부산대학교 도서관

We evaluated the effect of temperature regimes (six constant and four alternating temperatures), light qualities (five red : far red ratios) and water potentials (ΨW; seven NaCl and polyethylene glycol 6000 [PEG] solutions) on the percentage and germination rate, as well as the post-seminal development morphology, that allow Pilosocereus arrabidae seeds to germinate in a hot semiarid climate on the south-eastern Brazilian coast. The results showed that seeds germinated similarly between constant and alternating temperatures, with an optimal germination at 25/20°C and 20°C. Pilosocereus arrabidae seeds were photoblastic positive and the final germination percentage was inhibited at low red : far red ratios. Maximum germination was obtained in distilled water (0 MPa) and decreases of ΨW in the solutions reduced the germination, which was lower in NaCl than in iso-osmotic PEG solutions. Germination inhibition appears to be osmotic because the recovery response was high when non-germinated seeds from both iso-osmotic solutions were transferred to water. Seeds of P. arrabidae are small and germination is phaneroepigeal. Despite the slow growth typically seen in seedlings and adults of Cactaceae, germination in this species depends on the ability of the seeds to appropriately sense and react to environmental cues that correlate with times and places under low-risk growth conditions. [ABSTRACT FROM AUTHOR]