Factors controlling seed dormancy and germination response of Brachypodium hybridum growing in the hot arid mountains of the Arabian Desert

Abstract

Seed dormancy and germination have been studied in the genetic model Brachypodium species complex in cooler, moist higher latitudes. Studying environmental factors in arid mountains affecting dormancy and germination in Brachypodium complex could determine the factors controlling these processes. This study assesses the impacts of temperature during seed maturation, seed after-ripening, drought, photoperiod, and thermoperiod on final germination and germination rate index of B. hybridum in the Arabian Desert. Seeds were germinated under dark or light conditions and under different ratios of red:far-red light, with three diurnal thermoperiods. The final germination percentage was significantly greater at 15/25 °C and 20/30 °C than at 25/35 °C and in light rather than in darkness. Seeds that reached maturity at 15/25 °C attained greater germination rates and faster germination than those that reached maturity at 20/30 °C. One-year after-ripening enhanced the final germination percentage and reduced photoperiod requirements. Light quality did not affect final germination percentage. The seeds tolerated drought of up to –0.8 MPa polyethylene glycol. The tolerance of B. hybridum seeds produced at higher thermoperiods to moderate levels of osmotic stress and their higher dormancy indicate that this species has the potential to survive the projected global warming in its native and introduced ranges.

Roles of Hardened Husks and Membranes Surrounding Brachypodium hybridum Grains on Germination and Seedling Growth

“…Conversely, germination was observed as significantly lower in darkness and other light settings (white light, R: FR ratios of 0.25 and 0.87) (Figure 5). In a previous study, we found that germination of husked grains had a similar response to different light settings; i.e., they germinated more under red-rich light and less in darkness [20]. In dehusked-demembraned grains, however, there was no significant difference in the final germination triggered under different light qualities (Figure 5).…”

“…The inconsistency observed in the role of husks on germination in B. distachyon and B. hybridum respectively could be attributed to the maternal environment during seed development and maturation. Whereas B. distachyon is a summer annual in temperate climate at the northern latitudes [12], B. hybridum is a winter annual in the arid hot climate of the Arabian desert [20]. Environmental conditions can affect the chemical compositions of different parts of grasses, such as Lolium perenne [43].…”

“…All of these factors can affect seed dormancy and seedling establishment [18]. Additionally, dormancy and germination responses are controlled by conditions prevailing during seed soaking [19,20]. Therefore, the timing of seed germination is controlled by individual or multiple factors including structures surrounding the embryo, the maternal environment, storage conditions, and the suitability of environmental conditions during seed soaking.…”

In vitro spore germination and early gametophyte development of Cibotium barometz (L.) J. Sm. in different media

“…Germination of spore is defined as the set of mechanisms occurring in the dormant spore that culminates with the growth of cells to form a sporeling able to be established in the substrate (Gabriel y Galán et al 2015; Steinbrecher and Leubner-Metzger 2017; Yan and . Spore germination can be easily detected by observing signs of the emergence of particular organs such as radicle, protonema, filament or rhizoid (Suo et al 2015;Penfield 2017;Elgabra et al 2019). Spores of C. barometz are trilete, tri-radially symmetrical, non-chlorophyllous, and golden-yellow with a perine.…”