Physiological and molecular level understanding of advanced carbon dots to enhance maize drought tolerance: modulation of photosynthesis and signaling molecules

Abstract

Drought stress is posing a severe threat to the global crop production. Herein, we report a solution to combat drought stress by employing advanced carbon dots, which are rationally designed with the concerted strategies of nitrogen doping and surface modification with polyacrylic acid, defined as PNDs. Doping carbon dots (CDs) with nitrogen (N) improves the ability to eliminate reactive oxygen species (ROS), and polyacrylic acid could facilitate the penetration of CDs through plant cells into chloroplasts. Under drought stress, foliar-applied PNDs (5 mg L⁻¹) could decrease ROS accumulation, substantially improve the net photosynthesis rate (206.8%), and promote water uptake by increasing abscisic acid (ABA, 6.9%) and proline (Pro, 36.3%) in roots of maize, demonstrating multiple positive functions. PNDs could recover maize growth under drought stress by modulating photosynthesis and signaling molecules. The results of dynamic monitoring showed that ABA and Pro were synthesized in maize leaves first, and then accumulated in roots through long-distance transport. The elevated levels of ABA and Pro could promote aquaporin activity and maintain osmotic pressure in roots, thereby alleviating drought stress of maize. This work demonstrates that PNDs will be promising alternatives for sustainable nano-agriculture in responding to the global climate change and food security crisis.