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Quantifying Germination response to temperature of hibiscus tea (Hibiscus sabdariffa)
Maral Etesami, Ali Rahemi Karizaki, Benyamin Torabi,
Volume 2, Issue 1 ((Spring and Summer) 2015)
Abstract

Germination rate and percentage are maximal at optimum temperatures and then reach to zero at the base and ceiling temperatures. An experiment was conducted at the Gonbad Kavous University laboratory as a completely randomized design with 4 replications, to study germination response to temperature and evaluation of cardinal temperature on germination rate and percentage of hibiscus tea. Seeds germinated at 0 to 45 0C by 5 0C intervals. Results indicated that the response of germination percentage and rate adequately fitted with dent like and segmented functions, continually. Base and ceiling temperatures were 1.66 and 43.33 0C for germination percentage and 4.53 and 42.95 0C for germination rate. Optimum temperatures were 30 0C for germination rate and 11.56 and 33.63 0C for germination percentage. In conclusion, base and favorable temperatures for hibiscus tea seeds were 11 and 35 0C. Therefore it is recommended to cultivate at Gonbad kavous weather condition.


Effect of Temperature and Light on Germination Characteristics of Japanese Morning Glory (Ipomoea nil): Determination of Cardinal Temperatures of Germination
Hosein Sarani, Ebrahim Izadi, Ali Ghanbari, Ali Rahemi,
Volume 6, Issue 1 ((Spring and Summer) 2019)
Abstract


Extended Abstract
Introduction: In recent years, Japanese morning glory has been recognized as a new weed in some soybean cultivation areas in the Province of Golestan. Japanese morning glory, an annual herbaceous plant, belongs to Convolvulaceae family. Germination is the first step in the competitiveness of a weed in an ecological niche. Among the factors influencing seed germination, temperature and light are the most important environmental factors. The relationship between temperature and germination rate is mainly determined by nonlinear regression, and various models such as dent-like, segmented, beta, and second-order major models are used for this purpose. In this study, we examined the aspects of germination biology of this weed under the influence of temperature and light.
Materials and Methods: In order to investigate the effect of temperature and light on germination of Japanese morning glory, two separate experiments were conducted. Treatments included constant temperature at 7 levels (10, 15, 20, 25, 30, 35, 40) in the first experiment and alternating temperature at 6 levels (30/25, 10/15, 30/20, 35/25, 40/30, 45/35) and light conditions (14 hours of brightness 250 μmoles/m-2-sec-1) and darkness in the second experiment based on a completely randomized design with four replications. The number of germinated seeds was taken up to 4 days after stopping germination every day. Percentage and speed of germination and time reaching 50% germination were calculated. Three models of dent-like, segmented lines and beta were used to determine the cardinal temperature between the temperature and germination rate.
Results: The results showed that temperature had a significant effect on percentage, speed and time taken to reach 50% (D50) of germination of Japanese morning glory. The highest percentage of germination (95%) and germination rate (19.80 seeds per day) were observed in the alternating temperature of 20/30 ° C treatment, respectively. The lowest percentage of germination (83.33%) was observed at alternating temperatures 25/35 °C, and the lowest germination rate (15.10 seeds per day) was observed at 10-20 °C. The segmented lines, dent-like and beta were best fit based on the highest R2adj 0.95, 0.96 and 0.95, respectively. Light had no significant effect on germination, so that germination occurred under both light and dark conditions. According to the results, Japanese morning glory is able to germinate at a wide range of constant and alternating temperatures, although germination is faster at warmer temperatures. On the other hand, the lack of light for germination is another advantage that increases germination, competition, and expansion in agronomic environments.
Conclusion: The findings of the present study suggest that the highest percentage of germination and rate of germination were observed in alternating temperatures of 20/30 °C respectively. Among the nonlinear regression models, the dent-like model represented the best model for describing the germination rate against the temperature in Japanese morning glory. It seems that this weed has better germination at warmer temperatures. Probably from mid-spring following warmer weather, and upon the availability of water, this weed is in a good situation to germinate and compete. It was also found that light had no significant effect on the germination of this weed.

Highlights:
  1. Non-photoblastic seeds
  2. Superiority of dent-like model for predicting germination of Japanese morning glory

Evaluation of the allelopathic potential of barley (Hordeum spontaneum) on the germination morphophysiological, and biochemical characteristics of cress (Lepidium sativum)
Abdolhadi Mashreghi, Ebrahim Gholamalipour Alamdari, Ziba Avarseji, Ali Rahemi Karizaki,
Volume 11, Issue 1 ((Spring and Summer) 2024)
Abstract
Extended abstract
Introduction: Chemical compounds in plants include primary or secondary compounds. The allelopathic compounds are mainly of the secondary type, which are released by ways such as leaching, decomposition of plant residues, volatilization, and root exudation. Plants with allelopathic properties have a negative or even positive effect on the germination and growth of other plants by releasing substances in their surroundings. These effects depend on the type of organ, concentration, plant growth location, plant physiological maturity, etc.
Materials and Methods: An experiment was conducted to evaluate the allelopathic potential of Hordeum spontaneum weed on some germination, morphophysiological, and biochemical characteristics of a reference plant sensitive to the allelochemicals of cress (Lepidium sativum) in 2021. This experiment was conducted in the form of a completely randomized design with three replications. The treatments included different concentrations of H. spontaneum aqueous extract at 11 levels (0, 10, 20, 30, 40, 50, 60, 70, 80, 90, and 100%).
Results: The results showed that different concentrations of H. spontaneum aqueous extract had a significant decreasing effect on the percentage and rate of seed germination, radicle and shoot length, seedling length vigor index, radicle and shoot dry weight, as well as photosynthetic pigments (i.e., chlorophyll a, b, total, and carotenoids) of cress. Their effectiveness was dependent on the concentration threshold of the aqueous extract. In contrast, the amino acid content of proline, soluble sugars, ion leakage, catalase activity, guaiacol peroxidase enzymes, the concentration of malondialdehyde, and phenolic compounds showed an increasing trend compared with the control. In most cases, the highest increase of these compounds was obtained at the 100% aqueous extract concentration of H. spontaneum. This indicates oxidative stress and high cytotoxicity caused by harmful compounds present in the aqueous extract of H. spontaneum.
Conclusions: According to the results of this experiment, it can be stated that the aqueous extract of H. spontaneum, due to its allelopathic properties, prevented the germination and seedling growth of L. sativum. Therefore, according to the proof of the harmful effect of H. spontaneum and its high biomass, it may be possible to introduce the bioactive compounds present in this plant for the production of environmentally friendly herbicides or even the potential to produce new formulations of synthetic herbicides in case its positive effect on other species is proven.

Highlights:
  1. The difference in the effect of different concentrations of Hordeum spontaneum weed aqueous extract on the germination and seedling growth of a reference plant sensitive to the allelochemicals of Lepidium sativum is related to their concentration threshold.
  2. The significant decrease in germination characteristics and photosynthetic pigments of L. sativum, indicates the intensity of oxidative stress caused by the harmful compounds in the aqueous extract of H. spontaneum.
  3. The allelopathic characteristics of H. spontaneum weed can be a suitable candidate for the production of biological herbicides.

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