Karyogamy in rice zygotes. A and B, Alignment of a sperm cell expressing H2B-GFP with a wild-type egg cell on one of the electrodes under an alternating current field in a fusion droplet. C to R, Gametes in B were electrically fused, and the resulting fused cell (zygote) was observed at the time points indicated. Top shows fluorescent images, and bottom shows merged bright-field and fluorescent images. Black and white arrowheads indicate sperm cells expressing H2B-GFP and nucleoli, respectively. Bar = 20 μm. [See online article for color version of this figure.]