The movement and differential distribution of endogenous plant hormones are the determining factors for many developmental processes. Brassinosteroids (BRs) are a group of plant steroidal hormones that promote growth and development. Although synthesis and signalling of BRs are well described and characterized, the exit mechanism of these compounds from the cell remains uncharacterizd. Whether BRs are able to move within the apoplast and whether the BR synthesis in one cell can trigger the signalling in its neighbours is also unknown. Here, we draw the attention to these aspects of the BR biology, propose several BR cell export routes and discuss possible consequences of local BR hormonal gradients, resulting from localized biosynthesis and a short-distance transport, for plant development.

内源性植物激素的运动和差异分布是许多发育过程的决定因素。油菜素类固醇（BRs）是一组促进生长和发育的植物类固醇激素。尽管已经很好地描述和表征了BR的合成和信号传导，但这些化合物从细胞中退出的机制仍然没有特征。BRs是否能够在质外体中移动以及一个细胞中的BR合成是否可以触发其邻居中的信号传导还未知。在这里，我们提请注意BR生物学的这些方面，提出几种BR细胞输出途径，并讨论由局部生物合成和短距离运输导致的局部BR激素梯度对植物发育的可能后果。