Department of Agronomy, University of Missouri, Columbia, Missouri 65211.
Plant Physiol. 1991 Aug;96(4):1125-30. doi: 10.1104/pp.96.4.1125.
Seedlings of maize (Zea mays L. cv WF9 x Mo 17) growing at low water potentials in vermiculite contained greatly increased proline concentrations in the primary root growth zone. Proline levels were particularly high toward the apex, where elongation rates have been shown to be completely maintained over a wide range of water potentials. Proline concentration increased even in quite mild treatments and reached 120 millimolal in the apical millimeter of roots growing at a water potential of -1.6 megapascal. This accounted for almost half of the osmotic adjustment in this region. Increases in concentration of other amino acids and glycinebetaine were comparatively small. We have assessed the relative contributions of increased rates of proline deposition and decreased tissue volume expansion to the increases in proline concentration. Proline content profiles were combined with published growth velocity distributions to calculate net proline deposition rate profiles using the continuity equation. At low water potential, proline deposition per unit length increased by up to 10-fold in the apical region of the growth zone compared to roots at high water potential. This response accounted for most of the increase in proline concentration in this region. The results suggest that osmotic adjustment due to increased proline deposition plays an important role in the maintenance of root elongation at low water potentials.
在珍珠岩中生长的低水势下的玉米（Zea mays L. cv WF9 x Mo 17）幼苗，在主根生长区的脯氨酸浓度大大增加。脯氨酸水平在根尖处特别高，已证明在广泛的水势范围内，伸长率可以完全维持。即使在相当温和的处理下，脯氨酸浓度也会增加，在水势为-1.6 兆帕斯卡的情况下，根尖 1 毫米处的根中脯氨酸浓度达到 120 毫摩尔。这占该区域渗透压调节的近一半。其他氨基酸和甘氨酸甜菜碱浓度的增加则相对较小。我们评估了脯氨酸沉积速率增加和组织体积膨胀减少对脯氨酸浓度增加的相对贡献。将脯氨酸含量曲线与已发表的生长速度分布结合起来，使用连续性方程计算净脯氨酸沉积速率曲线。在低水势下，与高水势下的根相比，生长区根尖部位的脯氨酸沉积速率单位长度增加了多达 10 倍。这种反应解释了该区域脯氨酸浓度增加的大部分原因。结果表明，由于脯氨酸沉积增加而导致的渗透压调节在维持低水势下的根伸长中起着重要作用。
