Plants maintain water balance by varying hydraulic properties, and plasma membrane intrinsic proteins(PIPs) may be involved in this process. Leaf xylem and root hydraulic conductivity and the m RNA contents of four highly expressed Zm PIP genes(Zm PIP1;1, Zm PIP1;2, Zm PIP2;2, and Zm PIP2;5) in maize(Zea mays) seedlings were investigated. Under well-watered conditions, leaf hydraulic conductivity(K_(leaf)) varied diurnally and was correlated with whole-plant hydraulic conductivity. Similar diurnal rhythms of leaf transpiration rate(E), K_(leaf) and root hydraulic conductivity(K_(root)) in well-watered plants are important for maintaining whole-plant water balance. After 2 h of osmotic stress treatment induced by 10% polyethylene glycol 6000, the K_(root) of stressed plants decreased but K_(leaf) increased, compared with well-watered plants. The m RNA contents of four Zm PIPs were significantly up-regulated in the leaves of stressed plants, especially for Zm PIP1;2. Meanwhile, Zm PIP2;5 was significantly down-regulated in the roots of stressed plants. After 4 h of osmotic stress treatment, the E and leaf xylem water potentials of stressed plants unexpectedly increased. The increase in K_(leaf) and a partial recovery of K_(root) may have contributed to this process. The m RNA content of Zm PIP1;2 but not of the other three genes was up-regulated in roots at this time. In summary, the m RNA contents of these four Zm PIPs associated with K_(leaf) and K_(root) change in maize seedlings during short-term osmotic stress, especially for Zm PIP1;2 and Zm PIP2;5, which may help to further reveal the hydraulic resistance adjustment role of Zm PIPs. Leaf xylem and root hydraulic conductivity and the m RNA contents of four highly expressed Zm PIP genes (Zm PIP1; 1, Zm PIP1 Under well-watered conditions, leaf hydraulic conductivity (K_ (leaf)) varied diurnally and was correlated with whole-plant hydraulic conductivity (K_ (leaf)); 2, Zm PIP2; . Similar diurnal rhythms of leaf transpiration rate (E), K_ (leaf) and root hydraulic conductivity (K_ (root)) in well-watered plants are important for maintaining whole-plant water balance. After 2 h of osmotic stress treatment induced by 10% polyethylene glycol 6000, the K_ (root) of stressed plants decreased but K_ (leaf) increased, compared with well-watered plants. The m RNA contents of four Zm PIPs were significantly up-regulated in the leaves of stressed plants, especially for Zm PIP1; 2. Meanwhile, Zm PIP2; 5 After 4 h of osmotic stress treatment, the E and leaf xylem water potentials of stressed plants unexpectedly increased. The increase in K_ (leaf) and a partial recovery of K_ (root) may The RNA content of Zm PIP1; 2 but not of the other three genes was up-regulated in roots at this time. In summary, the m RNA contents of these four Zm PIPs associated with K_ (leaf) and K_ (root) change in maize seedlings during short-term osmotic stress, especially for Zm PIP1; 2 and Zm PIP2; 5, which may help further reveal the hydraulic resistance adjustment role of Zm PIPs.