Paul M J, Cockburn W
Department of Botany, University of Leicester, Leicester LEI 7RH, England.
New Phytol. 1990 Mar;114(3):391-398. doi: 10.1111/j.1469-8137.1990.tb00406.x.
Plants of Mesembryanthemum crystallinum L. were grown from seed in phosphate-sufficient and phosphate-deficient conditions. Separate plants were subjected to nitrate deficiency by removing nitrate from the rooting medium of previously nitrate-sufficient plants. Subsequently, they were also irrigated with 400 mM NaCl to induce CAM. Plants of M. crystallinum with induced CAM that had been grown in complete nutrient medium were deinduced by rehydration. Nitrate and phosphate deficiencies caused enhanced CAM activity prior to salt treatments. After salinisation, phosphate deficiency also caused higher background levels of malate. Prolonged nitrate deficiency reduced CAM activity. Endogenous P levels in phosphate-sufficient plants correlated with CAM activity. However in phosphate-deficient plants CAM occurred without a significant rise in P content. Levels of endogenous P appeared more related to nitrate deficiency than to CAM or salt treatment. Nitrate and phosphate deficiencies and salt treatment could all cause a nitrate deficiency within the leaf, causing high endogenous P when available in the rooting medium. It is speculated that a change in nitrogen status could play a role in the initiation of CAM induction in M. crystallinum. A further possibility is that CAM could be induced by reduced water potential due to dehydration and increased ion content in saline conditions, and by an inhibition of growth and concomitant accumulation of solutes in phosphate- and nitrate-deficient conditions.
将冰花（Mesembryanthemum crystallinum L.）的种子分别种植在磷充足和磷缺乏的条件下。对先前生长在硝酸盐充足环境中的植株，通过去除生根培养基中的硝酸盐使其处于硝酸盐缺乏状态。随后，用400 mM NaCl浇灌这些植株以诱导景天酸代谢（CAM）。对在完全营养液中生长且已诱导出CAM的冰花植株进行复水使其脱诱导。在盐处理之前，硝酸盐和磷酸盐缺乏会导致CAM活性增强。盐处理后，磷酸盐缺乏也会导致苹果酸的背景水平升高。长期的硝酸盐缺乏会降低CAM活性。磷充足的植株中内源磷水平与CAM活性相关。然而，在磷缺乏的植株中，CAM的发生并未伴随磷含量的显著增加。内源磷水平似乎与硝酸盐缺乏的关系比与CAM或盐处理的关系更大。硝酸盐和磷酸盐缺乏以及盐处理都可能导致叶片内硝酸盐缺乏，在生根培养基中有可利用的磷时会导致内源磷含量升高。据推测，氮状态的变化可能在冰花CAM诱导的起始过程中起作用。另一种可能性是，CAM可能由脱水导致的水势降低、盐胁迫条件下离子含量增加以及磷和硝酸盐缺乏条件下生长受抑制和溶质积累共同诱导产生。
