Ability of chestnut oak to tolerate acorn pruning by rodents
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ORIGINAL PAPER
Ability of chestnut oak to tolerate acorn pruning by rodents The role of the cotyledonary petiole Xianfeng Yi & Rachel Curtis & Andrew W. Bartlow & Salvatore J. Agosta & Michael A. Steele
Received: 24 April 2012 / Revised: 9 November 2012 / Accepted: 11 November 2012 / Published online: 24 November 2012 # Springer-Verlag Berlin Heidelberg 2012
Abstract Acorns of many white oak species germinate soon after autumn seed fall, a characteristic widely interpreted as a general adaptation to escape predation by small rodents. However, the mechanism by which early, rapid germination allows escape and/or tolerance of seed damage remains unclear. Here we reported how specific germination traits of chestnut oak (Quercus montana) acorns, and those of other white oak species, allow successful escape from acorn pruning by rodents. During germination, chestnut oak acorns develop elongated cotyledonary petioles, which extend beyond the distal end of the acorn (1–2 cm) to the point at which the epicotyl and radicle diverge. However, granivorous rodents often prune the taproots above or below the plumule when eating or caching these germinated acorns in autumn. Hence, we hypothesized elongation of cotyledonary petioles allows chestnut oaks to escape acorn pruning by rodents. We simulated pruning by rodents by cutting the taproot at different stages of germination (radicle length) to evaluate the
regeneration capacity of four resulting seedling remnants following taproot pruning: acorns with the plumule (remnant I), acorns without the plumule (remnant II), and pruned taproots with (remnant III) or without the plumule (remnant IV). Our results showed that remnant I germinated into seedlings regardless of the length of the taproot previously pruned and removed. Remnant III successfully germinated and survived provided that taproots were ≥6 cm in length, whereas remnant IV was unable to produce seedlings. Remnant II only developed adventitious roots near the severed ends of the cotyledonary petioles. Field experiments also showed that pruned taproots with the plumule successfully regenerated into seedlings. We suggest that the elongated cotyledonary petioles, typical of most white oak species in North America, represent a key adaptation that allows frequent escape from rodent damage and predation. The ability of pruned taproots to produce seedlings suggests a far greater resilience of white oaks to seed predation than previously anticipated.
Communicated by: Sven Thatje
Keywords White oak . Cotyledonary petioles . Seed damage . Acorn pruning . Embryo excision . Seedling establishment
X. Yi College of Agriculture, Henan University of Science and Technology, Luoyang 471003, China X. Yi : R. Curtis : A. W. Bartlow : M. A. Steele (*) Department of Biology, Wilkes University, Wilkes-Barre, PA 18766, USA e-mail: [email protected] X. Yi State Key Laboratory of Integrated Pest Management, Institute of Zoology, The Chinese Academy of Sciences, Beijing 100101, China S. J. Agosta Center for Environmental Studies and Dep
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