Phenotypic plasticity of plants in response to environmental changes is important for adapting to changing climate. Less attention has been paid to exploring the advantages of phenotypic plasticity in resource-rich environments to enhance the productivity of agricultural crops. Here, we examined genetic variation for phenotypic plasticity in indica rice (Oryza sativa L.) across two diverse panels: (1) a Phenomics of Rice Adaptation and Yield (PRAY) population comprising 301 accessions; and (2) a Multi-parent Advanced Generation Inter-Cross (MAGIC) indica population comprising 151 accessions. Altered planting density was used as a proxy for elevated atmospheric CO response. Low planting density significantly increased panicle weight per plant compared with normal density, and the magnitude of the increase ranged from 1.10 to 2.78 times among accessions for the PRAY population and from 1.05 to 2.45 times for the MAGIC population. Genome-wide-association studies validate three Environmental Responsiveness (ER) candidate alleles (qER1-3) that were associated with relative response of panicle weight to low density. Two of these alleles were tested in 13 genotypes to clarify their biomass responses during vegetative growth under elevated CO in Japan. Our study provides evidence for polymorphisms that control rice phenotypic plasticity in environments that are rich in resources such as light and CO .

(Y.M.).Selection for cultivars with superior responsiveness to elevated atmospheric CO 2 concentrations (eCO 2 ) is a powerful option for boosting crop productivity under future eCO 2 . However, neither criteria for eCO 2 responsiveness nor prescreening methods have been established. The purpose of this study was to identify traits responsible for eCO 2 responsiveness of soybean (Glycine max). We grew 12 Japanese and U.S. soybean cultivars that differed in their maturity group and determinacy under ambient CO 2 and eCO 2 for 2 years in temperature gradient chambers. CO 2 elevation significantly increased seed yield per plant, and the magnitude varied widely among the cultivars (from 0% to 62%). The yield increase was best explained by increased aboveground biomass and pod number per plant. These results suggest that the plasticity of pod production under eCO 2 results from biomass enhancement, and would therefore be a key factor in the yield response to eCO 2 , a resource-rich environment. To test this hypothesis, we grew the same cultivars at low planting density, a resource-rich environment that improved the light and nutrient supplies by minimizing competition. Low planting density significantly increased seed yield per plant, and the magnitude ranged from 5% to 105% among the cultivars owing to increased biomass and pod number per plant. The yield increase due to low-density planting was significantly positively correlated with the eCO 2 response in both years. These results confirm our hypothesis and suggest that high plasticity of biomass and pod production at a low planting density reveals suitable parameters for breeding to maximize soybean yield under eCO 2 .

Genotypes with high potential yield would improve crop production. Trials that examined potential yield have been conducted around the world, producing databases that can be mined to reveal "hidden" high-yield cultivars. However, yield data from different times and locations are not comparable because yield integrates the effects of cultivar-specific potential with the effects of weather and management practices. Here, we hypothesized that cultivar-specific yield can be expressed as a function of the climatic potential yield, which is calculated using a model based on daily solar radiation, temperature, and phenology data. To test this hypothesis, we used a rice Oryza sativa L. yield database from Japan, including only data from years with normal climatic conditions and trials with optimal N fertilization. For cv. 'Sasanishiki', which is widely grown in northern Japan, data from four prefectures and 20 years showed yield. The yield variations could be expressed by a single unique statistically significant regression across prefectures and years as a function of the climatic potential yield. This method demonstrated that 'Koshihikari' produced 10 less and 'Fukuhibiki' produced 19 more than 'Sasanishiki' for a given climatic potential yield 1000 g m 2 . We confirmed this ranking by direct comparisons of the cultivars in identical years and at the same locations. Our method can be used for data mining to identify high-yield cultivars through data from previous yield research. We discuss the limitations and advantages of this method, its potential for other crop species, and its potential for determining responses to abiotic and biotic stresses.

The long-term dynamics of the transcriptome under natural field conditions remain unclear. We conducted comprehensive gene expression analyses of rice leaves and roots grown under natural field conditions for a long period, from the tillering stage to the ripening stage. In this experiment, changes in the transcriptome were captured in relation to microclimatic parameters, particularly potential evaporation (Ep), which is a multiple meteorological factor and acts as an indicator of transpirational demand. The results indicated that many genes were regulated by changes in temperature and Ep in both leaves and roots. Furthermore, the correlation between gene expression and meteorological factors differed significantly between the vegetative and reproductive stages. Since Ep triggers transpiration, we analyzed aquaporin gene expression, which is responsible for water transport, and found that many aquaporin genes in leaves were positively correlated with Ep throughout the growth period, whereas in roots, two plasma membrane intrinsic aquaporins, PIP2;4 and PIP2;5 were strongly correlated with Ep during reproductive growth. Other genes closely related to productivity, such as those involved in nutrient absorption and photosynthesis, exhibited different responses to meteorological factors at different growth stages. The stagedependent shift in the microclimate response provides an important perspective on crop physiology in light of climate change.