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Russian biologists examined structure of division zone of plant roots

Biologists from the Novosibirsk State University (NSU) have addressed the 3D structure of a plant root apex, an essential domain of stem cells division.
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A root apex is assembled complexly and contains an area of apical meristem where stem cells can accumulate and undergo a cell division ensuring the growth of the root. To study the behavior of the cells in this particular area, the researchers from NSU, Institute of Cytology and Genetics of Siberian Division RAS, and other institutions of Russia and Germany have resorted to a trendy test object in physiology and genetics, Thale cress (Arabidopsis thaliana).

The nuclei of plant cells located on the root apex of Thale cress have been marked with fluorescent proteins, and then they have been scanned with laser confocal microscopy layer by layer without cutting the plant tissues. A special software has recognized the nuclei and also layer by layer has restored the 3D picture of the spatial structure. The obtained model has allowed for examining the interactions between the cells of the meristem.

The root of Thale cress contains two columns both of phloem (cortex) and xylem (wood pulp) which are conduction systems of a plant penetrating its whole length. They are located pairwise in such a way that one could draw two vertical planes with respect to which the composition and location of cells are symmetric. According to the scientists, such a structure signifies a well-balanced regime of division of stem cells and cell-precursors of mature tissues.

The «poles» of this structure is defined by the cells of protophloem and protoxylem which influence the rate of division of neighboring cells. In that way, the cells grasping protoxylem poles finish the division earlier, and transit to a «standby mode» which is preserved until these cells are not involved in the formation of side roots. The presence of such pole is characteristic also for the layer of tissue in the proximity around vascular cells (pericycle) and the next layer of cells (endodermis). The researchers suppose that this role of vessel system of a root is possible due to phytohormones with the gradient spreading from xylem in the transverse plane of a root.

The scientists have reported on the results in The Plant Journal.

Previously, Russian biologists found out that tomato growth undergoes in a mathematically optimal way.

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