Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843-2474.
Plant Physiol. 1990 Sep;94(1):77-84. doi: 10.1104/pp.94.1.77.
Four gibberellins, GA(53), GA(19), GA(20), and GA(1), were detected by bioassay, chromatography in two HPLC systems, and combined gas chromatography-mass spectroscopy-selected ion monitoring (GC-MS-SIM) in etiolated soybean (Glycine max [L.] Merr.) hypocotyls. GC-MS-SIM employed [(2)H(2)]-labeled standards for each endogenous gibberellin detected, and quantities estimated from bioassays and GC-MS-SIM were similar. This result plus the tentative detection of GA(44) and GA(8) (standards not available) indicates that the early-C-13-hydroxylation pathway for gibberellin biosynthesis predominates in soybean hypocotyls. Other gibberellins were not detected. Growth rates decreased after transfer to low water potential (psi(w)) vermiculite and were completely arrested 24 hours after transfer. The GA(1) content in the elongating region of hypocotyls had declined to 38% of the 0 time value at 24 hours after transfer to low psi(w) vermiculite, a level which was only 13% of the GA(1) content in control seedlings at the same time (24 hours posttransfer). Rewatering seedlings following 24 hours growth in low psi(w) vermiculite resulted in a complete recovery in elongation rate, an increase in GA(1) (20% at 2 hours, two-fold at 8 hours, eightfold at 24 hours), and a decrease in ABA levels (tenfold at 2 hours). Treatment of well-watered seedlings with the GA-synthesis inhibitor tetcyclacis (TCY) resulted in lowered GA(1) levels and increased ABA levels. When seedlings grown 24 hours in low psi(w) vermiculite were rewatered with TCY, recovery of the elongation rate was delayed and reduced, and the decline in ABA levels was slowed. Addition of GA(3) restored the elongation rate inhibited by TCY. Seedlings were growth responsive to exogenous GA(3), and this GA(3)-promoted growth was inhibited by exogenous ABA. The data are consistent with the hypothesis that changes in GA(1) and ABA levels play a role in adjusting hypocotyl elongation rates. However, the changes observed are not of sufficient magnitude nor do they occur rapidly enough to suggest they are the primary regulators of elongation rate responses to rapidly changing plant water status.
采用生物测定法、两种高效液相色谱法（HPLC）和衍生化气相色谱-质谱选择离子监测（GC-MS-SIM）在黄化大豆（Glycine max [L.] Merr.）下胚轴中检测到了 4 种赤霉素，GA(53)、GA(19)、GA(20)和 GA(1)。GC-MS-SIM 采用了每种内源性赤霉素的 [(2)H(2)]-标记标准品，生物测定法和 GC-MS-SIM 估算的含量相似。这一结果加上 GA(44)和 GA(8)（无标准品）的初步检测表明，赤霉素生物合成的早期 C-13-羟化途径在大豆下胚轴中占主导地位。其他赤霉素未被检测到。转移到低水势（psi(w)）蛭石后，生长速度下降，转移后 24 小时完全停止。转移到低 psi(w)蛭石后 24 小时，下胚轴伸长区的 GA(1)含量下降到 0 时间值的 38%，而同一时间（转移后 24 小时）对照幼苗中的 GA(1)含量为 13%。在低 psi(w)蛭石中生长 24 小时后重新浇水，伸长率完全恢复，GA(1)增加（2 小时增加 20%，8 小时增加一倍，24 小时增加 8 倍），ABA 水平降低（2 小时降低 10 倍）。用赤霉素合成抑制剂 tetcyclacis（TCY）处理水分充足的幼苗会降低 GA(1)水平并增加 ABA 水平。在低 psi(w)蛭石中生长 24 小时的幼苗重新浇水 TCY 时，伸长率的恢复延迟且减少，ABA 水平的下降速度减慢。添加 GA(3)可恢复 TCY 抑制的伸长率。幼苗对外源 GA(3)有生长反应，这种 GA(3)促进的生长被外源 ABA 抑制。数据与赤霉素和 ABA 水平的变化在调节下胚轴伸长率方面发挥作用的假设一致。然而，观察到的变化幅度不够大，也不够快，不足以表明它们是对植物水分状况快速变化的伸长率反应的主要调节因子。
