Acorn germination and seedling survival of Q. variabilis: effects of cotyledon excision

We studied the effects of acorn cotyledon loss by insect damage and artificial excision on germination and seedling survival of Quercus variabilis, to determine whether insect infestation decreases acorn germination and seedling establishment; and to what extent cotyledon damage can affect acorn germination and seedling establishment. Artificial excision partially imitated the effect of insect damage on acorn germination and seedling survival, and indicated that insect damage did not significantly decrease germination rate and seedling survival of Q. variabilis acorns. The viability of infested but still viable acorns strongly depends on which sector weevil larvae feed on. The cotyledon reserves at the apex of acorns were more important than those at the base in supporting acorn viability and seedling establishment. The excision of apical cotyledon has the most detrimental effects on acorn germination activity. The relatively low effect of larval infestation on acorn viability was likely related to the high frequency of feeding and escaping at the base, which was closely correlated with differentiation in pericarp thickness in Q. variabilis acorns. These could explain the low decrease in acorn germination and seedling survival experienced by infested acorns.