Evaluating desiccation sensitivity of Quercus rubra acorns using X-ray image analysis
Desiccation of northern red oak (Quercus rubra L.) acorns can impact seed viability. We examined use of X-ray image analysis of cotyledon damage in dried acorns to predict germination capacity and seedling vigor. Acorns collected from five half-sib sources were X-rayed before and after drying to one of four moisture content (MC) levels (30%, 25%, 20%, or 15%) or maintained as nondesiccated controls (35%38% MC). X-ray images were scored qualitatively according to degree of cotyledoncotyledon and cotyledon-pericarp separation. Following sowing, acorns were evaluated for number of days to reach each of three developmental stages (emergence of radicle, epicotyl, and first leaf flush) and growth for 80 d. Both MC and family significantly affected all variables. The percentage of acorns to reach each developmental stage, as well as final height and root-collar diameter declined with decreasing MC and dropped most notably between 20% and 15% MC. X-ray separation scores more effectively predicted the percentage of acorns to reach each of the first three developmental stages than MC level (R2 = 0.490.63 vs. 0.400.59). Our results confirm the recalcitrant nature of northern red oak acorns and demonstrate the potential of X-ray image analysis to provide a rapid and nondestructive means to successful predict acorn viability.