Table III.
Metabolism of 14C-labeled GAs by cell-free systems prepared from root tips of 7-d-old pumpkin seedlingsa
| Substratec
|
Productsb
|
||||
|---|---|---|---|---|---|
| Compounds Formed | Untreated Plants | LAB150978-Treated Plants | KRI | Characteristic Ions at m/z (% Relative of Base Peak)d | |
| pmol | pmol | ||||
| GA12-ald. | GA12 | 78.3 | 29.4 | 2422 | 368(0.01), 360(0.01), 308(100), 300(60), 291(27), 285(13), 247(37), 246(28), 241(25), 240(19) |
| GA12 | GA15 | 62.8 | 61.5 | 2746 | 352(15), 344(1), 320(8), 312(14), 290(44), 284(18), 245(100), 239(72), 197(57), 195(30) |
| GA24e | GA9 | 28.4 | 34.0 | 2418 | 332(4), 330(0), 300(96), 298 (30), 272(100), 270(9), 229(56), 228(75), 227(46), 226(35) |
| GA9f | GA4 | 24.1 | 58.8 | 2563 | 420(17), 418(4), 402(14), 400(4), 330(48), 328(17), 291(94), 289(38), 286(100), 284(83) |
| GA34 | 13.8 | 20.2 | 2672g | ||
| GA4f | GA34 | n.d.h | 40.4 | 2672 | 508(100), 506(0), 418(9), 416(2), 358(13), 356(2), 290(32), 288(22), 219(84), 217(40) |
Protein concentrations of root tips of untreated plants and of LAB150978-treated plants were 10.8 and 11.5 mg/mL, respectively.
Identification of 14C-GA metabolic products by GC-MS on the basis of mass spectra (Gaskin and MacMillan, 1992) and Kovats retention indices (KRI) of the methyl ester trimethylsilylether derivatives.
GA12-aldehyde and GA12 were (1-, 7-, 12-, 18-14C4)-labeled; GA24, GA9, and GA4 were (17-14C)-labeled.
Based on ions above a mass-to-charge ratio (m/z) of 50.
Incubation volumes 6 times the standard assay.
Incubation volumes 2 times the standard assay.
Spectrum was seriously contaminated with extraneous ions. The identification was made on the basis of co-occurence of characteristic ions (Gaskin and MacMillan, 1992) at the appropriate KRI.
Not determined.