Colored shade nets and green manure influence on the growth, phytochemistry and antioxidant metabolism of Origanum majorana L.

Abstract

The search for sustainable and efficient methods for plant growth and bioactive compound production has impacted the agricultural sector. In this context, factors such as light quality and green manure can boost sustainable agricultural practices and maximize the potential of species such as Origanum majorana L., known for its medicinal and aromatic properties. The objectives were (I) to evaluate the vegetative growth, essential oil content and chemical composition, total phenolic and flavones/flavonols content, and antioxidant capacity of O. majorana cultivated under different colored shade meshes. (II) to evaluate the potential of Cajanus cajan as a green manure on the vegetative growth, essential oil metabolism, photosynthetic pigments, and antioxidant activity of O. majorana. In experiment I, O. majorana plants were grown under three types of 50% shade mesh (blue, black, red), and full sun. The accumulation of total dry

matter and root dry matter, net photosynthetic rate, essential oil content and yield, and α- terpineol content were increased by 93%, 154%, 43%, 75%, 27%, and 62%, respectively, in

plants under full sun compared to the blue mesh. In addition, plants under full sun and red mesh significantly increased leaf, stem, and root dry matter, and relative growth rate. The red and black meshes significantly increased total and specific leaf area, and γ-terpinene content compared to the blue mesh and full sun. The red mesh provided an increase in ρ-cymene content by 39% compared to full sun. Total antioxidant capacity and total phenolics were significantly increased under full sun and black mesh. In experiment II, six treatments were used: five doses of green manure (0, 150, 300, 450 e 600 g plant-1

of C. cajan) and a control (inorganic

fertilization) in four replicates. Plants treated with 600 g plant-1

of C. cajan increased leaf, stem, and aerial part dry matter by 338%, 555%, and 414%, respectively, compared to no fertilization. The 450 g plant-1

dose increased total chlorophyll content by 14% and 18% compared to the

150 g plant-1

dose and the control, respectively. The lowest superoxide dismutase activity was

observed for inorganic fertilization. Doses of 0 and 150 g plant-1 m-2

increased catalase activity. However, ascorbate peroxidase activity decreased in the absence of fertilization. Essential oil yield was higher with the application of 600 g plant-1

of C. cajan and inorganic fertilization,

reaching EO yields of 0.050 and 0.056 mg plant-1

, representing an increase of 406% and 471%, respectively, compared to no fertilization. Green manure was shown to positively influence essential oil production, achieving levels and yields comparable to inorganic fertilization.

Cultivation conditions under full sun or the use of red mesh and the application of 600 g plant- 1

of C. cajan can improve the growth, yield, and chemical composition of the essential oil of O. majorana.