不同生長時期之玉米澱粉?活性表現的研究

Abstract

本論文探討玉米(Zea mays L.)之穀粒、根、莖、葉、雌蕊、花粉等器官中，α-澱粉?和β-澱粉?活性的分佈，並比較二者表現之異同，以期對兩種澱粉?，在生理上可能扮演的角色有所瞭解。 結果顯示，萌發玉米穀粒中，出現了五個澱粉水解?，命名為Amyl-1、2、3、4、5。其中Amyl-5為β-澱粉?為，其餘皆為α-澱粉?。不同品系之玉米，萌發後澱粉?種類大致相似，只有少數品系不具有Amyl-4。β-澱粉?的活性主要存在糊粉層，而α-澱粉?則分佈在內子葉、澱粉質胚乳和糊粉層各組織。發育中穀粒，在發育早期即有Amyl-3和β-澱粉?的產生；未授粉的子房即有β-澱粉?的表現，而α-澱粉詢則是在授粉後第八天，方有較強活性的表現。在乾燥穀粒中並無澱粉?的存在。利用活體同位素標定法，顯示發育穀粒的胚，以及萌發穀粒之內子葉和糊粉層中有以α-澱粉?的de novo合成作用；而在發育穀粒之果皮，以及萌發穀粒之糊粉層中，β-澱粉?亦以de novo方式合成。 花粉在萌發前，即有很強的Amy1-3及微弱β-澱粉?活性存在，萌發後Amy1-3及β-澱粉?的活性皆提高，且出現其他三種α-澱粉?。穗絲在發育初期，β-澱粉?活性較強；老化及授粉作用，使穗絲內之α-澱粉?活性增強，此說明瞭授粉過程，加速了穗絲的老化。 營養器官中的澱粉?，以Amy1-4和β-澱粉?為主，但β-澱粉?主要存在於年輕的器官，而Amy1-4則出現於老化的器官，同一植株中的老葉之α-澱粉?的活性，為嫩葉的28倍；而經老化處理的初生葉，也獲得相似的結果。此外葉中之α-澱粉?的活性，受畫夜規律調整，夜晚高而白天下降。而老化時之α-澱粉?活性增加，主要位在束鞘組織。根和莖中之澱粉?的活性較低，但在根則有兩個β-澱粉?活性帶。 綜合本文之試驗，雖不能瞭解β-澱粉?的生理角色，但明白α-澱粉?在澱粉運轉機制中扮演重要的角色，且瞭解α-澱粉?基因群的表現，具有極清晰的組織特異性及發育調控的差異性。

The study was aimed to reveal the role of alfa-and beta-amylases in plant growth and development. By using corn(Zea mays L.) as material, the distribution of activities of alfa-and beta-amylases in different organs, such as kernels, pistils, roots, stems leaves, etc. , was investigated. Five amylolytic bands were present in the germinating seeds resolved on native gel, and named as Amy1-1, 2, 3. 4 and 5. Amy1-5 was beta-amylase, the others were alfa-amylases. The amylolytical patterns in germinating maize kernels of various cultivars were mostly similar, although some cultivars lacked Arny1-4. Beta-amylase located mainly in the aleurone layer, whereas the activities of alfa-amylase can be detected in the scutellum, starchy endosperm, and aleurone layer. In the early developing stage of maize kernels, Amy1-3 and beta-amylase were expressed. Beta-amylase was present in the un-fertilized ovary and alfa-amylase appeared only eight days after pollination. In the mature maize kernels, there were almost no alfa and beta-amylase activities. According to the results or in vivo labeling, it was revealed that alfa-amylases were de novo synthesized in the embryo of the developing kernels, the scutellum and aleurone layer of the germinating kernels; and beta-amylase was synthesized in the pericarp of the developing kernels and in the aleurone layer of germinating kernels. Before germination, Amy 1-3 and a relatively weak beta-amylase exisited in the pollen. Upon germination, the activities of Amy 1-3 and beta-amylase in pollen increased and Amy-1, Amy-2, Amy-4 appeared. In the early developing stage of pistil, beta-amylase was the major amylase in silk. Aging and fertilization enhanced the activities of alpha-amylase in the silk. This indicated that fertilization would stimulate the aging process of the silk. The majority of the amylolytic activity in the vegetative organs was attributed to Amy 1-4 and beta-amylase. These two amylases, however, occured in different stages: beta-amylase mainly occured in young organs, but Amy 1-4 in senescing organs. In the senescent leaves of maize plants, alpha-amylase activity was 23-fold higher than that in the young leaves. To young leaves, aging treatment could enhance the increment of alpha-amylase activity as old leaves did. In addition, alpha-amylase activity in primary leaves showed diurnal rhythm: high at night and low during day-time. Alpha-amylase activity in the senescent leaves increased mainly within the bundle sheath. In stems and roots, the activities of amylases were low, although there were two beta-amylase activity bands in roots.