Reproductive trait variability and seed germination responses to electric field and low-dose gamma irradiation in Larix decidua Mill.

Larix decidua Mill. (European larch) is an ecologically and economically important deciduous conifer in European mountain ecosystems, whose regeneration success depends on reproductive trait variability and seed physiological quality. Under ongoing climate change, understanding provenance-related differences and identifying effective, environmentally safe pre-sowing treatments are increasingly important. This study assessed the phenotypic variability of cones and seeds across seven geographic provenances of L. decidua established in the Baciu seed orchard (Romania) and evaluated seed germination responses to physical stimulation using electric field exposure and low-dose gamma irradiation. Significant differences among provenances were observed for cone morphology and seed biometric traits, including seed weight, size, and number of seeds per cone. Provenances from Sinaia and Brașov V.P. exhibited the highest mean seed weights, while Brașov V.C produced lighter seeds. Germination experiments showed that electric field treatments significantly enhanced germination, with higher voltages and longer exposure times producing the strongest effects. Low-dose gamma irradiation induced a clear dose-dependent response, with the 2 Gy treatment consistently improving germination percentage, germination index, and early seedling vigor across most provenances. Multivariate analyses (canonical correspondence analysis and UPGMA clustering) revealed distinct provenance-specific physiological responses, with Anina and Sinaia showing divergent reaction patterns, while Gura Humorului, Brașov V.C and Brașov V.P. formed a more homogeneous group. The results indicate that reproductive trait variability and seed germination capacity in L. decidua are strongly influenced by provenance origin and can be effectively modulated by physical pre-sowing treatments, supporting their use in regeneration programs.