Migliaccio F, Galston A W
Department of Biology, Yale University, New Haven, CT 06511-8112, USA.
Plant Growth Regul. 1989;8:335-47. doi: 10.1007/BF00024664.
To determine whether Ca2+ plays a special role in the early graviresponse of shoots, as has been reported for roots, we treated etiolated pea epicotyls with substances known to antagonize Ca2+ (La3+), to remove Ca2+ from the wall (spermidine, EGTA), to inhibit calmodulin mediated reactions (chlorpromazine), or to inhibit IAA transport (TIBA). We studied the effect of these substances on IAA and Ca2+ uptake into 7 mm long subapical 3rd internode etiolated pea epicotyl sections and pea leaf protoplasts, on pea epicotyl growth, and graviresponse and on lateral IAA redistribution during gravistimulation. Our results support the view that adequate Ca2+ in the apoplast is required for normal IAA uptake, transport and graviresponse. Experiments with protoplasts indicate that Ca2+ may be controlling a labile membrane porter, possibly located on the external surface of cell membrane, while inhibitor experiments suggest that calmodulin is also implicated in both the movement of IAA and graviresponse. Since a major transfer of Ca2+ through free space during graviresponse has not yet been demonstrated, and since inhibition of calcium channels does not affect IAA redistribution (Migliaccio and Galston, 1987, Plant Physiology 85:542), we conclude that no clear evidence links prior Ca2+ movement with IAA redistribution during graviresponse in stems.
为了确定钙离子是否像在根中那样，在茎的早期重力反应中发挥特殊作用，我们用已知能拮抗钙离子的物质（镧离子）、从细胞壁中去除钙离子的物质（亚精胺、乙二醇双四乙酸）、抑制钙调蛋白介导反应的物质（氯丙嗪）或抑制生长素运输的物质（三碘苯甲酸）处理黄化豌豆上胚轴。我们研究了这些物质对7毫米长的黄化豌豆上胚轴第三节间亚顶端切段和豌豆叶原生质体对生长素和钙离子的吸收、对豌豆上胚轴生长、重力反应以及重力刺激期间生长素侧向再分布的影响。我们的结果支持这样一种观点，即质外体中充足的钙离子是正常生长素吸收、运输和重力反应所必需的。原生质体实验表明，钙离子可能控制着一种不稳定的膜转运体，可能位于细胞膜外表面，而抑制剂实验表明，钙调蛋白也与生长素的移动和重力反应有关。由于尚未证明在重力反应过程中有大量钙离子通过自由空间转移，而且由于抑制钙通道并不影响生长素的再分布（米利亚乔和高尔斯顿，1987年，《植物生理学》85:542），我们得出结论，没有明确证据表明在茎的重力反应过程中，先前的钙离子移动与生长素再分布有关。
