Regulating acorn germination and seedling emergence in Quercus pagoda (Raf.) as it relates to natural and artificial regeneration

Abstract

Dormancy break and germination requirements for Quercus pagoda (Raf.) acorns were determined, as well as the effects of acorn pretreatment and post-germination temperatures on epicotyl emergence, seedling development, and seedling biomass accumulation. There was an inverse linear relationship between length of cold stratification (5/1 °C for 0–12 weeks) and cumulative germination percentages in all incubation temperatures (15/6, 20/10, 25/15, 30/20 °C). Acorns required 12 weeks of cold stratification to break dormancy. Gibberellic acid substituted for cold stratification; although, it was not as effective as 12 weeks cold stratification. At 16 weeks of cold stratification, 20% of acorns had germinated, and the remaining 80% of ungerminated acorns reached ≥ 97 ± 1% cumulative germination within 4 days in all incubation temperatures. Post-germination time to epicotyl emergence and to leaf flush was a function of temperature, and time decreased with increased temperatures. With light held constant (50 μmol m−2 s−1), seedlings accumulated greater biomass in temperatures > 20/10 °C. Q. pagoda acorns possess Type 2 nondeep physiological dormancy, and this allows for artificial manipulation of timing and duration of germination. Extending cold stratification 4 weeks beyond dormancy break (i.e., 16 weeks) yields more uniform germination across a range of temperatures. Epicotyl emergence, seedling development, and biomass accumulation may be regulated by manipulating growing temperature. In this study, the most uniform seedling cohort with the greatest total biomass was produced when acorns received 16 weeks of cold stratification, followed by transfer of germinants to 30/20 °C.