Gramineous plants, such as rice, wheat, and maize, are essential crops. The cell wall composition of gramineous plants is distinguished from that of dicotyledons, such as Arabidopsis, pea, and mung bean. In cell walls of gramineous plants, arabinoxylans and β-glucans are the major matrix polysaccharides and they make network structure within cell wall architecture. Gravitational stimuli affect the metabolism of β-glucans in gramineous shoots; hypergravity suppressed the β-glucan breakdown, when it inhibited shoot elongation. The opposite results were obtained under microgravity conditions in space. On the other hand, the arabinoxylan and diferulic acid (DFA) contents increased under continuous hypergravity conditions. Since arabinoxylans are cross-linked by DFA-bridges, continuous hypergravity may stimulate the formation of arabinoxylan-DFA network within cell walls. These findings suggest that the β-glucan metabolism is primarily involved in the mechanism of growth regulation, while the arabinoxylan-DFA network has a load-bearing function against the gravitational force. The modification of these wall constituents may contribute to the capacity of gramineous plants to sustain their structure and growth under altered gravity conditions.
2009 by Japanese Society for Biological Sciences in Space