Different root low temperature response of two maize genotypes differing in chilling sensitivity

Here we report on the root hydraulic properties of intact and excised root systems of two maize genotypes differing in chilling sensitivity (Z7, tolerant and Penjalinan, sensitive) subjected for 3 d to 5 °C. When root hydraulic conductance (L) was measured under a hydrostatic force using an excised root system in a pressure chamber, an initial decrease of L was observed in both genotypes. However, the value of L increased in the chilling tolerant genotype after 30 h at 5 °C; in the chilling sensitive Penjalinan genotype there was no such increase. Osmotic root hydraulic conductance was measured in excised root systems exuding under atmospheric pressure. We observed a progressive decline during the chilling treatment of the osmotic root hydraulic conductance in the chilling sensitive Penjalinan plants; however, after 54 h at 5 °C, the chilling tolerant Z7 plants had a significantly higher osmotic hydraulic conductance. Moreover, in the chilling tolerant plants we found an increase in the inhibition caused by HgCl2 of the osmotic hydraulic conductance during the chilling treatment, indicating a possible increase in the contribution of aquaporins to root hydraulic conductance in the chilling tolerant Z7 plants during chilling treatment.