Biotechnological strategies for improved photosynthesis in a future of elevated atmospheric CO2.

MAIN CONCLUSION: The improvement of photosynthesis using biotechnological approaches has been the focus of much research. It is now vital that these strategies be assessed under future atmospheric conditions. The demand for crop products is expanding at an alarming rate due to population growth, enhanced affluence, increased per capita calorie consumption, and an escalating need for plant-based bioproducts. While solving this issue will undoubtedly involve a multifaceted approach, improving crop productivity will almost certainly provide one piece of the puzzle. The improvement of photosynthetic efficiency has been a long-standing goal of plant biotechnologists as possibly one of the last remaining means of achieving higher yielding crops. However, the vast majority of these studies have not taken into consideration possible outcomes when these plants are grown long-term under the elevated CO2 concentrations (e[CO2]) that will be evident in the not too distant future. Due to the considerable effect that CO2 levels have on the photosynthetic process, these assessments should become commonplace as a means of ensuring that research in this field focuses on the most effective approaches for our future climate scenarios. In this review, we discuss the main biotechnological research strategies that are currently underway with the aim of improving photosynthetic efficiency and biomass production/yields in the context of a future of e[CO2], as well as alternative approaches that may provide further photosynthetic benefits under these conditions.

Water use intensity of Canadian beef production in 1981 as compared to 2011.

The amount of beef produced per animal in Canada increased significantly from 1981 to 2011, due to enhanced production efficiency and increased carcass weight. This study examined the impact of improvements in production efficiency on water use intensity over this period. Temporal and regional differences in cattle categories, water use for drinking, feed production and meat processing, feeding systems, average daily gains, and carcass weight were considered in the analysis. Potential evapotranspiration (PET) was estimated by the National Drought Model (NDM) from 679 weather stations across Canada using the Priestley and Taylor equation. To adjust PET estimates for each crop included in cattle diets, FAO crop coefficients were used to calculate total feed water demand. Estimates of drinking water consumed by a given class of cattle accounted for physiological status, body weight and dry matter intake as well as ambient temperature. In both years, drinking water accounted for less than 1% of total water use with precipitation (i.e., green water) included for feed and pasture production. With exclusion of green water, drinking water accounted for 24% and 21% of total water use for Canadian beef production in 1981 and 2011, respectively. The estimated intensity of blue water (surface and groundwater) use per kilogram of boneless beef was 577L in 1981 and 459 in 2011, a 20% decline. The observed reduction in water use intensity over the past three decades is attributed to an increase in average daily gain and slaughter weight, improved reproductive efficiency, reduced time to slaughter as well as improvements in crop yields and irrigation efficiency. Given that feed production accounts for the majority of water use in beef production, further advances may be achieved by improving feeding efficiencies and reducing water use per unit of feed crop and pasture production.