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Ali Asharf Mehrabi, Somayeh Hajinia,
Volume 6, Issue 1 (9-2019)
Volume 6, Issue 1 (9-2019)
Abstract
Extended Abstract
Introduction: White Astragalus (Astragalus gossypinus Fisherr.) is one of the valuable plants for producing gum, which is of critical importance in soil conservation and the economy of the country. This plant is propagated by seed; its seeds are in the natural state of dormancy. Therefore, recognizing the factors affecting dormancy and creating optimal conditions for seed germination of this plant is necessary for the cultivation and reclamation of rangelands. This study was conducted with the aim of finding the best treatment for breaking the dormancy and improving seed germination under various chemical and physical treatments.
Materials and Methods: The experiment was carried out as a factorial based on a completely randomized design with four replications at the gene bank of cereal and legume Lab of Ilam University, 2017. The factors included two levels of scarification chemical (with and without sulfuric acid (H2SO4) for 10 minutes), three levels of stratification (control, moist chilling at +4 °C and dry chilling -20 °C), potassium nitrate in two levels (zero and 1% KNO3) and gibberellic acid in two levels (zero and 5 ppm GA3). Germination indices including germination percentage, germination rate, seedling and radicle length, seedling fresh weight and vigor index were measured.
Results: Initial assessment of vital indices in seed such as germination and primary growth showed that the simultaneous application of scarification by sulfuric acid and moist chilling at +4 °C has the most impact on removing dormancy and increasing germination percentage. The highest germination rate was observed in moist chilling at +4 °C, which was 32.19 percent more than that of the control treatment. Scarification by sulfuric acid reduced the mean germination time in moist chilling at +4 °C. Scarification by sulfuric acid increased the fresh weight of the seedling by 55.25 percent, compared with the control. Pre-treatments with potassium nitrate undre control conditions, moist chilling at +4 °C and dry chilling at -20 °C increased the fresh weight of seedlings, at 52.66, 30.94 and 17.18 percent, respectively. Application of potassium nitrate increased root length by about 60.7 percent, compared with control. The highest radicle length (78.71 mm) was obtained when the seed was treated with sulphuric acid with wet chilling at 4 ° C for two weeks, which was 30 percent higher than control. The highest seedling length (84.88 mm) was obtained in scarification with sulfuric acid, wet chilling, and potassium nitrate and gibberellic acid. The highest seed vigor index (61.85 %) was observed in the treatment of scarification with sulfuric acid under moist chilling, and pre-treatments of gibberellic acid and potassium nitrate.
Conclusions: In general, it can be concluded that seed dormancy of Astraglus gossypinus involves both physical and physiological dormancy. The best treatment for removing the dormancy of this species seems to be scarification with sulfuric acid for 10 minutes puls concentrated stratification in moist chilling at +4 °C for two weeks.
Highlights:
- Determination of the optimal seed dormancy techniques of white Astragalus for the purpose of increasing seed germination percentage.
- Comparison of the efficiency of different dormancy breaking techniques.
- The combined effect of sulfuric acid, chilling and priming with gibberellic acid and potassium nitrate on germination indices.
Sajad Mijani, Mehdi Rastgoo, Ali Ghanbari, Mehdi Nassiri Mahallati,
Volume 8, Issue 1 (9-2021)
Volume 8, Issue 1 (9-2021)
Abstract
Extended abstract
Introduction: Purple nutsedge (Cyperus rotundus L.) is one of the problematic weeds worldwide prevalent in tropical and subtropical regions. Tubers are major tools through which purple nutsedge is propagated, whereas its seeds have a low ability to germinate. Therefore, evaluation of the response of tubers against environmental agents is great of importance to know the germination and emergence time. Germination, in turn, is mostly affected by temperature, among other environmental factors. Various models that are recognized as the Thermal Time model have been introduced to describe the seed germination pattern against temperature. Since predicting the emergence of reproductive organs through the modeling is great of importance for improving the control strategies; the present study was carried out to investigate the response of tuber sprouting of purple nutsedge (Cyperus rotundus) against temperature using thermal time models.
Material and methods: The experiment was carried out as a randomized complete block design with three replications in a germinator. Each replicate was placed on a separate shelf. For each replicate, 15 tubers were placed inside a 20 cm Petri dish on a filter paper and then 100 ml of water was added. The experiment was performed separately for constant temperatures of 10, 15, 20, 25, 30, 35, and 40 °C in absolute darkness. To analyze the data as modeling, five thermal time models were evaluated based on the statistical distributions of normal, Weibull, Gumble, logistic and log logistic. Indices such as R2, RMSE, RMSE%, and AICc were used to evaluate the models.
Results: The results showed that all models predicted the germination response of purple nutsedge tuber with high accuracy (R2 = 0.95). A comparison of models based on AICc values showed significant superiority of the Gumble model over other models. According to this index, there was no difference between logistic and log logistic models with normal. Among the models, Weibull was identified as the most inappropriate model. Different models estimated the final germination (Gmax) between 0.93 to 0.94 (93 to 94%). The base temperature was estimated through different models from 7.10 to 7.47 °C. Among the models, the model based on the Gumble distribution proved the skew to the right of the thermal time and Tm. According to the Gumble model, the thermal time parameters required to reach 50% germination (θT (50)) equals 123.8 ° C day and the maximum temperature for germination at 50% probability (Tc (50)) was estimated to be 46.10 ° C.
Conclusion: the thermal time model based on the Gumble probability distribution was most plausible among the models. Also, a distributed right skewness related to the thermal time and Tm was proved through the Gumble model. The parameters obtained from the Gumble model can be used to predict the sprouting of purple nutsedge tubers.
Highlights:
Introduction: Purple nutsedge (Cyperus rotundus L.) is one of the problematic weeds worldwide prevalent in tropical and subtropical regions. Tubers are major tools through which purple nutsedge is propagated, whereas its seeds have a low ability to germinate. Therefore, evaluation of the response of tubers against environmental agents is great of importance to know the germination and emergence time. Germination, in turn, is mostly affected by temperature, among other environmental factors. Various models that are recognized as the Thermal Time model have been introduced to describe the seed germination pattern against temperature. Since predicting the emergence of reproductive organs through the modeling is great of importance for improving the control strategies; the present study was carried out to investigate the response of tuber sprouting of purple nutsedge (Cyperus rotundus) against temperature using thermal time models.
Material and methods: The experiment was carried out as a randomized complete block design with three replications in a germinator. Each replicate was placed on a separate shelf. For each replicate, 15 tubers were placed inside a 20 cm Petri dish on a filter paper and then 100 ml of water was added. The experiment was performed separately for constant temperatures of 10, 15, 20, 25, 30, 35, and 40 °C in absolute darkness. To analyze the data as modeling, five thermal time models were evaluated based on the statistical distributions of normal, Weibull, Gumble, logistic and log logistic. Indices such as R2, RMSE, RMSE%, and AICc were used to evaluate the models.
Results: The results showed that all models predicted the germination response of purple nutsedge tuber with high accuracy (R2 = 0.95). A comparison of models based on AICc values showed significant superiority of the Gumble model over other models. According to this index, there was no difference between logistic and log logistic models with normal. Among the models, Weibull was identified as the most inappropriate model. Different models estimated the final germination (Gmax) between 0.93 to 0.94 (93 to 94%). The base temperature was estimated through different models from 7.10 to 7.47 °C. Among the models, the model based on the Gumble distribution proved the skew to the right of the thermal time and Tm. According to the Gumble model, the thermal time parameters required to reach 50% germination (θT (50)) equals 123.8 ° C day and the maximum temperature for germination at 50% probability (Tc (50)) was estimated to be 46.10 ° C.
Conclusion: the thermal time model based on the Gumble probability distribution was most plausible among the models. Also, a distributed right skewness related to the thermal time and Tm was proved through the Gumble model. The parameters obtained from the Gumble model can be used to predict the sprouting of purple nutsedge tubers.
Highlights:
- Thermal time models were evaluated for prediction of tuber sprouting of purple nutsedge.
- The thermal time model based on the Gumble distribution was superior over the normal distribution.
- Thermal time and Tm for tuber sprouting of purple nutsedge were distributed as right skewness.
Mohammad Hossein Banakar, Hamzeh Amiri, Gholam Hassan Ranjbar, Mohammad Raza Sarafraz Ardakani,
Volume 8, Issue 2 (3-2022)
Volume 8, Issue 2 (3-2022)
Abstract
Extended Abstract
Introduction: Fenugreek, is a medicinal plant that has been considered as a salt tolerant crop. This research was conducted to investigate the effects of salt stress on seedling emergence characteristics and determination of the salt tolerance threshold, declivity of emergence and salt tolerance index of some fenugreek ecotypes.
Material and Methods: Seeds of five ecotypes (Ardestani, Isfahani, hendi, Mashhadi, Neyrizi) were subjected to seven levels of salinity (0.5, 3, 6, 9, 12, 15 and 18 dS/m) in a factorial experiment based on a completely randomized design with three replications. In this research, experimental models (linear, sigmoidal, exponential and multi-component) were used.
Results: Results showed that increasing levels of salinity decreased seedling emergence percentage and rate. In Ardestani and Isfahani ecotypes, increase of salinity up to 3 dS/m had no effect on seedling emergence percentage and thereafter, decreased it, significantly. The maximum seedling emergence percentage (94.62%) belonged to Hendi in control treatment. Hendi ecotype had also the highest emergence percentage (25.81%) at 18 dS/m. Although the highest seedling emergence rate (5.93 per day) belonged to Mashhadi ecotype in control treatment, it didn’t show any significant difference to Hendi, Neyrizi and Isfahani ecotypes. In Ardestani, Mashhadi and Neyrizi ecotypes, seedling length decreased significantly with increasing salinity, but this decrease was not significant in Isfahani ecotype between salinities of 3 and 6 dS/m and also 12 and 15 dS/m. In Hendi ecotype, seedling length at 3 dS/m was similar to control, but higher salinities caused a significant reduction. The maximum value of seedling vigor index (20.44) belonged to Mashhadi and Neyrizi ecotypes in control treatment and Ardestani ecotype had the lowest one (0.39) at 18 dS/m. Results showed that seedling dry weight was first unchanged up to salinity level of 3 dS/m and then gradually decreased with increasing salinity. In Hendi and Neyrizi ecotypes, applying salinities higher than 6 dS/m, gradually decreased seedling dry weight. The salt tolerance threshold of fenugreek for Ardestani, Isfahani, Hindi, Mashhadi and Neyrizi ecotypes was 4.69, 4.90, 7.83, 1.69 and 1.57 dS/m, respectively. Thus, the highest salt tolerance threshold (7.83 dS/m) and the declivity of emergence percentage (7.55%) was obtained from Hendi ecotype and the lowest one from Neyrizi ecotype (1.57 and 4.63 dS/m, respectively). Results of nonlinear models showed that the highest salinity in which 50 percent of seedlings emerged was obtained in Hendi ecotype (14.24 dS/m).
Conclusion: Based on the results, comparing the salt tolerance index of fenugreek ecotypes and also evaluating of some experimental models showed that Hendi ecotype may be introduced as the most tolerant ecotype to salinity stress at the emergence stage to exploit saline soil and water resources.
Highlights:
- Different fenugreek ecotypes in terms of salinity tolerance at seedling emergence stage were compared using some experimental models.
- The salt tolerance threshold, declivity of emergence and also salt tolerance index was reported for some fenugreek ecotypes.
Zahra Rezaei, Zeynab Roein, Atefeh Sabouri, Somayeh Hajinia,
Volume 11, Issue 1 (9-2024)
Volume 11, Issue 1 (9-2024)
Abstract
Extended abstract
Introduction: Seed germination and seedling establishment are the most sensitive stages in the life cycle of a plant. Among the environmental factors, water potential is an important factor affecting the seed germination of various plants. This research aims to evaluate the effects of water potential on germination indices and quantify the effect of water potential the germination responses of Thymus medicinal plant seeds.
Materials and Methods: A factorial experiment was carried out in the form of a completely randomized design with four replications at the laboratories of the Department of Agronomy and Plant Breeding, Ilam University in the winter of 2023. The factors of the experiment included two types of Thymus (Thymus daenensis and T. vulgaris) and water potential stress induced by polyethylene glycol (PEG-6000) at six levels (0, -0.1, -0.3, -0.5, -0.7, and -0.9 MPa).
Results: The results showed as the water potential decreased to -0.1, -0.3, -0.5, and -0.7 MPa, seed germination percentage respectively went down by 8.43, 43.26, 61.80, and 88.76% in T. daenensis and 19.74, 44.08, 61.18 and 92.76% in T. vulgaris compared with water potential stress-free conditions. Also, T. vulgaris did not germinate at a water potential of -0.9 MPa, whereas some seeds of the T. daenensis plant germinated under this condition. The highest germination rate in both T. daenensis and T. vulgaris species was observed under stress-free conditions, and there was significant difference between the species. Four statistical distributions including normal, logistic, log-logistic, and Gumbel, were compared to quantify the germination response of Thymus to water potential. In order to evaluate the models, corrected Akaike information criterion (AICc), the coefficient of determination (R2adj), and root mean square error (RMSE) were used. The lowest AICc index values for T. daenensis were associated with the log-logistic and logistic distributions (-2012 and -2006), and the Gumbel distribution (-1665) in T. vulgaris, suggesting the superior distributions for quantifying Thymus's response to water potential. Estimation of parameters related to the hydrotime model showed that T. daenensis species had a lower hydrotime constant value (θH)(23.91 MPa hour-1) compared with T. vulgaris (28.06 MPa hour-1), which indicated a higher germination rate in T. daenensis. The value of
Conclusions: In general, the results showed that the effects of water potential stress on the germination components of T. vulgaris were greater than those of T. daenensis, and according to the parameters of the hydrotime model, T. daenensis was more tolerant than T. vulgaris.
Highlights:
Introduction: Seed germination and seedling establishment are the most sensitive stages in the life cycle of a plant. Among the environmental factors, water potential is an important factor affecting the seed germination of various plants. This research aims to evaluate the effects of water potential on germination indices and quantify the effect of water potential the germination responses of Thymus medicinal plant seeds.
Materials and Methods: A factorial experiment was carried out in the form of a completely randomized design with four replications at the laboratories of the Department of Agronomy and Plant Breeding, Ilam University in the winter of 2023. The factors of the experiment included two types of Thymus (Thymus daenensis and T. vulgaris) and water potential stress induced by polyethylene glycol (PEG-6000) at six levels (0, -0.1, -0.3, -0.5, -0.7, and -0.9 MPa).
Results: The results showed as the water potential decreased to -0.1, -0.3, -0.5, and -0.7 MPa, seed germination percentage respectively went down by 8.43, 43.26, 61.80, and 88.76% in T. daenensis and 19.74, 44.08, 61.18 and 92.76% in T. vulgaris compared with water potential stress-free conditions. Also, T. vulgaris did not germinate at a water potential of -0.9 MPa, whereas some seeds of the T. daenensis plant germinated under this condition. The highest germination rate in both T. daenensis and T. vulgaris species was observed under stress-free conditions, and there was significant difference between the species. Four statistical distributions including normal, logistic, log-logistic, and Gumbel, were compared to quantify the germination response of Thymus to water potential. In order to evaluate the models, corrected Akaike information criterion (AICc), the coefficient of determination (R2adj), and root mean square error (RMSE) were used. The lowest AICc index values for T. daenensis were associated with the log-logistic and logistic distributions (-2012 and -2006), and the Gumbel distribution (-1665) in T. vulgaris, suggesting the superior distributions for quantifying Thymus's response to water potential. Estimation of parameters related to the hydrotime model showed that T. daenensis species had a lower hydrotime constant value (θH)(23.91 MPa hour-1) compared with T. vulgaris (28.06 MPa hour-1), which indicated a higher germination rate in T. daenensis. The value of
Conclusions: In general, the results showed that the effects of water potential stress on the germination components of T. vulgaris were greater than those of T. daenensis, and according to the parameters of the hydrotime model, T. daenensis was more tolerant than T. vulgaris.
Highlights:
- The best distribution in the hydrotime model was determined for predicting Thymus daenensis and Thymus vulgaris seed germination under water potential stress conditions.
- The threshold level of water potential stress causing a significant decrease in the germination components of Thymus daenensis and Thymus vulgaris was determined.
- Based on the hydrotime model, Thymus species was determined to be more tolerant to water potential stress during germination.
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