Flower Abundance, Premature Acorn Abscission, and Acorn Production in Quercus alba L.

Feret, Peter P.; Kreh, Richard E.; Merkle, S. A.; Oderwald, Richard G.

doi:10.1086/337292

Cited by 33 publications

(22 citation statements)

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“…The pattern of flower abortion a few weeks after pollination in both species considered (Q. suber and Q. ilex) was very consistent within the population, even in naturally pollinated flowers; less than 30% of the flowers reached the fully developed state (completion of ovule development) and very few remained until fruit maturity. Several reports on oak species examined the correlation between weather conditions and fruit set; however, the results are far from conclusive (Sharp and Sprague 1967;Wolgast and Stout 1977;Feret et al 1982). Premature flower/fruit abortion has been reported in several species as due to pollen limitation, interference of self-pollen (Campbell and Halama 1993;Seavey and Carter 1994;Ramsey 1995;Barret et al 1996), or to selective allocation of resources (Stephenson 1981;Stephenson and Bertin 1983).…”

Section: Discussionmentioning

confidence: 99%

Sexual reproduction in the cork oak ( Quercus suber L). II. Crossing intra- and interspecific barriers

Boavida¹,

Silva²,

Feijó³

2001

Sexual Plant Reproduction

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Intraspecific barriers promote outcrossing while interspecific mechanisms may contribute to the isolation of species; both control the exchange of genes between plants. In this paper we establish that post-pollination mechanisms promote outcross and act at different temporal and spatial levels to control seed set and quality in Quercus species. Controlled pollinations were performed to investigate intraspecific crossing barriers in Q. suber and pollen-pistil interactions following interspecific pollinations with some simpatric Quercus species. Cytological data of intraspecific crosses in Q. suber and Q. ilex have shown different kinetics on pollen tube growth after self and outcross pollination, but pollen tubes were able to reach the base of the styles in both species and seed set was successful. Although some prezygotic interaction is occurring at the style, the most important interaction takes place at ovary. The cross between Q. ilex and Q. suber is possible only in one direction, revealing a case of unilateral incongruity. We show that the lack of seed set observed in the cross Q. suber × Q. ilex is due to the inability of pollen tubes to penetrate the transmitting tissue after germination. With Q. suber mainly as female parent, pollinations with other simpatric Quercus species have shown different levels of constraint on pollen tube progression at stigma and style levels. Eventual hybridisation between Quercus species will depend on the compatibility of pollen-pistil interactions, on the competitive ability of pollen genotypes, and, most important, on the overlapping of geographical, phenological and ecological factors. Differences in seed set and seed allocation was evident in all crosses, and was particularly outstanding in interspecific and in self intraspecific crosses, determining the ultimate level of seed production and quality in Quercus species.

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Section: Discussionmentioning

confidence: 99%

Sexual reproduction in the cork oak ( Quercus suber L). II. Crossing intra- and interspecific barriers

Boavida¹,

Silva²,

Feijó³

2001

Sexual Plant Reproduction

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“…Supplemental pollen has also been shown to increase seed production in populations of several Betula species growing at high elevations (Holm 1994), where pollen availability was presumably limited due to spatial patchiness and unfavorable weather conditions. In wind-pollinated tree species that produce variable numbers of male flowers in different years, seed production is often greatest in years of high male flower production, presumably due to greater pollen availability (Feret et al 1982;Gysel 1958;Norton and Kelly 1988;Shibata et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Pollen-limited reproduction in blue oak: implications for wind pollination in fragmented populations

2001

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Human activities are fragmenting forests and woodlands worldwide, but the impact of reduced tree population densities on pollen transfer in wind-pollinated trees is poorly understood. In a 4-year study, we evaluated relationships among stand density, pollen availability, and seed production in a thinned and fragmented population of blue oak (Quercus douglasii). Geographic coordinates were established and flowering interval determined for 100 contiguous trees. The number of neighboring trees within 60 m that released pollen during each tree's flowering period was calculated and relationships with acorn production explored using multiple regression. We evaluated the effects of female flower production, average temperature, and relative humidity during the pollination period, and number of pollen-producing neighbors on individual trees' acorn production. All factors except temperature were significant in at least one of the years of our study, but the combination of factors influencing acorn production varied among years. In 1996, a year of large acorn crop size, acorn production was significantly positively associated with number of neighboring pollen producers and density of female flowers. In 1997, 1998, and 1999, many trees produced few or no acorns, and significant associations between number of pollen-producing neighbors and acorn production were only apparent among moderately to highly reproductive trees. Acorn production by these reproductive trees in 1997 was significantly positively associated with number of neighboring pollen producers and significantly negatively associated with average relative humidity during the pollination period. In 1998, no analysis was possible, because too few trees produced a moderate to large acorn crop. Only density of female flowers was significantly associated with acorn production of moderately to highly reproductive trees in 1999. The effect of spatial scale was also investigated by conducting analyses with pollen producers counted in radii ranging from 30 m to 80 m. The association between number of pollen-producing neighbors and acorn production was strongest when neighborhood sizes of 60 m or larger were considered. Our results suggest that fragmentation and thinning of blue oak woodlands may reduce pollen availability and limit reproduction in this wind-pollinated species.

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“…It is well known that most species of Quercus have a low level of fruit: flower ratio (Williamson 1966;Sharp and Sprague 1967;Shaw 1968;Matsuda 1982;Feret et al 1982;Saito et al 1987;Fujii 1993). Proximate causes for low fruit: flower ratio, in general, has been considered to be failure of pollination, lack of resource invested for reproduction, genetic defects, adverse weather condition, and predation (Stephenson 1981;Bierzychudek 1981;Campbell 1987;McCall and Primack 1987;Horvitz and Schemske 1988;Vaughton 1991).…”

Section: Introductionmentioning

confidence: 99%

Estimation for the timing of the internal developmental processes of acorns from fruit size in Quercus serrata Thunb. ex Murray

Kanazashi

2003

Journal of Forest Research

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To evaluate the relative importance of the factors affecting the premature abortion of acorns in Quercus serrata Thunb. ex Murray during the course of their development, inner developmental processes of acorns were observed by microscope, and applicability of the diameter of fruits (acorns with cupules) as an indicator of the inner developmental processes was discussed. Based on the observations using microscope, the developmental processes of acorns were classified into five stages; one prezygotic and four postzygotic stages (stages I to V). The diameter of sound fruits increased exponentially until 14 weeks after pollination, and the variance of diameter in each tree was fairly small (CV ϭ ~6%) during the process. Diameter of fruits can be used as a good indicator of developmental stages of acorns at individual level, and effective for the evaluation of the ecological factors affecting the premature abortion of acorns.

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Flower Abundance, Premature Acorn Abscission, and Acorn Production in Quercus alba L.

Cited by 33 publications

References 0 publications

Sexual reproduction in the cork oak ( Quercus suber L). II. Crossing intra- and interspecific barriers

Sexual reproduction in the cork oak ( Quercus suber L). II. Crossing intra- and interspecific barriers

Pollen-limited reproduction in blue oak: implications for wind pollination in fragmented populations

Estimation for the timing of the internal developmental processes of acorns from fruit size in Quercus serrata Thunb. ex Murray

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