PIXE analysis of trace elements in relation to chlorophyll concentration in Plantago ovata Forsk

Field assessment of yield and its contributing traits in cowpea treated with lower, intermediate, and higher doses of gamma rays and sodium azide

Across the globe, plant breeders of different organizations are working in collaboration to bring preferred traits to crops of economic importance. Among the traits, "high yielding potential" is the most important as it is directly associated with food security and nutrition, one of the sustainable development goals. The Food and Agriculture Organization acknowledges plant breeders' role and efforts in achieving local and global food security and nutrition. Recognizing the importance of pulses and increasing pressure on food security, the United Nations General Assembly declared 2016 the "International year of Pulses" owing to their preferred traits such as climate change resilience, wide adaptability, low agriculture input, and protein- and nutrient-rich crops. Keeping all these developments in consideration, we initiated an induced mutagenesis program by treating cowpea (Vigna unguiculata L. Walp.) with different doses of gamma rays and sodium azide aiming to enhance the yielding potential of an otherwise outstanding variety viz., Gomati VU-89 and Pusa-578. We noticed a substantial increase in mean values of agronomic traits in putative mutants raised from seeds treated with lower and intermediate doses of mutagens. Statistical analysis such as correlation, path, hierarchical clustering analysis (HCA), and principal component analysis (PCA) were used to assess the difference between mutagenized and control populations. A significant and positive correlation of yield with yield-attributing traits was recorded. However, among all the yield attributing traits, seeds per pod (SPP) depicted the maximum direct impact upon yield, and therefore, working on this trait may yield better results. A widely used PCA revealed 40.46% and 33.47% of the total variation for var. Gomati VU-89 and var. Pusa-578, respectively. Cluster analysis clustered treated and control populations into separate clusters with variable cluster sizes. Cluster V in the variety Gomati VU-89 and cluster V and VI in the variety Pusa 578 comprised of putative mutants were higher yielding and hence could be recommended for selection in future breeding programs. We expect to release such mutant lines for farmer cultivation in Northern parts of India depending on the performance of such high-yielding mutant lines at multilocations.

Effect of Preservation Methods on Physicochemical Quality, Phenolic Content, and Antioxidant Activity of Stevia Leaves

The effect of freeze-drying and gamma irradiation at 0.5, 1, and 2 kGy on the physicochemical composition (moisture, fat, ash, mineral, and chlorophyll contents), microstructure, total phenolic content, and antioxidant capacity of stevia leaves was investigated in the present study. The results obtained indicated that freeze-drying and gamma irradiation treatments caused significant reduction ( $p$  ≤ 0.05) of moisture and fat contents in comparison with those of commercial leaves, while ash content was not significantly affected. Mineral composition was analysed. Among the analysed elements, potassium and iron levels were higher in the freeze-dried and irradiated samples, respectively. The microstructure was analysed using a scanning electron microscope. Micrographs revealed that a higher porous size structure was obtained by freeze-drying, and degradation of cell wall structure was more clearly visualized by irradiation at 2 kGy. However, the main functional groups were stable as confirmed by Fourier transform infrared spectroscopy analysis. The effects on chlorophyll content, phenolic profile, and antioxidant properties were evaluated before and after ten months of storage. In terms of chlorophyll contents, the freeze-dried leaves exhibited the highest content. Chlorophylls a and b decreased when storage progressed for freeze-dried leaves as well as for gamma-irradiated leaves. Both preservation methods gave significant advantages in increasing the total phenolic content and DPPH scavenging activity. Moreover, a significant increase of bioactive compounds and antioxidant activity was observed as the gamma irradiation dose increased. In addition, the storage time increased the amounts of polyphenols and DPPH scavenging activity. After 10 months of storage, gamma-irradiated leaves had the highest total phenolic content as well as the DPPH scavenging activity followed by freeze-dried leaves. The results indicate that freeze-drying and gamma irradiation at the studied doses could be effective postharvest methods for preservation of stevia leaf quality.

Bacillus megaterium-Mediated Synthesis of Selenium Nanoparticles and Their Antifungal Activity against Rhizoctonia solani in Faba Bean Plants

Rhizoctonia root-rot disease causes severe economic losses in a wide range of crops, including Vicia faba worldwide. Currently, biosynthesized nanoparticles have become super-growth promoters as well as antifungal agents. In this study, biosynthesized selenium nanoparticles (Se-NPs) have been examined as growth promoters as well as antifungal agents against Rhizoctonia solani RCMB 031001 in vitro and in vivo. Se-NPs were synthesized biologically by Bacillus megaterium ATCC 55000 and characterized by using UV-Vis spectroscopy, XRD, dynamic light scattering (DLS), and transmission electron microscopy (TEM) imaging. TEM and DLS images showed that Se-NPs are mono-dispersed spheres with a mean diameter of 41.2 nm. Se-NPs improved healthy Vicia faba cv. Giza 716 seed germination, morphological, metabolic indicators, and yield. Furthermore, Se-NPs exhibited influential antifungal activity against R. solani in vitro as well as in vivo. Results revealed that minimum inhibition and minimum fungicidal concentrations of Se-NPs were 0.0625 and 1 mM, respectively. Moreover, Se-NPs were able to decrease the pre-and post-emergence of R. solani damping-off and minimize the severity of root rot disease. The most effective treatment method is found when soaking and spraying were used with each other followed by spraying and then soaking individually. Likewise, Se-NPs improve morphological and metabolic indicators and yield significantly compared with infected control. In conclusion, biosynthesized Se-NPs by B. megaterium ATCC 55000 are a promising and effective agent against R. solani damping-off and root rot diseases in Vicia faba as well as plant growth inducer.

Combined action of gamma radiation and exposure to copper ions on Lemna minor L

PURPOSE

Under natural conditions, the reaction of living organisms to the action of acute gamma radiation depends on other stressors, including heavy metals. The aim of this work was to study changes in morphometric parameters, the content of photoassimilation pigments and the level of oxidative stress in irradiated duckweed at various copper concentrations in the culture medium.

MATERIALS AND METHODS

As a model organism, we used Lemna minor L. Duckweed was exposed to acute γ-radiation at doses of 18, 42, 63 Gy. After irradiation, the plants were transferred into a medium containing 3, 5, 6.3 μmol/L Cu. On the 4th day of exposure, the levels of chlorophyll, carotenoids, malondialdehyde (MDA) were measured; after 7 days, the specific growth rate, the level of damage, the change in the frond area, copper concentration in plant tissues were determined.

RESULTS

The action of γ-radiation (18, 42, 63 Gy) and copper ions (3, 5, 6.3 μmol/L) reduced the growth rate, increased the membrane lipid peroxidation, reduced the area of the fronds more significantly than under the separate action of the factors. The factors acted antagonistically on the specific growth rate. The content of copper in the tissues of irradiated plants (42, 63 Gy) increased.

CONCLUSION

Irradiation of duckweed with acute doses of gamma radiation reduced the resistance of plants to excess copper in the environment.

Modes of action and adverse effects of gamma radiation in an aquatic macrophyte Lemna minor

High dose rates of ionizing radiation have been reported to cause adverse effects such as reduction in reproduction and growth, and damage to protein and lipids in primary producers. However, the relevant effects of ionizing radiation are still poorly understood in aquatic plants. This study was intended to characterize the biological effects and modes of action (MoAs) of ionizing radiation using gamma radiation as the prototypical stressor and duckweed Lemna minor as a model organism. Lemna minor was exposed to 1, 14, 24, 46, 70 mGy/h gamma radiation dose rates from a cobalt-60 source for 7 days following the testing principles of the OECD test guideline 221. A suite of bioassays was applied to assess the biological effects of gamma radiation at multiple levels of biological organization, including detection of reactive oxygen species (ROS), oxidative stress responses (total glutathione, tGSH; lipid peroxidation, LPO), DNA damage, mitochondrial dysfunctions (mitochondrial membrane potential, MMP), photosynthetic parameters (chlorophyll a, chl a; chlorophyll b, chl b; carotenoids; Photosystem II (PSII) performance; CO₂ uptake), intercellular signaling (Ca²⁺ release) and growth. Gamma radiation increased DNA damage, tGSH level and Ca²⁺ content together with reduction in chlorophyll content, maximal PSII efficiency and CO₂ uptake at dose rates between 1 and 14 mGy/h, whereas increases in cellular ROS and LPO, inhibition of MMP and growth were observed at higher dose rates (≥24 mGy/h). A network of toxicity pathways was proposed to portray the causal relationships between gamma radiation-induced physiological responses and adverse outcomes to support the development of Adverse Outcome Pathways (AOPs) for ionizing radiation-mediated effects in primary producers.

Improvement of rice seedling growth and nitrogen use efficiency by seed inoculation with endophytic denitrifiers

The aim of the present study is to investigate the effect of seed inoculation with endophytic denitrifiers on rice seedling growth and nitrogen use efficiency under low- and high-urea conditions. Pseudomonas sp. B2, Streptomyces sp. A9, and Fusarium sp. F3 were isolated from rice plant tissues. Rice seeds inoculated with the denitrifiers were sown in soil fertilized with 100 and 300 mg/kg urea concentrations, respectively. The denitrifiers increased soil ammonia concentrations or kept high ammonia concentration for a longer time in soils. However, soil nitrate concentrations with the denitrifier treatments were lower than that of the control. All the denitrifier treatments increased the chlorophyll content by more than 200% under the low urea condition. Compared to the control, the denitrifier inoculation treatments significantly increased shoot length, fresh weight, and dry weight of rice seedlings under the low- and high-urea conditions (P < 0.05). The chlorophyll concentrations, shoot length, wet weight, and dry weight of all the denitrifier treatments under the low urea fertilization were significantly higher than those of the control under the high-urea fertilization (P < 0.05). The nitrogen use efficiency of rice seedlings might be attributable to nitrate reductases of the denitrifiers, acting as the rice nitrate reductase. The treatment of endophytic denitrifiers significantly improved rice seedling growth and nitrogen use efficiency under both low- and high-urea conditions.

Bioanalytics in Quantitive (Bio)imaging/Mapping of Metallic Elements in Biological Samples

The aim of this article is to describe selected analytical techniques and their applications in the quantitative mapping/(bio)imaging of metals in biological samples. This work presents the advantages and disadvantages as well as the appropriate methods of scope for research. Distribution of metals in biological samples is currently one of the most important issues in physiology, toxicology, pharmacology, and other disciplines where functional information about the distribution of metals is essential. This issue is a subject of research in (bio)imaging/mapping studies, which use a variety of analytical techniques for the identification and determination of metallic elements. Increased interest in analytical techniques enabling the (bio)imaging of metals in a variety of biological material has been observed more recently. Measuring the distribution of trace metals in tissues after a drug dose or ingestion of poison-containing metals allows for the studying of pathomechanisms and the pathophysiology of various diseases and disorders related to the management of metals in human and animal systems.

Morphological and biochemical responses of Oryza sativa L. (cultivar MR219) to ion beam irradiation

OBJECTIVE

Heavy ion beam, which has emerged as a new mutagen in the mutation breeding of crops and ornamental plants, is expected to result in the induction of novel mutations. This study investigates the morphological and biochemical responses of Oryza sativa toward different doses of carbon ion beam irradiation.

METHODS

In this study, the dry seeds of O. sativa were irradiated at 0, 20, 40, 60, 80, 100, and 120 Gy, followed by in-vitro germination under controlled conditions. Morphological and biochemical studies were conducted to investigate the morphological and physiological responses of O. sativa towards ion beam irradiation.

RESULTS

The study demonstrated that low doses (10 Gy) of ion beam have a stimulating effect on the height, root length, and fresh weight of the plantlets but not on the number of leaves. Meanwhile, doses higher than 10 Gy caused reductions in all the morphological parameters studied as compared to the control samples. The highest total soluble protein content [(2.11 ± 0.47) mg/g FW] was observed in plantlets irradiated at 20 Gy. All irradiated plantlets were found to have 0.85% to 58.32% higher specific activity of peroxidase as compared to the control samples. The present study also revealed that low doses of ion beam (10 and 20 Gy) had negligible effect on the total chlorophyll content of O. sativa plantlets while 40 Gy had a stimulating effect on the chlorophyll content. Plantlets irradiated between 40 to 120 Gy were shown to be 0.38% to 9.98% higher in total soluble nitrogen content which, however, was not significantly different from the control samples.

CONCLUSIONS

Carbon ion beam irradiation administered at low to moderate doses of 10 to 40 Gy may induce O. sativa mutants with superior characteristics.

Radiation and chemical mutagen induced somaclonal variations through in vitro organogenesis of cotton (Gossypium hirsutum L.)

PURPOSE

The purpose of the investigation was to induce somaclonal variations by gamma rays (GR), ethylmethane sulphonate (EMS) and sodium azide (SA) during in vitro organogenesis of cotton.

MATERIALS AND METHODS

The shoot tip explants were irradiated with 5-50 Gray (Gy) GR (Cobalt 60), 0.5-5.0 mM EMS and SA separately, and inoculated on Murashige and Skoog (MS) medium fortified with plant growth regulator (PGR) for organogenesis. The plantlets with well-developed root systems were acclimatized and transferred into the experimental field to screen the somaclonal variations during growth and development.

RESULTS

The number of somaclonal variations was observed in growth of irradiated/treated shoot tips, multiplication, plantlet regeneration and growth in vitro and ex vitro. The lower doses/concentrations of mutagenic treatments showed significant enhancement in selected agronomical characters and they showed decreased trends with increasing doses/concentrations of mutagenic agents.

CONCLUSIONS

The results of the present study revealed the influence of lower doses/concentrations of mutagenic treatments on in vitro and ex vitro growth of cotton plantlets and their significant improvement in agronomical characters which needs further imperative stability analysis. The present observations showed the platform to use lower doses/concentrations of mutagenic agents to induce variability for enhanced agronomical characters, resistant and tolerant cotton varieties.

Gamma radiation effects on seed germination, growth and pigment content, and ESR study of induced free radicals in maize (Zea mays)

The effects of gamma radiation are investigated by studying plant germination, growth and development, and biochemical characteristics of maize. Maize dry seeds are exposed to a gamma source at doses ranging from 0.1 to 1 kGy. Our results show that the germination potential, expressed through the final germination percentage and the germination index, as well as the physiological parameters of maize seedlings (root and shoot lengths) decreased by increasing the irradiation dose. Moreover, plants derived from seeds exposed at higher doses (≤0.5 kGy) did not survive more than 10 days. Biochemical differences based on photosynthetic pigment (chlorophyll a, chlorophyll b, carotenoids) content revealed an inversely proportional relationship to doses of exposure. Furthermore, the concentration of chlorophyll a was higher than chlorophyll b in both irradiated and non-irradiated seedlings. Electron spin resonance spectroscopy used to evaluate the amount of free radicals induced by gamma ray treatment demonstrates that the relative concentration of radiation-induced free radicals depends linearly on the absorbed doses.

Ionizing radiation induced changes in phenotype, photosynthetic pigments and free polyamine levels in Vigna radiata (L.) Wilczek

Effects of gamma rays on the free polyamine (PA) levels were studied in Vigna radiata (L.) Wilczek. Seeds exposed to different doses of gamma rays were checked for damage on phenotype, germination frequency and alteration in photosynthetic pigments. Free polyamine levels were estimated from seeds irradiated in dry and water imbibed conditions. Polyamine levels of seedlings grown from irradiated seeds, and irradiated seedlings from unexposed seeds were also measured. Damage caused by gamma irradiation resulted in decrease in final germination percentage and seedling height. Photosynthetic pigments decreased in a dose dependent manner as marker of stress. Polyamines decreased in irradiated dry seeds and in seedlings grown from irradiated seeds. Radiation stress induced increase in free polyamines was seen in irradiated imbibed seeds and irradiated seedlings. Response of polyamines towards gamma rays is dependent on the stage of the life cycle of the plant.

Dose-dependent effects of gamma radiation on lettuce (Lactuca sativa var. capitata) seedlings

Abstract Purpose: The objectives of this study were to determine the effects of gamma radiation on lettuce growth and development, as well as on the content of photosynthetic pigments in 28 days lettuce leaf.

MATERIALS AND METHODS

Lettuce dry seeds were exposed to a (60)Co [Cobalt-60] gamma source at doses ranging from 2-70 Gray (Gy). The photosynthetic pigment content was determined spectrophotometrically.

RESULTS

Our results showed that an irradiation dose between of 2-30 Gy enhanced the growth parameters (final germination percentage, germination index, root and hypocotyl length) as compared to untreated plants. Seed germination test revealed that 30 Gy irradiation dose induced the highest increase of growth parameters, while at 70 Gy a significant decrease of plant vegetative growth was recorded. The results indicated that exposing the seeds at doses ranging from 2-30 Gy enhanced the photosynthetic pigments (chlorophyll a, chlorophyll b, carotenoids) content, while at higher doses (70 Gy)) the decrease of the assimilatory pigments was noticed.

CONCLUSION

The present results suggested that seed treatment with gamma radiations (0-30 Gy) was effective in stimulating plant growth and development, as well as the content of assimilatory pigments. At a higher dose of 70 Gy, there was a drastic reduction in the length of shoots and roots and also in the total chlorophyll content. These observations confirm that ionizing radiation stimulates physiological parameters up to certain low doses, and then it inhibits these parameters at higher doses.