Physiological Performance and Grain Yield Components of Common Buckwheat (Fagopyrum esculentum Moench) Cultivated Under Different N Rates.

Abstract

Buckwheat (Fagopyrum esculentum Moech) is a "gluten-free" pseudocereal with high-quality proteins and human health properties, increasing its cultivation worldwide. However, the role of nitrogen (N) in plant growth and yield components has received little attention in buckwheat. This study evaluated N's effect on plant traits, photosynthetic performance, and grain yield components in buckwheat under field conditions. For this, Buckwheat cv. "Mancan" seeds were sown using five N rates: 0, 30, 45, 60, and 90 kg N ha^-1. Then, physiological performance and grain yield components were evaluated at harvest. Our study revealed that buckwheat plants subjected to 0 and 30 kg N ha^-1 showed the greatest chlorophyll fluorescence a parameters including maximum quantum yield of PSII (Fv'/Fm'), effective quantum yield of PSII (ФPSII), and electron transport rate (ETR) among N treatments; meanwhile, at higher N rates (60 and 90 kg N ha^-1), these parameters decayed. Similarly, plants treated with 90 kg N ha^-1 showed the lowest CO₂ assimilation among N treatments. In general, stomatal conductance (g_s), transpiration (E), and intrinsic water use efficiency (WUE_i) showed no significant changes among N treatments, with the exception of 30 kg N ha^-1, which exhibited the highest WUE_i. Concerning plant traits, plants grown under 60 and 90 kg N ha^-1 exhibited the greatest plant height, number of branches, shoot biomass, and internode per plant among N treatments. By contrast, 30 kg N ha^-1 showed the highest grain number, yield per plant, and grain yield among N treatments in F. esculentum plants. Based on the physiological and productive parameters, F. esculentum seems to have a low N requirement, exhibiting better results under the lowest N rates (30 kg N ha^-1). Therefore, F. esculentum could be considered as an alternative for gluten-free food production with low N requirements in agricultural systems of southern Chile. Nonetheless, more studies are required to understand the effect of N biochemical and molecular regulation on plant traits and grain yield components in buckwheat.