Steam-mediated foliar application of catechol and plant growth regulators enhances the growth attributes, photosynthesis, and essential oil production of lemongrass [Cymbopogon flexuosus (Steud.) Wats

Abstract

Improvement in growth, yield, and essential oil production of plants through foliar application of PGRs and elicitors has been extensively studied in the authors' laboratory. Instead of using a sprayer machine, a new steam-spray method was applied to explore the possibility that if we could increase the growth, yield, and EO production of lemongrass. The foliage of lemongrass was steam-sprayed five times with 5 × 10−6 M of catechol and PGRs, viz. Indole acetic acid (IAA), kinetin (Kn), 6-benzyl aminopurine (BAP), salicylic acid (SA), triacontanol (TRIA), and ethrel at 90 days after transplantation (DAT). The steam spray was carried out using a calculated distance between the steam source and plant foliage so that the steam jet might not damage the plants. Lemongrass EO was extracted by Clevenger's method and then analyzed using GC-MS. All the parameters were studied at 150 DAT. The steam spray of SA and catechol proved the best for most of the parameters studied. Compared to the control, the application of SA enhanced the plant's fresh and dry weight by 26.1% and 43.4% and the total content of chlorophyll and carotenoids by 52.6% and 62.8% respectively, and chlorophyll fluorescence (Fv/Fm) by 15.2%. Catechol significantly improved the content (350%) and productivity (433.3%) of lemongrass essential oil, but it decreased the proline content (25.0%). SA treatment increased the content of active constituents of EO viz., neral and geranial, by 65.7% and 59.6%, respectively. After SA and catechol, the application of IAA also resulted in promising values for most parameters.