Effect of heat wave on N2 fixation and N remobilisation of lentil (Lens culinaris MEDIK) grown under free air CO2 enrichment in a mediterranean-type environment

The stimulatory effect of elevated [CO₂ ] (e[CO₂ ]) on crop production in future climates is likely to be cancelled out by predicted increases in average temperatures. This effect may become stronger through more frequent and severe heat waves, which are predicted to increase in most climate change scenarios. Whilst the growth and yield response of some legumes grown under the interactive effect of e[CO₂ ] and heat waves has been studied, little is known about how N₂ fixation and overall N metabolism is affected by this combination. To address these knowledge gaps, two lentil genotypes were grown under ambient [CO₂ ] (a[CO₂ ], ~400 µmol·mol^-1 ) and e[CO₂ ] (~550 µmol·mol^-1 ) in the Australian Grains Free Air CO₂ Enrichment facility and exposed to a simulated heat wave (3-day periods of high temperatures ~40 °C) at flat pod stage. Nodulation and concentrations of water-soluble carbohydrates (WSC), total free amino acids, N and N₂ fixation were assessed following the imposition of the heat wave until crop maturity. Elevated [CO₂ ] stimulated N₂ fixation so that total N₂ fixation in e[CO₂ ]-grown plants was always higher than in a[CO₂ ], non-stressed control plants. Heat wave triggered a significant decrease in active nodules and WSC concentrations, but e[CO₂ ] had the opposite effect. Leaf N remobilization and grain N improved under interaction of e[CO₂ ] and heat wave. These results suggested that larger WSC pools and nodulation under e[CO₂ ] can support post-heat wave recovery of N₂ fixation. Elevated [CO₂ ]-induced accelerated leaf N remobilisation might contribute to restore grain N concentration following a heat wave.

Elevated [CO2 ] effects on crops: Advances in understanding acclimation, nitrogen dynamics and interactions with drought and other organisms

Future rapid increases in atmospheric CO₂ concentration [CO₂ ] are expected, with values likely to reach ~550 ppm by mid-century. This implies that every terrestrial plant will be exposed to nearly 40% more of one of the key resources determining plant growth. In this review we highlight selected areas of plant interactions with elevated [CO₂ ] (e[CO₂ ]), where recently published experiments challenge long-held, simplified views. Focusing on crops, especially in more extreme and variable growing conditions, we highlight uncertainties associated with four specific areas. (1) While it is long known that photosynthesis can acclimate to e[CO₂ ], such acclimation is not consistently observed in field experiments. The influence of sink-source relations and nitrogen (N) limitation on acclimation is investigated and current knowledge about whether stomatal function or mesophyll conductance (g_m ) acclimate independently is summarised. (2) We show how the response of N uptake to e[CO₂ ] is highly variable, even for one cultivar grown within the same field site, and how decreases in N concentrations ([N]) are observed consistently. Potential mechanisms contributing to [N] decreases under e[CO₂ ] are discussed and proposed solutions are addressed. (3) Based on recent results from crop field experiments in highly variable, non-irrigated, water-limited environments, we challenge the previous opinion that the relative CO₂ effect is larger under drier environmental conditions. (4) Finally, we summarise how changes in growth and nutrient concentrations due to e[CO₂ ] will influence relationships between crops and weeds, herbivores and pathogens in agricultural systems.

Non-cardiogenic pulmonary oedema due to the intravenous administration of clove oil

Intravenous injection of clove oil induced non-cardiogenic pulmonary oedema, which was managed successfully with a conservative diagnostic and therapeutic approach.