcriptional Changes in Brassica rapa ssp. rapa Seedlings

Global deterioration of water, air, and soil quality by the release of toxic chemicals from anthropogenic pollutants is becoming a serious global problem. The extensive use of copper oxide nanoparticles (CuO NPs) can be environmentally hazardous when these NPs enter the atmosphere. The present study aimed to evaluate the role of CuO NPs on plant growth, photosynthetic capacity, and bioactive compounds, as well as their transcriptional level changes in Brassica rapa seedlings. Chlorophyll, carotenoid, and sugar content decreased, while proline and anthocyanins were significantly enhanced in the CuO NP-treated seedlings compared with the untreated controls. Reactive oxygen species (ROS), malondialdehyde (MDA), and hydrogen peroxide (H2O2) production were also enhanced in the seedlings exposed to CuO NPs, which could have caused DNA damage that was detected by a DNA laddering assay. The glucosinolate (GSL) and phenolic compound content were significantly increased in CuO NP-treated seedlings compared with that in control seedlings. Transcriptional variation of genes associated with oxidative stress (CAT, POD, and GST), R2R3-type MYB involved in GSL (BrMYB28, BrMYB29, BrMYB34, and BrMYB51), and phenolic compounds (ANS, PAP1, PAL, and FLS) biosynthesis was analyzed using real-time polymerase chain reaction. Significant upregulation of CAT, POD, GST, BrMYB28, BrMYB29, BrMYB34, BrMYB51, ANS, PAP1, PAL, and FLS genes was observed in seedlings exposed to different concentrations of CuO NPs relative to the untreated seedlings. Therefore, we suggest that the use of CuO NPs could stimulate the toxic effects and enhance phytochemicals (i.e., glucosinolates and phenolic compounds) in B. rapa.

STRAINS OF BACILLUS THURINGIENSIS WITH GROWTH-STIMULATING AND FUNGICIDAL ACTIVITY

The article presents the results of the study of growth-stimulating and antifungal activity of strainsBacillus thuringiensisssp.fukuokaensisssp.morrisoni, ssp.toumanoffi, ssp.dakotaand ssp.amagiensis. The positive effect of all studied strains on morphometric parameters of spring rape and spring wheat seedlings was revealed. Treatment of spring rape seeds with spore-crystal mixtures ofB. thuringiensiscontributed to a significant increase in the length of roots by 1.93.4 times and sprouts – by 1.3-1.9 times, depending on the strain. Stimulation of plant growth was also observed in the inoculation of spring wheat seeds with suspension strains ofB. thuringiensis. However, a significant positive effect was revealed only in the variant with the use of the strain ofB. thuringiensisssp.fukuokaensis. There was a downward trend in the number of spring wheat seedlings affected with root rot when the seeds were treated with the strains ofB. thuringiensisssp.morrisoni,ssp.dakota,ssp.amagiensis. In the experiments with pure cultures it was found that all tested strains ofB. thuringiensisshowed a high degree of antagonistic activity to two types of phytopathogens. The inhibitory activity of the strains ofB. thuringiensison the 10th day of the experiment with regard toFusarium oxysporumranged from 68 to 83%,Alternaria alternata– from 71 to 89%. The analysis showed that all studied strains ofB. thuringiensisstimulated the growth of plants of spring rape and spring wheat and showed antifungal activity. The obtained data are of interest for further research in order to create multifunctional biological preparations for plant protection.

Physiological effects of short-term copper stress on rape (Brassica napus L.) seedlings and the alleviation of copper stress by attapulgite clay in growth medium

Rape (Brassica napus L.) seedlings grown in vermiculite-based medium were subjected to short-term copper stress. With the increase of exogenous CuCl2 concentration, photosystem II (PSII) photochemistry and the chlorophyll (Chl) content of rape seedling leaves decreased, while Cu (copper) content of the seedlings, the levels of the soluble protein content, reactive oxygen species (ROS) production, and activities of antioxidant enzymes of the seedling leaves increased. Under the condition without copper stress, there was no significant differences in the measured physiological indexes between the seedlings grown in vermiculite and those grown in the attapulgite clay (AC)/vermiculite mixture with the volume ratio at 1:80, 1:50, or 1:30. After subjected to short-term copper stress, the rape seedlings grown in the mixture of AC/vermiculite had higher levels of Chl content and PSII photochemistry but lower levels of the Cu content, soluble protein content, ROS production, and activities of antioxidant enzymes, compared with the leaves of the seedlings grown in vermiculite. The volume ratio of AC/vermiculite at 1:50 or 1:30 seemed to be the most optimized content in alleviating the physiological effects by the short-term copper stress. These results indicate that AC at moderate content in the growth medium can alleviate the physiological stress of the rape seedlings when excess Cu emerges in the growth medium.

Changes in resource partitioning between and within organs support growth adjustment to neighbor proximity in Brassicaceae seedlings

In shade-intolerant plants, the perception of proximate neighbors rapidly induces architectural changes resulting in elongated stems and reduced leaf size. Sensing and signaling steps triggering this modified growth program have been identified. However, the underlying changes in resource allocation that fuel stem growth remain poorly understood. Through 14CO2 pulse labeling of Brassica rapa seedlings, we show that perception of the neighbor detection signal, low ratio of red to far-red light (R:FR), leads to increased carbon allocation from the major site of photosynthesis (cotyledons) to the elongating hypocotyl. While carbon fixation and metabolite levels remain similar in low R:FR, partitioning to all downstream carbon pools within the hypocotyl is increased. Genetic analyses using Arabidopsis thaliana mutants indicate that low-R:FR-induced hypocotyl elongation requires sucrose transport from the cotyledons and is regulated by a PIF7-dependent metabolic response. Moreover, our data suggest that starch metabolism in the hypocotyl has a growth-regulatory function. The results reveal a key mechanism by which metabolic adjustments can support rapid growth adaptation to a changing environment.

The influence of Stimpo and Regoplant for the growth, photosynthetic pigments and protein content in seedlings of rape on technogenically disturbed substrates

Effects of biotechnological drugs – growth regulators (GR) Stimpo and Regoplant (“Agrobiotech”, Ukraine) on morphometric growth parameters, the content of photosynthetic pigments and protein in the rape (Brassica napus L.) seedlings grown on a coal rocky dumps substrates of the Chervonograd Сentral Enrichment Factory were studied. The optimal concentrations for Stimpo and Regoplant – 0.1 and 0.25 ml/l, and the optimum time of seed soaking (1 hour) were revealed. Seed treatment with the regulators improved seedlings morphometric parameters both on the garden soil and on the rock dumps substrates of the coal mines. When treated with growth regulators, the chlorophyll content a was increased in seedlings on all substrates, as invariants treated with GC, and to a greater extent under the action of Regoplant and Stippo, when compared with variants without processing. Seedlings treatment with GR leads to increment of their light deficiency tolerance at all substrates, except the variants with the GA and Stimpo on the black damp substrate. The content of the protein was lower in seedlings on the substrate of the dump than on the garden soil, both with and without the processing of GR. When comparing the protein content of sprouts with growth on substrates, processing of GR increased its content. Thus, application of growth regulators Stimpo and Regoplant seems a promising tool for the stimulation of the rape growth and metabolism both on an ordinary soil and technogenically disturbed substrates.

Phytochrome B regulates resource allocation in Brassica rapa.

Crop biomass and yield are tightly linked to how the light signaling network translates information about the environment into allocation of resources, including photosynthates. Once activated, the phytochrome (phy) class of photoreceptors signal and re-deploy carbon resources to alter growth, plant architecture, and reproductive timing. Most of the previous characterization of the light-modulated growth program has been performed in the reference plant Arabidopsis thaliana. Here, we use Brassica rapa as a crop model to test for conservation of the phytochrome-carbon network. In response to elevated levels of CO2, B. rapa seedlings showed increases in hypocotyl length, shoot and root fresh weight, and the number of lateral roots. All of these responses were dependent on nitrogen and polar auxin transport. In addition, we identified putative B. rapa orthologs of PhyB and isolated two nonsense alleles. BrphyB mutants had significantly decreased or absent CO2-stimulated growth responses. Mutant seedlings also showed misregulation of auxin-dependent genes and genes involved in chloroplast development. Adult mutant plants had reduced chlorophyll levels, photosynthetic rate, stomatal index, and seed yield. These findings support a recently proposed holistic role for phytochromes in regulating resource allocation, biomass production, and metabolic state in the developing plant.

5-Aminolevulinic acid alleviates herbicide-induced physiological and ultrastructural changes in Brassica napus

It is well known that application of 5-aminolevulinic acid (ALA) could promote the plant growth under abiotic stress in oilseed rape (Brassica napus L.). However, the specifics of its physiological and ultrastructural regulation under herbicide stress conditions are poorly understood. In the present study, alleviating role of ALA in B. napus was investigated under four levels of herbicide propyl 4-(2-(4,6-dimethoxypyrimidin-2-yloxy) benzylamino) benzoate (ZJ0273) (0, 100, 200 and 500 mg L−1) with or without 1 mg L−1 ALA treated for 48 or 72 h. Results showed that after 48 h of herbicide stress, the growth of rape seedlings was significantly inhibited with the successive increases of the ZJ0273 concentrations from 0 to 500 mg L−1, but this inhibition was obviously alleviated by exogenous application of ALA. However, when treatment time prolonged to 72 h, the recovery effects of ALA could not be evaluated due to the death of plants treated with the highest concentration of ZJ0273 (500 mg L−1). Further, the root oxidizability and activities of antioxidant enzymes (superoxide dismutase, peroxidase and ascorbate peroxidase) were dramatically enhanced by the application of 1 mg L−1 ALA under herbicide stress. Therefore, plants treated with ALA dynamically modulated their antioxidant defenses to reduce reactive oxygen species (ROS) accumulation and malondialdehyde (MDA) content induced by herbicide stress. Additionally, exogenously applied ALA improved the ultrastructure's of chloroplast, mitochondria and nucleus, and induced the production of stress proteins. Our results suggest that ALA could be considered as a potential plant growth regulator for the improvement of herbicide tolerance through alleviation of the physiological and ultrastructural changes induced by the herbicide in crop production.

Proteomic analysis of the interaction between Plasmodiophora brassicae and Chinese cabbage (Brassica rapa L. ssp. Pekinensis) at the initial infection stage

The interaction between plants and pathogens that induces a defense response has been shown in previous studies. In our research, we used Plasmodiophora brassicae Woronin (Plasmodiophoraceae), the causal agent of clubroot disease, to infect the roots of Brassica rapa seedlings. Electron microscopic observation showed that the roots could be infected by Plasmodiophora brassicae on the fifth day after inoculation. We identified 438 and 414 differentially expressed proteins (DEPs) in the inoculated and control groups, respectively. Mass spectrometry was performed to identify 18 of the DEPs in which the relative protein abundance varied by >2-fold. In general, Gene Ontology (GO) analysis revealed that the DEPs reflected a wide range of molecular functions, including “response to stimuli” (39%) and “plant defense reaction” (8%) in the Biological Process domain. Among these, two proteins (DEPs 3038 and 3129) were found to be related to salicylic acid (SA)-mediated systemic acquired resistance (SAR), two proteins (DEPs 3414 and 2358) were found to be related to jasmonic acid (JA)/ ethylene (ET)-mediated induced systemic resistance (ISR), and DEP 4043 participated in both SAR and ISR. In addition, one pathogenesis-related protein (PR-1) was found in the extracellular cell component group, and KEGG analysis indicated that a DEP participates in plant-pathogen interaction signaling pathways. KEGG analysis also confirmed that these two pathways show some degree of cross-talk, rather than acting independently.

Short-term salt stress in Brassica rapa seedlings causes alterations in auxin metabolism

Salinity is one of major abiotic stresses affecting Brassica crop production. Here we present investigations into the physiological, biochemical, and hormonal components of the short-term salinity stress response in Chinese cabbage seedlings, with particular emphasis on the biosynthesis and metabolism of auxin indole-3-acetic acid (IAA). Upon salinity treatments (50–200 mM NaCl) IAA level was elevated in a dose dependent manner reaching 1.6-fold increase at the most severe salt treatment in comparison to the control. IAA precursor profiling suggested that salinity activated the indole-3-acetamide and indole-3-acetaldoxime biosynthetic pathways while suppressing the indole-3-pyruvic acid pathway. Levels of the IAA catabolites 2-oxoindole-3-acetic acid and indole-3-acetic acid-aspartate increased 1.7- and 2.0-fold, respectively, under the most severe treatment, in parallel with those of IAA. Conversely, levels of the ester conjugate indole-3-acetyl-1-O-ß-d-glucose and its catabolite 2-oxoindole-3-acetyl-1-O-ß-d-glucose decreased 2.5- and 7.0-fold, respectively. The concentrations of stress hormones including jasmonic acid and jasmonoyl-isoleucine (JA and JA-Ile), salicylic acid (SA) and abscisic acid (ABA) confirmed the stress induced by salt treatment: levels of JA and JA-Ile increased strongly under the mildest treatment, ABA only increased under the most severe treatment, and SA levels decreased dose-dependently. These hormonal changes were related to the observed changes in biochemical stress markers upon salt treatments: reductions in seedling fresh weight and root growth, decreased photosynthesis rate, increased levels of reactive oxygen species, and elevated proline content and the Na+/K+ ratio. Correlations among auxin profile and biochemical stress markers were discussed based on Pearson's coefficients and principal component analysis (PCA).

Ameliorative Effects of Nitric Oxide on Oilseed Rape (Brassica napus L.) Under Water Stress

The ameliorative effects of nitric oxide on oilseed rape seedlings, Okapy cultivar, under drought condition were investigated. Water stress at 60 and 30% field capacity, increased lipid peroxidation and H2O2 content in oilseed rape leaves. Among the different concentrations (25, 50, 75 and 100 µM) of sodium nitroprusside used, spraying plants leaves with 25 µM sodium nitroprusside a NO donor, reduced the damaging effects of water stress which was reflected by a decrease in malondialdehyde and hydrogen peroxide content in leaves. Drought stress enhanced leaves superoxide dismutase, peroxidase and ascorbate peroxidase activities but decreased catalase activity. Sodium nitroprusside treatment (25 µM) had a positive effect on antioxidant enzymes under water stress. At higher sodium nitroprusside concentrations, its ameliorative effects on water stress were decreased and the oxidative damages to the leaves were sustained. The reduction in drought induced oxidative damages by NO in oilseed rape is most likely mediated by the NO ability to induce and increase the activity of reactive oxygen species scavenging enzymes.

Interaction of boron and aluminum on the physiological characteristics of rape (Brassica napus L.) seedlings

It has been reported that aluminum (Al) toxicity is a major limiting factor for plant growth and production on acidic soils. Boron (B) is indispensable micronutrient for normal growth of higher plants, and its addition could alleviate Al toxicity. The rape seedlings were grown under three B (0.25, 25 and 500 μM) and two Al concentrations [0 (−Al) and 100 μM (+Al) as AlCl3·6H2O]. The results indicated that Al stress severely hampered root elongation and root activity at 0.25 μM B while the normal (25 μM) and excess (500 μM) B improved the biomass of rape seedlings under Al exposure. Additionally, normal and excess B treatment reduced accumulation of Al in the roots and leaves under Al toxicity, which was also confirmed by hematoxylin with light staining. This indicates that both normal and excess B could alleviate Al toxicity. Furthermore, it also decreased the contents of malondialdehyde and soluble protein under Al toxicity. Likewise, superoxide dismutase activity (SOD) improved by 97.82 and 131.96% in the roots, and 168 and 119.88% in the leaves at 25 and 500 µM B, respectively, while the peroxidase and catalase activities dropped as a result of Al stress. The study results demonstrated that appropriate B application is necessary to avoid the harmful consequences of Al toxicity in rape seedlings.

The effect of sowing time on pest spreading in spring oilseed rape crop

The field experiments were conducted at the Experimental Station of Aleksandras Stulginskis University in 2015–2017. The aim of the experiment was to evaluate the influence of sowing time on spreading of pests and diseases in spring oilseed rape crop. The first sowing occurred when soil reached physical maturity, the other sowing dates were every 5 days in 2015–2016 and every 7 days in 2017. In 2015, the sowing time did not have a significant effect on the distribution of Alternaria brassicae. Meteorological conditions strongly influenced the severity of the disease. The sowing date had a significant influence on the distribution of Verticillium dahliae: in the spring rape crop sown in May, the stems were damaged by 6.4%, less compared to the crop sown in April. In 2016–2017, the rape seedlings in the plots of the latest sowing were significantly more damaged compared with those of earlier sowing dates. In 2016, spreading of Verticillium longisporum significantly increased by 3.7 times in the crop of spring rape sown on 10 May compared to other sowing dates. In 2017, the spreading of Verticillium dahliae in spring rape crops was more influenced by a colder than usual vegetation period and an abundant rainfall than the sowing time. In 2015, the intensity of Phyllotreta spp. damage in the rape seedling period (BBCH 10-19) significantly increased by 2.7 times with the sowing date from 30 April to 20 May. The spreading of Meligethes aeneus was the least in the spring oilseed rape sown at the optimal time (30 April and 5 May). In 2016–2017, Phyllotreta spp. were more intensively spread in the crops sown in April, and rape seedlings were significantly more damaged. In 2016, Meligethes aeneus were most widely spread in the spring rape crop of the earliest sowing (4 October). A significant decrease in the number of pests was detected in the rape crops sown in May compared to that sown in April. In 2017, the highest number of Meligethes aeneus was evaluated in the rape crop sown on 2 June, significantly by 3.9 times more compared with that in the earlier sown crop and by 2.9 times in the crop sown one week later. It is believed that the other generation of Meligethes aeneus from winter rape crops went to the spring rape crops. In 2016, there was a very strong statistically significant correlation between the sum of positive temperatures for the 10-day period up to the sowing of rapeseed and the prevalence of Phyllotreta spp. in crops: r = 0.98, P ≤ 0.05, and the damage intensity of rape seedlings by Phyllotreta spp. of (BBCH 10-19): r = 0.92, P ≤ 0.05. The warmer the weather was before rape sowing, the more active Phyllotreta spp. were. In 2017, strong correlations were established between the number of Phyllotreta spp. and the intensity of crop damage by Phyllotreta spp. and the crop density 3 days after the emergence: r = –0.82, P ≤ 0.05; r = –0.89, P ≤ 0.01, and 7 days after the emergence of spring rape: r = –0.81, P ≤ 0.05; r = –0.88, P ≤ 0.01.

The effect of simulated microgravity on the Brassica napus seedling proteome.

The magnitude and the direction of the gravitational field represent an important environmental factor affecting plant development. In this context, the absence or frequent alterations of the gravity field (i.e. microgravity conditions) might compromise extraterrestrial agriculture and hence space inhabitation by humans. To overcome the deleterious effects of microgravity, a complete understanding of the underlying changes on the macromolecular level is necessary. However, although microgravity-related changes in gene expression are well characterised on the transcriptome level, proteomic data are limited. Moreover, information about the microgravity-induced changes in the seedling proteome during seed germination and the first steps of seedling development is completely missing. One of the valuable tools to assess gravity-related issues is 3D clinorotation (i.e. rotation in two axes). Therefore, here we address the effects of microgravity, simulated by a two-axial clinostat, on the proteome of 24- and 48-h-old seedlings of oilseed rape (Brassica napus L.). The liquid chromatography-MS-based proteomic analysis and database search revealed 95 up- and 38 downregulated proteins in the tryptic digests obtained from the seedlings subjected to simulated microgravity, with 42 and 52 annotations detected as being unique for 24- and 48-h treatment times, respectively. The polypeptides involved in protein metabolism, transport and signalling were annotated as the functional groups most strongly affected by 3-D clinorotation.

Effect of NO3 −:NH4 + ratios on growth, root morphology and leaf metabolism of oilseed rape (Brassica napus L.) seedlings

The effect of NO3 −:NH4 + ratio (14:1, 9:6, 7.5:7.5, 1:14, total 15 mmol/L N) in the nutrient solution on biomass, root morphology, and C and N metabolism parameter in hydroponically grown oilseed rape (Brassica napus L.) was evaluated. The dry weights of leaves and roots were significantly largest at the equal NO3 −:NH4 + ratio (7.5:7.5) compared with those of high NO3 −:NH4 + ratio (14:1) or low NO3 −:NH4 + ratio (1:14). Additionally, low NO3 −:NH4 + ratio (1:14) reduced total root length and root surface area compared with the equal NO3 −:NH4 + ratio (7.5:7.5), while high NO3 −:NH4 + ratio (14:1) did not show any significant effect on root morphology except average diameter. The maximum of chlorophyll a, chlorophyll b and carotenoid were obtained under 7.5:7.5 treatment, whereas the maximum of the leaf net photosynthetic (P n), stomatal conductance (G s) and transpiration rate (T r) were increased with increase in NH4 + concentration in the nutrient solution. The activity of nitrate reductase (NR) showed a significant difference at different NO3 −:NH4 + ratios and ranged 9:6 > 7.5:7.5 > 14:1 > 1:14, whereas the range of soluble sugar and soluble protein was 7.5:7.5 > 1:14 > 9:6 > 14:1. Our study reveals that oilseed rape growth is greater under 7.5:7.5 treatment than that under three other treatments. Oilseed rape growth at high or low NO3 −:NH4 + ratios was inhibited by decreased pigments, NR activity, soluble sugar, and soluble protein, whereas subdued root growth should be apprehended considerate under high NH4 + condition.

Aerial Warfare: A Volatile Dialogue between the Plant Pathogen Verticillium longisporum and Its Antagonist Paenibacillus polymyxa.

Verticillium wilt caused by Verticillium spp. results in severe yield losses in a broad range of crops. Verticillium outbreaks are challenging to control, and exacerbated by increases in soil temperatures and drought associated with global warming. Employing natural antagonists as biocontrol agents offers a promising approach to addressing this challenge. Paenibacillus polymyxa Sb3-1 was proven to reduce the growth of Verticillium longisporum during in vitro experiments and was shown to promote the growth of oilseed rape seedlings infested with V. longisporum. Our novel approach combined in vitro and in planta methods with the study of the mode of interaction between Sb3-1 and V. longisporum EVL43 via their volatile organic compounds (VOCs). Volatile and soluble substances, produced by both microorganisms as a reaction to one another's VOCs, were detected by using both gas and liquid chromatography-mass spectrometry. P. polymyxa Sb3-1 continually produced antimicrobial and plant growth promoting VOCs, such as 2-nonanone and 3-hydroxy-2-butanone. Several other antimicrobial volatile substances, such as isoamyl acetate and durenol, were downregulated. The general metabolic activity of Sb3-1, including protein and DNA biotransformations, was upregulated upon contact with EVL43 VOCs. V. longisporum increased its production of antimicrobial substances, such as 1-butanol, and downregulated its metabolic activities upon exposure to Sb3-1 VOCs. Additionally, several stress response substances such as arabitol and protein breakdown products (e.g., L-Isoleucyl-L-glutamic acid), were increased in the co-incubated samples. The results obtained depict an ongoing dialog between these microorganisms resulting in growth inhibition, the slowing down of metabolism, and the cell death of V. longisporum due to contact with the P. polymyxa Sb3-1 VOCs. Moreover, the results indicate that VOCs make a substantial contribution to the interaction between pathogens and their natural antagonists and have the potential to control pathogens in a novel, environmentally friendly manner.

Modeling Allometric Relationships in Leaves of Young Rapeseed (Brassica napus L.) Grown at Different Temperature Treatments.

Functional–structural plant modeling (FSPM) is a fast and dynamic method to predict plant growth under varying environmental conditions. Temperature is a primary factor affecting the rate of plant development. In the present study, we used three different temperature treatments (10/14°C, 18/22°C, and 26/30°C) to test the effect of temperature on growth and development of rapeseed (Brassica napus L.) seedlings. Plants were sampled at regular intervals (every 3 days) to obtain growth data during the length of the experiment (1 month in total). Total leaf dry mass, leaf area, leaf mass per area (LMA), width-length ratio, and the ratio of petiole length to leaf blade length (PBR), were determined and statistically analyzed, and contributed to a morphometric database. LMA under high temperature was significantly smaller than LMA under medium and low temperature, while leaves at high temperature were significantly broader. An FSPM of rapeseed seedlings featuring a growth function used for leaf extension and biomass accumulation was implemented by combining measurement with literature data. The model delivered new insights into growth and development dynamics of winter oilseed rape seedlings. The present version of the model mainly focuses on the growth of plant leaves. However, future extensions of the model could be used in practice to better predict plant growth in spring and potential cold damage of the crop.

A high-throughput stereo-imaging system for quantifying rape leaf traits during the seedling stage

BackgroundThe fitness of the rape leaf is closely related to its biomass and photosynthesis. The study of leaf traits is significant for improving rape leaf production and optimizing crop management. Canopy structure and individual leaf traits are the major indicators of quality during the rape seedling stage. Differences in canopy structure reflect the influence of environmental factors such as water, sunlight and nutrient supply. The traits of individual rape leaves traits indicate the growth period of the rape as well as its canopy shape.ResultsWe established a high-throughput stereo-imaging system for the reconstruction of the three-dimensional canopy structure of rape seedlings from which leaf area and plant height can be extracted. To evaluate the measurement accuracy of leaf area and plant height, 66 rape seedlings were randomly selected for automatic and destructive measurements. Compared with the manual measurements, the mean absolute percentage error of automatic leaf area and plant height measurements was 3.68 and 6.18%, respectively, and the squares of the correlation coefficients (R2) were 0.984 and 0.845, respectively. Compared with the two-dimensional projective imaging method, the leaf area extracted using stereo-imaging was more accurate. In addition, a semi-automatic image analysis pipeline was developed to extract 19 individual leaf shape traits, including 11 scale-invariant traits, 3 inner cavity related traits, and 5 margin-related traits, from the images acquired by the stereo-imaging system. We used these quantified traits to classify rapes according to three different leaf shapes: mosaic-leaf, semi-mosaic-leaf, and round-leaf. Based on testing of 801 seedling rape samples, we found that the leave-one-out cross validation classification accuracy was 94.4, 95.6, and 94.8% for stepwise discriminant analysis, the support vector machine method and the random forest method, respectively.ConclusionsIn this study, a nondestructive and high-throughput stereo-imaging system was developed to quantify canopy three-dimensional structure and individual leaf shape traits with improved accuracy, with implications for rape phenotyping, functional genomics, and breeding.

Effects of light intensity on leaf microstructure and growth of rape seedlings cultivated under a combination of red and blue LEDs

The aim of this study was to evaluate the growth of rape (Brassica napus L.) seedlings under different light intensities to select appropriate conditions for cultivation in an indoor system. Seedlings were grown under different light intensities of red and blue light provided by light-emitting diodes (LEDs) and their self-adjustment ability and changes in leaf microstructure were evaluated. Light was supplied by red LEDs with peak wavelengths of 630 (R1) and 660 nm (R2) and by blue LEDs (B) with a peak wavelength of 445 nm (the light intensity ratio of R1:R2:B was 3:3:2), at intensities of 400 (R1R2B400), 300 (R1R2B300), and 200 μmol m−2 s−1 (R1R2B200). Natural solar light served as the control (C). Plant height, stem diameter, root length, leaf area, and dry weight of rape seedlings gradually increased with increasing light intensity. The seedlings in the R1R2B400 treatment grew more vigorously, while those in the R1R2B200 treatment were weaker. The photosynthetic pigment contents did not differ significantly between the R1R2B400 treatment and C, but were significantly lower in the R1R2B300 and R1R2B200 treatments. The highest intercellular CO2 concentration, stomatal conductance, and transpiration rate were in the R1R2B300 treatment. The highest photosynthetic rate was in the R1R2B400 treatment, and was related to more compact leaves, thicker and tidier palisade and spongy tissues, and well-developed chloroplasts. In contrast, the seedlings in the R1R2B200 treatment had disordered mesophyll cells, round chloroplasts, and fractured and fuzzy grana lamellae, all of which inhibited plant growth. In conclusion, the seedlings in the R1R2B400 treatment had well-developed leaves, which favored photosynthesis. Compared with the light intensities below 300 μmol m−2 s−1, the light intensity of 400 μmol m−2 s−1 provided by a combination of red and blue LEDs was beneficial for cultivating strong and healthy rape seedlings in an artificial system.

Mitigative Effect of Different Forms of Boron on Aluminum Toxicity of Rape Seedlings and Its FTIR Characteristics

Mitigative Effect of Different Forms of Boron on Aluminum Toxicity of Rape Seedlings and Its FTIR Characteristics

Rising CO2 from historical concentrations enhances the physiological performance of Brassica napus seedlings under optimal water supply but not under reduced water availability.

The productivity of many important crops is significantly threatened by water shortage, and the elevated atmospheric CO2 can significantly interact with physiological processes and crop responses to drought. We examined the effects of three different CO2 concentrations (historical ~300 ppm, ambient ~400 ppm and elevated ~700 ppm) on physiological traits of oilseed rape (Brassica napus L.) seedlings subjected to well-watered and reduced water availability. Our data show (1) that, as expected, increasing CO2 level positively modulates leaf photosynthetic traits, leaf water-use efficiency and growth under non-stressed conditions, although a pronounced acclimation of photosynthesis to elevated CO2 occurred; (2) that the predicted elevated CO2 concentration does not reduce total evapotranspiration under drought when compared with present (400 ppm) and historical (300 ppm) concentrations because of a larger leaf area that does not buffer transpiration; and (3) that accordingly, the physiological traits analysed decreased similarly under stress for all CO2 concentrations. Our data support the hypothesis that increasing CO2 concentrations may not significantly counteract the negative effect of increasing drought intensity on Brassica napus performance.