Rainfall-induced premature senescence modulates biochemical and essential oils profiles in Pelargonium graveolens L′Hér. under sub-tropical climate

Abstract

Pelargonium graveolens L′Hér is a commercially important aromatic plant. The essential oil is used in fragrances, flavour and cosmeceutical industries. The essential oil is secreted in the glandular trichomes distributed mainly on the leaves. In India, P. graveolens is growing only in specific climatic conditions due to the susceptibility of plants to rainfall, high humidity and waterlogging stress. This study aims to analyze rainfall-induced premature senescence in P. graveolens at six phenotypic leaf senescence stages. The physiological and biochemical parameters, cell viability, trichomes density, essential oil yield and variation in chemical constituents were evaluated. Results show a significant increase in chlorophyll-a and b, and a decrease in anthocyanin content. Also, the protein content, MDA, SOD, H2O2, catalase, electrolyte leakage was significantly higher, and cell viability decreased with the progression of senescence. The gland density on leaves was reduced during the advancement of senescence. The GC and GC-MS analysis showed that the senescence significantly modulates oil constituents and oils yield (0.048–0.123%) at different senescence stages. Overall, this study confirms that rainfall induces premature senescence in P. graveolens, significantly affecting essential oil yield and constituents.