Cell differentiation in microsporangia of Pinus sylvestris with special attention to the tapetum. I. The pre–and early–meiotic periods

Walles, Björn; Rowley, John R.

doi:10.1111/j.1756-1051.1982.tb01435.x

Cited by 24 publications

(16 citation statements)

References 20 publications

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“…Differentiation toward a secretory condition prior to meiosis in MMCs, early and mid pachytene, and early diplotene was in each case asynchronous for tapetal cells of a rnicrosporangium. Cell walls were lysed prior to meiosis and thereafter TCs lacked cell walls and, during periods of differentiation, connections between cells (Walles & Rowley 1982, Rowley & Walles 1985. We found that dedifferentiation started asynchronously and was synchronous in conjunction with the formation of tempo-rary plasmodesma-like connections between tapetal cells.…”

Section: Discussionmentioning

confidence: 93%

Cell differentiation in microsporangia of Pinus sylvestris. III. Late pachytene

Rowley¹,

Walles²

1985

Nordic Journal of Botany

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Cycles of hyperactivity were observed in tapetal and microspore mother cells of Pinus sylvestris L. during the pachytene stage of meiosis in microspore mother cells. Hyperactive periods were characterized by dilated rough ER, hypersecretory dictyosomes, autophagic vesicles having one to two sequestration envelopes, and maze-like whorles of the endomembrane system. The extent and sequence of differentiation differed between the two cell types. During distinct phases of development there was either fibrillar flocculent or lipoidal material or both within dilations and at cell surfaces. Tapetal cell transfer of material involved endocytotic and exocytotic vesicles and channels opening directly to the cell surface. Dilations of the nuclear envelope of microspore mother cells in late pachytene intruded into the nucleus and, in conjunction with dilated ER, dominated cell profiles. Cellular morphogenesis in a microsporangium was seldom synchronous except for intervals of dedifferentiation when plasmodesma-like connections were formed between tapetal cells. Cycles of differentiation and dedifferentiation were correlated each spring season for five years with the progressive change of pachytene chromosomes, suggesting control by a genetic program rather than annual variations in the environment.

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Section: Discussionmentioning

confidence: 93%

Cell differentiation in microsporangia of Pinus sylvestris. III. Late pachytene

Rowley¹,

Walles²

1985

Nordic Journal of Botany

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“…The tapetum surrounding microspores acts not only as a nutrient supply (active in the synthesis and transport of proteins, lipids, carbohydrates), but also produces and secretes material utilised in the formation of sporopollenin in pollen walls (Chapman 1987;Mascarenhas 1990;Pacini and Franchi 1993;Pennell and Bell 1986;Rowley and Walles 1985a, 1985b, 1987, 1988Walles and Rowley 1982) and, in some angiosperms, produces pollenkitt and tryphine, which are involved in coating Tapetal cells surrounding the megaspores (Me) of a sterile ovule. Bars 5 m and pigmenting the pollen wall (Mascarenhas 1990).…”

Section: Discussionmentioning

confidence: 99%

“…There are detailed reports of tapetal development for conifer species (Chen et al 1987;Rowley and Walles 1985a, 1985b, 1987, 1988Walles and Rowley 1982); however, there are no reports of tapetal dysfunction leading to male sterility. Male sterility has only been reported in a few conifer species, including Pseudotsuga menziesii (Orr-Ewing 1978), Picea abies (Andersson 1947), and Cryptomeria japonica (Taira 2000), and only the latter study described anatomical detail.…”

Section: Discussionmentioning

confidence: 99%

Histology of sterile male and female cones in Pinus monticola (western white pine)

Wilson

Owens

2003

Sex Plant Reprod

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Two years of histological samples were collected from a Pinus monticola Dougl. (western white pine) tree identified as not producing mature pollen or seed cones. Anatomical information was collected to the ultrastructural level, to assess possible mechanisms for pollen and cone abortion resulting in sterility. Development of male and female gametophytes in the sterile western white pine tree was arrested after meiosis and before further cell divisions could take place. Sterile male gametophytes (pollen grains) had poorly developed pollen walls and sacci, reduced and degenerative cytoplasm, and no evidence of stored starch grains. The pollen cone aborted prior to pollen dehiscence. Meiosis of the megaspore mother cell in the ovule produced four megaspores, but development was stopped at the functional megaspore stage. The seed cone aborted in the first year of growth before winter dormancy. Tapetal tissue in sterile microsporangia appeared similar to that of fertile microsporangia, until the vacuolate, uninucleate microspore stage. Tapetal cells and thecal fluid surrounding the sterile microspores persisted well past the time when microsporangia on fertile trees started the process of maturation and desiccation. At pollen dehiscence, sterile pollen cones did not release any pollen and the microsporangia were filled with a sticky fluid. The behaviour of the tapetum in P. monticola sterile cones is compared with reports of tapetal function and malfunction reported in studies of angiosperm and other gymnosperm species. The occurrence and timing of gametophyte abortion in both cone sexes suggests a genetic rather than environmental basis for the sterility mechanism.

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“…The methods used for estimation of volume densities are outlined in Walles and Rowley (1982) and the methodological reference works of Steer (1981), Weibel (1980), andToth (1982). In the present report differentiation is much more dramatic than during earlier stages and can therefore be appreciated for many cytoplasmic structures in even a few selected figures for each phase.…”

Section: Sterometrymentioning

confidence: 95%

“…the six described in Walles and Rowley (1982), which include Nos. 2 and 3 above, plus a 1:l diluted Karnowsky mixture (No.…”

Section: Fixationmentioning

confidence: 98%

Cell differentiation in microsporangia of Pinus sylvestris. II. Early pachytene

Rowley

Walles

1985

Nordic Journal of Botany

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Tapetal cells of Pinus sylvesiris L. underwent one hypersecretory cycle during early pachytene and entered a second cycle by the time of mid pachytene in microspore mother cells. Initially in each cycle tapetal cells became papillaform then domeshaped and thereafter, in conjunction with radial narrowing of the cells, dilation of the ER system was intensive throughout the cytoplasm. Recovery from hyperactivity culminated with the presence of plasmodesma-like connections between tapetal cells and a period of mitosis in tapetal cells. The differentiation of tapetal cells occurred asynchronously within a microsporangium and their dedifferentiation began nonuniformly, becoming synchronous coincidental with the presence of "plasmodesmata". Microsporangia increased in size and tapetal cells were laterally wide before "plasmodesmata" receded and tapetal cells again differentiated asynchronously.

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Cell differentiation in microsporangia of Pinus sylvestris with special attention to the tapetum. I. The pre–and early–meiotic periods

Cited by 24 publications

References 20 publications

Cell differentiation in microsporangia of Pinus sylvestris. III. Late pachytene

Cell differentiation in microsporangia of Pinus sylvestris. III. Late pachytene

Histology of sterile male and female cones in Pinus monticola (western white pine)

Cell differentiation in microsporangia of Pinus sylvestris. II. Early pachytene

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