Inhibitor screen for limited-transpiration trait among maize hybrids

• Limited-transpiration trait can lead to increased drought tolerance and yield.
• Need preliminary screen of limited-transpiration trait for breeding efforts.
• Silver, gold, and zinc ions correlated with threshold vapor pressure deficit.
• Silver showed the highest correlation and offered most promise as screen.

A plant trait to minimize the impact of drought on crop yield is limited-transpiration rate (TR) under high ambient vapor pressure deficit (VPD) so that soil water is conserved to sustain grain fill. Variation among maize (Zea mays L.) hybrids has been identified for the existence of the limited-TR trait at high atmospheric VPD, and the VPD at which TR becomes limited. Further, it has been shown that the TR limitation at high VPD is related to plant hydraulic conductance, which may be due to differences in aquaporin expression. This paper reports studies to relate the TR response of 21 maize hybrids to treatment of leaves and intact plants with cycloheximide (CHX) and four aquaporin inhibitors: silver (AgNO3), gold (HAuCl4), zinc (ZnCl2), and mercury (HgCl2). There was no discrimination among hybrids based on treatment with Hg or CHX. Segregation between hybrids for response to increasing VPD corresponded with differences in leaf response to Ag and Au treatment and intact plant response to Zn. The highest correlation (r = 0.90) between VPD breakpoint and TR response to inhibitor was with Ag treatment of leaves. These results indicate that Ag may be an effective initial screen for expression of the limited-TR trait under high VPD.