The root cortex cell hydraulic conductivity is enhanced with increasing chromosome ploidy in wheat

Abstract Wheat ( Triticum spp.) root water uptake is enhanced with increasing chromosome ploidy, but the underlying mechanism is unclear. The leaf transpiration rate ( E ), individual root ( Lp r ) and cortical cell ( Lp c ) hydraulic conductivity, cortical cell volume ( V c ) and transcription levels of two putative plasma intrinsic aquaporin genes ( PIP s) were investigated in wheat seedlings with different chromosome ploidy ( Triticum monococcum (2X, AA); Triticum dicoccum (4X, BB); Triticum aestivum (6X, AABBDD)). The E , Lp r and Lp c of wheat increased with increasing ploidy, but the V c was reduced. Osmotic stress significantly reduced the E , Lp c , Lp r , and the relative mRNA content of TaPIP1;2 and TaPIP2 ; 5 in wheat. Under both well-watered and osmotic stress conditions, the Lp r was significantly and positively correlated with the E and Lp c , and the relative mRNA content of TaPIP1;2 and TaPIP2;5 was significantly and positively correlated with Lp c and Lp r , respectively. For well-watered or osmotically stressed wheat plants, the Lp c was reduced, but the Lp c / Lp r increased with increasing V c , suggesting that V c affects root radical water transport. Thus, the increased Lp c and transcription levels of TaPIP1;2 and TaPIP2;5 in wheat roots provides insight into the mechanisms underlying enhanced root water uptake with increasing chromosome ploidy during wheat evolution.