Poster: Tropisms
Abs #
669: Water uptake by cells in gravitropically bending root of Pisum sativum L.
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Presenter: |
Miyamoto, Naoko , nmiya@cc.tuat.ac.jp |
Authors | Miyamoto, Naoko (A) Katsuhara, Maki (B) Ookawa, Taiichiro (A) Kasamo, Kunihiro (B) Hirasawa, Tadashi (A) | | Affiliations: |
(A): Faculty of Agriculture, Tokyo University of Agriculture and Technology
(B): Research Institute for Bioresources, Okayama University
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Gravitropism of plant roots is very important phenomena in determining direction of root elongation. The process of gravitropism consists of three major stages: (1) perception of gravi-stimulus by root cap, (2) signal transmission to elongating region, (3) differential elongation. Difference in elongation rates between both sides of gravitropically bending root was significant and biggest in the region that had been 2-4 mm from the root tip at the start of the measurement. Volume increasing rate per unit surface area of cortical cells on the upper side of the root was bigger than the other side by factors of 2.8-3.8. There were no differences in water potential, osmotic potential and turgor pressure of elongating tissue between the both sides of the root. These potentials of mature tissue were not different between the both sides of the root as well. Water potential of the elongating tissue was lower than the mature tissue because of the lower value of osmotic potential. Since the root elongated in humid air, water moved from the mature tissue to the elongating tissue due to this water potential difference, that is growth-induced water potential. According to the Lockhartfs equation, it was found that the differential elongation was induced by the difference in hydraulic conductivity of the tissue. Antibodies were raised against the conserved region of water channel proteins including NPA motif. There were no significant differences in the amounts of putative water channel proteins between the both sides of the root. These results indicate that hydraulic conductivity in differentially elongating tissue might be regulated by changing the activity of water channel proteins, for example phosphorylaiton, rather than the amount of the proteins.
