Alleviation of Ammonium Toxicity in Salvia splendens 'Vista Red' with Silicon Supplementation

Synergistic Effects of Silicon and Aspartic Acid on the Alleviation of Salt Stress in Celery (Apium graveliens L.) "Si Ji Xiao Xiang Qin"

Salinity is one of the primary abiotic stresses that seriously hampers plant quality and productivity. It is feasible to reduce or reverse the negative effects of salt through the supplementation of silicon (Si) and aspartic acid (Asp). However, the question of how exogenous Si and Asp induce salt tolerance in celery remains incipient. Thus, this study was performed to determine the synergistic effects of Si and Asp on the alleviation of salt stress in celery. To this end, the celery plants were cultivated in a controlled regime (light for 14 h at 22 °C; darkness for 10 h at 16 °C) and treated with one of five treatments (CK, 100 mM NaCl, 100 mM NaCl + 75 mg/L Si, 100 mM NaCl + 100 mg/L Asp, and 100 mM NaCl + 75 mg/L Si + 100 mg/L Asp). Results showed that solely NaCl-treated celery plants developed salt toxicity, as characterized by decreased growth, declined photosynthetic ability, disturbed nutritious status and internal ion balance, and a boosted antioxidant defense system (Improved antioxidant enzymes and reduced ROS accumulation). In contrast, these adverse effects of NaCl were ameliorated by the additions of Si and Asp, regardless of Si, Asp, or both. Moreover, the mitigatory impacts of the co-application of Si and Asp on salt stress were more pronounced compared to when one of them was solely applied. Collectively, exogenous Si and Asp alleviate the degree of salt stress and thereby improve the salt tolerance of celery.

Ammonium to total nitrogen ratio affects the purslane (Portulaca oleracea L.) growth, nutritional, and antioxidant status

Purslane (Portulaca oleracea L.) is a widespread weed, which is greatly appreciated for its high nutritional value. The present work evaluated the effect of different ammonium/total nitrogen ratios (NH4/Total N: Nr 0.01-0.15) on growth, physiological and biochemical parameters, and nutrient accumulation in different plant parts of hydroponically grown purslane, under two growing seasons, spring and autumn. Young seedlings of purslane were transferred to a Nutrient Film Technique (NFT) system and they were exposed to different Nr levels. The pH and the electrical conductivity of the nutrient solution were kept constant at 5.8 and 2.3 mS cm-1, respectively. After the end of the cultivation periods (19 days for spring and 22 days for autumn), a series of assessments (growth parameters, mineral content in different plant organs, antioxidant status of the plant, etc.) were done. Plant height, leaf number, root fresh weight and plant biomass revealed decreased trends at the higher NH4/total N ratios, especially during the autumn growing season. Total phenols, flavonoids and antioxidant capacity appeared increased at Nr ≤ 0.10 during both seasons (autumn and spring), revealing higher nitrogen accumulation rates and increased water and nutrient use efficiency. Purslane plants grown in Nr 0.05-0.10 revealed a less intense oxidative stress, with decreased lipid peroxidation levels that was the result of the activation of both enzymatic (superoxide dismutase, catalase and peroxidase) and non-enzymatic (ascorbic acid) antioxidant capacity of the plant. Increased Nr resulted in the accumulation of potassium, while calcium and magnesium levels in leaves were decreased. Additionally, the greater water use efficiency was measured for plants grown under Nr 0.01-0.05. Therefore, the recommended ammonium/total nitrogen ratio for purslane production of increased yield, improved nutritional value and efficient use of water and nitrogen sources is to employ Nr of 0.05, while additional care should be addressed during autumn periods as plants are subjected to greater impacts of the Nr ratio.

Heavy Metal Toxicity Effects on Plants

Although heavy metals are naturally present in the soil, geologic and anthropogenic activities increase the concentration of these elements to amounts that are harmful to plants [...].

Silicon Supplementation Alleviates Adverse Effects of Ammonium on Ssamchoo Grown in Home Cultivation System

Ssamchoo is recently attracting attention as a household hydroponic vegetable in Korea. It has a refreshing texture and a rich content of vitamins and fiber. Ssamchoo with a wide leaf area is suitable for traditional ssam or vegetable wraps, as well as a vegetable for salads; thus, it can be used in a variety of dishes. However, Ssamchoo plants responds sensitively to the nutrient solution, and it is often difficult to secure sufficient leaf area and robust growth using a commercial nutrient solution for leafy vegetables. This study consisted of three experiments conducted to develop the nutrient solution for Ssamchoo grown in a newly developed home hydroponic cultivation system using light-emitting diodes as the sole source of light. In the first experiment, growth and development of Ssamchoo in a representative commercial nutrient solution, Peters Professional (20-20-20, The Scotts Co., Marysville, OH, USA), was compared with laboratory-prepared nutrient solutions, GNU1 and GNU2. As a result, the Ssamchoo grown in Peters Professional had a high NH₄⁺ content in the tissue, leaf yellowing, darkened root color, and suppressed root hair development. In addition, adverse effects of ammonium such as low fresh weight and shorter shoot length were observed. In the second experiment, Peters Professional was excluded, and the ratio of NO₃^- to NH₄⁺ in the GNU1 and GNU2 nutrient solutions was set to four levels each (100:0, 83.3:16.7, 66.7:33.3, and 50:50). As a result, the fresh weights of 83.3:16.7 and 66.7:33.3 were the greatest, and the leaf color was a healthy green. However, at 100:0 and 50:50 NO₃^-/NH₄⁺ ratios, the fresh weight was low, and leaf yellowing, tip burn, and leaf burn appeared. The nutrient solution with a 83.3:16.7 NO₃^-- to-NH₄⁺ ratio, which gave the greatest fresh weight in the second experiment, was chosen as the control, while the solution with a 50:50 NO₃^-/NH₄⁺ ratio with a lower nitrate content among the two unfavorable treatments was selected as a treatment group for the next experiment. In the third experiment, NH₄⁺ was partially replaced with urea to make four different ratios of NO₃^- to NH₄⁺ to urea (83:17:0, 50:50:0, 50:25:25, and 50:0:50) in combination with two levels of Si (0 and 10.7 mmol·L^-1 Si). The greatest fresh weight was obtained in the treatment in which the NO₃^-/NH₄⁺/urea ratio was 50:25:25. In particular, when Si was added to the solution, there was no decrease in the number of leaves, and plants with the greatest fresh weight, chlorophyll content, and leaf area were obtained. The number of leaves and leaf area are important indicators of high productivity since the Ssamchoo is used in ssam dishes. It can be concluded that a solution with a NO₃^-/NH₄⁺/urea ratio of 50:25:25 and supplemented with 10.7 mmol·L^-1 Si is the most suitable nutrient solution for growing Ssamchoo in the home hydroponic system developed.