Meiosis in the Genus Hypericum

Hoar, Carl Sherman; Haertl, Edwin J.

doi:10.1086/334248

Cited by 11 publications

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“…Nevertheless, based on the studies of Hoar and Haertl (1932) and Moraes (2007), who found regular meiosis in the sexual Hypericum and meiotic irregularities in the apomictic species, together with the rather regular meiosis, high pollen viability and homogeneity in pollen grain size observed for H. polyanthemum it could be suggested that this species reproduces sexually. On the other hand, the irregular meiosis, lower pollen fertility and high variation in pollen grain size of H. caprifoliatum and H. cf carinatum could indicate that these two species are apomictic.…”

Section: Resultsmentioning

confidence: 99%

“…The same author studied the mode of reproduction of these species and concluded that H. brasiliense is preferentially allogamous and that reproduction by apomixis could not be ruled out for H. cordatum. Hoar and Haertl (1932) Table 2). Several abnormalities at the tetrad stage, such as tetrads with microcytes, polyads, dyads and tryads, were frequent (Figure 2A-D).…”

Section: Resultsmentioning

confidence: 99%

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Cytogenetics of Hypericum caprifoliatum Cham. & Schltdl. (Clusiaceae) populations and other species of the genus

Navarini¹,

Schifino-Wittmann²,

Barros³

et al. 2008

CBAB

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Cytogenetics of Hypericum caprifoliatum Cham. & Schltdl. (Clusiaceae) populations and other species of the genus

Navarini¹,

Schifino-Wittmann²,

Barros³

et al. 2008

CBAB

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“…There are several reports of intraspecifi c chromosome number variation in the genus Hypericum such as H. elodes with n = 16 (AlBermani et al 1993) and 2n = 20 (Gibby 1981) and H. perforatum with n = 16, 17, and 18, and 2n = 32, 48 (Reynaud 1986). Hoar (1931) and Hoar & Haertl (1932) studied meiosis in the genus Hypericum and reported the tendency of H. perforatum chromosomes to clump diffi culting chromosome number counting. The same diffi culty was found in the present chromosome study of H. brasiliense.…”

Section: Discussionmentioning

confidence: 99%

Reproductive biology and cytology of Hypericum brasiliense Choisy (Hypericaceae)

Moraes¹,

Pinto-Maglio²,

Lombello³

2009

Rev. bras. Bot.

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-(Reproductive biology and cytology of Hypericum brasiliense Choisy (Hypericaceae)). This is the fi rst study of reproductive biology and cytology carried out with Hypericum brasiliense, a species with medicinal properties and potential agronomic interest. Three populations of H. brasiliense collected at Southeastern Brazil were studied. The results indicate that H. brasiliense is preferentially allogamous, self-compatible, facultative apomitic and anemophilous. Male sterility was observed in about 50% of individuals from the three populations. Anatomical studies evidenced structural abnormalities in anthers of male sterile fl owers, showing enlarged tapetal cells and thick secretion deposits on the tapetal cell surfaces that may cause nutritional defi cit for pollen mother cells. In cytogenetic studies several haploid chromosome numbers were observed like n = 4, 8, 9, 11, 16 and 17, including the presence of multivalents and micronuclei in tetrads, indicating the occurrence of abnormalities in the meiotic process of H. brasiliense. Despite these meiotic abnormalities the pollen viability and in vitro pollen germination rate observed in fertile fl owers may be considered high. The diploid chromosome number 2n = 16 was observed, and the chromosomes in metaphase were small and similar. Fluorochrome staining techniques using DAPI and CMA 3 were applied, with no positive bands observed.Key words -anatomy of anthers, apomixy, irregular meiosis, male sterility RESUMO -(Biologia da reprodução e citologia de Hypericum brasiliense Choisy (Hypericaceae)). Este é o primeiro estudo de biologia da reprodução e citologia realizado em Hypericum brasiliense, uma espécie com propriedades medicinais e de interesse agronômico. Três populações de H. brasiliense da região Sudeste do Brasil foram estudadas. Os resultados obtidos dos estudos indicam que H. brasiliense é uma espécie preferencialmente alógama, auto-compatível, apomítica facultativa e anemófi la. Foi observada macho-esterilidade em 50% dos indivíduos estudados nas três populações. Estudos anatômicos evidenciaram anormalidades estruturais nas anteras de fl ores macho-estéreis, como células do tapete aumentadas, com grossas camadas de secreções depositadas em sua superfície que podem originar defi ciências nutricionais para as células mães do pólen. Nos estudos citogenéticos diversos números haplóides foram observados, tais como n = 4, 8, 9, 11, 16 e 17, incluindo a presença de multivalentes e micronúcleos em tétrades, indicando a ocorrência de anormalidades no processo meiótico de H. brasiliense. Apesar das anormalidades meióticas a viabilidade polínica e o índice de germinação in vitro dos pólens observado para as fl ores férteis podem ser considerados altos. O número cromossômico diplóide registrado foi 2n = 16, com cromossomos metafásicos pequenos e similares entre si. Foram aplicadas técnicas de bandamento com fl uorocromos DAPI e CMA 3 , sem que bandas positivas fossem observadas.Palavras-chave -anatomia de anteras, apomixia, irregularidade meiótica, macho-e...

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“…It has been pointed out in the introduction that the 14 chromosomes of Oenothera are capable of forming mathematically 15 configurations in the form of rings or chains among themselves, and of these 13 configurations have already been reported. That is to say, the chromosome configurations in Oenothera are confined to the form of rings and chains, and nothing else, showing the existence of a peculiar organization among the chromosomes on the basis of affinity at the ends ; whereas the recent work of Hoare (1931Hoare ( , 1932 in the genus Hypericum has brought to our knowledge, that out of a number of species only one shows exact configuration (complete ring) like some Oenothera chromosomes. Again, Percival (1932) in a number of hybrids of wheat and segilops finds the chromosomes associated parasynaptically or telosynaptically in the same nucleus.…”

Section: Discussionmentioning

confidence: 97%

Meiosis in Oenothera missouriensis

1933

Proc. R. Soc. Lond. B.

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A cytological study of the meiotic phenomena in Oenothera may not need an excuse in spite of the exhaustive studies of the genus made by numerous competent cytologists of this century. Up to the present time, all the investigators of Oenothera cytology have been successful in establishing that the basic ( n ) number of chromosomes in this genus is 7; although tetraploid (Gates, 1911), triploid (Cathcheside, 1931), and trisomic numbers might occur either naturally (by mutation) or could be produced by experiment. It is also known that the somatic number of chromosomes corresponds with the number of chromosome bodies in the diakinesis and metaphase of the heterotypic division.. Thus in diploid Oenothera species, hybrid, or mutant at the diakinesis of pollen mother cells 14 chromosomes have been shown to exist, withouth any doubt, in the configuration of a closed circle, in 7 ring pairs, or a mixtrue of free pairs and closed circles. Mathematically, there are 15 possible configurations in which 14 chromosomes can arrange themselves in the form of closed circle, ring pairs, or a combination of ring pairs and closed circles (Cleland and Blakeslee, 1931; Darlington, 1931). Of these 15 Possible configurations 13 have already been reported in various Oenothera species, hybrids and mutants (Darlington, 1931). Regarding the origin and significance of these chromosome configurations invsestigators have not yet reached an agreed opinion. Apart from the genetical significance, the much disputed cytological question of parasynaptic and telosynaptic methods of chromosome pairing is yet far from a final solution. In oenothera both the methods of pairing have strong sup-porters in consideration of observed cytological facts. The fact are (i) the continuous spireme (in leptotene stage); (ii) the pachynema and the diakinesis consisting of the 14 chromosomes arranged end to end. This arragement, known as catenation of chromosomes, favours the telosynaptic rather than the parasynaptic union. Wheras (i) double threads at the prophase, (ii) the looping of the threads, and (iii) the half number of bodies (7 ring pairs) at the diakinesis support the parasynaptic method of pairing of chromosomes. The occurence of a complete catenation of 14 chromosomes in some Oenotheras and the presence of 7 free pairs in others naturally suggests the question-whether they can be correlated with the two methods of chromosome-pairing in the meiosis of Oenothera .

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Meiosis in the Genus Hypericum

Cited by 11 publications

References 0 publications

Cytogenetics of Hypericum caprifoliatum Cham. & Schltdl. (Clusiaceae) populations and other species of the genus

Cytogenetics of Hypericum caprifoliatum Cham. & Schltdl. (Clusiaceae) populations and other species of the genus

Reproductive biology and cytology of Hypericum brasiliense Choisy (Hypericaceae)

Meiosis in Oenothera missouriensis

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