Morphological and Physiological Responses of Rice (Oryza sativa) to Limited Phosphorus Supply in Aerated and Stagnant Solution Culture

• Background and Aims Rain-fed lowland rice commonly encounters stresses from fluctuating water regimes and nutrient deficiency. Roots have to acquire both oxygen and nutrients under adverse conditions while also acclimating to changes in soil-water regime. This study assessed responses of rice roots to low phosphorus supply in aerated and stagnant nutrient solution

Direct human influence on atmospheric CO2 seasonality from increased cropland productivity

Ground- and aircraft-based measurements show that the seasonal amplitude of Northern Hemisphere atmospheric carbon dioxide (CO2) concentrations has increased by as much as 50 per cent over the past 50 years1, 2, 3. This increase has been linked to changes in temperate, boreal and arctic ecosystem properties and processes such as enhanced photosynthesis, increased heterotrophic respiration, and expansion of woody vegetation4,5, 6. However, the precise causal mechanisms behind the observed changes in atmospheric CO2 seasonality remain unclear2, 3, 4. Here we use production statistics and a carbon accounting model to show that increases in agricultural productivity, which have been largely overlooked in previous investigations, explain as much as a quarter of the observed changes in atmospheric CO2 seasonality. Specifically, Northern Hemisphere extratropical maize, wheat, rice, and soybean production grew by 240 per cent between 1961 and 2008, thereby increasing the amount of net carbon uptake by croplands during the Northern Hemisphere growing season by 0.33 petagrams. Maize alone accounts for two-thirds of this change, owing mostly to agricultural intensification within concentrated production zones in the midwestern United States and northern China. Maize, wheat, rice, and soybeans account for about 68 per cent of extratropical dry biomass production, so it is likely that the total impact of increased agricultural production exceeds the amount quantified here

Adaptation of rice to flooded soils

This paper and its companion (Colmer et al., 2014) review research on the adaptation of rice (Oryza sativa L.) to the wide range of semi-aquatic environments in which it grows. The paper considers well-regulated flooding to 5-20 cm depth; the companion considers deeper flooding in rainfed conditions. Flooded environments are dominated by the very slow diffusion of gases in water and the resulting changes in soil chemical and biological conditions. Adaptations to these potentially toxic conditions hinge on an optimum ventilation network in the plant, providing O₂ to the roots and rhizosphere, both being critical for favourable nutrition and tolerance of reduced-soil toxins. Rice has become a model for studying adaptation to flooded soils and flood-prone environments because of its relatively simple genome and large genetic diversity, and its extreme tolerance of flooded soils compared with other crop species.39 page(s