Iranian Journal of Seed Research

Impacts of priming on germination and vigor of safflower (Carthamus tinctorius) seeds during artificial deterioration

Farshid Ghaderi-Far

Extended Abstract
Introduction: Safflower seeds are rich in unsaturated fatty acids with a high capacity for peroxidation, which have a high potential to reduce germination and seed vigor during the storage period. Therefore, Introducing appropriate methods to preserve or improve their germplasm during storage would be advantageous. The aim of this study was to investigate the effects of seed priming on germination and vigor of safflower seeds (Sofeh and Sina cultivars).
Materials and Methods: A three-factor experiment was conducted in a completely randomized design with three replications before and after artificial deterioration. The experimental factors included controlled deterioration of seeds at 45°C in six levels (no deterioration, 1, 2, 3, 4, and 6 days) and priming in four levels (no prime, hydropriming, salicylic acid 50 mg/l and sodium chloride 5 percent).
Results: Artificial aging strongly and linearly reduced the germination ability of safflower seeds, and germinability and seed vigor reach zero in a time interval which lasts between 2.5 to 4.5 days (depending on the treatment and the investigated trait). The use of priming prior to artificial aging was more advantageous than priming after artificial aging. In addition, priming with salicylic acid was more useful compared to other priming treatments.
Conclusion: Priming of safflower seeds before storage would result in the extended shelf-life of the stored seeds while also preserving the seed germination potential.

Highlights:

The effect of priming on germination and vigor of safflower seeds before and after artificial deterioration was compared and investigated.
The effect of priming before and after artificial deterioration on the improvement of safflower seed quality varied in different cultivars.

The effect of chitosan priming on germination indices and biochemical characteristics of French bean seeds (Phaseolus vulgaris cv. Sadri) under salinity stress

haniyeh saadat

Extended Abstract
Introduction: At present, the drastic increase in population has created an additional burden on the world's agricultural resources. As a result, meeting global food demand and increasing farmers' incomes has become a challenging task. Salinity is one of the abiotic stresses that strongly affect the germination, growth, and yield of crops. Seed priming is a simple technology that hydrates seeds to the point where the metabolic activity for germination is initiated without radicle emergence. In fact, the seeds are physiologically and biochemically prepared to germinate before being placed in their bed and exposed to environmental conditions. This research was conducted to investigate the effect of seed priming with chitosan on germination indices and biochemical traits of beans under salt stress.
Materials and Methods: This experiment was conducted at the University of Mohaghegh Ardabili in 2021 as a factorial in the form of a completely randomized design with four repetitions. The treatments included four levels of salinity (0, 50, 100, and 150 mM) and four levels of chitosan (0, 0.25, 0.50, and 0.75% w/v), all of which were dissolved in 1% acetic acid.
Results: The results showed that salinity stress decreased germination percentage (GP), peak value (PV), and germination value (GV). However, seed priming with different levels of chitosan, especially 0.75% chitosan, improved GP, PV, and GV by 7, 21, and 17%, respectively, compared to the control. Proline content and polyphenol oxidase enzyme activity went up with increasing salinity. However, the application of chitosan 0.75% increased these traits by 34% and 43%, respectively, compared to the control (priming with distilled water). Electrolyte leakage in priming with 0.75% chitosan decreased by 31% compared to the control, which indicates the maintenance of the cell membrane stability. The content of soluble sugars in the treatment with 0.75% chitosan and 150 mM salinity showed an increase of about 78% compared to the control. The highest correlation among traits was observed between peak value and germination coefficient (r²=0.99) and between proline and polyphenol oxidase enzyme (r²=0.92).
Conclusions: The results of this study show that among the different treatments, pre-treatment of seeds with 75 % Chitosan may be considered an effective way to improve germination indices and biochemical characteristics of beans and it can be used as a treatment to deal with salinity conditions in bean seedlings and improve their seedling growth.

Highlights:

Seed priming using chitosan improved germination indices of common bean seeds under salt stress.
Priming with chitosan increased proline and polyphenol oxidase enzyme.
A chitosan concentration of 0.75 V/W showed a better effect on germination indices and biochemical characteristics.
Priming with chitosan can be a suitable method to mitigate the negative effects of salinity, increase germination indices, and improve the biochemical characteristics of beans.

Evaluation of the generalized linear model to the germination percentage data and its comparison with the square root transformation

Majid Azimmohseni

Extended abstract
Introduction: In seed research, germination percentage data is the result of counting and has a binomial distribution. Therefore, seed researchers use data transformation, especially square root transformation, to stabilize the variance and normalize the data before performing analysis of variance and comparison of treatments. Despite the use of data transformation, this method has fundamental issues in the structure that misleads the test results. Therefore, it is important to introduce and replace a method that preserves the research assumptions and provides acceptable results for researchers without using data transformation. The use of generalized linear model is an alternative method for analyzing germination data with binomial distribution. In this research, the generalized linear model will be introduced first. Then, the efficiency of this method will be illustrated using simulated and actual germination data.
Materials and Methods: In this research, first the simulated data was generated by the Monte Carlo method. Based on the simulated data, the significance level and the power of test of generalized linear model were computed. Then the actual data related to three experiments including the effect of acidity on germination of wheat varieties, the effect of water stress and salinity on germination of yellow sweet clover seeds, and the effect of alternating temperatures on germination of three lavender populations were used and the results of the generalized linear model were compared with the square root transformation method based on the data of three experiments.
Results: The simulation results showed that the generalized linear model has a high efficiency to preserve the predetermined significance level and a high power in detecting significant differences in germination of the treatments. Moreover, the results of the comparison of the generalized linear model with the square root transformation method illustrated that the generalized linear model had a higher capability to detect significant differences between various treatments, especially in the treatments with unequal seeds in the Petri dish, and in the treatments in which the square root transformation method resulted in no significant difference among treatments, the generalized linear method showed a significant difference.
Conclusions: Generally, the results of this research demonstrated that the generalized linear model can be used as an alternative method to square root transformation in studies on the germination percentage of seeds with binomial distribution, without having the problems of the square root transformation method. Moreover, this model outperforms the square root transformation in detecting significant differences in germination of treatments with fixed and different seeds.

Highlights:

The generalized linear model was used for the analysis of germination percentage data.
The data simulated using the Monte-Carlo method was utilized to examine the significance level and power of the generalized linear model test.
The generalized linear model was compared with the square root transformation method during different germination experiments with fixed and different seeds in each Petri dish.

The effect of sodium nitroprusside levels on germination indices and antioxidant enzyme activity in soybean (Glycine max) seedlings under accelerated aging test

Haniyeh Saadat

Extended abstract
Introduction: Soybean is among the most important oil crops of the world. Currently, 55% of the world's oil is supplied by soybean. Seed aging, an undesirable feature of agriculture, is one of the main problems in agriculture that leads to economic losses. Although aging is an irreversible process, its speed is delayed by proper storage and optimal storage methods. While kept under inappropriate conditions after harvesting, its quality during storage declines. Priming has a direct and indirect effect on the growth and development of plants, and its indirect effects are more beneficial than its direct effects. Priming improves the longevity of low-vigor seeds. During the priming of these seeds, a long time can occur to repair metabolic damage before any progress in germination, which ultimately prevents further deterioration. Several studies have shown that seed treatment with sodium nitroprusside during reaction with reactive oxygen species and increased activity of antioxidant enzymes is essential to protecting plants against stress. The aim of this study was to the investigate the effect of sodium nitroprusside levels on germination indices and antioxidant enzyme activity in soybean seedlings under accelerated aging test.
Materials and Methods: This experiment was conducted in 2023 as a factorial in the form of a completely randomized design with 3 replications at the University of Mohaghegh Ardabili. Experimental treatments included accelerated aging treatment at three levels (0, 24, and 48 hours) and three levels of sodium nitroprusside (0, 100, and 200 ppm).
Results: The results showed that aging reduced germination indices including germination percentage (GP), germination value (GV), and mean daily germination (MDG). Also, priming with different levels of sodium nitroprusside, especially the 200 ppm level, improved these traits, but priming with sodium nitroprusside decreased the mean germination rate (MGR) and the mean germination time (MGT). The superoxide dismutase and ascorbate peroxidase enzyme activity due to priming with sodium nitroprusside 200 ppm compared to the control showed an increase of 22 and 26%, respectively. Also, the content of peroxidase enzyme activity showed an increase of about 34% compared to the control in priming with sodium nitroprusside 200 ppm and 48 hours aging compared to the control. The lowest catalase enzyme (7.7 units mg protein^-1 min^-1) was in pretreatment with sodium nitroprusside 100 ppm and without aging.
Conclusions: The results of this study show that among the different treatments, pre-treatment of seeds with sodium nitroprusside 200 ppm may be considered an effective way to improve germination indices and antioxidant enzymes activity of soybean and can be used as a treatment to deal with salinity conditions in soybean seedlings and improve their growth.

Highlights:

Seed priming using sodium nitroprusside improved germination indices of seed common soybean under aging.
Priming with sodium nitroprusside increased antioxidant enzyme activity.
The concentration of 200 ppm sodium nitroprusside showed a better effect on germination indices and biochemical characteristics.

Quantifying and analysis of germination responses of invasive weed Western ragweed (Ambrosia psilostachya) to temperature and under different water potential conditions

Jafar Asghari

Extended abstract
Introduction: The germination process is one of the most critical stages of a plant's growth and determines the success of the emergence of a weed in an agroecosystem because it is the first stage in which the weed competes for a niche. Various environmental factors, including temperature and moisture, affect the germination of weed seeds. Modeling techniques are capable of predicting germination, seedling emergence, and establishment of weed species. The ability to predict weed germination in response to environmental conditions is very effective for the development of control programs. The experiment was conducted to determine the cardinal temperature and evaluate the best model for quantifying the response of the germination rate of Western ragweed weed seeds under different water stress conditions.
Materials and Methods: A factorial experiment was conducted in the form of a completely randomized design in three replications. The investigated factors include temperature with eight levels (5, 10, 15, 20, 25, 30, 35, and 40 C˚) and water potential with six levels (0, -0.3, -0.6, -0.9, -1.2, and -1.5 MPa) on the germination of Western ragweed. In order to quantify the response of Western ragweed germination rate to temperature, three non-linear Dent-like, Beta, and Segmented regression models were used.
Results: The results showed that the effect of temperature, water potential, and their interactions on maximum germination, germination rate, and time required to reach 10, 50, and 90 percent germination were significant. Also, the results showed that by increasing the temperature from 10 to 25 C˚, the percentage and rate of germination increased whereas by increasing water potential, the percentage and rate of germination decreased. In comparing the models, based on RMSE, R², CV, and coefficients a and b parameters, the Beta model was the most suitable for estimating the temperatures of cardinal Western ragweed. The base, optimum, and ceiling temperatures using the Beta model were 3.88, 25, and 40 C˚, respectively.
Conclusions: The use of the Beta model to quantify the germination response of Western ragweed seeds to different levels of water potential at different temperatures had acceptable results. Therefore, by using the output of these models at different temperatures, it is possible to predict the germination rate at different potentials.

Highlights:
1- Germination cardinal temperatures and the effect of water potential on western ragweed weed were investigated.
2- Estimation of different models to quantify the response of germination rate to temperature and different water potentials.

Investigating physical and physiological characteristics of cotton (G. hirsutum) seeds during the delinting process at factory

Shahram Nowrouzieh

Extended abstract
Introduction: Currently, in most countries around the world, cotton seeds are used in delinted form. The fuzzy cotton seed often lead to slower germination, increased susceptibility of seeds and seedlings to pests and diseases, and disrupts mechanized cotton planting. Delinted cotton seeds have numerous advantages, including the possibility of mechanized planting, reduced seed consumption per unit area, faster germination in the soil, and more rapid field emergence of seedlings. Furthermore, delinted seeds are usually free from pathogenic agents, and the seed quality is improved with the availability of gravity separation and removal of broken, lightweight, and hollow seeds. One of the challenges faced by cotton seed delinting factories in Iran that employ acid-based methods is the reduction in the seed germination of the delinted seeds, which poses a challenge to the continued operation of these factories. This research was conducted to investigate the reasons behind the reduction in the viability cotton seeds in a delinting factory, to examine the physiological and mechanical characteristics of seeds at various stages of delinting in the factory.
Materials and methods: Seed sampling was carried out in a delinting factory in two replications. Traits such as seed vigor, germination percentage, ion leakage, seed density and volume, seed aging, level of abrasion and damage to the seed coat, and seed rupture force were studied. Finally, the data were analyzed using SAS, SPSS, and JMP software.
Results: The test results showed that seed sampling from both replications of the factory before centrifuge had the lowest germination percentage, leaf formation percentage, primary root length, primary stem length, dry weight of primary root, and dry weight of primary stem. These traits indicate that during the centrifugation stage, the seeds sustain significant mechanical damage, leading to a reduction in their vigor. The percentage of breakage, ion leakage, ageing, volume and density of seeds in the first repetition showed that these seeds had a lower quality compared to the seeds related to the second repetition. Therefore, different delinting stages in the factory have decreased the seed vigor. As the percentage of breakage and ion leakage increases, the seed rupture force declines non-linearly. Based on these findings, it can be concluded that acid contact with the cotton seed and the centrifugation process caused more mechanical damage to the seeds, leading to a significant reduction in seed rupture force.
Conclusion: The accuracy of operations at all stages of delinting significantly impacts seed quality. The centrifugation stage, the temperature of the dryer cylinders, and the acid neutralization process require greater attention and monitoring. Therefore, it is necessary to adjust the duration or concentration of the acid used for delinting in the delinting factory to match the seed condition in order to minimize damage to the seeds.

Highlights:

Delinting in the factory causes damage to the seeds, but proper management of temperature and acid concentration mitigates this damage.
It is necessary to adjust the duration or concentration of the acid used for delinting in the factory to match the seed condition in order to minimize damage to the seeds.
Managing the acid spray on the seeds and eliminating the centrifugation section in the delinting factory can prevent severe seed damage in this stage, and seed quality can be improved.
Neutralizing the seeds at the end of the delinting process in the delinting factory results in an increase in the storage of delinted cottonseed.

The effect of hormonal priming with cytokinin on deteriorated Nigella (Nigella sativa) seeds

Abdol Mehdi Bakhshandeh

Extended abstract
Introduction: Deterioration reduces the quality of seeds. Oilseeds like Nigella are highly susceptible to seed aging. Seed priming enhances the quality of deteriorated seeds by improving germination indices and increasing the activity of antioxidant enzymes. This research aimed to investigate the extent of damage caused by accelerated aging treatment on the germination characteristics and antioxidant enzyme activity of Nigella seeds and the possibility of mitigating the adverse effects of aging through hormonal priming with cytokinin.
Materials and methods: This research was carried out in the form of a completely random basic design with four replications in the seed technology laboratory of Khuzestan University of Agricultural Sciences and Natural Resources in 2017. The treatments included hormonal priming with cytokinin at five levels (0 (control), 10, 20, 40, and 80 m/l) for two durations (12 and 24 hours), and aging under 100% relative humidity and a temperature of 45 °C at five levels (no aging, 24, 48, 72, and 96 h).
Results: The analysis of variance results indicated that germination indices were only influenced by main and two-way effects at the 5% and 1% probability levels, while the three-way interactions, including aging, hormone concentration, and priming duration, were significant for plant growth and longitudinal and weight indices at the 1% probability level. Furthermore, it was evident that the priming treatment mitigated the negative effects of aging, with the concentration of 10 milligrams per liter of cytokinin for a duration of 12 h having the most significant impact among the hormone concentrations used on the measured traits. The highest germination percentage (88%) and the lowest germination percentage (63.33%) were observed at concentrations of 10 and 80 mg/l, respectively. The use of cytokinin at optimal concentration improved catalase activity and protein levels. The results showed that in the control conditions, the activity of the catalase enzyme was 0.76 units per mg of protein and the amount of protein was 0.51 mg/g, which reached 0.97 units per mg of protein and 0.79 mg/g with seed priming.
Conclusion: Based on the results obtained from this research, aging led to a reduction in germination indices, the activity of antioxidant enzymes, and seed protein content. The best treatment applied was cytokinin hormone priming for aged Nigella seeds at a concentration of 10 mg/l for 12 h. According to the results, the application of cytokinin at its optimal concentration (10 mg/l) improved the catalase enzyme activity and protein content. Therefore, it can be suggested that hormonal priming with cytokinin helps mitigate the adverse effects of aging in Nigella plants.

Highlights:

The impact of hormonal priming with cytokinin at concentrations of 10, 20, 40, and 80 mg/L on aged Nigella seeds was investigated.
The use of a concentration of 10 mg/l of cytokinin hormone for 12 hours was introduced as the best treatment.
Cytokinin was introduced as a significant hormone that enhances the activity of antioxidant enzymes and physiological traits in aged Nigella seeds.

Evaluation of mechanical damages to chickpeas due to free fall during handling under electrical conductivity and accelerated aging tests

Feizollah Shahbazi

Extended abstract
Introduction: The seeds of agricultural products are constantly subjected to impact forces from machines from the moment they are harvested to the time they are transferred into storage. Improper design and performance of machines in each of these stages can cause mechanical damage to seeds. Mechanical damage caused by free fall on the seed of agricultural products, which occurs during different stages of harvesting, transportation and other processes, causes a decrease in their quality and an increase in waste. This study aimed to evaluate the amount of mechanical damage caused to chickpea seeds due to the impact of free fall.
Materials and methods: The experiment was conducted as a factorial in the form of a completely randomized design with three replications. The factors included drop height (3, 6, 9 and 12 m), the contact surface (concrete, plywood, metal (iron) and seed-on-seed) and seed moisture content (10, 15, 20 and 25 %). The studied traits or the amount of damage to the seeds included the measurement of seed deterioration by the accelerated aging method (loss in germination percentage in the accelerated aging test) and the measurement of electrical conductivity.
Results: The results of the analysis of variance showed that all three factors (drop height, the contact surface and moisture content) had significant effects at p<0.01 on the loss in germination percentage in the accelerated aging test and changes in electrical conductivity of chickpea seeds. In terms of loss in germination percentage, the highest damage to seeds occurred in the metal contact (41.96%) and the least in the seed-on-seed treatments(29.71%). Also, the highest amount of electrical conductivity was related to the seeds dropped on the metal (36.09 μS cm^-1g^-1) and the lowest was related to seed-on-seed contact (21.68 μS cm^-1g^-1). As the drop height rose from 3 to 12 m, the loss in germination and electrical conductivity of seeds increased from 27.74 to 48.08% and from 18.72 to 40.47 μS cm^-1g^-1, respectively. Increasing the moisture content of chickpea seeds from 10 to 25% causes a decrease in the amount of damage to the seeds in terms of electrical conductivity (from 38.40 to 21.18 μS cm^-1g^-1). However, the damage was in the form of loss in germination percentage during the accelerated aging test (from 29.22 to 42.88 %).
Conclusion: The findings of this study revealed that the movement of chickpea seeds and the subsequent free fall had a notable impact on their latent damage, leading to a decrease in germination rate and alterations in electrical conductivity. Therefore, it is recommended to minimize fall height and prevent seeds from hitting hard surfaces during seed processing and transportation to mitigate the damage.

Highlights:

Seed deterioration tests using accelerated aging and electrical conductivity can be used as appropriate criteria to measure the mechanical damage to chickpea seeds.
When designing machines that come into contact with the seeds, it is important to choose surfaces made of soft materials to minimize the destructive effects of the seeds falling from greater heights.
The moisture content during the processing and transportation of the seeds should be at an optimal level of around 15%.

The effects of heat stress on germination and growth of tomato (Solanum lycopersicum) pollen grains under laboratory conditions

Reza Tavakkol Afshari

Extended abstract
Introduction: The effects of temperature increases on the growth of tomato fields are among the obvious results of global warming and are considered an important issue that should be investigated. To maintain and develop the cultivation systems of this crop, a proper understanding of the heat tolerance mechanisms and physiological responses in tomatoes should be achieved. The primary objective of this research is to discover the impact of heat stress on the germination and growth of pollen grains in research tomato germplasms. The researchers' knowledge about the response of different tomato cultivars to abiotic stresses is limited and only the effects of enzymes involved in the response process, heat shock proteins and some hormones have been investigated. The process of detecting heat stress-sensitive stages and their enhancement is facilitated by having a correct understanding of physiological processes.
Materials and methods: The seeds of heat-resistant (LA2661 and LA2662) and -sensitive (LA3911) research cultivars of tomato were used to evaluate the effects of increasing day and night temperatures. The obtained seedlings were grown under optimal temperature conditions (24^°C day/18^°C night), and after observing the first flower primordium, were incubated in growth chambers to apply daytime heat stress treatments, including temperatures of 28^°C, 32^°C and 36^°C day/18^°C night and night stress treatments including temperatures of 28^°C, 32^°C, and 36^°C at night/ 24^°C day for 7 days. Pollen grains were then evaluated for their survival, germination, and growth.
Results: The findings of the daytime heat stress tests show that the percentage of survival and germination of pollen grains and growth of pollen tubes of cultivars LA2661, LA2662 and LA3911 decreased as daytime temperature rose from 24 ^°C to 36 ^°C. This reduction is more noticeable for the sensitive cultivar LA3911. Degraded pollen grains increased in the LA3911 cultivar due to heat stress. The survival percentage of pollen grains in all three studied cultivars decreased due to the application of heat stress at night. The resistant cultivars LA2661 and LA2662 had a higher germination percentage compared to the sensitive cultivar LA3911. Pollen grains germination decreased by 50% as a result of increasing the night temperature from 18^°C to 36^°C. Pollen tube length was reduced in both cultivars and night treatments.
Conclusion: The effects of heat stress in the early stages of flowering when flowers are visible are high, and reproductive stages are very sensitive to high temperatures and affect fertility and processes after insemination, and finally, they lead to yield loss. The daytime temperature increase relative to the natural temperature range (22^°C to 24^°C) during growth severely impacts the number of pollen grains released from tomato flowers. The number of non-living pollen grains is higher at 36^°C day and 32^°C and 36^°C night temperatures compared to optimal temperature conditions. It appears that the increase in nighttime temperature results in more severe consequences than the increase in daytime temperature.

Highlights:

Night heat stress was assessed as a factor that influences the germination and survival of tomato pollen grains.
Image analysis was used to measure the length of the pollen tube.
The effect of thermal stress on pollination was investigated during a specific period of reproductive growth.

Application of the thermal time model to assess the effects of priming treatments on seed germination of rice (Oryza sativa) cultivars in response to temperature

Farshid Ghaderi-Far

Extended abstract
Introduction: With regard to the ever-growing water deficit in the world, the adoption of the direct-seeded rice cultivation system has been suggested as an alternative to the transplanting method. One of the disadvantages of the direct-seeded method is low and non-uniform germination and emergence due to low seed vigor in rice. Priming is a technique which improves the rate and uniformity of seed germination under these conditions. Thus, this study aimed to investigate the effects of priming treatments on seed germination of different rice cultivars under different temperature conditions using the thermal time model.
Materials and methods: This study was conducted in 2019 at the seed research laboratory of Gorgan University of Agricultural Sciences and Natural Resources. In this experiment, germination of primed and non-primed seeds in three rice cultivars (Nada, Anam, and Tolo) was investigated under different temperatures (15, 20, 25, 30, and 35°C). The priming treatments which consisted of control, hydropriming, and osmopriming with different chemicals (potassium chloride 2%, potassium nitrate 1%, calcium chloride 4%, glycine betaine 10 ppm, salicylic acid 10 ppm, and ascorbic acid 10 ppm) were investigated under different temperatures.
Results: The results showed that priming treatments had no significant effect on the seed germination percentage of rice cultivars at different temperatures. The thermal time model based on binomial distribution fitted well to cumulative germination percentages in all priming treatments. Among the parameters of the thermal time model, the greatest priming effect was on the reduction of the thermal coefficient, followed by the reduction of the sigma coefficient, which resulted in the increased rate and uniformity of germination. Priming treatments had no significant effect on base temperature. Also, the responses of rice cultivars to seed priming treatments varied so that in Anam and Neda, priming with calcium chloride but in Tolo, hydropriming was more effective on the model parameters, especially thermal time to 50% of germination.
Conclusion: In general, priming treatments did not affect the base temperature of germination in rice cultivars, but they significantly affected the rate and uniformity of seed germination. As the latter issue is one of the main problems in the direct-seeded rice system, suitable priming treatments for each cultivar can be adopted to increase the rate and uniformity of seed germination and emergence in this system.

Highlights:

The thermal time model can be used to select the appropriate priming treatment for improving seed germination components of rice cultivars.
The responses of rice cultivars to different seed priming treatments were different.
Priming treatments did not improve the base temperature of seed germination in rice cultivars, but they significantly affected seed germination rate and uniformity.

Evaluation of allelopathic stress of St. John's wort (Hypericum perforatum) on the germination, physiological, and biochemical characteristics of green pea (Pisum sativum), the benchmark plant sensitive to allelochemicals

Ebrahim Gholamalipour Alamdari

Extended abstract
Introduction: In agricultural systems, several environmental stresses can remarkably alter the growth, physiological, and biochemical responses of plants under stress. One of these factors is the biochemical reactions between plants along with the production of secondary compounds. Allelochemicals mainly have defence and cell wall ligninization roles in plants and do not directly play a role in the growth processes of plants. Thus, an experiment was carried out to evaluate the effect of allelopathic stress of Hypericum perforatum on the germination, physiological, biochemical, and antioxidant activity characteristics of green pea, the benchmark plant sensitive to allelochemicals.
Materials and methods: The treatments included different concentrations of H. perforatum at 11 levels (i.e., 0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100% of the aqueous extract). This research was carried out as a completely randomized design with three replications at the weed science laboratory of Gonbad Kavous University in 2023.
Results: The results of this study showed that one of the factors influencing the physiological, and biochemical characteristics of green pea is the concentration of the H. perforatum extract. In most cases, the percentage and rate of green pea germination, radicle and plumule length, and dry weight of radicle and plumule decreased with increased concentration of aqueous extract compared to the control, so that the greatest reduction in these characteristics was observed in 100% of H. perforatum extract. In contrast, the content of compatible osmolytes such as proline and soluble sugars, phenolic and flavonoid compounds, and antioxidant activity of green pea roots and plumules increased significantly in all studied treatments, with the highest increase in these characteristics observed at the concentration of 100% of H. perforatum aqueous extract. In general, the decrease in the dry weight of green pea seedlings due to the increase in the concentration of the aqueous extract of H. perforatum, despite the relative increase in the content of physiological and biochemical traits, indicates the high intensity of allelopathic stress of H. perforatum extract and their insufficiency, which leads to cytotoxicity against oxidative stress.
Conclusion: Considering the heterotoxicity effect of H. perforatum on green pea sensitive to allelochemicals and its distribution in gardens, barren lands, and wheat and corn fields, the possible effect of their residues in the next planting and even in case of presence in mixed cultivation should be considered.

Highlights:

Aqueous extract obtained from the H. perforatum drastically reduces the germination and seedling growth of green peas.
The difference in the effect of the aqueous extract of H. perforatum on green pea, the benchmark plant sensitive to allelochemicals, depends on their concentration threshold.
The high intensity of allelopathic stress of H. perforatum extract and insufficient non-enzymatic antioxidants lead to oxidative stress.

Evaluation of germination indices in Festuca spp. under chilling, osmo- and hormone priming

Hamideh Javadi

Extended abstract
Introduction: Festuca species are forage grasses that are very important in terms of fodder supply and soil protection. The seeds of these plants have internal dormancy (physiological) and are unable to germinate easily. Therefore, they must be subjected to various treatments to germinate. In nature, this dormancy is broken during the cold period of winter (chilling). The purpose of this research is to investigate different methods of dormancy breaking in Festuca species for large-scale production and accelerate the germination process.
Materials and methods: In this research, three species of Festuca (Festuca arundinacea, F. ovina, and F. rubra) were subjected to different treatments of chilling (4°C, 14 days), osmo-priming with potassium nitrate (KNO₃) 1.5% and gibberellic acid 150 and 200 ppm. After 14 days of germination test, various germination indices including percentage and rate of germination, mean germination time, seed vigor index, length of radicle, shoot and seedling, and the ratio of radicle to shoot length were calculated.
Results: The results of the analysis of variance showed a significant difference between species (except for germination percentage and root length traits) and treatments (for all traits). The interactions between the species and treatment were also significant for all traits (except for the length of radicle and seedling). Among the three species, the percentage of germination varied from 26.67 to 30.67% and the value of the germination rate varied from 1.92 to 3.31 n/d. The average time required for germination varied from 3.75 to 4.36 days and the seed vigor index varied from 26.74 to 43.02. The radicle length was between 37.22 and 45 mm and the shoot length was between 37.34 and 81.33 mm. Based on principal components analysis (PCA), percentage and rate of germination, seed vigor index, and length of radicle and seedling were introduced as the most important factors in creating diversity in Festuca species. In determining the correlation between traits, a high correlation of 70% was observed between germination percentage, germination rate, and seed vigor index.
Conclusion: Among the three species, Festuca rubra was superior to the other two species by having the highest percentage and rate of germination, seed vigor, radical length, and the shortest time required for germination. Among the applied treatments, 1.5% potassium nitrate (KNO₃) with chilling (4°C, for 14 days), had a positive effect on the percentage and rate of germination, radical length, and gibberellic acid (150 ppm) treatment had a positive effect on the length of shoot and seedling. The presence of high germination percentage and rate indicated higher seed vigor.

Highlights:

Using potassium nitrate as a pre-treatment of seeds is better than watering seeds with potassium nitrate.
The effect of osmo-priming (potassium nitrate 1.5%) on the germination characteristics of Festuca seeds is better than hormone priming (Gibberellic acid).
Pre-treatment with 1.5% potassium nitrate increases the number of germinated seeds, while treatment with 150 ppm gibberellic acid increases seedling length in Festuca seeds.