Impact of irrigation regime on morpho-physiological and biochemical attributes and centelloside content in Indian pennywort (Centella asiatica).

Indian pennywort (Centella asiatica (L.) Urban) is an important herbal plant with valuable medicinal properties. Irrigation with optimum freshwater is a basic crop requirement for plant growth, development, and secondary metabolite enrichment. The objective of the study was to evaluate the effect of different irrigation regimes on plant morphological, physiological, and biochemical responses as well as total centelloside content. Leaf greenness (SPAD), maximum quantum yield of PSII (Fv/Fm), and photon yield of PSII (ΦPSII) in plants grown under 64% field capacity (FC) were significantly reduced by 31.60%, 7.65%, and 25.91%, respectively, compared with plants grown under well irrigation (control; 100% FC). Remarkably, net photosynthetic rate (Pn), stomatal conductance (gs), and transpiration rate (Tr) in plants grown under 64% FC were more sensitive to water shortage, leading to a decline by 68.76%, 87.50%, and 84.08%, respectively, over the control. Leaf temperature (Tleaf) and crop water stress index (CWSI) under limited irrigation conditions (64% FC) were, respectively, increased by + 3.97 °C and 0.72 over the control in relation to decreased Tr (0.43 mmol H2O m−2 s−1) and altered stomatal functions indicated by low gs (0.02 mmol H2O m−2 s−1). Enhancement of glucose (2.70-fold over the control), fructose (2.14-fold over the control), and total soluble sugar (2.52-fold over the control) played a key role in osmotic adjustment when plants were exposed to moderate irrigation conditions (75% FC). Asiaticoside, asiatic acid, and total centellosides in the leaf tissues were enriched under limited irrigation conditions than those in the control, leading to the maximum centellosides yield at 75% FC. Number of green leaves, leaf area, stolon length, and shoot fresh weight in moderately irrigated plants (75% FC) were increased by 1.23, 1.24, 1.13, and 1.15-folds, respectively, over the control. The basic information obtained from this investigation provides a better understanding of the response of Indian pennywort under limited irrigation schedule and suggests an alternative way to manipulate biomass production and yield of total centellosides using moderate level of irrigation (75% FC). [ABSTRACT FROM AUTHOR]