Foliar Application of Signal Molecules can Augment Quality in Andrographis paniculata under Prolonged Water Deficit Stress

Abstract

The quality of a medicinal plant is decided by the content of specific secondary metabolite respective to the plant species. Therefore, an attempt was made to assess the effect of water deficit (WD) stress and signal molecules on physiological and biochemical responses of Andrographis paniculata under polyhouse condition. To keep the soil at field capacity (FC) in control (well-watered) treatment, a pre-measured quantity of water was applied to the pots once in a week. The signal molecules (i) ascorbic acid @200 mg l−1, (ii) glutamic acid @150 mg l−1 and salicylic acid @200 mg l−1 applied foliar at 10, 25, 40 and 55 days after WD treatment. Total chlorophyll, total carotenoid and proline content increased due to WD stress at 50 days after treatment (DAT) whereas, total chlorophyll and total carotenoid content decreased but, proline content increased at 80 DAT. Ascorbic acid enhanced the ascorbate peroxidase activity and glutamic acid enhanced guiacol peroxidase activity of leaves under WD stress. WD stress reduced actual efficiency of photosynthesis (Fv’/Fm’) and energy utilized for photochemistry (¦PSII) at 80 DAT. WD stress during 20–50 DAT did not improve the andrographolide content in leaves of A. paniculata. However, a prolonged WD stress till 80 DAT hastened andrographolide content in leaves. Foliar application of salicylic acid under polyhouse condition indicated its scope to augment the quality of Andrographis paniculata under prolonged WD stress.