Reductions in soil water availability for plants increase the risk of plant mortality and decrease crop yield in regions prone to desertification. Phloem – a thin vascular tissue, through which fixed carbon (C) compounds are mobilized and distributed throughout plants – is key for plants and crops to maintain yield and functioning under reduced water availability and increased frequencies of extreme climatic events.
To better understand phloem functioning responses to changes in water availability, direct measurements of its C dynamics are needed. However, little reliable direct evidence exists due to methodological difficulties, stemming from phloem’s nature, and from the use of invasive methods, resulting in biases of phloem flow estimations.
Using 11C isotope as a tracer, combined with positron emission tomography imaging, we have a tool to study phloem functioning non-invasively and reliably. 11C is a short-lived radioactive isotope of C, from which gaseous 11CO2 can be created. Following its fixation through photosynthesis, 11C is metabolized and distributed similarly to other C isotopes.
Here, we labeled wheat plants with 11CO2, estimated phloem C dynamics, and assessed the impact of reduced water availability. We estimated the velocity of newly fixed 11C in flag leaves, as well as its allocation into the ears in vivo, and over several phenophases. Preliminary results show differences between ear phenophases, water availability, and grains within an ear.
The method presented here will further our understanding on water availability effects on C dynamics, and greatly improve our ability to predict phloem functioning in plants experiencing reductions in water availability.