Response of American sycamore seedlings to maleic hydrazide and sodium chloride

American sycamore (Platanus occidentals L.) seedlings grown in a hydroponics system were treated with a growth regulator, maleic hydrazide (MH) or sodium chloride, or a combination of the two. Application of maleic hydrazide or sodium chloride retarded plant growth, but combined application did not show significant interaction effects. Treatment with both sodium chloride and MH reduced the dry weight of plant tissue to a greater extent than sodium chloride application alone. Elemental analyses of various plant parts revealed that MH was generally without effect on the level of either sodium or chloride ions. In old stem tissue, however, treatment with MH had no effect in the absence of sodium chloride but was associated with lower chloride content in its presence.     

An Explanation for Symmetry-Induced Isotopic Fractionation in Ozone

Application of a theory of nuclear symmetry-based reaction restrictions to the O2 + O --> O3 reaction provides a potential explanation for the symmetry-induced isotopic enrichment observed for laboratory and atmospherically produced O3. Within this theory, the rate of formation of O3 from collisions of O and isotopically homonuclear O2 depends on whether the O2 molecule is in an f (allowed) or an e (restricted) parity label state. The restriction can be relaxed by various potential energy surface coupling terms, and the assumption that approximately 78 percent of the restricted O2(e) levels produce O3 with the same efficiency as the allowed O2(f) levels can account for laboratory-observed isotopic fractionation. In particular, the theory explains the special enhanced formation of the completely asymmetric isotopomer 16O17O18O.