Timing of premature acorn abortion in Quercus serrata Thunb. is related to mating pattern, fruit size, and internal fruit development

Abstract

Timing of acorn development and abortion is an important maternal strategy in oak sexual reproduction. To understand the significance of acorn abortion in Quercus serrata, artificial pollination of different mating patterns (outcross, self-, and nonpollination) was performed, and the timing of abortion and the size and internal development of acorns from each mating type were investigated. Acorns were aborted similarly in every pollination treatment until 80 days after pollination. Almost all self-and nonpollinated acorns were rapidly aborted during the period 80-120 days after pollination. During that period, differences in internal fruit development between outcross-pollinated and unsuitably pollinated (self-and nonpolinated) acorns were observed. In addition, cotyledon development and a rapid increase in fruit size were observed in the acorns gained by outcross pollination. The correspondence between the timing of abortion and the timing of rapid size growth and the development of storage organs suggests that this acorn-maintenance strategy may be the consequence of a maternal adaptation that allows better reproductive success under resource limitation.

Holm oak fecundity does not acclimate to a drier world

“…Studies investigating the effects of both meteorological conditions and trees’ internal resource dynamics on reproduction are scarce, and only a few have tried to disentangle their relative effects (Bogdziewicz et al ., 2017b; Fernández‐Martínez et al ., 2017; Nussbaumer et al ., 2018; Moreira et al ., 2019). Three stages of reproduction seem particularly key for determining the number of mature fruits produced at the end of the season in Quercus ilex : female flower initiation and development that determines the number of receptive female flowers at pollination, fertilisation that determines fruit set, that is the number of fruits initiated, and fruit development until maturity (Sork & Bramble, 1993; Tsuruta et al ., 2011). Our aim in this study was therefore to identify the main drivers of fruit production at the key stages of the reproductive cycle of Q. ilex in a context of increasing aridity, and to disentangle their relative effects.…”

No Effect of Selective Maturation on Fruit Traits for a Bird-Dispersed Species, Sambucus racemosa

“…Selective abortion is a phenomenon wherein maternal plants selectively abort lower-quality ovules or immature fruits before fruit maturation to mature only those fruits or seeds that are of a higher quality [ 1 , 2 , 3 , 4 , 5 , 6 , 7 ] and thereby save resources [ 3 ], though resource limitation is not the sole factor that controls abortion in plants [ 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 ]. The process of selective abortion also has been considered as a mode of developmental selection [ 5 ], which states that as a result of completion among genetically diverse embryos, higher-fitness ones, such as those with more vigor or more developmental stability [ 5 , 16 ], are selectively developed into mature seeds [ 8 , 17 ].…”

“…Although fruits of this species are drupes [ 42 ], the effects of selective abortion on fruit traits was not investigated in their study. Selective abortion was also reported for acorns of oaks ( Quercus ilex [ 5 ] and Q. serrata [ 10 ]), which are dispersed by birds and animals by means of scatter hoarding after primary gravitational fall [ 43 , 44 , 45 , 46 ]. However, because acorns themselves are foods for their dispersers, their fruit traits cannot be directly compared with those of fruits that are primarily dispersed by birds, which is the main focus of the present study.…”