Ru Zhao,Xinyu Yang,Aoqi Zhang,Tieyang Zhou,Yunwei Zhou,Lei Yang
Microwave-mediated immiscible binary solvent extraction (MIBSE) was applied to simultaneously extract oil and epigoitrin from Orychophragmus violaceus seeds . The upper phase of n -hexane was used to obtain oil, and the lower phase of ethanol solution was used to obtain epigoitrin. Factors potentially affecting the yields of oil and epigoitrin were systematically investigated. The optimum conditions were an ethanol volume fraction of 65%, liquid–solid ratio of lower-phase of 20 mL/g, liquid–solid ratio of upper-phase of 12 mL/g, microwave irradiation power of 393 W, and microwave irradiation time of 29 min. The actual yields of oil and epigoitrin were 34.08% ± 1.38% and 11.86 ± 0.47 mg/g, respectively. GC–MS analysis illustrated that the seed oils obtained by MIBSE and Soxhlet extraction exhibited similar fatty acid compositions. The separated epigoitrin was determined by HPLC analyses, which obtained a purity of 91.25% ± 3.83%, follwed by NMR determinations.
Ammonium (NH4+) toxicity impairs plant growth, but nitrate (NO3−) can mitigate this effect through unresolved mechanisms. Using leaf δ13C values (photosynthetic capacity) and a bidirectional15N tracer (NH4+assimilation efficiency and source utilization), this study investigated these mechanisms in 35-day-oldOrychophragmus violaceusplantlets grown in modified Murashige and Skoog media under varying NH4+:NO3−ratios.15N isotope fractionation during NH4+(same fixed 20 mM NH4Cl) assimilation decreased with increasing NO3−supply (10, 20, and 40 mM NaNO3). Under 20 mM NH4+(δ15N = −2.64‰) at two15NO3−-labels (δ15N-NO3−= 8.08‰, low15N,L) and (δ15N-NO3−= 22.67‰, high15N,H), increasing NO3−concentrations enhanced NO3−assimilation, alleviating acidic stress from NH4+and improving photosynthesis. Higher NO3−levels also increased NH4+utilization efficiency, reducing futile NH4+cycling and decreasing associated15N fractionation during assimilation. Our results demonstrate that NO3−alleviates NH4+toxicity primarily by enhancing photosynthetic performance and optimizing NH4+utilization efficiency.
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