MSU-DOE Plant Research Laboratory, Michigan State University, East Lansing, Michigan 48824.
Plant Physiol. 1979 Mar;63(3):518-23. doi: 10.1104/pp.63.3.518.
Mobilization of N from leaves of barley (Hordeum vulgare L.) during water stress, and the role of proline as a mobilized species, were examined in plants at the three-leaf stage. The plants responded to water stress by withdrawing about 25% of the total reduced N from the leaf blades via phloem translocation. Most of this N loss was during the first 2 days while translocation of (14)C-photosynthate out of the stressed blade still remained active. Free proline accumulation in the blade was initially slow, and became more rapid during the 2nd day of stress. Although a major free amino acid, proline accounted for only about 5% of the total N (soluble + insoluble) retained in severely stressed blades. When the translocation pathway in water-stressed leaves was interrupted just below the blade by a heat girdle, a cold jacket, or by blade excision, N loss from the blade was prevented and proline began to accumulate rapidly on 1st day of stress. Little free proline accumulated in the blades until after the ability to translocate was lost. Proline was, however, probably not a major species of N translocated during stress, because proline N accumulation in heat-girdled stressed leaves was five times slower than the rate of total N export from intact blades.
在三叶期，我们研究了大麦（Hordeum vulgare L.）叶片中氮的动员，以及脯氨酸作为动员物种的作用。植物通过韧皮部转运从叶片中撤回了大约 25%的总还原氮来应对水分胁迫。大部分氮损失发生在最初的 2 天，而受胁迫叶片中（14）C 光合产物的韧皮部转运仍然活跃。叶片中游离脯氨酸的积累最初很慢，在胁迫的第 2 天变得更快。尽管脯氨酸是一种主要的游离氨基酸，但它只占严重受胁迫叶片中总氮（可溶性+不溶性）保留量的 5%左右。当用热带、冷套或叶片切除在叶片下方切断水分胁迫叶片中的转运途径时，叶片中的氮损失被阻止，脯氨酸在胁迫的第 1 天开始迅速积累。在失去转运能力之前，叶片中几乎没有游离脯氨酸积累。然而，脯氨酸可能不是胁迫下转运的主要氮物种，因为热带胁迫叶片中脯氨酸氮的积累速度比完整叶片中总氮输出的速度慢五倍。
