Size variability in embryonic axes, cotyledons, acorns and seedlings in fifteen species of the genus Quercus

Abstract

Embryonic axes of acorns have greater variability of mass than cotyledons or pericarp. Above/below ground seedling mass depends on oak species. Species of the genus oak are of great importance for forest ecosystems in almost all of the Holarctic. Knowledge of the diversity of the size of acorns and their parts would allow better use of the opportunity of genetic resources storage, both for the protection of endangered oak species and for forestry practices. The initial development of seedlings in reference to the size of the acorn, its parts and acorn maturation time was also investigated. The fresh and dry mass of individual acorns, embryonic axes and cotyledons of 15 species (Quercus agrifolia, Q. gambelli, Q. kelloggii, Q. alba, Q. bicolor, Q. coccinea, Q. falcata, Q. lyrata, Q. nigra, Q. prinus, Q. rubra, Q. cerris, Q. ilex, Q. petraea, and Q. robur) were determined. In the second part of the study, the mass of the ca. 3-month-old seedlings that had completed the first stage of growth, with a division on the leaves, the shoot and the root, was measured. The greatest variation in mass both between and within the species was demonstrated for the embryonic axis. The mass of seedlings depends on the size of the acorn and the cotyledons contained therein; whereas, the mass of the embryonic axis has no significant influence on the mass of seedlings.