Document Type : Original Article

Authors

• Fatemeh Pirmoradi ¹
• Abdelmehdi Bakhshandeh ²
• SeyedAmir Moosavi ³
• Mohammad Hossain Gharineh ²
• Ali Moshatati ³

¹ Master student of seed science and technology, Department of Plant Production and Genetics, Agricultural Sciences and Natural Resources University of Khuzestan

² Professor, Department of Plant Production and Genetics, Agricultural Sciences and Natural Resources University of Khuzestan

³ Associate Professor, Department of Plant Production and Genetics, Agricultural Sciences and Natural Resources University of Khuzestan

Abstract

Introduction
Seeds play a crucial role in the reproduction and dispersal of plants. Ziziphus nummularia is a valuable plant species suitable for cultivation in arid and semi-arid regions of Iran. This plant can provide ground cover, increase biodiversity, and produce raw materials for the pharmaceutical industry Z. nummularia is well-adapted to dry and low-rainfall areas and can be cultivated and utilized as a multipurpose plant for forest restoration and the production of valuable medicinal materials. Successful planting and establishment of a plant species by humans depend on the availability of high-quality seeds and the necessary knowledge of its response to environmental stresses. Water resource limitations and changes in precipitation patterns and distribution due to climate change are among the most serious challenges facing most regions of the world. For the propagation of valuable plants such Z. nummularia, it is necessary to investigate and study the role of these stresses, particularly during the germination stage, which is one of the most sensitive stages of plant life. The present study was conducted to investigate the simultaneous effect of temperature and salinity stress on the germination of Z. nummularia seeds.
Materials and methods
The present study was conducted to investigate the simultaneous effect of temperature and drought stress on the germination of sandy ziziphus seeds. The experiment was carried out as a factorial based on a completely randomized design with three replications. The experimental treatments included germination temperatures (5, 10, 15, 20, 25, 30, 35 and 40 degrees Celsius) and water stress levels (-0.2, -0.4, -0.6, -0.8, -1, -1.2, -1.4 MPa) that were created using polyethylene glycol 6000. Each experimental unit consisted of a petri dish with a diameter of 10 cm and 5 ml of osmotic solution was poured into each container. There were 25 sandy ziziphus seeds in each petri dish and they were transferred to germinators with a specified temperature setting for germination test. Each experimental treatment was repeated three times. The germination characteristics of the seeds included: final germination percentage, germination speed coefficient, mean germination time and germination index, which were calculated based on counting the germinated seeds 24 hours after the start of the experiment and every day at the same fixed time. Seeds with a radicle length of 2 mm or more were considered germinated. Also, the length of the root and stem, as well as the seed vigor, were measured and reported.
Results and discussion
The results of this experiment showed that under non-water stress conditions, seed germination began at 15°C up to a water potential of -0.4 MPa. With increasing water stress to -0.6 MPa, seeds were no longer able to germinate. Under non-water stress conditions, maximum germination was observed at 25°C (66.54%), which showed no significant difference from germination at 20 (52%), 30 (33.53%), and 35 °C (66.52%). At a water stress level of -0.2 MPa, Z. nummularia seed germination at 20, 25, 30, and 35°C was 66.28%, 66.48%, 66.44%, and 33.41%, respectively. The results showed that non-water stress conditions and 25°C resulted in the highest germination rate (24.42 seeds per day). With increasing water stress intensity to -0.2 MPa, the germination rate index significantly decreased at all temperature levels from 15 to 40°C, with a significant decrease at 25°C. The germination rate index was minimized at a water stress level of -0.8 MPa. The highest vigor index of Z. nummularia seeds was observed under non-water stress conditions and at 25°C (8.172). Increasing water stress level to -0.2 MPa resulted in a significant decrease in the vigor index, especially at 25°C (9.142).
Conclusion
Z. nummularia seed germination exhibits differential sensitivity to water stress under fluctuating temperature conditions. Z. nummularia was unable to germinate at temperatures below 10°C, and with increasing temperatures to 15 and 20°C, germination showed a significant increase in both percentage and germination index. Water stress beyond -0.2 MPa caused a significant decrease in most germination indices, including germination percentage, germination rate index, germination index, radicle length, hypocotyl length, and seedling vigor index (length), reaching a minimum at -0.8 MPa and resulting in germination inhibition.

Keywords

• Osmotic potential
• Regression Models
• Vigor

Main Subjects

• Drought stress