Cyr D R, Buxton G F, Webb D P, Dumbroff E B
Department of Biology, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Tree Physiol. 1990 Sep;6(3):293-303. doi: 10.1093/treephys/6.3.293.
The effects of drought on the free amino acid pools in 21- to 23-week-old seedlings of black spruce (Picea mariana (Mill.) Britt.), white spruce (Picea glauca (Moench.) Voss) and jack pine (Pinus banksiana Lamb.) were followed during soil drying. Although water and pressure potentials were sensitive to water deficits, large changes in osmotic potential were not recorded until after the development of severe drought. Total soluble amino nitrogen in the shoots and roots of the three species rose as turgor declined, with peak concentrations attained late in the drought period when the pressure potentials of the shoots approached zero. All white spruce seedlings were alive at zero turgor and showed large decrements in osmotic potential, but concentrations of free amino nitrogen in the roots and shoots showed only modest increases, reaching 125 to 150% of their control values. In contrast, large numbers of black spruce and jack pine were dead or severely damaged at zero turgor, and only small changes in osmotic potential were detected during soil drying. Nevertheless, concentrations of soluble amino nitrogen in both species reached 150 to 200% of control values a few days before the seedlings died. Alanine, arginine, aspartic acid/asparagine, glutamic acid/glutamine, glycine, hydroxyproline and proline were the major components of the free amino acid pools under both water-stressed and non-stressed conditions, with the largest and most consistent increases observed in the roots of all three conifers. Although proline was an important and dynamic component of the free pools, absolute concentrations were commony equalled or exceeded by other free amino acids in the roots and shoots and nearly always exceeded by the concentration of aspartic acid/asparagine in both tissues. Differences in drought resistance among the three conifers were not reflected by unique patterns of amino acid accumulation or by large differences in absolute concentrations of the free amino acid pools.
在土壤干燥过程中，对21至23周龄黑云杉（Picea mariana (Mill.) Britt.）、白云杉（Picea glauca (Moench.) Voss）和短叶松（Pinus banksiana Lamb.）幼苗中游离氨基酸库受干旱的影响进行了跟踪研究。尽管水势和压力势对水分亏缺敏感，但直到严重干旱发展之后才记录到渗透势的大幅变化。随着膨压下降，这三个物种地上部分和根部的总可溶性氨基氮含量上升，在干旱后期，当地上部分压力势接近零时达到峰值浓度。所有白云杉幼苗在膨压为零时仍存活，且渗透势大幅下降，但根部和地上部分游离氨基氮的浓度仅略有增加，达到对照值的125%至150%。相比之下，大量黑云杉和短叶松在膨压为零时死亡或受到严重损害，在土壤干燥过程中仅检测到渗透势的微小变化。然而，这两个物种的可溶性氨基氮浓度在幼苗死亡前几天达到对照值的150%至200%。在水分胁迫和非胁迫条件下，丙氨酸、精氨酸、天冬氨酸/天冬酰胺、谷氨酸/谷氨酰胺、甘氨酸、羟脯氨酸和脯氨酸都是游离氨基酸库的主要成分，在所有三种针叶树的根部观察到最大且最一致的增加。尽管脯氨酸是游离库的一个重要且动态的成分，但在根部和地上部分，其绝对浓度通常等于或低于其他游离氨基酸，在两个组织中几乎总是低于天冬氨酸/天冬酰胺的浓度。这三种针叶树抗旱性的差异并未通过氨基酸积累的独特模式或游离氨基酸库绝对浓度的巨大差异反映出来。
