Development of gravitropic response: unusual behavior of flax phloem G-fibers

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• 作者：Nadezda N. Ibragimova ; Marina V. Ageeva ; Tatyana A. Gorshkova
• 关键词：Callose ; Cell wall ; G ; layer ; Gravitropic response ; Linum usitatissimum ; Phloem fibers
• 刊名：Protoplasma
• 出版年：2017
• 出版时间：March 2017
• 年：2017
• 卷：254
• 期：2
• 页码：749-762
• 全文大小：
• 刊物类别：Biomedical and Life Sciences
• 刊物主题：Cell Biology; Plant Sciences; Zoology;
• 出版者：Springer Vienna
• ISSN：1615-6102
• 卷排序：254

文摘

The major mechanism of gravitropism that is discussed for herbal plants is based on the nonuniform elongation of cells located on the opposite stem sides, occurring in the growing zone of an organ. However, gravitropic response of flax (Linum usitatissimum L.) is well-pronounced in the lower half of developing stem, which has ceased elongation long in advance of plant inclination. We have analyzed the stem curvature region by various approaches of microscopy and found the undescribed earlier significant modifications in primary phloem fibers that have constitutively developed G-layer. In fibers on the pulling stem side, cell portions were widened with formation of “bottlenecks” between them, leading to the “sausage-like” shape of a cell. Lumen diameter in fiber widening increased, while cell wall thickness decreased. Callose was deposited in proximity to bottlenecks and sometimes totally occluded their lumen. Structure of fiber cell wall changed considerably, with formation of breaks between G- and S-layers. Thick fibrillar structures that were revealed in fiber cell wall by light microscopy got oblique orientation instead of parallel to the fiber axis one in control plants. The described changes occurred at various combinations of gravitational and mechanical stimuli. Thus, phloem fibers with constitutively formed gelatinous cell wall, located in nonelongating parts of herbal plant, are involved in gravitropism and may become an important element in general understanding of the gravity effects on plants. We suggest flax phloem fibers as the model system to study the mechanism of plant position correction, including signal perception and transduction.