Comparison of radiosensitivity response to acute and chronic gamma irradiation in colored wheat

Complexity of responses to ionizing radiation in plants, and the impact on interacting biotic factors

In nature, plants are simultaneously exposed to different abiotic (e.g., heat, drought, and salinity) and biotic (e.g., bacteria, fungi, and insects) stresses. Climate change and anthropogenic pressure are expected to intensify the frequency of stress factors. Although plants are well equipped with unique and common defense systems protecting against stressors, they may compromise their growth and development for survival in such challenging environments. Ionizing radiation is a peculiar stress factor capable of causing clustered damage. Radionuclides are both naturally present on the planet and produced by human activities. Natural and artificial radioactivity affects plants on molecular, biochemical, cellular, physiological, populational, and transgenerational levels. Moreover, the fitness of pests, pathogens, and symbionts is concomitantly challenged in radiologically contaminated areas. Plant responses to artificial acute ionizing radiation exposure and laboratory-simulated or field chronic exposure are often discordant. Acute or chronic ionizing radiation exposure may occasionally prime the defense system of plants to better tolerate the biotic stress or could often exhaust their metabolic reserves, making plants more susceptible to pests and pathogens. Currently, these alternatives are only marginally explored. Our review summarizes the available literature on the responses of host plants, biotic factors, and their interaction to ionizing radiation exposure. Such systematic analysis contributes to improved risk assessment in radiologically contaminated areas.

Genome-Wide Association Study to Identify Marker-Trait Associations for Seed Color in Colored Wheat (Triticum aestivum L.)

This study conducted phenotypic evaluations on a wheat F3 population derived from 155 F2 plants. Traits related to seed color, including chlorophyll a, chlorophyll b, carotenoid, anthocyanin, L*, a*, and b*, were assessed, revealing highly significant correlations among various traits. Genotyping using 81,587 SNP markers resulted in 3969 high-quality markers, revealing a genome-wide distribution with varying densities across chromosomes. A genome-wide association study using fixed and random model circulating probability unification (FarmCPU) and Bayesian-information and linkage-disequilibrium iteratively nested keyway (BLINK) identified 11 significant marker-trait associations (MTAs) associated with L*, a*, and b*, and chromosomal distribution patterns revealed predominant locations on chromosomes 2A, 2B, and 4B. A comprehensive annotation uncovered 69 genes within the genomic vicinity of each MTA, providing potential functional insights. Gene expression analysis during seed development identified greater than 2-fold increases or decreases in expression in colored wheat for 16 of 69 genes. Among these, eight genes, including transcription factors and genes related to flavonoid and ubiquitination pathways, exhibited distinct expression patterns during seed development, providing further approaches for exploring seed coloration. This comprehensive exploration expands our understanding of the genetic basis of seed color and paves the way for informed discussions on the molecular intricacies contributing to this phenotypic trait.

Impact of induced mutation-derived genetic variability, genotype and varieties for quantitative and qualitative traits in Mentha species

PURPOSE

The genus Mentha spp. is an aromatic herb from the family 'Lamiaceae'. It is extensively predominant in temperate and sub-temperate regions of the world. The essential oil of this species is enriched with broad aroma constituents extensively utilized in food, beverages, flavor, cosmetics, perfumery, and pharmaceutical enterprises. With the global menthol market size estimated to be worth USD 765 million in 2022, India (accompanied by China and Brazil) is the world's primary manufacturer, consumer, and exporter of Mentha oil. Despite prominent global demand, the crucial bottleneck in mint cultivation is the need for more superior commercial cultivars. Predominant vegetative propagation mode with difficulties in manual emasculation, differential blooming times, sterile/sub-sterile hybrids, and low seed viability are the primary containment in creating genetic variability by classical breeding approaches. Therefore, genetic complications encountered in conventional breeding have led the breeders to apply mutation breeding as an alternative crop improvement approach in Mentha spp. These attempts at mutation breeding have produced some distinctive mutants as genetic pools for plant breeding programs, and some novel mutant mint cultivars have been made available for commercial cultivation.

CONCLUSIONS

The prime strategy in mutation-based breeding has proven an adept means of encouraging the expression of recessive genes and producing new genetic variations. The present review comprises a significant contribution of mutation breeding approaches in the development of mutant mint species and its effects on physiological variation, photosynthetic pigment, essential oil content and composition, phytochemical-mediated defense response, pathogen resistivity, and differential expression of genes related to terpenoid biogenesis. Development and diversification have led to the release of varieties, namely Todd's Mitcham, Murray Mitcham, Pranjal, Tushar, and Kukrail in M. piperita L., Mukta, and Pratik in M. cardiaca Baker, Neera in M. spicata L., Kiran in M. citrata Ehrh., and Rose mint in M. arvensis L. that have revolutionized and uplifted mint cultivation leading to economic gain by the farmers and entrepreneurs.

Gamma Irradiation Promotes the Growth Rate of Thai Pigmented Rice As Well As Inducing the Accumulation of Bioactive Compounds and Carbohydrate Hydrolyzing Enzymes Inhibitors (α-Glucosidase and α-Amylase) under Salt Conditions

Rice contains many bioactive compounds that perform various biological activities. Some of these compounds have been identified as α-glucosidase and α-amylase inhibitors, including guaiacol, vanillin, methyl vanillate, vanillic acid, syringic acid, and 2-pentyl furan. In this study, we assessed the growth rate, photosynthetic pigment content, phenolic content, and flavonoid content of gamma-irradiated Thai pigmented rice. Bioactive components of gamma-irradiated rice that had been subjected to salt treatment were also investigated. The findings showed that production of photosynthetic pigments, which are associated with plant growth, was induced by low gamma exposure. Phenolic and flavonoid content of rice was increased after gamma irradiation at 5 to 1,000 Gy. Both gamma irradiation and the salt conditions changed the quantity of vanillin, methyl vanillate, and vanillic acid in the rice. However, at a salt concentration of 40 mM, the salt stress had more of an effect than the gamma dosage. However, the high concentrations of methyl vanillate and vanillic acid detected in the rice under salt conditions were ameliorated by gamma irradiation. Guaiacol served as the substrate of guaiacol peroxidase for catalyzed reactive oxygen species, as evidenced by the observation that the guaiacol content of rice decreased between increased gamma dosages. A gamma dose of 40 to 1,000 Gy resulted in the production of syringic acid. Under salt stress, syringic acid buildup was also seen to be ameliorated by gamma irradiation. In comparison to salt conditions, particularly for 20 mM salt, gamma irradiation had less of an impact on the 2-pentyl furan in rice.

Effect of low-dose ionizing radiation on spatiotemporal parameters of functional responses induced by electrical signals in tobacco plants

Plants growing under an increased radiation background may be exposed to additional stressors. Plant acclimatization is formed with the participation of stress signals that cause systemic responses-a change in the activity of physiological processes. In this work, we studied the mechanisms of the effect of ionizing radiation (IR) on the systemic functional responses induced by electrical signals. Chronic β-irradiation (31.3 μGy/h) have a positive effect on the morphometric parameters and photosynthetic activity of tobacco plants (Nicotiana tabacum L.) at rest. An additional stressor causes an electrical signal, which, when propagated, causes a temporary change in chlorophyll fluorescence parameters, reflecting a decrease in photosynthesis activity. Irradiation did not significantly affect the electrical signals. At the same time, more pronounced photosynthesis responses are observed in irradiated plants: both the amplitude and the leaf area covered by the reaction increase. The formation of such responses is associated with changes in pH and stomatal conductance, the role of which was analyzed under IR. Using tobacco plants expressing the fluorescent pH-sensitive protein Pt-GFP, it was shown that IR enhances signal-induced cytoplasmic acidification. It was noted that irradiation also disrupts the correlation between the amplitudes of the electrical signal, pH shifts, changes in chlorophyll fluorescence parameters. Also stronger inhibition of stomatal conductance by the signal was shown in irradiated plants. It was concluded that the effect of IR on the systemic response induced by the electrical signal is mainly due to its effect on the stage of signal transformation into the response.

Chronic Ionizing Radiation of Plants: An Evolutionary Factor from Direct Damage to Non-Target Effects

In present times, the levels of ionizing radiation (IR) on the surface of Earth are relatively low, posing no high challenges for the survival of contemporary life forms. IR derives from natural sources and naturally occurring radioactive materials (NORM), the nuclear industry, medical applications, and as a result of radiation disasters or nuclear tests. In the current review, we discuss modern sources of radioactivity, its direct and indirect effects on different plant species, and the scope of the radiation protection of plants. We present an overview of the molecular mechanisms of radiation responses in plants, which leads to a tempting conjecture of the evolutionary role of IR as a limiting factor for land colonization and plant diversification rates. The hypothesis-driven analysis of available plant genomic data suggests an overall DNA repair gene families' depletion in land plants compared to ancestral groups, which overlaps with a decrease in levels of radiation exposure on the surface of Earth millions of years ago. The potential contribution of chronic IR as an evolutionary factor in combination with other environmental factors is discussed.

Flowering under enhanced ionising radiation conditions and its regulation through epigenetic mechanisms

As sessile organisms, plants have to deal with unfavourable conditions by acclimating or adapting in order to survive. Regulation of flower induction is one such mechanism to ensure reproduction and species survival. Flowering is a tightly regulated process under the control of a network of genes, which can be affected by environmental cues and stress. The effects of ionising radiation (IR) on flowering, however, have been poorly studied. Understanding the effects of ionising radiation on flowering, including the timing, gene pathways, and epigenetics involved, is crucial in the continuing effort of environmental radiation protection. The review shows that plants alter their flowering pattern in response to IR, with various flowering related genes (eg. FLOWERING LOCUS C (FLC), FLOWERING LOCUS T (FT), CONSTANS (CO), GIGANTEA (GI), APETALA1 (AP1), LEAFY (LFY)) and epigenetic processes (DNA methylation, and miRNA expression eg. miRNA169, miR156, miR172) being affected. Thereby, showing a hypothetical IR-induced flowering mechanism. Further research on the interaction between IR and flowering in plants is, however, needed to elucidate the mechanisms behind the stress-induced flowering response.

Physiological and biochemical markers of gamma irradiated white radish (Raphanus sativus)

PURPOSE

A field experiment was performed to investigate the impact of low-dose gamma rays on growth parameters and bioactive compounds of white radish.

MATERIALS AND METHODS

White radish seeds were irradiated by gamma rays dose levels (10, 20, 40 and 80 Gy) beside control. Physiological and biochemical markers were done to follow the effect of gamma rays on white radish.

RESULTS

The results revealed that gamma rays increased growth parameters with increasing irradiation to a dose of 40 Gy. The maximum increments were found at 14.64 (cm), 48.30 (cm), 20.84 (cm) and 5.51 (cm) for leaves number, leaves length, roots length and roots diameter, respectively, with a dose of 40 Gy. By increasing the irradiation dose to 80 Gy, the results showed reduction in all parameters studied. Ascorbic acid gave the maximum increase with the dose of 40 Gy, while phenols, flavonoids, antioxidant activity, peroxidase, and polyphenol oxidase showed the highest increase with the dose 80 of Gy in radish leaves. Similar trend was observed for the radish roots. Furthermore, the protein and isoenzyme profiles of peroxidase and polyphenol oxidase changed and induced alteration by different irradiation dose levels.

CONCLUSION

Gamma rays can be a useful tool for increasing the growth and biochemical content of white radish plants and perhaps other food crops.

Cytogenetic and Biochemical Responses of Wheat Seeds to Proton Irradiation at the Bragg Peak

The present study aimed to evaluate the morphological, cytogenetic and biochemical changes in wheat seedlings as affected by seed exposure to a proton beam at the Bragg peak. The average energy of the proton beam was of 171 MeV at the entrance into the irradiator room while at the point of sample irradiation the beam energy was of 150 MeV, with the average value of the Linear Energy Transfer of 0.539 keV/μm and the dose rate of 0.55 Gy/min, the radiation doses being of the order of tens of Gy. Cytogenetic investigation has revealed the remarkable diminution of the mitotic index as linear dose-response curve as well as the spectacular linear increase of the aberration index. Analyzing some biometric parameters, it was found that neither dry matter nor water content of wheat seedlings was influenced by proton beam exposure. Studying the biochemical parameters related to the antioxidant defense system, we found that the irradiation caused the slight increasing tendency of peroxidase activity as well as the decreasing trend in the activity of superoxidedismutase in the seedlings grown from the irradiated seeds. The level of malonedialdehyde (MDA) and total polyphenols showed an increasing tendency in all seedling variants corresponding to irradiated seeds, compared to the control. We conclude that the irradiation clearly induced dose-response curves at the level of cytogenetic parameters together with relatively slight variation tendency of some biochemical parameters related to the antioxidant defense system while imperceptible changes could be noticed in the biometric parameters.

Ionizing Radiation: Effective Physical Agents for Economic Crop Seed Priming and the Underlying Physiological Mechanisms

To overcome various factors that limit crop production and to meet the growing demand for food by the increasing world population. Seed priming technology has been proposed, and it is considered to be a promising strategy for agricultural sciences and food technology. This technology helps to curtail the germination time, increase the seed vigor, improve the seedling establishment, and enhance the stress tolerance, all of which are conducive to improving the crop yield. Meanwhile, it can be used to reduce seed infection for better physiological or phytosanitary quality. Compared to conventional methods, such as the use of water or chemical-based agents, X-rays, gamma rays, electron beams, proton beams, and heavy ion beams have emerged as promising physics strategies for seed priming as they are time-saving, more effective, environmentally friendly, and there is a greater certainty for yield improvement. Ionizing radiation (IR) has certain biological advantages over other seed priming methods since it generates charged ions while penetrating through the target organisms, and it has enough energy to cause biological effects. However, before the wide utilization of ionizing priming methods in agriculture, extensive research is needed to explore their effects on seed priming and to focus on the underlying mechanism of them. Overall, this review aims to highlight the current understanding of ionizing priming methods and their applicability for promoting agroecological resilience and meeting the challenges of food crises nowadays.

Transcriptome Analysis of MYB Genes and Patterns of Anthocyanin Accumulation During Seed Development in Wheat

Plants accumulate key metabolites as a response of biotic/abiotic stress conditions. In seed coats, anthocyanins, carotenoids, and chlorophylls can be found. They have been associated as important antioxidants that affect germination. In wheat, anthocyanins can impart the seed coat color which have been recognized as health-promoting nutrients. Transcription factors act as master regulators of cellular processes. Transcription complexes such as MYB-bHLH-WD40 (MBW) regulate the expression of multiple target genes in various plant species. In this study, the spatiotemporal accumulation of seed coat pigments in different developmental stages (10, 20, 30, and 40 days after pollination) was analyzed using cryo-cuts. Moreover, the accumulation of phenolic, anthocyanin, and chlorophyll contents was quantified, and the expression of flavonoid biosynthetic genes was evaluated. Finally, transcriptome analysis was performed to analyze putative MYB genes related to seed coat color, followed by further characterization of putative genes. TaTCL2, an MYB gene, was cloned and sequenced. It was determined that TaTCL2 contains a SANT domain, which is often present in proteins participating in the response to anthocyanin accumulation. Moreover, TaTCL2 transcript levels were shown to be influenced by anthocyanin accumulation during grain development. Interaction network analysis showed interactions with GL2 (HD-ZIP IV), EGL3 (bHLH), and TTG1 (WD40). The findings of this study elucidate the mechanisms underlying color formation in Triticum aestivum L. seed coats.

Biological Effect of Gamma Rays According to Exposure Time on Germination and Plant Growth in Wheat

Gamma rays as a type of ionizing radiation constitute a physical mutagen that induces mutations and could be effectively used in plant breeding. To compare the effects of gamma and ionizing irradiation according to exposure time in common wheat (Keumgang, IT 213100), seeds were exposed to 60Co gamma rays at different dose rates. To evaluate the amount of free radical content, we used electron spin resonance spectroscopy. Significantly more free radicals were generated in the case of long-term compared with short-term gamma-ray exposure at the same dose of radiation. Under short-term exposure, shoot and root lengths were slightly reduced compared with those of the controls, whereas long-term exposure caused severe growth inhibition. The expression of antioxidant-related and DNA-repair-related genes was significantly decreased under long-term gamma-ray exposure. Long-term exposure caused higher radiosensitivity than short-term exposure. The results of this study could help plant breeders select an effective mutagenic induction dose rate in wheat.

Gamma irradiation to induce beneficial mutants in proso millet (Panicum miliaceum L.): an underutilized food crop

PURPOSE

Proso millet is a potential crop for food, nutritional security, and sustainable agriculture, particularly in the context of climate change. It is one of the traditional millet crops in cultivation in Tamil Nadu and India. Self-pollinated nature of this crop makes evolutionary process a terminal one and creating variability to broaden the genetic base is important. The objective of the study was to optimize mutagenic dose of gamma mutagen, document types of mutations and identify mutants for high grain yield (GY) and fodder yield (FY), hence to determine the feasibility of gamma mutagenesis in proso millet crop improvement.

MATERIALS AND METHODS

A mutation breeding program with 10 doses of gamma irradiation, i.e. 100, 200, 300, 400, 500, 600, 700, 800, 900 and 1000 Gy were imposed on seeds of variety ATL 1, a popular variety in India. Roll paper method, tray method and field evaluation were carried out to determine the LD₅₀ and GR₅₀ doses. Based on viable mutation frequency in M₂ generation, mutagenic effectiveness and efficiency was estimated. Targeted selection for yield and yield contributing traits was carried out in M₂, M₃ and M₄ generation to identify high yielding mutants.

RESULTS

The LD₅₀ and GR₅₀ doses of gamma were estimated to be 418 Gy and 542 Gy, respectively. Based on results from probit analysis, mutagenic effectiveness, mutagenic efficiency and mutation spectrum, the optimum treatment dose of gamma was concluded to be 400 Gy. High frequency, i.e. 10.96% of phenotypic mutants was identified in the M₂ generation. The broad range of mutants identified in M₂ generation had mutations for plant height, plant habit, panicle shape, compactness, and length, days to 50% flowering (DFF), lodging resistance, tillering, leaf phenotype, apiculus color, culm branching, stem and leaf hairiness, sheath pigmentation, seed color and shape and seed coat attachment. Eight high yielding mutant families were isolated in M₄ generation. The mean single plant GY and FY of these mutants ranged between 25 to 51 g and 40 to 68 g respectively while in control it was 15 g and 30 g, respectively.

CONCLUSIONS

The wide spectrum and high frequency of mutations both for qualitative and quantitative traits suggest mutation induction as a promising method for creating novel variations in proso millet. The high yielding mutants identified can be utilized for varietal development both for grain and fodder purpose after further stability and quality evaluations in the advanced generations.

The protective effect of exogenous salicylic and gallic acids ameliorates the adverse effects of ionizing radiation stress in wheat seedlings by modulating the antioxidant defence system

Plant growth regulatory substances play a significant role in maintaining developmental and physiological processes in plants under abiotic stress. Apart from traditional plant hormones, the phenolic acids, salicylic acid (SA) and gallic acid (GaA), are emerging players with pivotal roles in alleviating various environmental perturbations. The present study compared the stress alleviation effect of these two phenolic acids in wheat (Triticum aestivum L. 'Gönen-98') seedling whose seeds were used in this study pre-treated with increasing doses of gamma irradiation (IR, 100 > 400 Gy). Leaves from seedlings hydroponically grown for 10 days in medium containing 100 μmol/l SA and GaA were used in the measurements and determinations. Accordingly, exogenous treatment with SA and GaA significantly improved plant growth and photosynthetic activity and regulated stress-induced osmolyte accumulation against γ-irradiation. Treatments also led to significant reductions in TBARS and H₂O₂ contents. Antioxidant enzyme activities were further stimulated by SA and GaA treatment in comparison to IR alone. The phenolic pool including phenolic acids and GSH content in whole seedlings were promoted by IR and further SA and GaA applications. Contents in phenolic acids liberated from soluble free, soluble ester-conjugated and soluble glycoside-conjugated SA and GaA contents in roots and leaves increased following SA and GaA treatments alone in comparison to the control and IR groups. The present results indicate that SA and GaA can alleviate the ameliorative effects of IR, leading to further oxidative stress, and can improve the tolerance of stressed wheat seedlings by stimulating enzymatic and non-enzymatic antioxidant defence system components.

Comparative Analysis of the Effect of Carbon- and Titanium-Ions Irradiation on Morpho-Anatomical and Biochemical Traits of Dolichos melanophthalmus DC. Seedlings Aimed to Space Exploration

The realization of manned missions for space exploration requires the development of Bioregenerative Life Support Systems (BLSSs) to make human colonies self-sufficient in terms of resources. Indeed, in these systems, plants contribute to resource regeneration and food production. However, the cultivation of plants in space is influenced by ionizing radiation which can have positive, null, or negative effects on plant growth depending on intrinsic and environmental/cultivation factors. The aim of this study was to analyze the effect of high-LET (Linear Energy Transfer) ionizing radiation on seed germination and seedling development in eye bean. Dry seeds of Dolichos melanophthalmus DC. (eye bean) were irradiated with two doses (1 and 10 Gy) of C- and Ti-ions. Seedlings from irradiated seeds were compared with non-irradiated controls in terms of morpho-anatomical and biochemical traits. Results showed that the responses of eye bean plants to radiation are dose-specific and dependent on the type of ion. The information obtained from this study will be useful for evaluating the radio-resistance of eye bean seedlings, for their possible cultivation and utilization as food supplement in space environments.

Effect of chilling acclimation on germination and seedlings response to cold in different seed coat colored wheat (Triticum aestivum L.)

BACKGROUND

Flavonoids can protect plants against extreme temperatures and ROS due to their antioxidant activities. We found that deep-purple seed coat color was controlled by two gene interaction (12:3:1) from the cross between yellow and deep-purple seed coat colored inbreds. F_2:3 seeds were grouped in 3 by seed coat color and germinated under chilling (4 °C) and non-acclimated conditions (18 °C) for a week, followed by normal conditions (18 °C) for three weeks and a subsequent chilling stress (4 °C) induction. We analyzed mean daily germination in each group. Additionally, to study the acclimation in relationship to the different seed coat colors on the germination ability and seedling performances under the cold temperatures, we measured the chlorophyll content, ROS scavenging activity, and expression levels of genes involved in ROS scavenging, flavonoid biosynthetic pathway, and cold response in seedlings.

RESULTS

The results of seed color segregation between yellow and deep purple suggested a two-gene model. In the germination study, normal environmental conditions induced the germination of yellow-seed, while under chilling conditions, the germination ratio of deep purple-seed was higher than that of yellow-colored seeds. We also found that the darker seed coat colors were highly responsive to cold acclimation based on the ROS scavenging enzymes activity and gene expression of ROS scavenging enzymes, flavonoid biosynthetic pathway and cold responsive genes.

CONCLUSIONS

We suggest that deep purple colored seed might be in a state of innate pre-acquired stress response state under normal conditions to counteract stresses in a more effective way. Whereas, after the acclimation, another stress should enhance the cold genes expression response, which might result in a more efficient chilling stress response in deep purple seed seedlings. Low temperature has a large impact on the yield of crops. Thus, understanding the benefit of seed coat color response to chilling stress and the identification of limiting factors are useful for developing breeding strategies in order to improve the yield of wheat under chilling stress.

Effects of Acute and Chronic Gamma Irradiation on the Cell Biology and Physiology of Rice Plants

The response to gamma irradiation varies among plant species and is affected by the total irradiation dose and dose rate. In this study, we examined the immediate and ensuing responses to acute and chronic gamma irradiation in rice (Oryza sativa L.). Rice plants at the tillering stage were exposed to gamma rays for 8 h (acute irradiation) or 10 days (chronic irradiation), with a total irradiation dose of 100, 200, or 300 Gy. Plants exposed to gamma irradiation were then analyzed for DNA damage, oxidative stress indicators including free radical content and lipid peroxidation, radical scavenging, and antioxidant activity. The results showed that all stress indices increased immediately after exposure to both acute and chronic irradiation in a dose-dependent manner, and acute irradiation had a greater effect on plants than chronic irradiation. The photosynthetic efficiency and growth of plants measured at 10, 20, and 30 days post-irradiation decreased in irradiated plants, i.e., these two parameters were more severely affected by acute irradiation than by chronic irradiation. In contrast, acutely irradiated plants produced seeds with dramatically decreased fertility rate, and chronically irradiated plants failed to produce fertile seeds, i.e., reproduction was more severely affected by chronic irradiation than by acute irradiation. Overall, our findings suggest that acute gamma irradiation causes instantaneous and greater damage to plant physiology, whereas chronic gamma irradiation causes long-term damage, leading to reproductive failure.

Adaptation to ionizing radiation of higher plants: From environmental radioactivity to chernobyl disaster

The purpose of this work is to highlight the effects of ionizing radiation on the genetic material in higher plants by assessing both adaptive processes as well as the evolution of plant species. The effects that the ionizing radiation has on greenery following a nuclear accident, was examined by taking the Chernobyl Nuclear Power Plant disaster as a case study. The genetic and evolutionary effects that ionizing radiation had on plants after the Chernobyl accident were highlighted. The response of biota to Chernobyl irradiation was a complex interaction among radiation dose, dose rate, temporal and spatial variation, varying radiation sensitivities of the different plants' species, and indirect effects from other events. Ionizing radiation causes water radiolysis, generating highly reactive oxygen species (ROS). ROS induce the rapid activation of detoxifying enzymes. DeoxyriboNucleic Acid (DNA) is the object of an attack by both, the hydroxyl ions and the radiation itself, thus triggering a mechanism both direct and indirect. The effects on DNA are harmful to the organism and the long-term development of the species. Dose-dependent aberrations in chromosomes are often observed after irradiation. Although multiple DNA repair mechanisms exist, double-strand breaks (DSBs or DNA-DSBs) are often subject to errors. Plants DSBs repair mechanisms mainly involve homologous and non-homologous dependent systems, the latter especially causing a loss of genetic information. Repeated ionizing radiation (acute or chronic) ensures that plants adapt, demonstrating radioresistance. An adaptive response has been suggested for this phenomenon. As a result, ionizing radiation influences the genetic structure, especially during chronic irradiation, reducing genetic variability. This reduction may be associated with the fact that particular plant species are more subject to chronic stress, confirming the adaptive theory. Therefore, the genomic effects of ionizing radiation demonstrate their likely involvement in the evolution of plant species.

Impact of Proton Beam Irradiation on the Growth and Biochemical Indexes of Barley (Hordeum vulgare L.) Seedlings Grown under Salt Stress

The present paper examines the effects of salt stress on the growth, pigments, lipid peroxidation and antioxidant ability of barley (Hordeum vulgare L.) seedlings raised from proton beam irradiated caryopses. In order to assess the effects of radiation on the early stages of plant growth and analyze its possible influence on the alleviation of salinity, 3 and 5 Gy doses were used on dried barley seeds and germination occurred in the presence/absence of NaCl (100 mM and 200 mM). After treatment, photosynthetic pigments increased in the 5 Gy variant, which registered a higher value than the control. Among the antioxidant enzymes studied (SOD, CAT, and POD) only CAT activity increased in proton beam irradiated seeds germinated under salinity conditions, which indicates the activation of antioxidant defense. The malondialdehyde (MDA) content declined with the increase of irradiation doses on seeds germinated at 200 mM NaCl. On the other hand, the concentration of 200 mM NaCl applied alone or combined with radiation revealed an increase in soluble protein content. The growth rate suggests that 3 Gy proton beam irradiation of barley seeds can alleviate the harmful effects of 100 mM NaCl salinity, given that seedlings' growth rate increased by 1.95% compared to the control.

High-Throughput Phenotyping (HTP) Data Reveal Dosage Effect at Growth Stages in Arabidopsis thaliana Irradiated by Gamma Rays

The effects of radiation dosages on plant species are quantitatively presented as the lethal dose or the dose required for growth reduction in mutation breeding. However, lethal dose and growth reduction fail to provide dynamic growth behavior information such as growth rate after irradiation. Irradiated seeds of Arabidopsis were grown in an environmentally controlled high-throughput phenotyping (HTP) platform to capture growth images that were analyzed with machine learning algorithms. Analysis of digital phenotyping data revealed unique growth patterns following treatments below LD50 value at 641 Gy. Plants treated with 100-Gy gamma irradiation showed almost identical growth pattern compared with wild type; the hormesis effect was observed >21 days after sowing. In 200 Gy-treated plants, a uniform growth pattern but smaller rosette areas than the wild type were seen (p < 0.05). The shift between vegetative and reproductive stages was not retarded by irradiation at 200 and 300 Gy although growth inhibition was detected under the same irradiation dose. Results were validated using 200 and 300 Gy doses with HTP in a separate study. To our knowledge, this is the first study to apply a HTP platform to measure and analyze the dosage effect of radiation in plants. The method enabled an in-depth analysis of growth patterns, which could not be detected previously due to a lack of time-series data. This information will improve our knowledge about the effects of radiation in model plant species and crops.