Department of Horticulture, Division of Applied Life Science (BK21 Four), Graduate School of Gyeongsang National University, Jinju 52828, Korea.
Institute of Agriculture and Life Science, Gyeongsang National University, Jinju 52828, Korea.
Int J Mol Sci. 2022 Aug 11;23(16):8943. doi: 10.3390/ijms23168943.
Deficiency or excess of iron (Fe) and improper medium pH will inhibit the growth and development of plants, reduce the transfer and utilization of energy from the root to the leaf, and affect the utilization efficiency of inorganic nutrients. The most common symptom of Fe deficiency in plants is chlorosis of the young leaves. In this study, the effects of the iron source, in combination with the medium pH, on plant growth and development, plant pigment synthesis, and nutrient uptake in a model plant cultured in vitro were investigated. Iron sulfate (FeSO·7HO) or iron chelated with ethylenediaminetetraacetic acid (Fe-EDTA) were supplemented to the MNS (a multipurpose nutrient solution) medium at a concentration of 2.78 mg·L Fe, and the treatment without any Fe was used as the control. The pH of the agar-solidified medium was adjusted to either 4.70, 5.70, or 6.70 before autoclaving. The experiment was carried out in an environmentally controlled culture room with a temperature of 24 °C with 100 µmol·m·s photosynthetic photon flux density (PPFD) supplied by white light emitting diodes (LEDs) during a photoperiod of 16 h a day, 18 °C for 8 h a day in the dark, and 70% relative humidity. Regardless of the Fe source including the control, the greatest number of leaves was observed at pH 4.70. However, the greatest lengths of the leaf and root were observed in the treatment with Fe-EDTA combined with pH 5.70. The contents of the chlorophyll, carotenoid, and anthocyanin decreased with increasing medium pH, and contents of these plant pigments were positively correlated with the leaf color. The highest soluble protein content and activities of APX and CAT were observed in the Fe-EDTA under pH 5.70. However, the GPX activity was the highest in the control under pH 4.70. In addition, the highest contents of ammonium (NH) and nitrate (NO) were measured in the FeSO-4.7 and EDTA-5.7, respectively. More than that, the treatment of Fe-EDTA combined with pH 5.70 (EDTA-5.7) enhanced nutrient absorption, as proven by the highest tissue contents of P, K, Ca, Mg, Fe, and Mn. The genes' ferric reduction oxidase 1 and 8 ( and ), iron-regulated transporter 1 (), nitrate transporter 2.5 (), and deoxyhypusine synthase () were expressed at the highest levels in this treatment as well. In the treatment of EDTA-5.7, the reduction and transport of chelated iron in leaves were enhanced, which also affected the transport of nitrate and catalyzed chlorophyll level in leaves. In conclusion, when the medium pH was adjusted to 5.70, supplementation of chelated Fe-EDTA was more conducive to promoting the growth and development of, and absorption of mineral nutrients by, the plant and the expression of related genes in the leaves.
缺铁（Fe）或铁过量以及不当的培养基 pH 值会抑制植物的生长和发育，减少根部到叶片的能量转移和利用，并影响无机养分的利用效率。植物缺铁最常见的症状是嫩叶失绿。本研究探讨了在体外培养的模式植物中，铁源与培养基 pH 值联合作用对植物生长发育、植物色素合成和养分吸收的影响。在 MNS（多用途营养溶液）培养基中添加硫酸亚铁（FeSO·7HO）或乙二胺四乙酸螯合铁（Fe-EDTA），浓度为 2.78mg·L Fe，不添加任何铁的处理作为对照。在高压灭菌前，将琼脂固化培养基的 pH 值调整为 4.70、5.70 或 6.70。实验在环境控制室中进行，温度为 24°C，白光发光二极管（LED）提供 100µmol·m·s 的光合光子通量密度（PPFD），每天光照 16 小时，黑暗 18°C 持续 8 小时，相对湿度为 70%。无论铁源是否包括对照，在 pH 值为 4.70 时观察到的叶片数量最多。然而，在含有 Fe-EDTA 并结合 pH 值为 5.70 的处理中，叶片和根的长度最大。叶绿素、类胡萝卜素和花青素的含量随培养基 pH 值的升高而降低，这些植物色素的含量与叶片颜色呈正相关。在 pH 值为 5.70 时，Fe-EDTA 处理下可溶性蛋白含量和 APX 和 CAT 的活性最高。然而，在 pH 值为 4.70 时，对照处理下 GPX 活性最高。此外，在 FeSO-4.7 中测量到的铵（NH）和硝酸盐（NO）含量最高，分别为 4.7 和 5.7。不仅如此，Fe-EDTA 与 pH 值 5.70 联合处理（EDTA-5.7）增强了养分吸收，这从组织中 P、K、Ca、Mg、Fe 和 Mn 的最高含量中得到了证明。在该处理中，铁还原氧化酶 1 和 8（和）、铁调节转运蛋白 1（）、硝酸盐转运蛋白 2.5（）和脱羟鸟氨酸合酶（）的基因表达水平也最高。在 EDTA-5.7 处理中，叶片中螯合铁的还原和转运得到增强，这也影响了硝酸盐的转运，并催化叶片中叶绿素水平。综上所述，当培养基 pH 值调整为 5.70 时，添加螯合态 Fe-EDTA 更有利于促进植物的生长和发育，以及对植物矿物养分的吸收和叶片中相关基因的表达。
