PDF(Pubmed)
Abstract：
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-1 (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 a 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-1) (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 Fv/Fm (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-1.
摘要：
自1980年代以来，中国农业一直有意使用稀土元素（REE）来提高作物产量。在世界各地,稀土元素也通过磷肥不由自主地施用于土壤。已知这些元素可以减轻植物在非生物胁迫下的损害，然而，没有关于这些元素在植物生理学中如何发挥作用的信息。REE的作用模式属于恐怖效应的范围，有低剂量刺激和大剂量不良反应。这项研究旨在验证REE如何影响水稻植物的生理，以测试REE可以在这些植物中充当生物刺激剂的阈值剂量。在实验1中，REE混合物的0.411kgha-1（叶面施用）（含41.38％Ce，23.95%La,13.58%Pr,和4.32%Nd)被应用，以及两种分别含有41.38%Ce和23.95%La的产品。叶绿素a的荧光特性，气体交换，SPAD索引，和生物量（盆栽条件）进行了评估。对于实验2，使用REE混合物（0、0.1、0.225、0.5和1kgha-1）（田间条件）的增加率来研究其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增加了生物量产量(Ce为23%，31％与La，和63%与REE混合施用)由于提高了光合速率(8%与Ce,15%与La,和27%与稀土混合)，受更高的电子流（光合电子传输链）（增加17％）和更高的Fv/Fm（增加14％）和光系统II的量子产率（Ce和La增加20％，和29%的稀土元素混合)，以及增加气孔导度（增加36％）和SPAD指数（增加10％与Ce，12%与La,和15%与稀土混合)。此外，添加稀土元素通过增加水稻叶片N，增强了光合过程，Mg,K,和锰浓度(24-46%)。REE混合物的较高水稻籽粒产量（增加113％）的剂量估计为0.72kgha-1。
