Lignosulfonate (LS) is a by-product obtained during sulfite pulping process and is commonly used as a growth enhancer in plant growth. However, the underlying growth promoting mechanism of LS on shoot growth remains largely unknown. Hence, this study was undertaken to determine the potential application of eco-friendly ion-chelated LS complex [sodium LS (NaLS) and calcium LS (CaLS)] to enhance recalcitrant indica rice MR 219 shoot growth and to elucidate its underlying growth promoting mechanisms. In this study, the shoot apex of MR 219 rice was grown on Murashige and Skoog medium supplemented with different ion chelated LS complex (NaLS and CaLS) at 100, 200, 300 and 400 mg/L The NaLS was shown to be a better shoot growth enhancer as compared to CaLS, with optimum concentration of 300 mg/L. Subsequent comparative proteomic analysis revealed an increase of photosynthesis-related proteins [photosystem II (PSII) CP43 reaction center protein, photosystem I (PSI) iron-sulfur center, PSII CP47 reaction center protein, PSII protein D1], ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), carbohydrate metabolism-related proteins (glyceraldehyde-3-phosphate dehydrogenase 3, fructose-bisphosphate aldolase) and stress regulator proteins (peptide methionine sulfoxide reductase A4, delta-1-pyrroline-5-carboxylate synthase 1) abundance in NaLS-treated rice as compared to the control (MSO). Consistent with proteins detected, a significant increase in biochemical analyses involved in photosynthetic activities, carbohydrate metabolism and protein biosynthesis such as total chlorophyll, rubisco activity, total sugar and total protein contents were observed in NaLS-treated rice. This implies that NaLS plays a role in empowering photosynthesis activities that led to plant growth enhancement. In addition, the increased in abundance of stress regulator proteins were consistent with low levels of peroxidase activity, malondialdehyde content and phenylalanine ammonia lyase activity observed in NaLS-treated rice. These results suggest that NaLS plays a role in modulating cellular homeostasis to provide a conducive cellular environment for plant growth. Taken together, NaLS improved shoot growth of recalcitrant MR 219 rice by upregulation of photosynthetic activities and reduction of ROS accumulation leading to better plant growth.

木质素磺酸盐 (LS) 是在亚硫酸盐制浆过程中获得的副产品，通常用作植物生长的生长促进剂。然而，LS 对芽生长的潜在生长促进机制在很大程度上仍是未知的。因此，本研究旨在确定环保型离子螯合 LS 复合物 [钠 LS (NaLS) 和钙 LS (CaLS)] 的潜在应用，以增强顽固性籼稻水稻 MR 219 芽生长并阐明其潜在的促生长机制。在本研究中，MR 219 水稻的茎尖生长在 Murashige 和 Skoog 培养基上，培养基中添加了 100、200、300 和 400 毫克/升的不同离子螯合 LS 复合物（NaLS 和 CaLS）。结果表明 NaLS 是更好的芽与 CaLS 相比，生长促进剂的最佳浓度为 300 mg/L。随后的比较蛋白质组学分析显示光合作用相关蛋白 [光系统 II (PSII) CP43 反应中心蛋白、光系统 I (PSI) 铁硫中心、PSII CP47 反应中心蛋白、PSII 蛋白 D1]、核酮糖-1,5-双磷酸羧化酶/加氧酶 (Rubisco)，碳水化合物代谢相关蛋白（甘油醛-3-磷酸脱氢酶 3，果糖二磷酸醛缩酶）和应激调节蛋白（肽甲硫氨酸亚砜还原酶 A4、δ-1-吡咯啉-5-羧酸合酶 1）在 NaLS 处理的水稻中的丰度与对照 (MSO) 相比。与检测到的蛋白质一致，在 NaLS 处理的水稻中观察到光合活性、碳水化合物代谢和蛋白质生物合成（如总叶绿素、rubisco 活性、总糖和总蛋白质含量）的生化分析显着增加。这意味着 NaLS 在增强光合作用活动中发挥作用，从而促进植物生长。此外，压力调节蛋白丰度的增加与在 NaLS 处理的水稻中观察到的过氧化物酶活性、丙二醛含量和苯丙氨酸解氨酶活性水平较低是一致的。这些结果表明 NaLS 在调节细胞稳态中发挥作用，为植物生长提供有利的细胞环境。总之，NaLS 通过上调光合活性和减少 ROS 积累来改善顽固的 MR 219 水稻的枝条生长，从而导致更好的植物生长。