Seed germination characteristics of Phillyrea angustifolia L. and P. latifolia L. (Oleaceae), two Mediterranean shrub species having lignified endocarp

Abstract

Abstract. The aim of this study was to determine the germination characteristics of Phillyrea angustifolia L. and P. latifolia L. seeds in order to develop an optimized propagation protocol for Phillyrea species. Seeds of P. angustifolia and P. latifolia were collected from wild plants growing in Cáceres province (CW Spain) and Andalucía (S Spain), respectively. Percentage of water uptake for P. latifolia seeds was calculated. Seeds with and without endocarp were germinated at different constant and alternating temperatures. Seeds without endocarp were soaked in distilled water or gibberellic acid, and then set to germinate. Seeds with endocarp of both species were stratified at 5 ºC for 30 or 90 days and then the endocarp was completely removed from the seeds before they were sowed. Chemical scarification with sulfuric acid and mechanical scarification were tested on P. angustifolia seeds with endocarp. Phillyrea endocarp was permeable to water, since Phillyrea seeds with endocarp imbibed water, but water uptake was faster when the endocarp was removed. Moreover, the encodarp could interfere mechanically in the emergence of the radicle, since seed germination of Phillyrea species was promoted by the complete removal of the lignified endocarp surrounding each seed. Optimal germination temperature for both species was 15 ºC, and lower temperatures produced secondary dormancy. Soaking in distilled water or gibberellic acid did not significantly enhance seed germination. Cold stratification and chemical scarification treatments were detrimental for seed germination.

Effect of pre-treatments on the germination of jasmin box (Phillyrea latifolia) seeds in Greece

“…This clearly shows a certain positive effect of GA 3 on the germination of P. latifolia seeds, which is not present in all other pre-treatments (figure 4). Similar results (21 %) of the effect of GA 3 at 1,000 mg L -1 on the germination are reported by Mira et al (2015). The positive effect of high GA 3 concentrations on seeds germination is reported in studies for other forest species such as the Arbutus unedo (Smiris et al 2006).…”

“…Mira et al (2015) found that cold stratification at 5 °C had a negative effect on seed germination of P. angustifolia and P. latifolia seeds in Spain, probably inducing secondary dormancy. In contrast, 30.1 % germination after two months of cold stratification at 3-4 °C for P. latifolia seeds is reported by the Aygün et al (2011), which directly contradicts our results.…”

“…The second set of incubation temperatures of 20 °C for 16 hours light, alternate with 15 °C for 8 hours dark proved to be the appropriate germination temperature for all seed pre-treatments. Mira et al (2015) tried different incubation temperatures, from 5 to 25 °C for the germination of P. angustifolia and P. latifolia seeds in Spain and found that the optimum germination temperature for both species was 15 °C. Temperatures approaching 30 °C are common during the summer months in the Mediterranean zone and this fact sets the seeds automatically at dormant stage, in order to overcome the summer high temperatures.…”

“…They usually present double dormancy due to the impermeability of the seed coats because of hardness of the coat, the oily substances that may prohibit the water penetration and embryo physiological dormancy (Bachiller 1991, Takos andEfthimiou 2002). However, Mira et al (2015) found that the Phillyrea spp. seeds imbibe water and thus do not present morphological dormancy.…”

“…Traveset et al (2001) studied the effect of the fruits of bird dispersed trees that passed through bird guts and found interspecific differences in seed germination characteristics of P. latifIolia growing in Balearic Islands. More recently, Mira et al (2015) studied the seed germination characteristics of both P. angustifolia and P. latifolia growing in Cáceres and Andalucía, Spain. The effect of fruit collection date on the germination of P. latifolia growing in Erdigir, Southwestern Turkey, was conducted by Yücedağ and Gültekin (2011).…”