Background and Objectives: In order to adapt to different ecological conditions, trees produce different variations by changing their morphological traits. In terms of tolerance to environmental stresses such as drought, there are often differences in the provenance of the species. Since there is a great variety of provenance in species, it can help us to choose the most tolerant provenance, which will lead to more success in forest restoration implementation programs. Considering that the mountain almond is one of the valuable and important shrub species with a wide ecological range in Iran, especially in the Zagros and Iranian-Turanian regions, also, the poor condition of the Zagros Forest ecosystem and the need to use shrub species, have caused more attention to this species in forestry. Therefore, this research aimed to investigate the effect of seed origin on the germination and growth of almond seedlings (Amygdalus scoparia) under different irrigation regimes (once a week and once every two weeks) in Fars province.
Materials and Methods: For this purpose, the seeds of the target species were collected from five habitats with different altitudes above sea level in Fars province, namely Keshvari, Sirj, Horgan, Haji Abad 1 and Haji Abad 2, and after three months of stratification treatment in moist sand at 4 ºC, the seeds were transferred to culture medium and planted in three replicates in a completely randomized design. So that the treated seeds were planted in the same pots according to their origin. Then, they were equally cared for and irrigated. It should be noted that the watering schedule included once a week and once every two weeks, but the amount of water used was completely the same between the experimental materials in each watering schedule. After the start of germination, the number of germinated seeds in each pot and after four months, survival traits, length of shoot and root, number of leaves, fresh and dry weight of shoot and root on seedlings were measured and recorded. Germination related traits included germination percentage, germination speed, average germination time and seed vigor index. Analysis of variance was used with factorial model and in the form of completely randomized design. Grouping of means was done by Duncan's multiple range test.
Results: Results of variance analysis showed that the effect of seed origin on germination percentage, average germination time, seed vigor index, shoot length, (P value <0.01) and root length and number of leaves (P value <0.05) was significant. Irrigation period also showed a significant effect on germination percentage, average germination time, seed vigor index, survival and shoot length (P value <0.01). Also, the interaction effect of seed origin and irrigation cycle on shoot length was significant. Results of the comparison of average effect of seed origin on the studied traits showed that the seeds obtained from Horgan origin (90%) and then Keshvari (85.3%) had the highest germination percentage. In terms of the average germination time, the Haji Abad 1, Haji Abad 2 and Keshvari had the highest percentage. Also, Keshvari and Haji Abad 1 and 2 showed the highest average seed vigor index, shoot length and root length. Regarding the number of leaves trait, the seedlings obtained from Haji Abad 2 source had the lowest average, but no significant difference was observed between the other four sources in this regard. Results of the comparison of average effect of irrigation cycle on the characteristics of germination percentage, average germination time, seed vigor index, survival, and shoot length (89.6%, 82.28, 38.08, 22% and 19.23 cm, respectively) indicated that once a week irrigation significantly increased the average germination time and decreased and increased other traits. Results of the comparison of the average interaction effect of seed origin and irrigation frequency showed that maximum length of the aerial part (27.12 cm) was related to Haji Abad 1 with weekly irrigation.
Conclusion: Results of the present study showed that the effect of seed origin on the longitudinal growth characteristics of root and stem, as well as germination percentage, average germination time, seed germ, viability and number of leaves had a significant effect. Results of the present research also indicated that generally, the seedlings obtained from the seeds collected from Haji Abad 1 with a lower altitude than the other studied provenance (1650 m above sea level) and after that, Horgan (altitude 1950 m above sea level) and Keshvari (altitude of 2400 m above sea level) had better germination, growth and establishment. The reason for this can be related to the altitude conditions or the latitude and longitude of the origin of the seed. Considering that the seed origin of Haji Abad and Horgan are placed in a lower altitude class; probably the resulting climatic conditions have caused a difference in the average growth of the seedlings obtained from the seeds of these two origins compared to other provenances. Regarding the lack of growth observed in the seedlings obtained from the source at an altitude of 2400 m above sea level in the present research, it can be said that considering that the mountain almond species is among the trees whose main habitat is sandy soil and environment Fakir is one of the nutrients, so probably the resistance of the plant against harsh environmental conditions, as well as further development of the root system in seedlings located at higher altitudes, especially in the tree border for better absorption of nutrients and water, has caused the seedlings to Higher regions (country origin) do not show significant growth reduction compared to other populations. Finally, based on the findings of the present research, it is suggested that due to the significant decrease in the yield of the seeds of Sirj and Haji Abad 2 sources, the use of Haji Abad 1 seeds for the production of mountain almond seedlings in the study area should be prioritized. After that, Horgan and Keshvari provenances are recommended.