02728naa a2200277 a 450000100080000000500110000800800410001902400350006010000240009524501690011926000090028852019290029765000090222665000100223565000090224565000100225465300230226470000210228770000200230870000190232870000180234770000200236570000150238570000190240077300310241919615412023-05-19       2013    bl uuuu     u00u1 u    #d7 a10.1007/s11104-013-1662-82DOI1 aCOELHO FILHO, M. A.  aThe involvement of gibberellin signalling in the effect of soil resistance to root penetration on leaf elongation and tiller number in wheat.h[electronic resource]  c2013  aBackground and aims The concept of root-sourced chemical signals that affect shoot growth in response to drought is widely reported; in particular the role of ABA in regulating stomatal conductance has received much attention. ABA, alone, does not fully explain all the effects of abiotic stresses in the root zone on shoot architecture. An increase in mechanical impedance, which can occur on even relatively modest soil drying, results in reduced root and shoot growth, processes that are potentially regulated by gibberellins (GAs). Methods In this study we explored the role of mechanical impedance and exogenous gibberellin (GA3) on root and shoot architecture in wheat seedlings containing the Rht-B1a (tall), Rht-B1b (semi-dwarf) or Rht-B1c (dwarf) alleles in the April-Bearded or Mercia backgrounds. Our experiments were based on the use of the sand culture system which allows the mechanical impedance of the root growth environment to remain constant and independent of water and nutrient availability. We investigated the effects of the application of exogenous GA3 to the root system. Results We found that impeding soil reduced leaf elongation in the tall and semi-dwarf lines, confirming the stunting effect of mechanical impedance which is widely reported. However, leaf elongation in the dwarf lines was not affected by root impedance. Application of GA3 to the roots restored leaf elongation in the tall and semi-dwarf lines growing in impeding soil, with some growth response even in the dwarf line, the longest leaves being obtained when GA was applied to impeded roots of a tall line. Both exogenous GA and root impedance reduced the number of tillers, but there was no interaction with the Rht genotype. The genetic background did not affect the results. Conclusion We suggest that the GA signaling pathway has an unidentified role in the leaf elongation response to mechanical impedance to root growth.  aSoil  aWheat  aSolo  aTrigo  aAlongamento foliar1 aCOLEBROOK, E. H.1 aLLOYD, D. P. A.1 aWEBSTER, C. P.1 aMOONEY, S. J.1 aPHILLIPS, A. L.1 aHEDDEN, P.1 aWHALLEY, W. R.  tPlant ad Soil, March 2013.