1、 Plant hormones are organic substances that play a major role in regulating growth. Some hormones are produced in one tissue and transported to another tissues, where they produce special physiological responses; others act with the same tissues where they are produced. Hormones are active in very s
2、mall quantity. The word hormone comes from the Greek horman, meaning “to set in motion”. It is now clear, however, that some hormones have inhibitory influences. 7.1生长素类(auxins) 7.1.1发现和种类 7.1.1.1The Darwin Experiments(1880)：单方向光照，胚芽鞘向光弯曲；如果切去胚芽鞘的尖端或在尖端套以锡箔小帽，即使是单侧光照也不会使胚芽鞘向光弯曲。 The Darwins experime
3、nt. (a) Seedlings normally bend toward the light. (b) When the tip of a seedling was covered by a lightproof collar, this bending did not occur, this bending did occur when the tip of a seedling was covered with a transparent collar.) (c) When a lightproof collar was placed below the tip, the charac
4、teristic lightsponse took place. From these experiments, the Darwins concluded that, in response to light, an “influence“ that causes bending is transmitted from the tip of the seedling to the area below the tip where bending normally occurs.7.1.1.2 Boysen-Jensens Experiments(1913) 背光面插 入云母片 向光面插 入云
5、母片7.1.1.3 Went experiments(Avena test，燕麦试验法 ,1926)Went 实验的原始照片 (Courtesy of Dr. Kenneth V. Thimann) Auxin的发现和定名 Bioassay(生物测定法 )： the use of living tissue to determine the amount of a substance. The Avena test soon revealed that substances with auxin activity occur widely in nature. One of the most
6、potent was first isolated from human urine. It was indole-3-acetic acid (IAA) and turned out to be the auxin actually used by plants.吲哚乙酸， IAA) 具有生长素活性的生长物质7.1.2生长素的分布和运输 7.1.2.1分布：生长素在高等植物中分布很广，根、茎、叶、花、果实、种子及胚芽鞘中都有。它的含量甚微， 1g鲜重植物材料一般含 10 100ng生长素。生长素大多集中在生长旺盛的部分 (如胚芽鞘、芽和根尖端的分生组织、形成层、受精后的子房、幼嫩种子等 )，而在趋向衰老的组织和器官中则甚少。 7.1.2.2化学状态：易于从各种溶剂中提取的生长素称为自由生长素 (free auxin)；通过酶解、水解或自溶作用从束缚物释放出来的那部分生长素，称为束缚生长素 (bound auxin）。自由生长素具有活性，而束缚生长素则没有活性。
