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Signals flowing from mature tissues to shoot apical meristem affect phyllotaxis in coniferous shoot

100%
Banasiak A., Zagorska-Marek B.
Acta Societatis Botanicorum Poloniae
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2006
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tom 75
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nr 2
113-121
Axial homodromy in growing shoots of perennial plants with spiral phyllotaxis is the case when the chirality of phyllotactic pattern does not change in consecutive growth increments of the same axis. In conifers such as Picea or Abies this rule is strictly observed, except for the rare cases of discontinuous phyllotactic transitions. In Torreya, however, the chirality changes, at random, every year. The pattern of primordia packing, executed by vegetative shoot apical meristem (SAM), depends in Torreya on their identity. The primordia of bud scales are initiated in the decussate and those of needles in bijugate spiral pattern. The decussate, achiral i.e. neutral pattern always precedes the formation of new spiral pattern and thus facilitates random selection of its chiral configuration. Periodic change in organ identity cannot itself be responsible for the special behavior of Torreya, because in other conifers it also exists. There is, however, one important difference: in Torreya, when the initiation of bud scales begins at SAM, the distance between differentiated protoxylem and the initiation site gradually increases, while in other conifers it remains constant and small. In Torreya, at this phase of development, the rate of xylem differentiation and the rate of organogenesis become uncoupled. Closer anatomical examination shows that the decussate pattern in a bud scale zone develops slowly suggesting gradual decrease of the putative signal flowing acropetally from differentiated protoxylem, responsible for positioning of primordia. We hypothesize that in the absence of this signal SAM starts acting autonomously, distributing primordia according to their identity only. A constant presence of the signal in other conifers assures the continuation of the same phyllotactic pattern throughout the period of bud scale formation, despite the change in organ identity.
2
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Geometric parameters of the apical meristem and the quality of phyllotactic patterns in Magnolia flowers

100%
Wiss D., Zagorska-Marek B.
Acta Societatis Botanicorum Poloniae
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2012
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tom 81
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nr 3
The ratio of primordium size to the meristem size (P/M ratio) is regarded by some geometrical models of phyllotaxis as the parameter, which determines the quality of spiral and whorled patterns of lateral organ arrangement. This assumption was tested on floral meristems in four genets representing four Magnolia taxa: M. × salicifolia, M. stellata, M. denudata and M. acuminata. In successive zones of Magnolia flower, lateral organs are initiated in specific phyllotactic patterns and at specific values of the meristem and primordia sizes. The elements of perianth, usually positioned in three trimerous whorls, are initiated as large primordia on relatively small meristem. The switch in the identity of primordia, from tepals to stamens is accompanied by an abrupt increase in the size of the meristem and decrease in the primordia size. Small values of P/M ratio and frequent occurrence of qualitative transformations of phyllotaxis contribute to the exceptionally rich spectrum of spiral patterns in androecium zone. New spiral patterns emerge when bigger primordia of carpels are initiated on the meristem, which at the same time starts diminishing in size either abruptly (M. × salicifolia, M. stellata, M. acuminata) or slowly (M. denudata). Spiral patterns identified in gynoecia have lower numbers of parastichies than the patterns of androecia and occur in frequencies specific for the genet. Although noted ranges of the meristem and primordia sizes, justify the occurrence of phyllotactic patterns observed in successive zones of Magnolia flower, they do not explain genet-specific frequencies of the patterns observed in gynoecium zone. The lack of straightforward relationship between frequency of the patterns and P/M ratio in gynoecium suggests that more complex geometrical factors or factors of non-geometrical nature are engaged in determination of Magnolia floral phyllotaxis.
3

Morphogenetic effects in shoot apices of Torreya nucifera Sieb.et Zucc. cultured in vitro

100%
Matkowski A.
Acta Biologica Cracoviensia. Series Botanica. Supplement
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1999
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tom 41
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nr 1
4
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Effect of ascorbic acid concentration on structural characteristics of apical meristems on in vitro Aloe barbadensis Mill.

80%
Kaviani B.
Acta Scientiarum Polonorum. Hortorum Cultus
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2014
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tom 13
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nr 3
Ascorbic acid is one of the major metabolite in higher plants cells which is known as effective factor when the cells enter to “S” phase from “G1” phase of cytokinesis. This metabolite has antioxidant activity and increases plant tolerance against stressors such as salinity, pathogens, ozone, UV rays, etc. The current study used the common cellular and histological methods to evaluate the effect of 0.05 to 2.5 mM ascorbic acid on vegetative meristems of Aloe barbadensis plants obtained from stem explants propagated in vitro culture conditions. Results showed that low concentrations of ascorbic acid (0.5 to 1 mM) increase mitotic index in apical meristem and root quiescent center (QC). Moreover, treatment with ascorbic acid increases cellular dimensions in cell elongation region of root and mitotic divisions in this region. In some measurements, it was clear that in addition to increase root length in plants treated with ascorbic acid, distance from root hairs zone to root cap increases compared to the control, which is a logical conclusion from increasing cell elongation and divisions in cell elongation zone. Also, ascorbic acid increased production of secondary roots through stimulating cells of pericycle and increasing divisions in this region. Apical meristem of stem treated with ascorbic acid had more convexity homogenous with more chromophilic level. Increasing stem length and number of leaves in plants treated with ascorbic acid could be related to the high cells’ mitotic activity in stem apical meristem. Moreover, ascorbic acid could stimulate cell division, increasing area of meristem zone, and effective on severity of differentiation
5

How real is a computer-made phyllotactic lattice of magnolia's generative shoot?

80%
Wiss D., Zagorska-Marek B.
Biological Letters
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2005
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tom 42
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nr 2 Spec.Vol.
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