جستجوی مقالات مرتبط با کلیدواژه "hydrotime" در نشریات گروه "زراعت"

Environmental stresses, especially drought and salinity stresses are considered as inhibitors of plant growth and development. The salinity stress cause delay in germination, decrease in the rate and percentage of germination and delay in the emergence of roots and stems in the germination stage. It seems that if seed could pass through the germination stage under stress conditions, the seedling will have more opportunity to grow and develop, and will have the higher ability to tolerate and overcome adverse environmental conditions. This greatly depends on the biochemical and physiological structures of the seedlings. The response is also species and genotypes dependent and depends on the length and severity of the salinity, the age, and stage of development. Differences in the salt tolerance have variation among species within a genus, and of genotypes within a species. black caraway (Nigella sativa L.) is an annual plant with valuable medicinal properties belong to Ranunculaceae family. Because Black caraway growth is slow at the beginning of the season, and on the other hand, salinity and drought are some limiting and effective factors on germination and other stages of plant growth, the aim of this study was to evaluate different N. sativa ecotypes in terms of tolerance to salinity and drought.

In order to investigate the effects of salinity and drought stress on seed germination factors of fourteen black caraway, two separate experiments were carried out in a completely randomized design in the Seed Technology Laboratory of the University of Tehran in 2018. The treatments consisted of fourteen black caraway ecotypes (Ashkzar, Arak, Isfahan, Eqlid, Bejestan, Khaf, Khomeini Shahr, Razan, Zabol 1, Zabol 2, Sarayan, Semirum, Gardmiran, Hamedan), six salinity stress levels (0 , 40, 80, 120, 160 and 200 mM) and four levels of drought stress (0, 0.3, -0.6 and -0.9 MPa) with four replicates in each level. Salinity stress levels were due to different concentrations of sodium chloride and levels of drought stress were due to different concentrations of polyethylene glycol 6000. Distilled water was used to create a zero stress level (control treatment) in both experiments. To conduct the experiments, 50 seeds were placed on filter paper in 8 cm diameter Petri dishes containing 7 mL of each solution. Petri dishes were kept in the growth chamber at a constant temperature of 20°C. The number of seeds germinated was recorded daily until no germination was observed for two consecutive days. The Germin program was used to calculate germination percentage and rate of germination. In addition, to illustrate the germination response to drought stress, the hydrotime model was used.

salinity experiment; The highest Ymax (germination percentage) was found in Razan, Arak, and Ashkzar ecotypes (99.5, 99.33 and 99.16% respectively) and the lowest in Khomeini-e-Shahr ecotype (85.83%). The highest salinity tolerance threshold (X0) was detected in Semirum ecotype (37.17 mM). Arak ecotype had the highest rate of germination (0.013 per hour) in salinity conditions. Thus, Semirom ecotype was the most tolerance ecotype due to the higher salinity tolerance threshold. Drought experiment; The minimum hydrotime constant (θH= 284.040 MPa h) was related to the Bejestan ecotype, and the lowest water potential (Ψb(50)= -0.563 MP ) was observed in the Isfahan ecotype. Since there is a positive correlation between the less water potential )Ψb(50) ( and the emergence percentage and rate of seedling emergence, the Isfahan ecotype was the most tolerant among biotypes that were studied.

In general, the results of these experiments showed that salinity and drought stresses reduced the percentage and rate of germination. Germination percentage response shape and germination rate were different between various ecotypes. Hydrotime model and salinity regression have high ability in separating ecotypes for germination components. The Bejestan and the Isfahan ecotypes are recommended for cultivation in drought conditions. In salt stress conditions, the Semirom ecotype was the most tolerant ecotype among ecotypes.

This research was conducted to investigate the effects of different seed coating treatments on the seed germination of canola under drought and salinity stresses. In order to, two factorial experiments were conducted based on completely randomized design with four replications in laboratory. In both experiments, one of the factors were 10 different seed coating treatments. The second factor was different in two experiments: in the first experiment, the levels of drought stress of 0, -0.8, -1, and -1.2 MPa were considered, and in the second experiment, the levels of salinity stress of 0, 7, 14 and 21 ds/m NaCl were investigated. Results indicated that the lowest hydrotime constant (θH) were observed in T9 (22.627 MPa h), T3 (22.538 MPa h), and T6 (22.263 MPa h). The lowest base water potential (Ψb (50)) were belonged to T4 (-1.332 MPa) and T1 (-1.324 MPa). The maximum of germination percentage under salinity stress (Gmax) was observed in T2 (86.75%). The highest threshold to salinity tolerance (Xo) was belonged to T3 (16.38 ds/m). The highest germination rate was belonged to T3 in all levels of salinity. Totally, seed coating treatments of T3, T6 and T9 were the best treatments under drought stress and T3 was the best treatment under salinity stress.

Egyptian spinach (Corchorus olitorius L.) and Asian spiderflower (Cleome viscosa L.) are two of most important weeds in Khouzestan province corn fields. This experiment was conducted to quantifying the effect of osmotic and salt stress on germination of these weeds. In order to describing effect of reduced water potential on germination of these weeds solutions were prepared with osmotic potentials of 0, -0.2, -0.4, -0.6, -0.8 and -1.0 MPa by dissolving appropriate amounts of polyethylene glycol 6000 in distilled water. Also, Water solutions with salinity of 0, 50, 100, 150, 200, 250, 300, 400 and 500 mM were prepared by dissolving NaCl in distilled water. The hydrotime constant (θH), the base or threshold water potential (Ψb(0)) and the median base water potential (Ψb(50)) of these weeds were as follows: C. viscose (14.30 MPa h, -1.32 and 0.89 MPa) and C. olitorius (11.85, -1.13 and -0.88 MPa), respectively. Threshold response of 50% maximum germination reduction to salinity of C. viscose and C. olitorius were 246.80 mM and 217.00 mM, respectively. Totally, seed germination of C. viscose and C. olitorius were partially tolerate and tolerant to osmotic stress and salinity, respectively.

Hydrotime analysis of seed lots allows them to be ranked them according to their potential for successful emergence. An experiment was done on 10 wheat seed lots (N-80-19 cv) to evaluate water potential for determining seed vigor by hydrotime analysis in research field and seed research laboratory on the Gorgan University of Agricultural Sciences and Natural Resources. Seed lots were planted in complete block design whit three replications in field. Water potential was created with PEG6000 at seven levels (0, -0.3, -0.6, -0.9, -1.2, -1.5, and -1.8 MPa). Maximum germination percent for all seed lots were same. Because there were significant differences in maximum emergence percent in field for seed lots it was demonstrated that seed lots vigor were significantly different. According to hydrotime model's parameters, the seed lots that had more emergence their hydrotime constant (θH) were lower, but their base water potential (Ψb(50)) were higher. Uniformity constant (σψb) for all seed lots were same. Unlike the maximum germination percent result, the hydrotime model output results showed that there is difference in terms of seed lots vigor among this study's seed lots. This study results demonstrate that hydrotime model has a great ability in determining wheat seed lots vigor. This model can predict emergence percentage in stressful situations.