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

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 (Lpr) and cortical cell (Lpc) hydraulic conductivity, cortical cell volume (Vc) and transcription levels of two putative plasma intrinsic aquaporin genes (PIPs) were investigated in wheat seedlings with different chromosome ploidy (Triticum monococcum (2X, AA); Triticum dicoccum (4X, BB); Triticum aestivum (6X, AABBDD)). The E, Lpr and Lpc of wheat increased with increasing ploidy, but the Vc was reduced. Osmotic stress significantly reduced the E, Lpc, Lpr, and the relative mRNA content of TaPIP1;2 and TaPIP2;5 in wheat. Under both well-watered and osmotic stress conditions, the Lpr was significantly and positively correlated with the E and Lpc, and the relative mRNA content of TaPIP1;2 and TaPIP2;5 was significantly and positively correlated with Lpc and Lpr, respectively. For well-watered or osmotically stressed wheat plants, the Lpc was reduced, but the Lpc/Lpr increased with increasing Vc, suggesting that Vc affects root radical water transport. Thus, the increased Lpc 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.