Brassica rapa L. seed development in hypergravity

Abstract

Previous experiments had shown that microgravity adversely affected seed development in Brassica rapa L. We tested the hypothesis that gravity controls seed development via modulation of gases around the developing seeds, by studying how hypergravity affects the silique microenvironment and seed development. Using an in vitro silique maturation system, we sampled internal silique gases for 16 d late in the seed maturation sequence at 4 g or 1 g. The carbon dioxide level was significantly higher inside the 4-g siliques, and the immature seeds became heavier than those maturing at 1 g. Pollination and early embryo development were also studied by growing whole plants at 2 g or 4 g for 16 d inside chambers mounted on a large-diameter centrifuge. Each day the rotor was briefly stopped to permit manual pollination of flowers, thereby producing cohorts of same-aged siliques for comparison with stationary control material. The loss of starch and soluble carbohydrates during seed development was accelerated in hypergravity, with seeds developing at 4 g more advanced by 2 d than those at 1 g. Seeds produced at 4 g contained more lipid than those at 1 g. Taken together, these results indicate that hypergravity enhances gas availability to the developing embryos. Gravity's role in seed development is of importance to the space programme because of the plan to use plants for food production and habitat regeneration in extraterrestrial settings. These results are significant because they underscore the tight co-regulation of Brassica seed development and the atmosphere maintained inside the siliques.

Centrifuges for Microgravity Simulation. The Reduced Gravity Paradigm

“…Centrifuges are applied in various disciplines mainly in material and particle technology like for separation (Sahuquillo et al, 1999;Kuang et al, 2015), for nanomaterials classification (Wohlleben, 2012), casting (Huisman et al, 1994;Liu and Barnett, 2002;Dikel et al, 2005;Velhinho and Rocha, 2011), combustion (Merzhanov, 1995), but also in areas like geology (Gopal Madabhushi, 2004;Costa et al, 2016), life sciences in plants (Musgrave et al, 2009;Herranz et al, 2013;Hoson and Wakabayashi, 2015), single cells (Loesberg et al, 2006;Tavakolinejad et al, 2015), animals (van Loon, 2001;van Loon et al, 2005;Tateishi et al, 2015) and humans (Akima et al, 2005;van Loon et al, 2012;Goswami et al, 2015).…”

Effects of specific organs on seed oil accumulation in Brassica napus L.

“…To determine the suitable sucrose concentration for rapeseed tissue culture, siliques from seven developmental stages (10,14,18,22,26,30, and 34 d after flowering [daf]) were sampled from 6F313 line grown in the field. Sucrose contents in silique walls and ovules were measured according to the method reported by Roe [35].…”

“…The pod culture followed the procedure described by Musgrave et al [30]. To summarize briefly, a small piece of the bottom carpopodium was removed and four siliques were placed in flatbottom test tubes containing 10 ml of liquid 1/2 Murashige and Skoog medium (MS) (PhytoTechnology Laboratory, Shawnee Mission, KS, USA) with different sucrose concentrations (w/v).…”

“…Ovary and ovule culture for embryo rescue has enabled interspecific Brassica hybrids and intergeneric hybrids of B. napus and Sinapis alba to overcome incongruity barriers [26][27][28][29][30].…”

Oxygen dependency of germinating Brassica seeds

“…For example, weightlessness prevents water run-off and water may form a diffusive barrier that reduces gas exchange compared to ground conditions and leads to hypoxia (Musgrave, 2002). The lack of buoyancy leads to hypoxia in the root zone (Stout et al, 2001) and differences in seed development between weightlessness one-g and hypergravity indicate that developmental processes are sensitive to gravity (Kuang et al, 2005;Musgrave et al, 2009). Therefore, it is necessary to understand the effect of hypoxia on plants in conjunction with space requirements and related growth conditions such as elevated levels of ethylene that are routinely observed in closed (space) systems (Kiss et al, 2000).…”