Roelfsema M Rob G, Konrad Kai R, Marten Holger, Psaras George K, Hartung Wolfram, Hedrich Rainer
Molecular Plant Physiology and Biophysics, Julius-von-Sachs Institute for Biosciences, Biocenter, Würzburg University, Germany.
Plant Cell Environ. 2006 Aug;29(8):1595-605. doi: 10.1111/j.1365-3040.2006.01536.x.
Stomatal openings can be stimulated by light through two signalling pathways. The first pathway is blue light specific and involves phototropins, while the second pathway mediates a response to photosynthetically active radiation (PAR). This second pathway was studied with the use of albino Vicia faba plants and variegated leaves of Chlorophytum comosum. Treatment of V. faba with norflurazon (Nf) inhibits the synthesis of carotenoids and leads to albino leaves with guard cells that lack functional green chloroplasts. Guard cells in albino leaf patches of C. comosum, however, do contain photosynthetically active chloroplasts. Stomata in albino leaf patches of both plants did not respond to red light, although blue light could still induce stomatal opening. This shows that the response to PAR is not functioning in albino leaf patches, even though guard cells of C. comosum harbour chloroplasts. Stomata of Nf-treated plants still responded to CO2 and abscisic acid (ABA). The size of Nf-treated guard cells was increased, but impalement studies with double-barrelled microelectrodes revealed no changes in ion-transport properties at the plasma membrane of guard cells. Blue light could hyperpolarize albino guard cells by triggering outward currents with peak values of 37 pA in albino plants and 51 pA in green control cells. Because of the inhibition of carotenoid biosynthesis, Nf-treated V. faba plants contained only 4% of the ABA content found in green control plants. The ABA dose dependence of anion channel activation in guard cells was shifted in these plants, causing a reduced response to 10 microM ABA. These data show that despite the dramatic changes in physiology caused by Nf, the gross responsiveness of guard cells to blue light, CO2 and ABA remains unaltered. Stomata in albino leaf patches, however, do not respond to PAR, but require photosynthetically active mesophyll cells for this response.
气孔开放可通过两条信号通路被光刺激。第一条通路是蓝光特异性的，涉及向光素，而第二条通路介导对光合有效辐射（PAR）的响应。利用白化蚕豆植株和吊兰的杂色叶片对第二条通路进行了研究。用去甲草净（Nf）处理蚕豆会抑制类胡萝卜素的合成，导致叶片白化，其保卫细胞缺乏功能性的绿色叶绿体。然而，吊兰白化叶斑中的保卫细胞确实含有光合活性叶绿体。两种植物白化叶斑中的气孔对红光均无反应，尽管蓝光仍可诱导气孔开放。这表明，即使吊兰的保卫细胞含有叶绿体，白化叶斑中对PAR的响应也不起作用。经Nf处理的植株的气孔对二氧化碳和脱落酸（ABA）仍有反应。经Nf处理的保卫细胞大小增加，但用双管微电极进行的刺入研究表明，保卫细胞质膜的离子转运特性没有变化。蓝光可通过触发外向电流使白化保卫细胞超极化，白化植株中的外向电流峰值为37 pA，绿色对照细胞中的为51 pA。由于类胡萝卜素生物合成受到抑制，经Nf处理的蚕豆植株的ABA含量仅为绿色对照植株的4%。这些植株中保卫细胞阴离子通道激活的ABA剂量依赖性发生了改变，导致对10 microM ABA的反应减弱。这些数据表明，尽管Nf引起了生理上的巨大变化，但保卫细胞对蓝光、二氧化碳和ABA的总体反应性保持不变。然而，白化叶斑中的气孔对PAR无反应，而这种反应需要光合活性叶肉细胞。
