The Impact of Greenhouse Tomato (Solanales: Solanaceae) Floral Volatiles on Bumble Bee (Hymenoptera: Apidae) Pollination

Greenhouse tomato (Lycopersicon esculentum Mill) production relies on pollination by commercially-produced bumble bee (Bombus impatiens Cresson) colonies. Inadequate pollination by bumble bees has been a problem for growers at certain times of year; however, its cause has yet to be determined. Bumble bees have been shown to exit tomato greenhouses to forage on flowers of other plants. This study investigates tomato's floral characteristics and their affect on bumble bee pollination by 1) observing foraging preferences for bumble bees on greenhouse tomato, 2) determining if the plant's floral advertisements could be used by the bees to estimate pollen availability, and 3) identifying temporal changes in floral display which correspond to peak bumble bee activity. Flower size (petal length, anther cone width, and anther cone length) and floral scent (release of beta-phellandrene, 2-carene, alpha-pinene, and p-cymene) were evaluated to identify the pollinator-important characteristics of tomato flowers. Our results indicate that 1) bumble bees preferred to pollinate flowers which produce less beta-phellandrene and 2-carene in comparison to flowers producing more of these volatiles, 2) flower size and floral scent are not likely used by the bees to estimate pollen availability, and 3) cultivars are inconsistent in their production of floral volatiles during peak bumble bee activity. beta-phellandrene and 2-carene may be antiherbivory volatiles and reduced production during peak bee activity may help to facilitate pollination of tomato. Pollinator-repellent volatiles may help to protect flowers from damage caused by over-pollination.

温室番茄（Lycopersicon esculentum Mill）的生产依赖于商业化养殖的熊蜂（Bombus impatiens Cresson）蜂群授粉。在一年中的某些时候，熊蜂授粉不足一直是种植者面临的一个问题；然而，其原因尚未确定。研究表明熊蜂会离开番茄温室去其他植物的花朵上觅食。本研究通过以下方式调查番茄的花部特征及其对熊蜂授粉的影响：1）观察熊蜂在温室番茄上的觅食偏好；2）确定蜜蜂是否可以利用植物的花部特征来估计花粉的可获取性；3）确定与熊蜂活动高峰相对应的花部特征的时间变化。对花的大小（花瓣长度、花药筒宽度和花药筒长度）和花香（β - 水芹烯、2 - 蒈烯、α - 蒎烯和对伞花烃的释放）进行了评估，以确定番茄花对传粉者重要的特征。我们的研究结果表明：1）与产生较多这些挥发性物质的花朵相比，熊蜂更倾向于为产生较少β - 水芹烯和2 - 蒈烯的花朵授粉；2）蜜蜂不太可能利用花的大小和花香来估计花粉的可获取性；3）在熊蜂活动高峰期间，不同品种的番茄花产生的挥发性物质不一致。β - 水芹烯和2 - 蒈烯可能是抗食草动物的挥发性物质，在蜜蜂活动高峰期间其产量减少可能有助于促进番茄的授粉。驱避传粉者的挥发性物质可能有助于保护花朵免受过度授粉造成的损害。