Microsurgical removal of epidermal and cortical cells: evidence that the gravitropic signal moves through the outer cell layers in primary roots of maize |
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Authors: | Rick L Yang Michael L Evans Randy Moore |
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Institution: | (1) Department of Botany, Ohio State University, 43210 Columbus, OH, USA;(2) Department of Biological Sciences, Wright State University, 45435 Dayton, OH, USA |
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Abstract: | There is general agreement that during root gravitropism some sort of growth-modifying signal moves from the cap to the elongation
zone and that this signal ultimately induces the curvature that leads to reorientation of the root. However, there is disagreement
regarding both the nature of the signal and the pathway of its movement from the root cap to the elongation zone. We examined
the pathway of movement by testing gravitropism in primary roots of maize (Zea mays L.) from which narrow (0.5 mm) rings of epidermal and cortical tissue were surgically removed from various positions within
the elongation zone. When roots were girdled in the apical part of the elongation zone gravitropic curvature occurred apical
to the girdle but not basal to the girdle. Filling the girdle with agar allowed curvature basal to the girdle to occur. Shallow
girdles, in which only two or three cell layers (epidermis plus one or two cortical cell layers) were removed, prevented or
greatly delayed gravitropic curvature basal to the girdle. The results indicate that the gravitropic signal moves basipetally
through the outermost cell layers, perhaps through the epidermis itself. |
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Keywords: | Auxin and gravitropism Gravitropism (signal transmission Root (gravitropism) Zea (gravitropism) |
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