Zinc (Zn) pollution of croplands can have negative impacts on yields through its effects on key physiological functions such as transpiration rate (TR). Previous long-term experiments indicated that differential tolerance among soybean genotypes following exposure to high Zn levels existed in the shoots. There are, however, no studies of the possibility that short-term responses to Zn directly limit shoot TR. Measurements of TR of eight soybean genotypes were measured over 220 minutes after placing de-rooted shoots in 500 μM Zn solution. Six genotypes exhibited TR that decreased slowly in a linear fashion over time while two genotypes ('PI 416937' and 'N01-11136') exhibited very rapid decrease in TR following a Boltzmann sigmoid response. One possibility to explain these results is that there exists a Zn-sensitive AQP population in the leaves of 'PI 416937' and 'N01-11136' with abundance or activity that is much higher than in the leaves of the remaining six lines.
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We gratefully acknowledge the financial support provided by the United Soybean Board.