The Effects of Zinc Application and Cutting on Growth, Herb, Essential Oil and Flavonoids in Three Medicinal Lamiaceae Plants

Abstract

Aims: The objective of this study was to investigate the effect of zinc on growth, fresh herb, essential oil and flavonoids content of Dracocephalum moldavica, Hyssopus officinalis and Salvia officinalis plants at two successive cuttings before flowering stage. Study Design: Our study consisted of three experiments. Each study contained 4 treatments, two time of cuttings (90 and 180 days after transplanting) in each plant and two levels of                      foliar application treatments of Zn EDTA [(Z1) = 0, tap water; (Z2) = 200 ppm)], which was                   sprayed directly on the plants 4 times at monthly intervals, starting 30 days after transplanting.                    The design of each experiment was factorial and planned in a complete randomized block                        with three replications. Place and Duration of Study: A field experiment was carried out during two successive seasons, 2014 and 2015 at the Agricultural Research and Experimental Station, Faculty of Agriculture, Cairo University, Giza, Egypt. Methodology: Dracocephalum moldavica, Hyssopus officinalis and Salvia officinalis seeds were sown in the nursery in 25th November, of 2013 and 2014. On February 1, 2014 and 2015 seasons, seedlings were transplanted into the field. Foliar applications of zinc EDTA was sprayed 4 times at monthly intervals. Growth characters and chemical constituent's determinations were carried out at the first and second cuts after 90 and 180 days from transplanting, respectively before flowering. Plant height (cm), number of branches/plant, herb fresh weight (g/plant) was recorded. The content of total flavonoids % was determined in the fresh herb. Essential oil was obtained by hydro distillation and essential oil % was expressed as ml 100 g-1 fresh herb. Chemical composition of the essential oil was studied using GC-MS and compounds were identified based on their mass spectra and literature. Results: Zinc spraying gave the best results of plant height, number of branches, herb fresh weight, essential oil % and total flavonoids % in the vegetative stage than control treatments in the three plants. Also, the second cut gave the best values from these characters in all plants under study compared to the first one. The main compounds of Dracocephalum moldavica essential oil was neral (19.93-20.56%), geranial (22.57-24.56%), geraniol (15.69-17.91%) and geranyl acetate (28.85-29.60%). β-pinene (23.43-24.99%), trans-pinocamphone (16.78-17.97%) and trans-pinocamphone (29.49-29.95%) were found to be the main compounds in Hyssopus officinalis oil. Moreover, α-thujone (13.82-13.92%), 1,8 cineol (17.45-18.83%) and camphor (26.38-27.51%) were considered as major compounds in Salvia officinalis oil. Conclusion: Zinc foliar spray stimulative affect in fresh biomass, essential oil and flavonoids % were observed. It can be concluded that cutting moldavian balm, hyssop and sage plants in the second cut is essential for maximizing the production of fresh herb, essential oil and flavonoids %.  These changes could be relevant to the quality of essential oil and its use in certain food, medicinal uses and cosmetic applications.