Gibberellic acid sensitivity determines the length of the extension zone in wheat leaves
1991
Paolillo, D.J. Jr | Sorrells, M.E. | Keyes, G.J.
To test the hypothesis that gibberellic acid (GA) sensitivity affects the length of the extension zone (LEZ) of leaf No. I of wheat seedlings, we performed a gene dosage experiment using Rht dwarfing genes that condition GA insensitivity. We utilized nearly isogenic lines, at Rht-dosage levels of 0, 2 and 4 alleles. Anatomical markers (distances between successive stomates) were used to infer the distribution of growth along the axis of the leaf. Interstomatal distance (ISD) and LEZ were inverse linear functions of Rht-dosage, The number of stomates matured per hour was independent of Rht-dosage. The relationship between ISD and distance along the axis within the extension zone (EZ) was indistinguishable from linear. Rht-dosage did not affect the slope of the regression of ISD against distance along the EZ. A-REST (AR; ancymidol, a potent GA synthesis inhibitor) reduced LEZ. Wild type was more sensitive to AR than double dwarf. AR affected growth of leaf No. I more than length of the coleoptile, regardless of Rht-dosage. AR-dosage affected cell division, whereas Rht-dosage did not.
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