德国科学家发现，植物激素茉莉酸不仅可控制油菜花萌芽阶段的生长，还能激发花蜜生产。该研究对油菜的高产将产生十分积极的影响，相关成果发表在近日美国《公共科学图书馆综合》杂志网络版上。
很久以来，人们都不清楚花朵是如何触发和控制花蜜生产的。现在，德国马普研究院的博士生拉迪卡文卡特桑通过研究甘蓝型油菜发现，是存在于植物体内的内源生长调节物质茉莉酸控制了花朵的生长，并激发花蜜的生产。
茉莉酸及其相关分子是植物组织分子信号传导链的重要组成成分。它属于植物激素组中的信号物质，例如当毛毛虫吃植物时它就会应激合成。通过产生茉莉酸，植物可刺激合成毒素，以此来防御病虫害。茉莉酸还能控制生产“花外花蜜”。这种特殊的花蜜，不是由花的组织产生的，而是由一个名为“花外蜜腺”的特殊腺体产生的，“花外花蜜”吸引蚂蚁，可间接保护植物不被食草动物蚕食。花蜜中含有的糖分则是对保护植物的蚂蚁的奖励。
不过，研究人员发现，在花的早期发育阶段，无论植物有没有受到食草类动物的攻击，茉莉酸都会被合成，随即花蜜的生产也会启动。且茉莉酸在不同的植物组织有不同的功能：在叶片，它激活植物对食草动物的防御机制；而在花朵，它控制花蜜的生产。
茉莉酸和花蜜生产之间的相互联系还可通过一种抑制剂实验得到：当用可抑制茉莉酸合成的菲尼酮对花进行处理后，花蜜生产便会停止。当用这种抑制剂喷洒还未开放的花蕾时，花的开放也会得到抑制，这证实茉莉酸在花的成长过程中也起着重要作用。
研究人员强调，人类对激素在花的生长和花蜜，乃至油菜仔的生产中所起的作用知道得越多，就越能合理利用这些知识来保证高产。油菜是全世界10种最重要的农作物之一。因此，加强研究使油菜这一广泛种植的农作物获得高产，意义十分重大。
生物谷推荐原文出处：
PLoS ONE doi:10.1371/journal.pone.0009265
The Role of Jasmonates in Floral Nectar Secretion
Venkatesan Radhika1, Christian Kost1, Wilhelm Boland1, Martin Heil2*
Plants produce nectar in their flowers as a reward for their pollinators and most of our crops depend on insect pollination, but little is known on the physiological control of nectar secretion. Jasmonates are well-known for their effects on senescence, the development and opening of flowers and on plant defences such as extrafloral nectar. Their role in floral nectar secretion has, however, not been explored so far. We investigated whether jasmonates have an influence on floral nectar secretion in oil-seed rape, Brassica napus. The floral tissues of this plant produced jasmonic acid (JA) endogenously, and JA concentrations peaked shortly before nectar secretion was highest. Exogenous application of JA to flowers induced nectar secretion, which was suppressed by treatment with phenidone, an inhibitor of JA synthesis. This effect could be reversed by additional application of JA. Jasmonoyl-isoleucine and its structural mimic coronalon also increased nectar secretion. Herbivory or addition of JA to the leaves did not have an effect on floral nectar secretion, demonstrating a functional separation of systemic defence signalling from reproductive nectar secretion. Jasmonates, which have been intensively studied in the context of herbivore defences and flower development, have a profound effect on floral nectar secretion and, thus, pollination efficiency in B. napus. Our results link floral nectar secretion to jasmonate signalling and thereby integrate the floral nectar secretion into the complex network of oxylipid-mediated developmental processes of plants.
