Morphological development and starch accumulation of Konara oak (Quercus serrata) Acorns as a wildlife food source

Japanese beech trees are considered to have mast seeding habit. Their acorns are consumed by wild mammals and birds. As a food for wildlife, acorns are considered a nutritional source of non-structural carbohydrates, mainly starch. The purpose of this study was to verify the morphological development of acorns of Quercus serrata during maturation and compare amylose and amylopectin contents as a major component of starch in the foraged seed embryo. Acorns were collected at two different sampling sites, Okutama and Ome, which are located at different altitudes. At the maturation, acorn size (major axis) and embryo weight (on a dry matter basis) at the sampling sites, Okutama and Ome, ranged from 2.13cm to 2.47cm and from 0.57g to 0.63g, respectively. Starch content in the acorn embryo was higher at Ome (40.4%) than at Okutama (30.2%) at the maturation stage. The percentage of amylopectin and amylose contents in the embryo were 52.4% and 47.6% at Okutama and 67.0% and 33.0% at Ome, respectively. Thus, the amounts of amylopectin and amylose in the acorn embryos were higher for the samples from Ome (252.2mg) than those from Okutama (174.0mg). Consequently, the present study showed that the profiles of the acorn development process were similar at both sampling sites, while starch accumulated as amylopectin and amylose in the acorn embryos of Quercus serrata differed between the sites. All our results are useful for understanding acorn development through its growth period and the nutritional quality of starch in acorn embryos as a food for wildlife. Furthermore, the extent of amylose and amylopectin accumulation in the embryo might be affected by the environmental factors where the mother trees grow.

Author(s): Norio Tokita, Saki Miyata, Sachie Nakiri and Teruaki Tokita

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