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

Abstract

Ammonium ((Formula presented.)) toxicity hinders the cabbage yield because most subspecies or varieties exhibit extreme sensitivity to (Formula presented.). Current knowledge indicates that silicon (Si) can alleviate or reverse the ammonium toxicity severity. However, few investigations have been conducted on (Formula presented.) -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 (Formula presented.) toxicity. We applied one of three (Formula presented.) : (Formula presented.) 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% (Formula presented.) application were ameliorated in the presence of Si. The (Formula presented.) 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, (Formula presented.), and H2O2), as well as lipid peroxidation (MDA, malondialdehyde) in (Formula presented.) -stressed cabbages were mitigated with added Si. The lower observed oxidative stresses in solely (Formula presented.) -treated plants were conferred by the boosted antioxidant enzymes (SOD, superoxide dismutase; CAT, catalase). Concomitantly, Si-treated plants showed higher activities of key (Formula presented.) assimilation enzymes (GS, glutamine synthetase; GOGAT, glutamate synthase; NADH-GDH, glutamate dehydrogenase) and (Formula presented.) content in leaves. However, excessive (Formula presented.) assimilations cause the acidic stress, which has been demonstrated to be the primary cause of (Formula presented.) toxicity. Therefore, further investigation regarding the Si effects on H+ regulation and distribution should be warranted.