Effects of Corm Treatment with Cold Plasma and Electromagnetic Field on Growth and Production of Saffron Metabolites in Crocus sativus

<i>Crocus sativus</i> L. is a widely cultivated traditional plant for obtaining dried red stigmas known as "saffron," the most expensive spice in the world. The response of <i>C. sativus</i> to pre-sowing processing of corms with cold plasma (CP, 3 and 5 min), vacuum (3 min), and electromagnetic field (EMF, 5 min) was assessed to verify how such treatments affect plant performance and the quality and yield of herbal raw materials. The results show that applied physical stressors did not affect the viability of corms but caused stressor-dependent changes in the kinetics of sprouting, growth parameters, leaf trichome density, and secondary metabolite content in stigmas. The effect of CP treatment on plant growth and metabolite content was negative, but all stressors significantly (by 42-74%) increased the number of leaf trichomes. CP3 treatment significantly decreased the length and dry weight of flowers by 43% and 60%, respectively, while EMF treatment increased the length of flowers by 27%. However, longer CP treatment (5 min) delayed germination. Vacuum treatment improved the uniformity of germination by 28% but caused smaller changes in the content of stigma compounds compared with CP and EMF. Twenty-six compounds were identified in total in <i>Crocus</i> stigma samples by the HPLC-DAD method, including 23 crocins, rutin, picrocrocin, and safranal. Processing of <i>Crocus</i> corms with EMF showed the greatest efficiency in increasing the production of secondary metabolites in saffron. EMF increased the content of marker compounds in stigmas (crocin 4: from 8.95 to 431.17 mg/g; crocin 3: from 6.27 to 164.86 mg/g; picrocrocin: from 0.4 to 1.0 mg/g), although the observed effects on growth were neutral or slightly positive. The obtained findings indicate that treatment of <i>C. sativus</i> corms with EMF has the potential application for increasing the quality of saffron by enhancing the amounts of biologically active compounds.