Growth and Photosynthesis Responses of a Super Dwarf Rice Genotype to Shade and Nitrogen Supply

Abstract

Specific aspects of plant cultivation require tests under fully controlled environmental conditions with restricted energy supply, such as orbit-based space laboratories and low-light conditions. For these growing conditions, super dwarf plants have been developed as model crops, and a gibberellin- deficient Super Dwarf Rice genotype was proposed as a model crop for space flight plant experiments. We tested this genotype in a climate chamber experiment under different illumination and nitrogen supply levels to assess its suitability under scenarios with limited resource availability. A 25% reduction in illumination led to a 75% reduction in yield, mainly due to a 60% reduction in formed tillers and 20% reduction in grain weight, and a 80% reduction in illumination caused total yield loss. Leaf area under reduced illumination was significantly lower, and only marginal changes in the dimensions of leaves were observed. Plant photosynthesis was not significantly different between control and 75% illumination. This was explained by a higher photochemical efficiency under lower light conditions and a reduced mesophyll resistance. Therefore, we concluded that this genotype is well-suited for plant experiments under space and light-limited conditions since it kept its small stature and showed no shade avoidance mechanisms, such as leaf elongation, which would complicate experiments under low-light conditions. Nitrogen concentrations of 2.8 and 1.4 mmol/L led to no differences in plant growth. We concluded that a nitrogen concentration of 1.4 mmol/L is sufficient for this genotype under the light intensities.