Iranian Journal of Seed Research

Introduction: Drought stress is one of the major problems in sugar beet production in Iran, and is the most important limiting factor for germination and establishment of sugar beet in the early stages of growth. Seed priming with chemical, nutrient elements or pre-chilling techniques are the most effective methods to improve germination percentage and speed, leading to uniform and tolerant seedlings in adverse environmental conditions.

Material and Methods:  In order to assess the effect of cold stratification and HCl treatments on the germination of sugar beet seed, cv. Ekbatan, under drought stress conditions, a RCBD factorial experiment with three replications was conducted in Seed Science and Technology Lab of Shahrekord University.  The first factor was stratification in two levels; the second factor was  seven levels of pretreatments including 2, 4 and 6 hours’ soaking in water and 0.03 HCL accompanied with control, and the third factor was four drought levels (control, -2, -4, -6 bar).

Result: Compared with the control, seed germination percentage and germination rate increased by at least 5-fold, relative germination by 50% and root and shoot length by 10%, due to stratification and duration of exposure to HCl treatments. With no stratification, germination traits increased with increases in exposure time in acid, and the highest values were obtained for the seeds exposed to HCl 0.03 normal for 6 hours. Although under optimal conditions, the effect of HCl was compensated for by stratification, in drought conditions, the highest values ​​were observed in stratified seeds and those placed in acid.

Conclusions: Since successful establishment of sugar beet seedlings at drought stress conditions is critical to achieving optimum density and yield, application of stratification treatments for one week and seed exposure to HCl increased the seed performance under stress conditions. This trend continued to increase with drought stress intensity, and placement of seeds in acid doubled seed germination in -2 bar drought conditions, which continued by 4 times in -6 bar, compared with stratified control seeds. Compared to separate application of the treatments, application of stratification and HCl treatments had synergistic effects on sugar beet seed performance, especially under drought stress conditions.

Extended abstract
Introduction: Gundelia tournefortii (L.) is a species of Irano-Turanian origin belonging to the Asteraceae family. The strongly lignified disseminule from the secondary capitulum on seeds causes certain challenges for the propagation of this plant. This study aimed to evaluate the best methods for breaking seed dormancy to enable large-scale production of Gundelia tournefortii (L.).
Materials and Methods: Initially, the interactive effects of various scarification methods (hot water, hydrochloric acid, scalpel, and sandpaper) with cold stratification (0, 1, 2, and 3 weeks) or GA3 (0, 250, 500, and 1000 ppm) on seed dormancy breaking were investigated in two separate factorial experiments. Subsequently, the combined effect of GA3 and cold stratification on seed dormancy breaking of seeds scarified with a scalpel was assessed in a third experiment.
Results: The results indicated that all scarification methods significantly increased the emergence percentage and growth parameters of plantlets. Cold stratification and GA3 treatments enhanced these attributes more effectively in plantlets grown from seeds scarified with a scalpel or sandpaper compared to seeds treated with acid or hot water. In the first experiment, the highest emergence percentage (77%) was achieved from seeds scarified with a scalpel combined with 3 weeks of cold stratification. In the second experiment, the maximum emergence percentage (77%), plantlet length (17 cm), and the minimum mean emergence time (11 days) were obtained from seeds scarified with a scalpel and treated with 500 ppm GA3. The results of the third experiment showed that the application of GA3 reduced the required duration of cold stratification by approximately 1 week to achieve the maximum emergence percentage, dry weight of plantlets, and the minimum mean emergence time.
Conclusions: The findings demonstrate that Gundelia tournefortii (L.) seeds exhibit a combination of physical and non-deep physiological dormancy. The highest emergence percentage (81.5%) and the lowest mean emergence time (8 days) can be achieved through scarification with a scalpel followed by cold stratification or GA3 treatment.

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