When pollen grains are released from anthers and then captured on the surface of the stigma, they obtain water and other resources from the stigma for germination and pollen tube elongation. Once the pollen tube penetrates the outer layer of the stigmatic cell wall, it grows in the apoplastic space down to the ovary for fertilization. In the ovary, two sperm cells are released from the tip of the pollen tube; one of these fertilizes the egg cell and the other the central cell, termed double fertilization, resulting in seed development. Because pollination is mediated by wind, insects and birds, pollen of other species, pathogens and dust, as well as pollen of the same species, may arrive at the stigma surface. Therefore stigmas require the ability to select suitable pollen to bring about successful fertilization.

Although pollination has been studied for many years, the molecular mechanisms involved are still largely unclear. An accurate knowledge of morphological aspects of pollination is also still far from complete. A new paper in Annals of Botany focuses on pollen behaviour during pollination. For the morphological characterization of pollination, time-lapse image analysis was used to record detailed pollen behaviour during self- and cross-pollinations in Brassica rapa. This approach demonstrated that pollen exhibits various behaviours on an individual stigma, in both self- and cross-pollinations, and the ratios of the different types of pollen behaviour are critical for successful pollination.