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Showing 3 results for Alternating Temperature
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 (9-2019)
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 Velvetleaf (Abutilon theophrasti) Maneh-Samalghan Ecotype Seed Response to Temperature and Light
Mahdi Asadi, Majid Rahimizadeh,
Volume 8, Issue 1 (9-2021)
Abstract

Extended abstract
Introduction: Velvetleaf is one of the most important weeds of cotton, corn, tomato, and soybean fields. Certainly, knowledge of weed seed response to environmental factors (light and temperature) is essential for better understanding the germination mechanism and establishment patterns of weeds community. The present study aimed to evaluate the interaction between light regimes and alternate temperature on the seed germination of velvetleaf.
Materials and Methods: The experiment was conducted in 2015 at the plant physiology laboratory of Bojnourd Branch, IAU. This study was performed as a factorial experiment based on a completely randomized design (CRD) with four replications. The treatments were temperature regimes at four levels (constant temperatures 25°C, alternating temperatures 25-15, 30-20 and 35-25°C) and photoperiod treatments at three levels (continuous darkness, 12-12 light and dark and 16-8 light and dark). Germination percentage, germination rate, germination uniformity, time to 10% germination, and time to 90% germination were evaluated by the Germin program.
Results: The results showed that all traits were affected by temperature and light. Velvetleaf seeds germinated better in the presence of light and alternating temperature. The percentage and rate of germination increased as temperature rised to 30°c and then decreased. However, seed reaction to the night temperature was higher than that of the day temperature. The highest germination percent (98 percent) was achieved under alternating temperature 25-15°C with 12-12h light-dark. In this study, the lowest time required for 10% and 90% germination and highest germination uniformity were observed under alternating temperatures 30-20°C in darkness.
Conclusion: According to the results of this experiment, velvetleaf seeds are able to germinate in a wide range of light and temperature conditions, although they germinate better in the presence of light and alternate temperatures. Therefore, plowing with a moldboard plow can stimulate germination and drain the soil seed bank.

Highlights:
1- Since light stimulates the germination of velvetleaf seeds, so no-tillage system is able to control this weed.
2- Increasing the environment temperature reduces the chance of germination of velvetleaf seeds.             


Study on optimal temperature, light, duration, and substrate conditions for tree Salicornia species seed germination
Aidin Hamidi, Bita Oskuoei, Ali Shayanfar,
Volume 11, Issue 2 (3-2025)
Abstract
Extended abstract
Introduction: Seed germination has always been of interest to plant ecologists due to its key role in plant population establishment. Also, due to the importance of this process in seed certification, this phenomenon is of interest to control and seed certification experts. Temperature, access to sufficient humidity, and the presence of light in light-sensitive species for seed germination are considered to be the most important natural factors for seed germination. Additionally, the time required for germination and sufficient early seedling growth are important to determine the potential seed germination. Therefore, determining the temperature, the need or lack of light, as well as the time required for germination and the suitable substrate for planting seeds, are of great importance in the process of seed certification laboratory tests.
Materials and Methods: In order to determine the optimal conditions for seed germination of three species of Salicornia persica, S. persepolitana, and S. bigelovi, the seeds were grown under three constant temperatures of 20, 25, and alternating temperatures of 20-25 °C (8-16 hours light-dark), two culture beds (top-of-paper (TP) and between-paper (BP)), and two germination periods of 7 and 12 days.
Results: The results showed that the seeds of S. bigelovi species had the highest percentage of normal seedlings at 25 °C constant temperature for 7 days in the top-of-paper (TP) substrate. Also, the seeds of S. persica had the highest percentage of normal seedlings at 20-25 °C alternating temperature for 7 days in the top-of-paper (TP) substrate. S. persepolitana seeds at 25 °C constant temperature for 7 days on the top-of-paper (TP) substrate had the highest percentage of normal seedlings. S. persica, S. bigelovi, and S. persepolitana seeds had a higher percentage of normal seedlings in both germination durations and temperatures, respectively.
Conclusions: The results of this research showed that the seeds of the studied Salicornia species did not require light for germination. Also, in terms of temperature requirements, the time required for germination, and the substrate, they differed from each other. The seeds of S. persica reached the maximum percentage of normal seedlings at 20-25 °C alternating temperatures. The seeds of S. bigelovi and S. persica species needed a shorter time to reach the maximum percentage of normal seedlings, while the seeds of S. persepolitana needed a longer time to germinate and reach the maximum percentage of normal seedlings. Therefore, it was determined that the best temperature, duration, and substrate to achieve the maximum percentage of normal seedlings in the standard seed germination test were 25 °C for 7 days and top-of-paper (TP) substrate for S. bigelovi, 20-25 °C alternating temperature for 7 days and top-of-paper (TP) substrate for S. persica, and 20 °C constant temperature for 7 days and top-of-paper (TP) substrate for S. persepolitana species.

Highlights:
  1. Light was not necessary for the studied Salicornia species seeds' germination.
  2. The studied Salicornia species seeds' germination response to optimum temperature was different.
  3. The studied Salicornia species seeds' optimum germination duration was different.

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