Pollination and embryo development in Brassica rapa L. in microgravity

Plant reproduction under spaceflight conditions has been problematic in the past. In order to determine what aspect of reproductive development is affected by microgravity, we studied pollination and embryo development in Brassica rapa L. during 16 d in microgravity on the space shuttle (STS‐87). Brassica is self‐incompatible and requires mechanical transfer of pollen. Short‐duration access to microgravity during parabolic flights on the KC‐135A aircraft was used initially to confirm that equal numbers of pollen grains could be collected and transferred in the absence of gravity. Brassica was grown in the Plant Growth Facility flight hardware as follows. Three chambers each contained six plants that were 13 d old at launch. As these plants flowered, thin colored tape was used to indicate the date of hand pollination, resulting in silique populations aged 8–15 d postpollination at the end of the 16‐d mission. The remaining three chambers contained dry seeds that germinated on orbit to produce 14‐d‐old plan...