Toorop P E, van Aelst A C, Hilhorst H W
Laboratory of Plant Physiology, Wageningen University, Arboretumlaan 4, NL-6703 BD Wageningen, The Netherlands.
J Exp Bot. 2000 Aug;51(349):1371-9.
The role of abscisic acid (ABA) in the weakening of the endosperm cap prior to radicle protrusion in tomato (Lycopersicon esculentum Mill. cv. Moneymaker) seeds was studied. The endosperm cap weakened substantially in both water and ABA during the first 38 h of imbibition. After 38 h the force required for endosperm cap puncturing was arrested at 0.35 N in ABA, whereas in water a further decrease occurred until the radicle protruded. During the first 2 d of imbibition endo-beta-mannanase activity was correlated with the decrease in required puncture force and with the appearance of ice-crystal-induced porosity in the cell walls as observed by scanning electron microscopy. Prolonged incubation in ABA resulted in the loss of endo-beta-mannanase activity and the loss of ice-crystal-induced porosity, but not in a reversion of the required puncture force. ABA also had a distinct but minor effect on the growth potential of the embryo. However, endosperm cap resistance played the limiting role in the completion of germination. It was concluded that (a) endosperm cap weakening is a biphasic process and (b) inhibition of germination by ABA is through the second step in the endosperm cap weakening process.
研究了脱落酸（ABA）在番茄（Lycopersicon esculentum Mill. cv. Moneymaker）种子胚根突出前胚乳帽弱化过程中的作用。在吸胀的最初38小时内，胚乳帽在水和ABA中均显著弱化。38小时后，在ABA中穿透胚乳帽所需的力稳定在0.35 N，而在水中，该力进一步下降直至胚根突出。在吸胀的前两天，内切β-甘露聚糖酶活性与所需穿刺力的降低以及扫描电子显微镜观察到的细胞壁中冰晶诱导孔隙率的出现相关。在ABA中长时间培养导致内切β-甘露聚糖酶活性丧失和冰晶诱导孔隙率丧失，但所需穿刺力并未恢复。ABA对胚的生长潜力也有明显但较小的影响。然而，胚乳帽抗性在种子萌发完成过程中起限制作用。得出的结论是：（a）胚乳帽弱化是一个双相过程；（b）ABA对萌发的抑制作用是通过胚乳帽弱化过程的第二步实现的。
