Abstract
Seed germination and early seedling development have been studied in the recalcitrant species Quercus ilex using targeted transcriptional, hormonal, and sugar analysis. Embryos and seedlings were collected at eight morphologically defined developmental stages, S0–S7. A typical triphasic water uptake curve was observed throughout development, accompanied by a decrease in sucrose and an increase in glucose and fructose. Low levels of abscisic acid (ABA) and high levels of gibberellins (GAs) were observed in mature seeds. Post-germination, indole-3-acetic acid (IAA), increased, whereas GA remained high, a pattern commonly observed during growth and development. The abundance of transcripts from ABA-related genes was positively correlated with the changes in the content of the phytohormone. Transcripts of the drought-related genes Dhn3 and GolS were more abundant at S0, then decreased in parallel with increasing water content. Transcripts for Gapdh, and Nadh6 were abundant at S0, supporting the occurrence of an active metabolism in recalcitrant seeds at the time of shedding. The importance of ROS during germination is manifest in the high transcript levels for Sod and Gst, found in mature seeds. The results presented herein help distinguish recalcitrant (e.g., Q. ilex) seeds from their orthodox counterparts. Our results indicate that recalcitrance is established during seed development but not manifest until germination (S1–S3). Post-germination the patterns are quite similar for both orthodox and recalcitrant seeds.
Highlights
Quercus ilex subsp. ballota [Desf.] Samp. is the dominant tree in forest ecosystems over large areas of the Western Mediterranean Basin (Pulido et al, 2001; de Rigo and Caudullo, 2016)
Changes in morphology were observed during germination; at stage S2, the rupture of the testa was appreciable, with radicle emergence starting to be visible at stage S3, and plumule emergence from cotyledonary petioles at 216 h (S7) (Figures 1A–C)
These changes indicate that the Q. ilex seed germination covers the first 24 h after imbibition, under our experimental conditions; followed by early seedling growth (Figure 1D)
Summary
Quercus ilex subsp. ballota [Desf.] Samp. is the dominant tree in forest ecosystems over large areas of the Western Mediterranean Basin (Pulido et al, 2001; de Rigo and Caudullo, 2016). As a Quercus species, it produces recalcitrant seeds, which are shed, and germinate, at a relatively high-water content (Connor and Sowa, 2003; Pasquini et al, 2012; Joët et al, 2013; SghaierHammami et al, 2016). They are susceptible to desiccation injury, and become inviable when stored for long periods (Pasquini et al, 2012). In a previous study of Quercus robur it was found that recalcitrance does not on accumulation of dehydrins, abscisic acid (ABA), or soluble sugars during seed maturation (Finch-Savage and Blake, 1994)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
