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Abstract Detail



Ecological Section

Akhalkatsi, Maia [1], Togonidze, Natalia [2], Smith, William K.  [3].

Seed germination requirements in two dominant treeline species – Betula litwinowii and Rhododendron caucasicum, in the Central Greater Caucasus.

In the Central Greater Caucasus Mountains, Georgia, Betula litwinowii occurs on north-facing slopes, forms the alpine timberline, and reaches its treeline limit only when associated with the broadleaf evergreen shrub, Rhododendron caucasicum. We studied seed germination requirements to temperature and light at different developmental phases of seed imbibition, germination and seedling development under constant environmental conditions in both species. The germination tests at different light conditions, in the permanent darkness and day-light illumination with a photoperiod 15 h, under artificial lightening, have shown that no germination has occurred in R. caucasicum in the dark. B. litwinowii was germinated in both treatments. Germination tests at different temperature have shown that highest germination percentage occurred at room temperature in both species. The duration of phenological phases of seed imbibition, germination and seedling performance differed significantly in investigated species. Seed imbibition was prolonged in R. caucasicum (3 weeks), but germination and cotyledon formation were happened very rapidly (2 days). Seeds of B. litwinowii were already imbibed after 48 h and were germinated after 4 days. Although, cotyledon formation and seedling grows need about 2 weeks. Radicle of the birch develops root hairs soon after emergence and is very sensitive to drying. Seedlings isolated from Petri dish dry up already after 3 min. Radicle of R. caucasicum has no root hairs until first leaf develops and seedlings are more resistant to drying. They remain viable several hours in dry condition. We suppose that seed germination requirements of studied species determine their distribution patter in natural environment. R. caucasicum grows in better illuminated habitats under open subalpine krummholz and above treeline. But, it does not enter birch forest with closed canopy at lower elevations. Shaded and moist microhabitat under Rhododendron shrubs may facilitate successful establishment of birch seedlings at the treeline. There was no correlation among seed number in the soil, germination ability of seeds harvesting in different study sites and seedling abundance in the sites. This might be indicative that the number of produced seeds and their quality are not the main determinants to successful establishment of seedlings and maintenance of the plant community structure, but in all probability, ecological “facilitation” in the germination and establishment process created by the presence of other plant species and favorable microsites plays more important role in plant propagation and maintenance of community structure.


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1 - Institute Of Botany, Ilia State University, Plant Genetic Resources, K. Cholokashvili Ave. 3/5, Tblisi, Republic Of Georgia, 0162, Georgia
2 - Institute of Botany Ilia State University, Plant Genetic Resources, Cholokashvili Ave. 3/5, Tbilisi, 0162, Republic of Georgia
3 - Wake Forest University, DEPT BIOLOGY, REYNOLDA STATION, PO BOX 7325, WINSTON-SALEM, NC, 27109-7325, USA

Keywords:
Treeline
seed bank
birch
Rhododendron.

Presentation Type: Poster:Posters for Sections
Session: P
Location: Eyrie/Boise Centre
Date: Monday, July 28th, 2014
Time: 5:30 PM
Number: PEC031
Abstract ID:161
Candidate for Awards:None


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