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found in seeds collected from Maçka provenance at 1234 m in Soil + Peat (SP) growth medium. While the seeds collected from Zigana provenance at 1744 m also had a high germination percentage of 82.5% in Soil + Peat (SP), the seeds collected from Zafanos provenance (592 m)was determined in Soil (S) medium with a high germination percentage of 73.1%. Rhododendrons typically exhibit their best growth in forest soil and in soils with rich organic matter (Clarke 1982; Reiley 1995; Brenzel 1997). A similar study conducted with Rhododendron ponticum also demonstrated that the survival rate of the seedlings was better in soil rich in organic matter (Var and Dincer 2006).
Based on the analysis of variance results, seedling plant and root length values were statistically significant (P <0.01). The seedlings developed from the seeds collected from Zafanos provenance at 592 m exhibited a higher size and root length when compared to the seeds collected in other provenances (Table 3). Plant height and root lengths of the seedlings from the seeds collected from high altitudes were determined lower. Similar results were obtained in a study conducted with Carpinus betulus seeds collected from different populations in different altitudes. It was reported that the lowest seedling heights developed from seeds obtained from populations at high altitudes (Hatipoglu 2013).
The maximum seedling height (6.91 cm) was observed in seeds collected at Zafanos provenance, however there were no significant differences between the seedling sizes of seeds collected from Macka and Zigana provenances, which both had high altitudes. When the length of seedling roots was examined, it was observed that there were three different groups. The seeds with the highest weight of 1000g and that demonstrated the most successful germination, that is, those collected from the Macka provenance at 1234 m, provided the lowest seedling height and root length. Rhododendrons, whose natural habitats are generally the mountainous, have higher seed weight and germination success at higher provenance. However, outside the growing areas, these seedlings developed at lower altitudes, had lower height and root length. At the same time it was determined that the seedlings from Zafanos provenance at 592 m, with the lowest seed weight and germination success, had the best height and root development. It was found that seed weights and germination success were not positively correlated with the seedling size and root development.
Rhododendron ponticum, a shrub that offers unique attributes in planting schemes due to its form, foliage and flower properties could be effective in many areas in addition to its aesthetical properties. Due to their visual and functional qualities, they are among species that need to be cultivated and propagated, and their use in landscape architecture planting designs should be promoted. In the present study, the effect of different provenances on germination in Rhododendron ponticum seed cultivation was investigated and it was determined that seeds from high altitudes possessed greater germination success. In addition, germination in soil and peat media has been more successful. Although the germination success of high altitude seeds is high, it should be taken into consideration that seedling height and root lengths are not better.
This study is a part of the project (with code number 9733) supported by the Scientific Research Projects Department, Karadeniz Technical University.
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