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101.
102.
Summary A steep, oscillating tip-focused gradient in cytosolic free calcium ([Ca2+]c) has been implicated in pollen tube growth. Further understanding of the biological causes and consequences of these processes relies on the precise imaging of [Ca2+]c during the different growth phases. In this work, the minimum technical requirements for confocal [Ca2+]c imaging ofAgapanthus umbellatus pollen tubes were examined. A range of dyes, dye forms, and loading methods were compared. Non-ratio and ratio imaging were critically analysed, in terms of the detection of the [Ca2+]c gradient and its fluctuations over time. Both ratiometric and nonratiornetric methods detected relative changes in [Ca2+]c. However, visualisation of the [Ca2+]c gradient, with an accurate spatial definition, was only possible with ratiometric methods. The gradient observed in this study ranged from 1.8 M (tip) to 180–220 nM (basal level), within the first 4–10 m. Apical [Ca2+]c fluctuations with an amplitude between 415 nM and 1.8 M showed a period of 40 to 75 s. All protocols for dye-loading proved to have strengths and weaknesses. Thus, the choice of a dye and its loading procedure should consider the required imaging period, extent of sequestration, effect on cell performance and viability, ease of loading procedure, and aim of the study. The present study constitutes an examination of the [Ca2+]c gradient in pollen tubes by these criteria.Abbreviations CLSM
confocal laser scanning microscope
- [Ca2+]c
cytosolic free calcium
- PT
pollen tube
Dedicated to Professor Walter Gustav Url on the occasion of his 70th birthday 相似文献
103.
In laboratory experiments, we used fluorescent dye markers to investigate processing of organic matter by larvae of Psectrocladius
limbatellus (Holm.) (Diptera: Chironomidae). 59% of the organic matter used was incorporated into tubes, 39% was present in
faecal pellets (both after 24 h), and 2% was found in the larval gut at the end of experiments. Ingested matter passed through
the gut rapidly, resulting in the gut being emptied more than 20 times each day. Further 24-h experiments using dye-marked
faecal pellets showed that 6% of pellets produced were re-ingested and 12% were incorporated into tubes. There was no preference
for conditioned faecal pellets as food over those that had recently been egested and tubes also provided a food reserve on
which larvae feed. Chironomid larvae recycle organic matter resulting in its mineralization and their ‘engineering’ has a
dramatic effect on the substratum.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
104.
The callose synthase (UDP-glucose: 1,3-β-d-glucan 3-β-d-glucosyl transferase; EC 2.4.1.34) enzyme (CalS) from pollen tubes of Nicotiana alata Link et Otto is responsible for developmentally regulated deposition of the cell wall polysaccharide callose. Membrane preparations
from N. alata pollen tubes grown in liquid culture were fractionated by density-gradient centrifugation. The CalS activity sedimented to
the denser regions of the gradient, approximately 1.18 g · ml−1, away from markers for Golgi, endoplasmic reticulum and mitochondria, and into fractions enriched in ATPase activity and
in membranes staining with phosphotungstic acid at low pH. This suggests that pollen-tube CalS is localised in the plasma
membrane. Callose synthase activity from membranes enriched by downward centrifugation was solubilised with digitonin, which
gave a 3- to 4-fold increase in enzyme activity, and the solubilised activity was then enriched a further 10-fold by product
entrapment. The complete procedure gave final CalS specific activities up to 1000-fold higher than those of pollen-tube homogenates.
Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that several polypeptides co-fractionated with CalS activity
through purification, with a polypeptide of 190 kDa being enriched in product-entrapment pellets.
Received: 24 September 1997 / Accepted: 12 November 1997 相似文献
105.
百合花粉及花粉管内微丝和微管的分布 总被引:7,自引:0,他引:7
利用免疫荧光定位及荧光定位方法,结合共焦激光扫描显微镜,对百合(LiliumdavidiDuch.)花粉及花粉管内微丝及微管的分布进行了观察,得出了一些新的结果:1化学固定方法可以较好地保存花粉和花粉管内的微丝,从而可以在此条件下较好地进行微管和微丝的双标记,并进行两者相互关系的研究;2在距花粉管顶端10~20μm的范围内,用化学固定及TRITC鬼笔碱标记显示微丝的存在是很微弱的,基本上无法看到明显的微丝束,而同时用免疫荧光法标记却发现此部位微管很丰富,在花粉管顶端微管形成浓密的网状,而且其末端与花粉管顶端质膜相连;3在花粉管中,只有少数微丝与微管相互平行排列,而其中大多数微丝骨架与微管骨架并不存在共分布现象。为了解花粉管内微管和微丝的功能及相互关系提供了新的证据。 相似文献
106.
Pollen tube growth is a vital process for angiosperm fertilisation and is dependent on the presence of a tip-focused gradient
of cytosolic free calcium ([Ca2+]c). In order to clarify some of the target molecules which convey the Ca2+ signal information, we investigated calmodulin distribution during tube growth. Fluorescently labelled calmodulin was pressure
microinjected into pollen tubes and its distribution monitored by confocal microscopy. Calmodulin distributes evenly throughout
the cell, but some of its binding sites form a V-shaped collar behind the apical region. This specific association dissipates
upon growth arrest, and suggests an interaction of calmodulin with cytoskeletal-bound target proteins. The distribution of
calmodulin mRNA was also analysed by microinjection of fluorescently labelled mRNA. No specific pattern was observed, with
an even localisation in the body of tube and a lower concentration in the cell apex. Studies with localised application of
inhibitors/activators indicate that calmodulin plays a crucial role in tip elongation but does not direct tube orientation.
Received: 6 March 1998 / Revision accepted: 20 April 1998 相似文献
107.
V. Negrón-Ortiz 《Sexual plant reproduction》1998,11(4):208-212
Opuntia spinosissima (Martyn) Mill. (Cactaceae) is an extremely rare taxon with a single remaining wild population of 13 plants located on Little
Torch Key, Florida. The plants rarely set viable seeds and most ovaries abscise without initiation of fruits. Pollination
and breeding system were examined in Little Torch Key and in plant accessions located at Fairchild Tropical Garden. Four pollination
treatments were carried out to test for apomixis, self-pollination, outcrossing, and autogamy; a control treatment was also
monitored. Additionally, pollen viability, pollinators, and seed set and viability were investigated. On selfed, crossed,
and open (control) stigmas pollen grains germinated, but the tubes usually did not reach the base of the style. This suggests
that O. spinosissima has pre-zygotic self-incompatibility. None of the pairwise crosses set seed, so the extant plants were apparently not inter-compatible.
Out of 173 manipulated and control flowers, only one set fruit. Although this flower was outcrossed, no pollen tubes germinated
on the stigma; this suggests agamospermy, a process common in the Cactaceae. In those flowers where pollen tubes did reach
the ovary they failed to penetrate ovules, suggesting ovarian inhibition or that this taxon has lost the ability to be fertilized.
Most field-collected seeds were viable, but there is no seedling recruitment under natural conditions, and vegetative reproduction
is common. Based on these findings, I hypothesize that O. spinosissima is a sterile polyploid and that the 13 extant plants are asexually derived from a single lineage.
Received: 17 April 1998 / Revision accepted: 3 July 1998 相似文献
108.
外源钙调素和钙调素拮抗剂对烟草离体花粉管生长和生殖核分裂的调节 总被引:1,自引:0,他引:1
外源花椰菜钙调素(CaM)、牛脑CaMagarose以及CaM拮抗剂TFP对花粉管生长与生殖核分裂的作用均具有浓度和时间效应,CaM在花粉管生长早期,较低浓度能促进花粉管生长和生殖核分裂;但后期,较高浓度则有抑制作用。ITP在花粉管生长早0000000000000期,较高浓度抑制花粉管生长和生殖核分裂。 相似文献
109.
110.
U.S. women of childbearing age who are at possible increased risk of a neural tube defect‐affected pregnancy due to suboptimal red blood cell folate concentrations,National Health and Nutrition Examination Survey 2007 to 2012
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