Microgravity-Science and Technology
https://doi.org/10.1007/s12217-018-9626-5
ORIGINAL ARTICLE
Flowering in space
Hui Qiong Zheng
1
Received: 12 March 2018 / Accepted: 11 May 2018
© Springer Science+Business Media B.V., part of Springer Nature 2018
Abstract
The reproductive success of plants is often dependent on their flowering time being adapted to the terrestrial environment,
in which gravity remain constant. Whether plants can follow the same rule to determine their flowering time under
microgravity in space is unknown. Although numerous attempts have been made to grow a plant through a complete life
cycle in space, apparently no published information exists concerning the flowering control of plants under microgravity
in space. Here, we focused on two aspects. Firstly the environmental and intrinsic factors under microgravity related to
flowering control. Secondly, the plant-derived regulators are involved in flowering control under microgravity condition.
The potential environmental and intrinsic factors affect plant flowering under microgravity may include light, biological
circadian clock as well as long-distance signaling, while the plant-derived flowering regulators in response to microgravity
could include gibberellic acid, ethylene, microRNA and sugar. The results we have obtained from the space experiments
on board the Chinese recoverable satellites (the SJ-8 and the SJ-10) and the experiment on the Chinese space lab TG-2 are
also introduced. We conclude by suggesting that long-term space experiments from successive generations and a systematic
analysis of regulatory networks at the molecular level is needed to understand the mechanism of plant flowering control
under microgravity conditions in space.
Keywords Microgravity · Photoperiod · Flowering · Chinese recoverable satellite · Long-term
Introduction
Plants have evolved in and are highly adapted to 1-g con-
dition of Earth. Removal of gravitational acceleration by
spaceflight caused a wide range of morphogenesis and cel-
lular and molecular changes in plants (Cogoli and Gmu
¨
nder
1991; Hampp et al. 1997;Pauletal.2013; Hoson 2014;
Zhang and Zheng 2015a). Under microgravity conditions,
plants exhibit spontaneous curvatures or changes in growth
direction (Driss-Ecole et al. 2008). Much progress on plant
growth and development at the molecular levels in response
and adaptation to microgravity has recently been made due
This article belongs to the Topical Collection: Approaching the
Chinese Space Station - Microgravity Research in China
Guest Editors: Jian-Fu Zhao, Shuang-Feng Wang
Hui Qiong Zheng
hqzheng@sibs.ac.cn
1
CAS Center for Excellence in Molecular Plant Sciences,
Shanghai Institute of Plant Physiology and Ecology, Chinese
Academy of Sciences, 300 Fenglin Road Shanghai 200032,
China
to advances in plant genomics and proteomics (Zheng et al.
2015; Zhang et al. 2015b). However, the opportunities of
space missions were scarce and they needed detailed and
well-characteristic ground studies. For this reason, most of
previous space experiments focused on response of plant to
short-term microgravity (Kiss et al. 1998; Driss-Ecole et al.
2008; Kordyum 2014). The research is currently experienc-
ing a renewed interest in the context of future long-term
space missions, where higher plants in a life support system
are required to supply food and fiber, purify ambient air, and
recycle human waste and water (Massa et al. 2017).
Several early attempts to grow plants through a complete
life cycle in space were unsuccessful because of delayed
development (Mashinsky et al. 1994). Plants frequently died
in the transition from the vegetative to the reproductive stage
(Halstead and Dutcher 1987; Nechitailo and Maskinsky
1993). Even when Arabidopsis thaliana plants were pre-
grown to the flowering stage on Earth and allowed to for
seeds on orbit only 55% of seeds were fertile (27% aborted
and 18% had non-viable embryos). The first successful
complete plant life cycle in microgravity occurred in 1983
with Arabidopsis on board Salyut 7 (Table 1). Although
development was delayed, the plants flowered and produced
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