Growth and acetylene reduction of black alder seedlings in response to water stress

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Abstract
Black alder, A. glutinosa (L.) Gaertn., seedlings were grown and kept well watered for 10 wk, and then subjected to moisture stress conditioning for 5 subsequent weeks, where 1/2 of the seedlings were watered only when visibly wilted. The remaining seedlings (controls) were kept well watered. Moisture stress conditioning greatly reduced shoot, root, nodule, and total plant dry weight. The root-shoot ratio (g/g) of seedlings was significantly increased from 0.28 in the control seedlings to 0.33 in the water-stressed treatment. Acetylene reduction rates decreased only slightly in the range of water potentials between -0.50 and -1.29 MPa [megapascal] then dropped rapidly below water potentials of -1.30 MPa. Moisture stress conditioning had no significant influence on this response. Although not significantly different, leaf and nodule osmotic potentials were consistently lower in the water-stressed plants.
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