Photoperiod-controlling Guttation and Growth of Rice Seedlings Under Microgravity on Board Chinese Spacelab TG-2

Guttation has been shown to play a crucial role in controlling plant growth and development by involvement of the transport of water, but how does this water transport in plant from roots to leaves work against pull of gravity is still unknown. The aim of the present study was to evaluate the influence of microgravity on photoperiod-controlling guttation and growth of rice (Oryza sativa L.) seedlings on board the Chinese Spacelab TongGong-2(TG-2). The growth rate of rice seedlings was closely correlated with guttation under both the microgravity and the ground conditions, which was increased by microgravity under both a 16-h long-day (LD) and an 8-h short-day (SD) photoperiod conditions. In addition, guttation of the TG-2 grown rice under the LD condition was more significant in comparison with that under the SD condition. These results indicated that microgravity affected the photoperiod-controlling growth of rice seedlings could be related to the enhanced guttation in space.