Transition from a maternal to external nitrogen source in maize seedlings.

Area of Science:

• Plant Physiology
• Nutrient Uptake
• Molecular Biology

Background:

• Maximizing nitrate (NO3-) uptake during seedling development is vital for plant growth and yield.
• Understanding the initiation of root NO3- uptake capacity in developing seedlings is limited.

Purpose of the Study:

• To examine physiological processes in root NO3- uptake and metabolism.
• To understand how the NO3- uptake system responds to demand during the transition from seed N to external N capture in maize seedlings.

Main Methods:

• Monitoring changes in seed-derived free amino acids and shoot nitrogen percentage (N%).
• Assessing root NO3- uptake capacity.
• Analyzing transcript levels of nitrate transporter genes (ZmNRT2.1 and ZmNRT2.2).

Main Results:

• Seed-derived free amino acid concentrations rapidly decrease in root and shoot tissues within eight days after imbibition (DAI).
• Shoot N% decreases and stabilizes 12-13 DAI.
• Root NO3- uptake capacity increases following the decrease in free amino acids, coinciding with a rise in ZmNRT2.1 and ZmNRT2.2 transcript levels.

Conclusions:

• The study elucidates the physiological and molecular mechanisms underlying the initiation of root nitrate uptake capacity in maize seedlings.
• This transition is driven by the depletion of internal nitrogen reserves and the subsequent activation of nitrate transporters to meet plant demand.