Silicon Mitigates Ammonium Toxicity in Cabbage (Brassica campestris L. ssp. pekinensis) ‘Ssamchu’

Abstract

Ammonium (NH4+) toxicity hinders the cabbage yield because most subspecies or varieties exhibit extreme sensitivity to NH4+. Current knowledge indicates that silicon (Si) can alleviate or reverse the ammonium toxicity severity. However, few investigations have been conducted on NH4+-stressed cabbage to elucidate the mechanism underlying the Si alleviation. The study described herein analyzes induced physio-chemical changes to explore how Si helps mitigate NH4+ toxicity. We applied one of three NH4+:NO3- ratios (0:100, 50:50, and 100:0) at a constant N (13 meq·L−1) to the cabbage plants, corresponding with two Si treatment levels (0 and 1.0 meq·L−1). Chlorosis and foliage necrosis along with stunted roots occurred following 100% NH4+ application were ameliorated in the presence of Si. The NH4+ toxicity ratio was reduced accordingly. Similarly, inhibition on the uptake of K and Ca, restricted photosynthesis (chlorophyll, stomatal conductance, and Fv/Fm), and accumulation of reactive oxygen species (ROS, O2·-, and H2O2), as well as lipid peroxidation (MDA, malondialdehyde) in NH4+-stressed cabbages were mitigated with added Si. The lower observed oxidative stresses in solely NH4+-treated plants were conferred by the boosted antioxidant enzymes (SOD, superoxide dismutase; CAT, catalase). Concomitantly, Si-treated plants showed higher activities of key NH4+ assimilation enzymes (GS, glutamine synthetase; GOGAT, glutamate synthase; NADH-GDH, glutamate dehydrogenase) and NH4+ content in leaves. However, excessive NH4+ assimilations cause the acidic stress, which has been demonstrated to be the primary cause of NH4+ toxicity. Therefore, further investigation regarding the Si effects on H+ regulation and distribution should be warranted.

Synergistic Effects of Silicon and Preservative on Promoting Postharvest Performance of Cut Flowers of Peony (Paeonia lactiflora Pall.)

“…The ROS damage and oxidative stress degree are signposted by MDA, which is defined as the final product of lipid peroxidation [ 51 ]. The benefits of Si on the physiological and morphological aspects of plants have been extensively witnessed [ 16 , 52 ]; concurrently, Si inflicted the increase in the antioxidant production which was monitored to counteract the ROS accumulation [ 53 ].…”

“…Subsequently, the stems were transferred to the vase solutions and placed in a controlled environment (uninterrupted white LED light at 300 PPFD and a constant temperature at 21 °C), provided by a refrigerated showcase (Refrigeration + LLC, Colorado Springs, CO, USA). The vase solutions designed in this study consisted of four treatments: distilled water ‘W’ (the control), distilled water supplemented with a standard preservative (a commercial floral preservative) prepared following the manufacturer’s manual (HydraFlor 100, FlorBelle, Oasis Corp, Seoul, Korea) ‘W + P’, distilled water supplemented with optimized Si sourced from a pure Si solution at 75 mg·L −1 [ 8 , 16 ] ‘W + Si’, and the co-applications of the commercial floral preservative and Si solubilized in distilled water ‘W + P + Si’. The main ingredients of the commercial floral preservative are glucose and citric acid, and it is free of Si [ 64 ].…”

“…The use of silicon (Si) fertilization is one of these attempts that successfully extends the vase life of cut flowers, even though it is not recognized as a necessary element for higher plants [ 8 , 16 ]. Si has been suggested to reduce the transpiration rate by the formation of silica deposits on the leaf epidermis, which contributes to less water loss [ 17 ].…”

Characterization of Physiology, Photosynthesis, and Nutrition Based on Induced Deficiencies of Macro- and Micronutrients in Basil (Ocimum basilicum L.)

“…Subsequently, the treatment solutions were designated on the basis of a multipurpose nutrient solution (MNS) [22,23] without nutrient omission (complete solution-CS) and with the specific nutrient (-N, -P, -K, -Ca, -Mg, -NH 4 + , -NO 3 − , -S, -Fe, -Mn, -B, -Zn, -Mo, and -Cu) omitted for deprivation treatments. The detailed recipe and chemicals used are shown in Table 1.…”

Bicarbonate-Dependent Detoxification by Mitigating Ammonium-Induced Hypoxic Stress in Triticum aestivum Root

“…Exogenous α-ketoglutarate (KGA), a key C skeleton for N assimilation, alleviates NH 4 + stress in tomato (Solanum lycopersicum L.) [27]. Silicon (Si) alleviates NH 4 + toxicity by accelerating NH 4 + assimilation via the actions of glutamine synthetase, glutamate synthase, and glutamate dehydrogenase in cabbage (Brassica campestris L.) [28] or increasing the shoot cytokinin content in tomato [29].…”