Effect of plant population and soil moisture stress on herbage yield and andrographolide content in Andrographis paniculata

Spacing and irrigation levels influenced dry weight of leaves and fresh and dry weight of stems significantly. Plant spacing of 15 x 15 cm produced higher herbage yields of 707.8, 742.3 and 690.6 g.m−2 in well-watered control, mild and severe water stress treatments, respectively. Low yields were recorded under 30 × 45 cm spacing in control, mild and severe water stress treatments, respectively. Among the treatments, andrographolide content in the leaves was highest in severely water stressed plants. Increasing the plant spacing positively influenced the andrographolide content in the leaves under the severe water stressed plants with highest andrographolide content in wider spacing (30 × 45 cm). In the stems, highest andrographolide content of 1.75% was in 15 × 15cm plant spacing and lowest was in 30 × 45cm under no stress control. Similar trend was noticed in mild and severe water stressed plants under various spacing treatments. Andrographolide yield from herbage was maximum in control followed by mild and severe water stressed conditions in the closer spacing. Lowest yield of andrographolide was recorded under 30 x 45 cm spacing under control condition. Dry matter yield was lower under mild and severe water stress conditions even under closer spacing, but the loss of andrographolide yield was partly compensated by its higher content. In A. paniculata, increased accumulation of andrographolide in leaves of mild and severe water stressed plants compared to well watered control may be attributed to the response of stress signalling.