赤霉素是一类能促进植物生长的，具赤霉素烷环结构的植物激素。以游离型和结合型两种形式存在。一般植物体内至少有两种或两种以上的赤霉素，不同赤霉素之间可以相互转变。叶、芽、根以及未成熟种子的幼嫩组织是赤霉素的主要合成部位。
赤霉素的主要作用在于，可促进作物生长发育，使之提早成熟；还能快速打破种子休眠，促进快速发芽；也能减少花、果脱落，提高果实结果率。
具有促进茎的伸长，诱导长日植物在短日条件下抽薹开花，打破休眠，促进坐果和单性结实以及细胞分裂与分化等生理效应。
赤霉素最显著的作用是促进组织生长，使植株高度明显增加，对若干遗传性矮生植物的伸长效应特别明显。赤霉素可代替红光刺激休眠的种子(四季豆、莴苣等)发芽；可诱导α-淀粉酶的合成，使淀粉水解为糖。这个极其专一的反应已用作对赤霉素的生物鉴定，并被用于啤酒生产中，在啤酒工业上，用GA3促进大麦种子的萌发，起到了节约粮食，降低成本，缩短生产周期，保证啤酒品质的作用。用高浓度(500～1000ppm)赤霉素处理玉米植株，能导致部分或完全的雄性不育。这对培育玉米自交系杂种非常有利。
在低温和弱光下，赤霉素能打破牧草的休眠，有利于绿肥栽培；在夏季干旱或低温下，可促进甘蔗的生长；在早春低温下，可促进豌豆和菜豆提早发芽，迅速出苗。在农业上常用赤霉素提高无籽葡萄的产量，打破马铃薯休眠，在杂交水稻制种中用于促进抽穗，提高杂交种子产量。

Gibberellin is a kind of plant hormones with the alkane ring structure of gibberellin, which can promote plant growth. It exists in both dissociative and conjugated forms. There are at least two or more kinds of GIBberellins in plants, and different gibberellins can be converted to each other. Leaves, buds, roots and young tissues of immature seeds are the main synthesis sites of GIBberellin.
The main function of gibberellin is to promote the growth and development of crops and make them mature earlier. It can also quickly break seed dormancy and promote rapid germination; It can also reduce flower and fruit shedding and improve fruit bearing rate.
It has physiological effects such as promoting stem elongation, inducing lichen extraction and flowering of long-day plants under short-day conditions, breaking dormancy, promoting fruit setting, parthenogenesis and cell division and differentiation.
The most significant effect of gibberellin is to promote tissue growth and increase plant height, especially to some hereditary dwarf plants. Gibberellin can stimulate dormant seeds (green beans, lettuce, etc.) to germinate instead of red light; It can induce the synthesis of α -amylase and hydrolyze starch to sugar. This extremely specific reaction has been used for the biological identification of gibberellin, and has been used in beer production. In the beer industry, GA3 is used to promote the germination of barley seeds, which has played a role in saving grain, reducing costs, shortening production cycle and ensuring the quality of beer. Maize plants treated with high concentrations of GIBberellin (500 ~ 1000ppm) can be partially or completely male sterile. This is very beneficial for breeding maize inbred line hybrids.
Under low temperature and weak light, gibberellic acid could break the dormancy of herbage and was beneficial to green manure cultivation. In summer drought or low temperature, can promote the growth of sugarcane; Under the low temperature in early spring, peas and beans can be promoted to germinate early and sprout quickly. Gibberellin is commonly used in agriculture to increase the yield of seedless grapes, break potato dormancy, and promote heading and increase hybrid seed yield in hybrid rice seed production.