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Rhodamine-phalloidin staining of winter oilseed rape suspension cells revealed that the structure of actin cytoskeleton changes
with the phase of cell growth. In small, 4-day-old cells, entering the exponential phase of growth, a dense and uniformly
distributed cortical microfilament networks was seen. In six-day-old vacuolated cells, which reached the stationary phase
of growth, the actin cytoskeleton was composed of thicker microfilament cables in irregular arrangements. In cells acclimated
in cold for 7 days a dense, uniformly distributed and cortical microfilament network was still seen. The fine microfilament
network was sensitive to extracellular freezing since the structures underwent depolymerization at −3 °C (in the presence
of extracellular ice), both in non-acclimated and cold-acclimated cells. The thicker transvacuolar cables in cells of the
stationary growth phase resisted freezing to −7 °C. Acclimation of suspensions at 2 °C resulted in slowing down growth of
cells and in the increased freezing tolerance of cells as indicated by a decrease of LT50 from −11 °C to −17.5o or to −25 °C when determined 7 or 20 days after the beginning of the cold treatment, respectively. Freezing tolerance of
non-acclimated cells decreased from −11 °C to −8 °C during subculture, showing a transient increase to −17 °C on the day 6.
Results indicate that the arrangement of actin microfilaments and their sensitivity to freezing-induced depolymerization depends
on the phase of cell growth rather than on cell acclimation status. Possible mechanisms involved in the freezing-induced depolymerization
of actin microfilaments are discussed.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
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Stefania Egierszdorff 《Biologia Plantarum》1981,23(2):110-115
In a 9-year-old pine girdled during the winter cambial activity was observed below the girdle in the next spring. This indicates
that cambial activity was initiated without auxin produced in the spring by buds. The auxin produced in apical shoots successively
flows down the stem, where as a result of periodic restriction in transport it remains over the winter till the next year.
This auxin of apical origin but locally stored over the winter in the stem is responsible for the activation of cambium before
the new flow of auxin produced in the apical meristems arrives. Calculations based on seasonal changes in auxin levels can
explain both, earlier spring activation of cambium in the crown and the temporary cambial divisions below the girdle, without
assumption of direct auxin synthesis in the lateral meristems. 相似文献
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