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Digitale Medien

Effects of prior self-pollination on outcrossed seed set in tristylous Pontederia sagittata (Pontederiaceae) (1994)

Scribailo, R. W. ; Barrett, S. C. H.

Springer

Sexual plant reproduction 7 (1994), S. 273-281

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ISSN: 1432-2145

Schlagwort(e): Pollen-pistil interference ; Prior self-pollination ; Tristyly ; Self-incompatibility Stylar senescence

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract The potential inhibitory effects of incompatible pollen on outcrossed seed set were investigated in mass-flowering, self-incompatible, tristylous Pontederia sagittata. Prior application of self pollen, followed after 2, 4, or 6 h by compatible pollen, was conducted on five genotypes of each of the three style morphs under uniform glasshouse conditions. The greatest reductions in seed set occurred in pollinations of the long-styled (L) morph at the 6 h time interval. Smaller reductions were also found for this treatment in the mid-styled (M) morph. No significant reductions in seed set were observed in the short-styled (S) morph or in the other morphs at shorter time intervals. Observations of pollen germination and pollen tube growth indicated that the lack of inhibitory effects in the S morph may occur because relatively few pollen grains adhered to stigmas in selfpollinations. In the L and M morphs, early germination of self pollen may cause physical clogging of the stigma and style, resulting in a reduced number of compatible pollen tubes in styles. Observations of the structural integrity of styles indicated that prior germination of self pollen resulted in more rapid onset of pistil senescence, particularly in the L morph. These influences may contribute to the morph-specific differences in seed set observed following prior self-pollination of outcrossed flowers. The negative effects of incompatible pollen are likely to be most evident where ecological factors cause delays in the delivery of outcross pollen to stigmas.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00227709

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Digitale Medien

Pollinator foraging behavior and pollen collection on the floral morphs of tristylous Pontederia cordata L. (1987)

Wolfe, L. M. ; Barrett, S. C. H.

Springer

Oecologia 74 (1987), S. 347-351

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ISSN: 1432-1939

Schlagwort(e): Pontederia cordata ; Bombus ; Tristyly ; Pollination ; Behavior

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary The foraging behavior of the pollinators of tristylous Pontederia cordata was studied to determine if differences in floral morphology would lead to preferential visitation of the floral morphs. Although nectar production is not different in the three floral morphs, differences in the production and size of pollen grains produced by the three anther levels results in the morphs offering variable amounts of resources to pollen-collecting insects. Bumblebees (Bombus spp.) and the solitary bee Melissodes apicata used P. cordata primarily as a nectar source and therefore did not seem to exhibit any morph preference. In contrast, honeybees visited flowers mainly for pollen and preferred to forage on long-level anthers of the short-and mid-styled morphs. An analysis of the composition of corbicular pollen loads indicated that, relative to the frequency of production in the population: 1) honeybees collected an excess of pollen from long-level anthers; 2) bumblebees collected the three types of pollen without any apparent preference; and 3) M. apicata preferentially collected pollen from the short-level anthers — presumably because their proboscides are modified by the presence of tiny hairs. The results suggest that P. cordata in Ontario is serviced by a diverse, unspecialized pollinator fauna which is not co-adapted to the tristylous floral polymorphism.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00378928

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Digitale Medien

Variation in expression of trimorphic incompatibility in Pontederia cordata L. (Pontederiaceae) (1985)

Barrett, S. C. H. ; Anderson, J. M.

Springer

Theoretical and applied genetics 70 (1985), S. 355-362

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ISSN: 1432-2242

Schlagwort(e): Trimorphic incompatibility ; Pontederia cordata L.

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Summary Pontederia cordata L. (Pontederiaceae), a perennial diploid, possesses the rare genetic polymorphism tristyly. A controlled pollination programme was conducted over a three year period, under glasshouse conditions, on 36 clones of P. cordata var. cordata to examine the nature of the self-incompatibility system. The three major findings of the pollination study were: (1) the three floral morphs display different levels of self-incompatibility, (2) pollen from the two anther levels within a flower exhibits different compatibility behaviour in self-pollinations, (3) considerable individual genetic variation in the expression of self-incompatibility is evident among clones within floral morphs. Similar results were also obtained from a smaller study on 15 clones of P. cordata var. lancifolia conducted over a 6 month period. In common with other Pontederia species the mid-styled morph (M) of P. cordata produces large amounts of seed when self-pollinated with pollen from long-level anthers. A developmental model is proposed to explain the high level of self-compatibility of the M morph in Pontederia species. Self-pollination of segregating progenies from M and S morphs of known incompatibility status demonstrated that the expression of incompatibility is closely associated with style length. It is suggested that overall differences in incompatibility behaviour among the floral morphs may be due to the pleiotropic effects of major genes controlling sub-characters of the tristylous syndrome, rather than linked modifier genes. However, the variable expression of trimorphic incompatibility within floral morphs suggests that this variation may be polygenic in origin.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00273739

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Digitale Medien

Investigations into the development of the pituitary gland-thyroid tissue axis and distribution of tissue thyroid hormone content in embryonic coho salmon (Oncorhynchus kisutch) from Lake Ontario (1993)

Leatherland, J. F. ; Barrett, S. B.

Springer

Fish physiology and biochemistry 12 (1993), S. 149-159

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ISSN: 1573-5168

Schlagwort(e): salmon ; eggs ; embryos ; larvae ; thyroid hormones ; development ; ontogeny ; pituitary gland ; thyrotropic cells

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Total organism content of L-thyroxine (T4) and triiodo-L-thyronine (T3) were measured in the early developmental stages of a stock of Lake Ontario coho salmon from the egg to the yolk absorption stage. Whole organism T4 levels were constant between the egg and pre-hatch embryo stages, but fell progressively during yolk absorption. T3 levels were low from egg to eye-pigment appearance, but then increased prior to hatch and fell again during the post-hatch yolk absorption period. When expressed as ng/tissue, T4 content of the body compartment rose progressively between days 67 and 87 post-fertilization, whilst T4 content of the yolk compartment fell progressively during the same period; the pattern was not evident for tissue T3 content. When expressed as ng/g dry weight of tissue, the inverse relationship was found for T4, and T3 content of the body and yolk compartments decreased progressively and increased progressively, respectively during the same period, suggesting that thyroid hormones were selectively retained in the yolk compartment. Intensely “immunostained” (using anti-human β-TSH antibody) thyrotropic cells were present in small numbers in the pars distalis of the embryonic pituitary at the eye-pigment appearance stage, and the numbers increased markedly until the pre-hatch period. Administration of either bovine thyrotropic hormone (bTSH) or ovine growth hormone (oGH) had no effect on thyroid hormone content of larvae challenged during the yolk absorption period, suggesting that the thyroid tissue was not responsive to exogenous bTSH challenge at this time, and that oGH-sensitive 5′-monodeiodination was either not present or at levels that were too low to cause an elevation in total T3 content, or that the substrate levels were insufficient to permit a measureable increase in whole body T3 content.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00004380

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Digitale Medien

Changes in the lipid composition and maximisation of the polyunsaturated fatty acid content of three microalgae grown in mass culture (1993)

Dunstan, G. A. ; Volkman, J. K. ; Barrett, S. M. ; [weitere]

Springer

Journal of applied phycology 5 (1993), S. 71-83

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ISSN: 1573-5176

Schlagwort(e): Isochrysis ; lipid ; mariculture ; mass culture ; microalgae ; Nannochloropsis ; nutrition ; Pavlova ; polyunsaturated fatty acids

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Notizen: Abstract Three species of microalgae were grown in mass culture to investigate the influence of culture technique and growth phase on the production of 20:5(n−3) and 22:6(n−3). These polyunsaturated fatty acids (PUFA) are considered to be essential in many marine animals diets for high growth and survival rates. The species of microalgae examined wereNannochloropsis oculata, Pavlova lutheri andIsochrysis sp. (clone T.Iso). All batch cultures (logarithmic and stationary phase) and semi-continuous cultures (logarithmic phase) examined contained high levels of the long-chain (n−3) PUFA, but production could be maximised by harvesting at specific times and growth phases. Maximum cellular content (pg cell-1) of long-chain PUFA was found in logarithmic phase batch cultures ofN. oculata and in stationary phase cultures ofP. lutheri. The cellular content of PUFA in cultures ofIsochrysis sp. did not change significantly with culture technique or growth phase. Alternatively, stationary phase cultures of all three species showed increased proportions (%) and cellular contents of triacylglycerols, and saturated and monounsaturated fatty acids with correspondingly decreased proportions of polar lipids and most PUFA relative to logarithmic phase cultures. The exception was the proportion and cellular content of 22:6(n−3) inP. lutheri which increased with triacylglycerol content. The mass of long-chain (n−3) PUFA per volume of culture was significantly higher in stationary phase cultures due to the higher cell counts per volume. These findings indicate that the opportunity exists to maximise PUFA production by microalgae with the potential to improve animal growth and reduce production costs in mariculture operations and may be of use in the large scale culture and harvesting of microalgae for the biotechnology industry.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF02182424

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