Sexual reproduction in the cork oak ( Quercus suber L.). I. The progamic phase

Boavida, Leonor C.; Varela, Maria Carolina; Feijó, José A.

doi:10.1007/s004970050162

Cited by 49 publications

(46 citation statements)

References 27 publications

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“…These results do not confirm the theory of a continuous or multiple female flowering, one which is widely accepted as an explanation for the multiplicity of crops in Iberian Quercus suber (Natividade 1950;Montoya 1988). The absence of summer or autumn female flowering in this study is consistent ripening and dispersal of second (November) and late (January) crops (annual acorns); (c) quiescent flower which will ripen in autumn of year n+2, following the biennial pattern with findings in Italy and Portugal which support the notion that this phenomenon occurs only in certain years and in a scarce number of individuals (Machado 1938;Corti 1955;Boavida et al 1999). This same behaviour has been observed in other Mediterranean oak species such as Quercus ilex (Currµs and Laguna 1986) and Q. coccifera Schirone 1982, 1985;Caaeellas 1993) and has been related to an early rainy period in autumn.…”

Section: Relationship Between Acorn Crops and Floweringsupporting

confidence: 85%

Biennial acorn maturation and its relationship with flowering phenology in Iberian populations of Quercus suber

Díaz-Fernández

Climent

Gil

2004

Trees

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Since the XIX century, there is a controversy about the existence of biennial maturation of the acorns in Quercus suber L. While some authors recognised biennial cycles as an adaptation to habitats with short vegetative periods, other authors discarded the biennial pattern. Successive flowering events from spring to autumn and annual acorn ripening are proposed as an explanation of the multiple acorn crops typical of Iberian forests. To clarify this discussion, the presence of annual and biennial acorns was assessed in seven cork oak stands, covering a wide range of environmental conditions. In each stand, 100 individuals were sampled once in spring and once in autumn. Biennial acorns were observed with variable frequencies in all populations. There was a significant and positive relationship between latitude and the percentage of trees with biennial acorns within northern and central populations. On the contrary, this trend was not significant among southern populations. The hypothesis that the presence of biennial acorns in Quercus suber is related to individual female flowering phenology was confirmed in four populations located in the southwestern Iberian Peninsula. Unregarding local differences in the distribution of phenological stages anticipated trees bore significantly less biennial acorns than delayed individuals of the same stand. This result is coherent with the idea that the length of the vegetative period plays a crucial role in the frequency of annual and biennial acorn ripening patterns. The relationship between annual and biennial ripening cycles and the multiple acorn crops is discussed.

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Section: Relationship Between Acorn Crops and Floweringsupporting

confidence: 85%

Biennial acorn maturation and its relationship with flowering phenology in Iberian populations of Quercus suber

Díaz-Fernández

Climent

Gil

2004

Trees

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“…To identify intraspecific barriers and their potential contribution to interspecific mating, a complete diallele cross was performed. Pollen tube measurements were carefully made, considering previous data which have shown that pollen tube reduction across the pistil would determine that no more than 2-3 pollen tubes enter the ovary (Boavida et al 1999). All measurements were made during pollen tube progression within the style and prior to entry of the latent phase, which precedes ovary penetration and fertilisation.…”

Section: Resultsmentioning

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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“…In fagalean species, however, the pollen tube spends Ͼ1 month in the pistil before fertilization occurs, because the ovules are not yet mature when the pistil receives pollen grains on the stigma (9)(10)(11). We recently reported the pollentube growth pattern in Casuarinaceae (Fagales), where a unique mode of fertilization (i.e., chalazogamy) in place of the ordinary mode (i.e., porogamy) was reported (12, 13) (for details regarding chalazogamy and porogamy, see Fig.…”

mentioning

confidence: 99%

Intermittent pollen-tube growth in pistils of alders ( Alnus )

Sogo

Tobe

2005

Proc. Natl. Acad. Sci. U.S.A.

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In alders, where fertilization occurs Ϸ8 weeks after pollination, the pollen tube (male gametophyte) grows intermittently in four steps in close association with the development of the ovary and its ovules. Pollen tubes stop growing in the style, at the ovarian locule, and at the chalaza (ovule), before reaching an embryo sac for fertilization. At the stage when the ovary develops an ovule primordium in each of the two locules, many pollen tubes germinate on the stigma, and a few of them reach the style, where they remain for Ϸ7 weeks. Thereafter, a single tube resumes growing; with a short stop in the upper space of the ovarian locule, it reaches the older of the two ovules when it has developed a two-nucleate embryo sac. Except in the last step, where the tube grows from the chalaza to an embryo sac (female gametophyte), an eight-nucleate mature embryo sac is not necessary for pollen-tube guidance in the pistil. Although the intermittent pollen-tube growth appears to play an important role in the selection of a single pollen tube from many and one ovule from two, its detection provides insight into the study of the mechanism of pollen-tube guidance.Betulaceae ͉ chalazogamy ͉ Fagales ͉ fertilization ͉ ovule I n flowering plants, fertilization occurs when the pollen tube (male gametophyte) reaches the embryo sac (female gametophyte) through the tissue of the pistil (sporophyte), unifying a sperm nucleus with an egg nucleus. This process suggests interaction not only between the pollen tube and the embryo sac, but also between the pollen tube (and embryo sac) and an intervening tissue, i.e., the tissue of the pistil. Recent studies using mutants of Arabidopsis thaliana that lacked normally developed ovules or embryo sacs showed that the pollen tubes lost their way to the target within the pistil (1-3). However, these studies mainly paid attention to interaction between pollen tubes and the embryo sac, and analysis of the correlation between the pollen-tube growth and the developmental stage of the pistils is still scarce.In a majority of cases, the length of time between pollination and fertilization ranges from 24 to 48 h, and in some plants it is even shorter (4-8). In fagalean species, however, the pollen tube spends Ͼ1 month in the pistil before fertilization occurs, because the ovules are not yet mature when the pistil receives pollen grains on the stigma (9-11). We recently reported the pollentube growth pattern in Casuarinaceae (Fagales), where a unique mode of fertilization (i.e., chalazogamy) in place of the ordinary mode (i.e., porogamy) was reported (12, 13) (for details regarding chalazogamy and porogamy, see Fig. 5A, which is published as supporting information on the PNAS web site). In Casuarina equisetifolia (12), fertilization occurs in five discontinuous steps of pollen tube growth from the stigma to the embryo sac. We suggested that the pollen tube exhibited repeated steps of growth in accordance with the development of the ovary and ovule(s). However, C. equisetifolia develops four to eight emb...

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Sexual reproduction in the cork oak ( Quercus suber L.). I. The progamic phase

Cited by 49 publications

References 27 publications

Biennial acorn maturation and its relationship with flowering phenology in Iberian populations of Quercus suber

Biennial acorn maturation and its relationship with flowering phenology in Iberian populations of Quercus suber

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

Intermittent pollen-tube growth in pistils of alders ( Alnus )

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