Development of Super-Dwarf Wheat Under Stress Conditions Simulating Those on the Space Station MIR

Super-Dwarf wheat plants were grown in simulation growth chambers under 12 treatments with three photoperiods (18 h, 21 h, 24 h) and four carbon-dioxide levels (360, 1200, 3000, and 7000 μmol/mol). Carbon-dioxide concentrations affected flower initiation rates of Super-Dwarf wheat. The optimum CO2 level for flower initiation and development was 1200 μmol•mol-1. Super-optimum CO2 levels delayed flower initiation, but did not decrease final flower bud number per head. Longer photoperiods not only accelerated flower initiation rates, but also decreased deleterious effects of super-optimum C02. Flower bud size and head length at the same developmental stage were larger under longer photoperiods. But final flower bud number was not affected by photoperiod. Stomatal densities on the abaxial surface were more sensitive to the variation of photoperiod and CO2level than those on the adaxial surface for Super-Dwarf wheat. Stomatal density did not significantly change on the adaxial surface, but was significantly decreased on the abaxial surface under longer photoperiods and higher CO2 levels at 27 day after planting (DAP). Cell-walls of both stem and leaf tissues did not significantly change with variation of photoperiod and carbon-dioxide levels at either seedling stage or mature stage. McDowell fixative was suitable for long-term storage of plant tissue for use in light microscopy. When stored up to 180 d, there was no significant change in leaf thickness, shape and size of mesophyll cells, and shape of chloroplasts for wheat leaves under the light microscope