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Root gravitropism
Author(s) -
Masson Patrick H.
Publication year - 1995
Publication title -
bioessays
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.175
H-Index - 184
eISSN - 1521-1878
pISSN - 0265-9247
DOI - 10.1002/bies.950170207
Subject(s) - gravitropism , auxin , apoplast , biophysics , elongation , amyloplast , root cap , coleoptile , toad , pericycle , root hair , asymmetry , microbiology and biotechnology , botany , physics , biology , cell wall , plastid , meristem , arabidopsis , biochemistry , materials science , ecology , chloroplast , quantum mechanics , shoot , ultimate tensile strength , gene , mutant , metallurgy
When a plant root is reoriented within the gravity field, it responds by initiating a curvature which eventually results in vertical growth. Gravity sensing occurs primarily in the root tip. It may involve amyloplast sedimentation in the columella cells of the root cap, or the detection of forces exerted by the mass of the protoplast on opposite sides of its cell wall. Gravisensing activates a signal transduction cascade which results in the asymmetric redistribution of auxin and apoplastic Ca 2+ across the root tip, with accumulation at the bottom side. The resulting lateral asymmetry in Ca 2+ and auxin concentration is probably transmitted to the elongation zone where differential cellular elongation occurs until the tip resumes vertical growth. The Cholodny‐Went theory proposes that gravity‐induced auxin redistribution across a gravistimulated plant organ is responsible for the gravitropic response. However, recent data indicate that the gravity‐induced reorientation is more complex, involving both auxin gradient‐dependent and auxin gradient‐independent events.