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赤霉素
,无编辑摘要
关于赤霉素的作用机理，研究得较深入的是它对去胚大麦种子中淀粉水解的诱发。用赤霉素处理[[灭菌]]的去胚大麦种子，发现GA3显著促进其糊粉层中 α-[[淀粉酶]]的新合成，从而引起淀粉的水解。在完整大麦种子发芽时，胚含有赤霉素，分泌到糊粉层去。此外，GA3还刺激糊粉层[[细胞]]合成蛋白酶，促进[[核糖核酸酶]]及[[葡聚糖酶]]的分泌。
==主要应用==
赤霉素应用于农业生产，在某些方面有较好效果。例如提高无籽葡萄产量，打破马铃薯休眠；在酿造啤酒时，用GA3来促进制备[[麦芽糖]]用的大麦种子的萌发；当晚稻遇阴雨[[低温]]而抽穗迟缓时，用赤霉素处理能促进抽穗；或在杂交水稻制种中调节花期以使父母本花期相遇。
如果使用赤霉素过量,[[副作用]]可造成倒伏,所以要使用助壮素进行调节,同时增施钾肥.
赤霉素最突出的作用是加速细胞的伸长（赤霉素可以提高植物体内生长素的含量，而生长素直接调节细胞的伸长），对细胞的分裂也有促进作用，它可以促进细胞的扩大（但不引起[[细胞壁]]的酸化）
Gibberellin
Any of the members of a family of higher-plant hormones characterized by the ent-gibberellane skeleton. Some of these compounds have profound effects on many aspects of plant growth and development, which indicates an important regulatory role.
There are two classes of gibberellins: the 19-carbon gibberellins and the 20-carbon gibberellins. The 19-carbon gibberellins, formed from 20-carbon gibberellins, are the bio-logically active forms. Gibberellins also vary according to the position and number of hydroxyl groups linked to the carbon atoms of the ent-gibberellane skeleton. Hydroxylation has a profound influence on biological activity.
Probably the best-defined role for gibberellins in regulating the developmental processes in higher plants is stem growth. The cellular basis for gibberellin-induced stem growth can be either an increase in the length of pith cells in the stem or primarily the production of a greater number of cells. Applied gibberellins can often promote germination of dormant seeds, a capability suggesting that gibberellins are involved in the process of breaking dormancy. Gibberellins are intimately involved in other aspects of seed germination as well. Applied gibberellins promote or induce flowering in plants that require either cold or long days for flower induction. Gibberellin is probably not the flowering hormone or floral stimulus, because the floral stimulus appears to be identical or similar in all response types. The application of gibberellins often modifies sex expression, usually causing an increase in the number of male flowers. See also Dormancy; Flower; Plant growth; Seed.
Although gibberellins have limited use in agriculture compared with other agricultural chemicals such as herbicides, several important applications have been developed, including the production of seedless grapes. Application of gibberellin at bloom results in increased berry size and reduced berry rotting. Gibberellins are also used to increase barley malt yields for brewing and to reduce the time necessary for the malting process to reach completion. Gibberellins have found significant applications in plant breeding. Other uses for gibberellin in agriculture include reduction of rind discoloration in citrus fruits, increased yield in sugarcane, stimulation of fruit set in fruit trees, and increased petiole growth in celery. See also Plant hormones
[[分类:生物学]][[分类:抗生素]][[分类:霉菌]]
