de Oliveira Cynthia, Ramos Silvio Junio, Dinali Guilherme Soares, de Carvalho Teotonio Soares, Martins Fábio Aurélio Dias, Faquin Valdemar, Castro Evaristo Mauro de, Sarkis Jorge Eduardo Souza, Siqueira José Oswaldo, Guilherme Luiz Roberto Guimarães
Departamento de Ciência do Solo, Universidade Federal de Lavras (UFLA), Lavras 37203-202, Brazil.
Instituto Tecnológico Vale-Desenvolvimento Sustentável, Rua Boaventura da Silva, 955, Belém 66055-090, Brazil.
Plants (Basel). 2024 May 22;13(11):1435. doi: 10.3390/plants13111435.
Rare earth elements (REEs) have been intentionally used in Chinese agriculture since the 1980s to improve crop yields. Around the world, REEs are also involuntarily applied to soils through phosphate fertilizers. These elements are known to alleviate damage in plants under abiotic stresses, yet there is no information on how these elements act in the physiology of plants. The REE mode of action falls within the scope of the hormesis effect, with low-dose stimulation and high-dose adverse reactions. This study aimed to verify how REEs affect rice plants' physiology to test the threshold dose at which REEs could act as biostimulants in these plants. In experiment 1, 0.411 kg ha (foliar application) of a mixture of REE (containing 41.38% Ce, 23.95% La, 13.58% Pr, and 4.32% Nd) was applied, as well as two products containing 41.38% Ce and 23.95% La separately. The characteristics of chlorophyll fluorescence, gas exchanges, SPAD index, and biomass (pot conditions) were evaluated. For experiment 2, increasing rates of the REE mix (0, 0.1, 0.225, 0.5, and 1 kg ha) (field conditions) were used to study their effect on rice grain yield and nutrient concentration of rice leaves. Adding REEs to plants increased biomass production (23% with Ce, 31% with La, and 63% with REE Mix application) due to improved photosynthetic rate (8% with Ce, 15% with La, and 27% with REE mix), favored by the higher electronic flow (photosynthetic electron transport chain) (increase of 17%) and by the higher F/F (increase of 14%) and quantum yield of photosystem II (increase of 20% with Ce and La, and 29% with REE Mix), as well as by increased stomatal conductance (increase of 36%) and SPAD index (increase of 10% with Ce, 12% with La, and 15% with REE mix). Moreover, adding REEs potentiated the photosynthetic process by increasing rice leaves' N, Mg, K, and Mn concentrations (24-46%). The dose for the higher rice grain yield (an increase of 113%) was estimated for the REE mix at 0.72 kg ha.
自20世纪80年代以来，中国农业中就有意使用稀土元素（REEs）来提高作物产量。在全球范围内，稀土元素也会通过磷肥被无意地施用于土壤中。已知这些元素能减轻非生物胁迫下植物的损伤，但关于这些元素在植物生理学中的作用方式尚无相关信息。稀土元素的作用模式属于兴奋效应的范畴，即低剂量刺激和高剂量不良反应。本研究旨在验证稀土元素如何影响水稻植株的生理机能，以测试稀土元素在这些植物中作为生物刺激剂的阈值剂量。在实验1中，施用了0.411千克/公顷（叶面喷施）的稀土元素混合物（含41.38%的铈、23.95%的镧、13.58%的镨和4.32%的钕），以及两种分别含41.38%铈和23.95%镧的产品。对叶绿素荧光、气体交换、SPAD指数和生物量（盆栽条件）的特征进行了评估。在实验2中，使用了不同施用量的稀土元素混合物（0、0.1、0.225、0.5和1千克/公顷）（田间条件）来研究它们对水稻籽粒产量和水稻叶片养分浓度的影响。向植物中添加稀土元素可提高生物量产量（铈处理提高23%，镧处理提高31%，稀土元素混合物处理提高63%），这归因于光合速率的提高（铈处理提高8%，镧处理提高15%，稀土元素混合物处理提高27%），光合速率的提高得益于更高的电子流（光合电子传递链）（提高17%）、更高的F/F（提高14%）以及光系统II的量子产率（铈和镧处理提高20%，稀土元素混合物处理提高29%），同时气孔导度增加（提高36%）和SPAD指数增加（铈处理提高10%，镧处理提高12%，稀土元素混合物处理提高15%）。此外，添加稀土元素通过提高水稻叶片中的氮、镁、钾和锰浓度（24% - 46%）来增强光合过程。估计稀土元素混合物在施用量为0.72千克/公顷时，水稻籽粒产量最高（提高113%）。
