Patchy nitrate promotes inter-sector flow and ¹⁵N allocation in Ocimum basilicum: a model and an experiment

Area of Science:

• Plant Physiology
• Soil Science
• Biochemistry

Background:

• Root conductance plasticity is a key trait for nutrient uptake.
• Sectoriality in roots may limit nutrient and water transport between xylem pathways.
• Nitrate availability influences root hydraulic properties and nutrient distribution.

Purpose of the Study:

• To investigate the impact of high nitrate patches on root conductance and water uptake.
• To determine if root conductance plasticity mediates nitrogen allocation between root sectors.
• To simulate and empirically test the effects of nitrate availability on water and nitrogen transport in split-root basil plants.

Main Methods:

• Simulations were used to model the effects of high nitrate patches on root conductance, water uptake, and inter-sector water transport.
• Empirical testing involved split-root hydroponic basil (Ocimum basilicum L.) exposed to nitrate patches.
• Nitrogen distribution was traced using 15N-labeled ammonium nitrate (14NH415NO3).

Main Results:

• Simulations indicated that the proportion of water uptake from a nitrate patch depends on root resistance and sectoriality.
• Empirically, water flow through excised basil roots was 1.4 times higher under high nitrate conditions.
• Nitrate patches led to a significant increase in water uptake from the patch, and water uptake patterns predicted 15N distribution.

Conclusions:

• Root conductance plasticity plays a role in regulating water uptake in response to localized nutrient availability.
• Nitrate-induced changes in root conductance can influence nitrogen allocation between different root sectors.
• This study highlights a previously unrecognized benefit of root conductance plasticity in mediating nutrient distribution within plants.