Differences in water use efficiency and aquaporin gene expression in waxy maize varieties under different stress conditions

Aquaporin (AQP) is critical in coupling water and nutrients, which is an important mechanism of crop water (WUE) and nutrient (NUE) use efficiency. Differences in leaf water use efficiency (LWUE) and in aquaporin gene expression in waxy maize varieties were tested under various stress conditions. The stress conditions used in the study included low nitrogen (0.5N, half dose nitrogen of 0.5 Hoagland solution), high nitrogen (1.5N, 1.5 times nitrogen of 0.5 Hoagland solution), drought (10% PEG with -0.1 MPa water potential ) and salt (200 mmol·L^-1 NaCl). Expressions of three AQP genes in the roots of waxy maize were tested by the RT-PCR method. The results showed that LWUE in three waxy maize varieties was less under 0.5N treatment than that under CK. It was, however, higher than that of CK under 1.5N and PEG treatments. TIP2a, TIP2b and TIP3.1 genes expressions were partially or completely suppressed under 0.5N stress treatment. The gene expressions were, however, amplified under 1.5N (for 6 h) and PEG (for 9 h) treatments. This suggested that TIP gene family was enhanced by nitrogen, drought and salt stress. Furthermore, the expression of TIP and LWUE were weaker under 0.5N treatment than under CK, but stronger on different degrees under PEG and 1.5N treatments than under CK. Close relations were noted between TIP gene expression and change in WUEL. These findings indicated that WUE was largely controlled by the levels of TIP expression, which was different among waxy maize varieties.