Rao Rong-Yu, Huang Wei-Lin, Yang Hui, Shen Qian, Huang Wei-Tao, Lu Fei, Ye Xin, Yang Lin-Tong, Huang Zeng-Rong, Chen Li-Song
College of Resources and Environment, Fujian Agriculture and Forestry University, Fuzhou 350002, China.
Plants (Basel). 2025 Aug 2;14(15):2390. doi: 10.3390/plants14152390.
Manganese (Mn) excess and low pH often coexist in some citrus orchard soils. Little information is known about the underlying mechanism by which raising pH reduces Mn toxicity in citrus plants. 'Sour pummelo' ( (L.) Osbeck) seedlings were treated with 2 (Mn2) or 500 (Mn500) μM Mn at a pH of 3 (P3) or 5 (P5) for 25 weeks. Raising pH mitigated Mn500-induced increases in Mn, iron, copper, and zinc concentrations in roots, stems, and leaves, as well as nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, copper, iron, and zinc distributions in roots, but it mitigated Mn500-induced decreases in nitrogen, phosphorus, potassium, calcium, magnesium, sulfur, and boron concentrations in roots, stems, and leaves, as well as nutrient imbalance. Raising pH mitigated Mn500-induced necrotic spots on old leaves, yellowing of young leaves, decreases in seedling growth, leaf chlorophyll concentration, and CO assimilation (A), increase in root dry weight (DW)/shoot DW, and alterations of leaf chlorophyll fluorescence (OJIP) transients and related indexes. Further analysis indicated that raising pH ameliorated Mn500-induced impairment of nutrient homeostasis, leaf thylakoid structure by iron deficiency and competition of Mn with magnesium, and photosynthetic electron transport chain (PETC), thereby reducing Mn500-induced declines in A and subsequent seedling growth. These results validated the hypothesis that raising pH reduced Mn toxicity in 'Sour pummelo' seedlings by () reducing Mn uptake, () efficient maintenance of nutrient homeostasis under Mn stress, () reducing Mn excess-induced impairment of thylakoid structure and PEPC and inhibition of chlorophyll biosynthesis, and () increasing A and subsequent seedling growth under Mn excess.
在一些柑橘园土壤中，锰（Mn）过量和低pH值常常同时存在。关于提高pH值降低柑橘植物锰毒性的潜在机制，人们了解甚少。以“酸柚”（(L.) Osbeck）幼苗为材料，在pH值为3（P3）或5（P5）的条件下，分别用2（Mn2）或500（Mn500）μM的锰处理25周。提高pH值减轻了Mn500诱导的根、茎和叶中锰、铁、铜和锌浓度的增加，以及根中氮、磷、钾、钙、镁、硫、铜、铁和锌的分布变化，但减轻了Mn500诱导的根、茎和叶中氮、磷、钾、钙、镁、硫和硼浓度的降低以及营养失衡。提高pH值减轻了Mn500诱导的老叶坏死斑点、幼叶黄化、幼苗生长下降、叶片叶绿素浓度降低和CO2同化（A）减少、根干重（DW）/地上部DW增加以及叶片叶绿素荧光（OJIP）瞬变和相关指标的变化。进一步分析表明，提高pH值改善了Mn500诱导的营养稳态受损、铁缺乏导致的叶片类囊体结构以及锰与镁的竞争对光合电子传递链（PETC）的影响，从而减少了Mn500诱导的A下降和随后的幼苗生长下降。这些结果验证了以下假设：提高pH值通过（1）减少锰吸收、（2）在锰胁迫下有效维持营养稳态、（3）减少锰过量诱导的类囊体结构和PEPC损伤以及叶绿素生物合成抑制、（4）在锰过量条件下增加A和随后的幼苗生长，降低了“酸柚”幼苗中的锰毒性。
