Foliar Application of Diammonium Phosphate Increases Essential Oil Content and Changes its Compositions in Mexican Marigold (Tagetes minuta L.)

Abstract

A Pot experiment was carried out to determine the effects of foliar application of diammonium phosphate on the quantity and quality of essential oil (EO) of Mexican marigold (Tagetes minuta L.), an important medicinal plant. Diammonium phosphate was applied at the rates of 0, 2.4, 4.8, 7.2, 9.6, and 12 at three stages of plant growth (i.e. stem formation, two weeks later and at floral budding). Results indicated that EO content increased with increasing diammonium phosphate levels up to 7.2 %. A foliar spray of 7.2 enhanced the biosynthesis of EO to the extent of 0.50 % over the control, however, no significant differences were found between 7.2, 9.6, and 12 % diammonium phosphate on EO content. The results of EO analysis showed that the amounts of dihydro tagetone (62.5 – 74.6 %) and Z-tagetone (9 – 11.2 %) as two major oil components increased gradually with increasing diammonium phosphate levels, however, the amounts of Z-β-ocimene (12.9 – 7 %) and Z-ocimenone (4.5 – 1.8 %) decreased with increasing diammonium phosphate levels. The role of phosphorus as a central and pivotal metabolic and regulatory nutrient element has also been discussed.