Study On The Mechanism Of Carbon Nano-Materials Regulating Maize Photosynthesis And The Technology Of Improving Its Bioavailability

Conventional agricultural technologies have been unable to meet the growing population’s demand for food,while nanoparticles（NPs）have attracted increasing attention due to their high activity,low environmental pollution,and easy synthesis characteristics in agricultural applications.Compared to traditional fertilizers,NPs exhibit higher activity（20%-30%）and significantly promote crop growth and development.Among them,carbon nanomaterials have shown powerful applications in the field of agricultural production due to their unique properties that can increase the light absorption range of crops.However,there have been few reports on how carbon nanomaterials affect the photosynthesis system of crops to maximize their bioavailability in the present.Therefore,in this study,g-C₃N₄ and NanoSi-CDs were targeted as carbon nanomaterials.Maize,a commonly used crop,was used as the test object.On the one hand,the intrinsic mechanism of graphite carbon nitride（g-C₃N₄）regulating photosynthesis in maize was deeply explored.Furthermore,the enhancement of carbon dots（CDs）in maize photosynthesis by the adhesion ability of silicon based nanomaterials（NanoSi）was systematically elaborated.This study provides a favorable theoretical basis and data support for revealing the enormous potential of carbon nanomaterials in crop production applications.The main research results are as follows:（1）g-C₃N₄,CDs,and NanoSi-CDs were synthesized successfullyThe g-C₃N₄ with good fluorescence characteristics,stable structure,and nanocomposites of nano silicon combined with CDs（NanoSi-CDs）with fluorescence characteristics,adhesion characteristics,and stable structure were successfully synthesized.NanoSi with a larger specific surface area(131.5 m²·g^-1)was selected to load CDs;Ultraviolet light(λ_ex=313 nm),the synthesized g-C₃N₄ nanoflakes emitted strong blue fluorescence with a high fluorescence quantum yield of 6.4%.At the same time,NanoSi-CDs exhibited strong blue fluorescence at an excitation wavelength of 360 nm;The N-release experiment and fluorescence release experiment proved that the structure of g-C₃N₄ nanoflakes and NanoSi-CDs is stable.（2）The intrinsic mechanism of fluorescent g-C₃N₄ to enhance photosynthesis in maizeAfter continuous exposure of maize roots to 10 mg·L^-1 g-C₃N₄ nanosheets for 9 days,g-C₃N₄ was observed to be absorbed into the roots and migrated upward into the leaves.In addition,g-C₃N₄ enhanced crop light capture by expanding crop light absorption,improved photon utilization in photosystem I,significantly up-regulated gene expression of photosynthesis-related genes psb A（photosystem II reaction center protein A）and psa A（photosystem I reaction center protein A）by 56.3%and 26.8%,respectively.And accumulation of nutrients（Mg,P,Fe and Mn）increased by 1.1%,51.8%,44.6%and 121.8%,respectively.The activities of phosphoenolpyruvate carboxylase（PEPC）and ribulose-1,5-bisphosphate carboxylase/oxygenase（Rubisco）were inhanced by 242.3%and 156.3%,respectively.Accelerated CO₂ fixation in the Calvin cycle,and increased carbohydrate content.In conclusion,this study provides a new perspective for the use of g-C₃N₄nanoparticles to promote plant growth and develop nanotechnology for agriculture.（3）Carbon nanomaterials enhance bioavailabilityFoliar application of NanoSi-CDs(10 mg·L^-1)for 7 days significantly increased the net photosynthetic rate（110.0%-140.0%）,fresh weight（327.1%for roots,247.2%for aboveground parts）,and dry weight（212.0%for roots,118.5%for aboveground parts）of maize.Interestingly,at 20^th day after spraying NanoSi-CDs,the net photosynthetic rate remained significantly increased,while CDs also did not have this effect.It was confirmed that NanoSi has a huge cavity structure and suitable pores that can accommodate a large number of CDs and reduce their release rate,extending the action cycle of CDs.In addition,rainfall simulation experiments have verified that NanoSi-CDs have stronger adhesion than CDs.In summary,NanoSi carriers can be a promising method to improve the bioavailability of carbon nanomaterials in sustainable agriculture and provide theoretical support for technological research.