Influence of tree age on seed germination response to environmental factors and inhibitory substances in Pinus pinaster

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Abstract
The present study analyses the reproductive behaviour of Pinus pinaster at different ages of the parent trees after subjecting the seeds to variations in environmental factors and inhibitory substances. An experiment was designed in which seeds from mature (43 years old) and young (13 years old) trees were subjected to different environmental factors: darkness, thermal shocks and the presence of inhibitory substances from the needles and the undergrowth humus of P. pinaster. A control treatment was also carried out for the seeds of each age. The results obtained indicate that the age of the parent trees has a significant effect on mean germination time after experimental treatments: shock temperatures, darkness, and leaf and humus exudates. Seeds from young populations have shorter mean germination times than those from adult populations. Similarly, mature P. pinaster populations show more diversity in the length of innate dormancy of their seeds than younger populations. However, age has no significant effect on total percentage germination. Significant reductions in germination were observed when seeds from mature and young trees were exposed to temperatures equal to or above 150°C for 5 min. Increased temperature also produces a delay in the onset of germination in both populations.