An investigation of the effects of Ca2+ channel inhibitors on branching and chemotropism in the oomycete Achlya bisexualis: Support for a role for Ca2+ in apical dominance

The mitotic cycle can be arrested in the apical summit of vegetative terminal buds of Tradescantia paludosa by restricting the level of nitrogen or light available to the plant. Cells in this portion of the bud are much more sensitive to these stress conditions than those in the subjacent portion of the meristem. This differential response induced the establishment of a quiescent "central zone" which is distinguished from the rest of the meristem by the apparent absence of mitosis and DNA synthesis, larger nuclear volume, and a lower histone content of chromatin. These features are identical with those imposed by apical dominance in apices of inhibited lateral buds.The results support the view that competition for nutrients is an important causal factor in apical dominance. They suggest also that competition for nutrients within the terminal bud meristem is important in the regulation of growth in vegetative shoots in respones to conditions of the environment.

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Meristem allocation and life-history evolution in herbaceous plants

Canadian Journal of Botany ◽

10.1139/b05-154 ◽

2006 ◽

Vol 84 (1) ◽

pp. 143-150 ◽

Cited By ~ 17

Author(s):

Stephen P. Bonser ◽

Lonnie W. Aarssen

Keyword(s):

Life History ◽

Apical Dominance ◽

Reproductive Effort ◽

Life History Evolution ◽

Meristem Development ◽

Vegetative Traits ◽

History Evolution ◽

Meristem Allocation ◽

Branching Intensity ◽

Iteroparous Species

Generalisations of life histories in plants are often framed in terms of allocation to reproduction. For example, relative allocation to reproduction is commonly found to be higher in semelparous than in iteroparous plant species. However, the association between vegetative traits and life history has been largely unexplored. In higher plants, reproductive and vegetative function can be measured in terms of meristem allocation. Under this approach, two vegetative traits (apical dominance (the suppression of axillary meristem development) and branching intensity (the commitment of axillary meristems to branches)) can be measured as well as one reproductive trait (reproductive effort). We used phylogenetically independent contrasts to compare reproductive and vegetative function in annual semelparous and perennial iteroparous species. Twenty congeneric species pairs (each species pair represented by one semelparous and one iteroparous species) across nine families were selected based on availability of herbarium specimens. Semelparous life-history evolution was associated with higher reproductive effort. Conversely, iteroparous life-history evolution was associated with higher apical dominance. Branching intensity was not associated with life history. An evolutionary association between life history and apical dominance but not branching intensity suggests a complex relationship between allocation to vegetative traits and the evolution of plant strategies across environments.

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Actin has multiple roles in the formation and architecture of zoospores of the oomycetes, Saprolegnia ferax and Achlya bisexualis

Journal of Cell Science ◽

10.1242/jcs.102.3.611 ◽

1992 ◽

Vol 102 (3) ◽

pp. 611-627 ◽

Cited By ~ 3

Author(s):

I. BRENT HEATH ◽

RUTH L. HAROLD

Keyword(s):

Cell Wall ◽

Germ Tube ◽

Multiple Roles ◽

Rhodamine Phalloidin ◽

Saprolegnia Ferax ◽

Functional Changes ◽

Specific Effects ◽

Changing Patterns ◽

Microtubular Root ◽

Achlya Bisexualis

Very similar changing patterns of actin are described with rhodamine-phalloidin labelling during the zoosporic life cycle of the oomycetes, Saprolegnia ferax and Achlya bisexualis. By comparing the changes with previously described ultrastructural and functional changes, we show that actin functions in numerous previously unrecognized processes. Most spectacularly, the directed vesicle expansions of the cytokinetic system involve newly formed actin which outlines the developing zoospores. Disruption of this actin with cytochalasins leads to abnormal cleavage as witnessed by the formation of enlarged and irregular cysts. Prior to cytokinesis, two new types of organelle are synthesized and one, known as K bodies, clusters around the nuclei. These organdies are actin-rich during development and clustering, consistent with actin functioning in their positioning. In the zoospores, actin is concentrated around the water expulsion vacuoles, indicating that they are contractile, and permeates the cytoplasm, probably with a skeletal role. This concept is supported by the first demonstration of actin specifically associated with a microtubular root in the secondary zoospore. Upon encystment there is a dramatic increase in stained actin in the form of peripheral plaques associated with the newly synthesized cell wall. When the cysts germinate, a fibrillar actin cap, comparable to that previously described in hyphal tips, forms in the germ tube apex, but only after cell wall softening to permit germ tube protrusion. This sequence is consistent with the actin cap modulating turgor-driven expansion of the tip as previously discussed for hyphae. In addition to disrupting cleavage-associated actin, cytochalasins show developmental stage, dose and drug (CE≥CD≥CB) specific effects on zoosporulation-related actin, which indicates that, contrary to previous suggestions, rhodamine-phalloidin staining is a useful indicator of actin behaviour in response to cytochalasins. These responses include differential effects on adjoining actin arrays, some of which are transient in the continued presence of the drugs, indicating a mechanism of drug adaptation.

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Axillary Bud Development in Pea: Apical Dominance, Growth Cycles, Hormonal Regulation and Plant Architecture

Cellular Communication in Plants ◽

10.1007/978-1-4757-9607-0_12 ◽

1993 ◽

pp. 75-86 ◽

Cited By ~ 11

Author(s):

Joel P. Stafstrom

Keyword(s):

Apical Dominance ◽

Hormonal Regulation ◽

Plant Architecture ◽

Axillary Bud ◽

Growth Cycles ◽

Bud Development

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Cost of apical dominance in two monocarpic herbs, Erysimum strictum and Rhinanthus minor

Canadian Journal of Botany ◽

10.1139/b00-033 ◽

2000 ◽

Vol 78 (5) ◽

pp. 591-599 ◽

Cited By ~ 5

Author(s):

Ari-Pekka Huhta ◽

Juha Tuomi ◽

Pasi Rautio

Keyword(s):

Apical Dominance ◽

Fruit Production ◽

Severe Damage ◽

Positive Effects ◽

Vegetative Biomass ◽

Branch Development ◽

Rhinanthus Minor ◽

Delayed Flowering ◽

The Cost ◽

Number Of Branches

Apical dominance is advantageous in conditions favoring rapid growth in height and unbranched architecture. The cost of apical dominance, on the other hand, should be expressed in conditions where fecundity increases along with an increasing number of branches. Apical damage can be used to measure such costs: when suppressed meristems are released from apical inhibition, the vegetative and reproductive productivity of initially unbranched plants should increase owing to the regrowth and increased branch development following damage. We studied these regrowth responses in two monocarpic herbs, Erysimum strictum P. Gaertn., B. Mey., and Scherb. and Rhinanthus minor L., after both apical damage (10% of the shoot cut) and more extensive damage (50 and 75% cutting). Both species tolerated apical damage, although severe damage had detrimental effects on the performance of both, especially R. minor. Apical damage had positive effects on most of the measured performance parameters of Erysimum. However, the success of seed germination collapsed, presumably due to delayed flowering and less successful pollination. The response was parallel in Rhinanthus; apical damage affected neither the vegetative biomass nor fecundity, but heavier damage, especially 75% clipping, led to severe reductions in most performance measures. The differences in regrowth responses are presumably due to the different habitat requirements of the species. Rhinanthus prefers relatively dense vegetation and starts to branch and produce flowers after a certain threshold in height has been reached, whereas Erysimum prefers gaps in vegetation. In this species, unbranched architecture may be favored in closed vegetation and branched architecture in less competitive habitats. In both species, fruit production correlated positively with the number of branches in both control and clipped plants, which is consistent with the assumption of the cost of apical dominance.Key words: apical dominance, competition, damage, meristem, overcompensation, regrowth.

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Media composition affects seed dormancy, apical dominance and phenolic profile of Knautia sarajevensis (Dipsacaceae), Bosnian endemic

Acta Botanica Croatica ◽

10.1515/botcro-2017-0011 ◽

2018 ◽

Vol 77 (1) ◽

pp. 70-79 ◽

Cited By ~ 1

Author(s):

Erna Karalija ◽

Sanja Ćavar Zeljković ◽

Petr Tarkowski ◽

Edina Muratović ◽

Adisa Parić

Keyword(s):

Apical Dominance ◽

Germination Rate ◽

Natural Habitat ◽

Basal Medium ◽

Shoot Proliferation ◽

Mineral Nutrient ◽

Total Phenolic ◽

Endemic Plant ◽

High Concentrations

AbstractKnautia sarajevensisis an endemic plant of the Dinaric Alps and is mainly distributed on Bosnian Mountains. Due to the quite large flower heads and easy maintenance, this plant has a potential use as a substitute ornamental plant forK. arvensisin perennial beds. The current study evaluated the germination process in different treatments in an attempt to suppress dormancy and increase germination rate, and to develop a successful protocol for micropropagation. An over 60% germination rate was achieved through cultivation of seeds on MS basal medium with reduced mineral nutrient composition and the absence of sucrose. On the other hand, a below 10% germination rate was achieved with untreated seeds. Suppression of apical dominance was achieved through application of high concentrations of kinetin, apical shoot decapitation or cultivation of shoots in liquid media. Overall, liquid cultures were more successful as a micropropagation system for this plant. Shoots spontaneously developed roots on multiplication treatments and were successfully acclimatized. Moreover, phenolic compound profile was analysed in the light of the possible medicinal potential of this plant. Variable amounts of total phenolic compounds as well as individual phenolics were recorded, according to treatment and solidification of media. An increase in rosmarinic acid content was reported for kinetin treatments and acclimatized plants comparing to mother plants in natural habitat. The present study shows that choice of cytokinin concentration, explant type as well as culture type influences not only shoot proliferation and apical dominance suppression but alsoin vitroproduction of phenolics.

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