Abstract
Background and Aims: Understanding interactions between water and nitrate fluxes in response to nitrate availability and transpiration rate is crucial to select more efficient plants for the use of water and nitrate.Methods: Some of these interactions were investigated in intact Brassica napus plants by combining a non-destructive gravimetric device with 15NO3- labeling. The set-up allowed high-resolution measurement of the effects of a cross-combination of two concentrations of KNO3 or KCl (0.5 and 5 mM) with two different rates of transpiration controlled by the relative humidity during a day–night cycle.Key Results: Results show that (1) high external nitrate concentrations increased root water uptake significantly whatever the transpiration rate, (2) nitrate translocation depended both on the rate of nitrate uptake and loading into xylem (3) dilution-concentration effect of nitrate in the xylem was mainly modulated by both external nitrate availability and transpiration rate, (4) dynamic changes in 15N translocation in the xylem modified shoot growth and capacitance, and (5) variations in tissue concentrations of NO3- induced by the experimental conditions were balanced by changes in concentrations of chloride and sulfate ions. These effects were even more amplified under low transpiration condition and 0.5 mM external nitrate concentration.Conclusion: Taken together, these results highlight the fine and rapid adjustment of anion contents, nitrate and water flows to changes in transpiration rate and nitrate availability during a day–night cycle. The use of this non-invasive gravimetric device is therefore a powerful tool to assess candidates genes involved in nitrogen and water use efficiency.
Highlights
A better understanding of the dynamic interactions between nitrate and water fluxes submitted to different transpiration rates is becoming critical for agriculture because of the worldwide increase in food demand, climate change and the increase in fertilizer costs (Good et al, 2004)
Comparison of the diurnal patterns showed that water uptake and transpiration rates were parallel over the day–night period (Figures 3A,B and Supplementary Figure S3)
The strong reduction in water and transpiration rates observed in low transpiring condition (LT) conditions (Figures 3A,B) demonstrates that the use of this gravimetric device is relevant for accurate analysis of relationships between the flows of water and 15NO3 for shoot growth in relation to the driving forces when temperature and light intensity are stable
Summary
A better understanding of the dynamic interactions between nitrate and water fluxes submitted to different transpiration rates is becoming critical for agriculture because of the worldwide increase in food demand, climate change and the increase in fertilizer costs (Good et al, 2004) Unraveling these interactions requires the development of non-invasive methods avoiding excised roots and/or pressurization of the root system, in order to analyze simultaneously the dynamic interactions of water and nitrate fluxes in intact transpiring plants during a day–night cycle (Windt et al, 2006; Schulze-Till et al, 2009; Wegner, 2015). A literature survey shows that non-invasive methods to measure either water flow or nitrate flow already exist These methods have been used in intact plants with a low temporal resolution (day-to-week) and without the aid of 13NO3− or 15NO3− tracers (Shaner and Boyer, 1976; Schulze and Bloom, 1984). Understanding interactions between water and nitrate fluxes in response to nitrate availability and transpiration rate is crucial to select more efficient plants for the use of water and nitrate
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
