Т.В. Тарелкина, Л.Л. Новицкая.
Влияние экзогенной сахарозы на формирование флоэмы березы повислой, ольхи серой и осины
Keywords: sucrose; phloemogenesis; storage parenchyma; sclereids; fibers; starch
The study is a continuation of a series of experiments to identify the role of sucrose in the anomalous morphogenesis of conducting tissues of deciduous woody plants. Previously it was found that the exposure of the trunk tissue to solutions with a high concentration of sucrose causes birch and alder to form xylem, which has common features with the figured woods of these species, while aspen xylem does not differ in structure from typical wood. In this paper, the effect of sucrose solutions of various concentrations on the phloem formation is analyzed. In alder and aspen, high concentrations of sucrose (10% and 20%) was found to have no effect on the structure of the late phloem; the reaction of these species was manifested through a change in the functional state of parenchyma cells (an appearance of large central vacuole, accumulation of starch). At the same time there was a tendency to enhance parenchymatization of the birch late phloem with increasing concentration of sucrose in the solution, but the observed differences were not significant. In all studied species, in the variants with a sucrose concentration 1% - 5%, sclerenchyma elements differentiated in the conductive phloem, the latter is a structural anomaly for birch, but typical for alder and aspen. It was concluded that with an increase in the concentration of sugars in the cambial zone of birch above a certain threshold value, their utilization within the framework of the previous structure of tissues is not enough, and the formation of new storage cells and sclereids occurs. It has been suggested that alder and aspen have mechanisms that maintain the level of sucrose within the limits necessary for normal phloemogenesis, one of which, apparently, is the formation of thick-walled sclerenchyma elements. The difference in the metabolites stored by parenchyma cells under the experimental conditions is only a reason to believe that a large excess of sugars is normally absent in the tissues of the trunk of grey alder and aspen.
Indexed at RSCI