Plant Archives Vol. 19 No. 2, 2019 pp. 2093-2098 e-ISSN:2581-6063 (online), ISSN:0972-5210 *Author for correspondence : E-mail : somanan.liphan@ gmail.com RESPONSE OF KALMEGH (ANDROGRAPHIS PANICULATA (BURM. F.) NEES) TO SHADING AT DIFFERENT GROWTH STAGES Somanan Liphan* and S. Detpiratmongkol Department of Plant Production Technology, Faculty of Agricultural Technology, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, Thailand, 10520. Abstract Kalmegh (Andrographis paniculata (Burm. F.) Nees) is a very useful medicinal herb widely used for treatments of various human diseases and symptoms: fever, cold, laryngitis, diarrhea and inflammation. However, its enhanced growth and yield as a response to shading at different growth stages have not been studied yet. Therefore, in this study, an experiment was undertaken, from January to April 2018, to investigate the effects of shading at different growth stages on the growth, yield and quality of kalmegh. The design of this pot experiment was split plot with three replications; three local kalmegh cultivars— Prachinburi, Phichit 4-4 and Phisanulok 5-4—were the main plots. The four sub-plots were 20% shading at 3 stages of growth viz: 30, 60 and 90 days after planting (DAP) till harvest and no shading which was the control. Several agronomic characteristics of kalmegh such as plant height, stem, dry weight of leaf and root, total dry weight and leaf dry weight yield were recorded. The results indicated that Prachinbuti cultivar gave the tallest plant and stem heights as well as the highest dry weight of leaf and root, total dry weight and leaf dry weight yield, followed by Phisanulok 5-4 and Phichit 4-4. Shading at different stages of growth clearly affected the growth and yield of kalmegh. No shading resulted in the least growth and yield while shading at 90 DAP promoted some growth and yield that was higher than no shading but lower than shading at 30 and 60 DAP. The maximum values of growth and yield were observed under 20% shading at 30 DAP. Key words : Yield, Andrographolide, Kalmegh, Shading. Introduction Medicinal plants are essential for human beings who utilize them for basic preventive and curative health care. Kalmegh (Andrographis paniculata (Burm. F.) Nees) is an important herb for treatments of fever, diarrhea, dysentery, cough, sore throat, bronchitis, arthralgia, haematometra, hypertension and snake bite (Madav et al., 1995; Matsuda et al., 1994). Kalmegh that is continuously harvested from trees in the forest may become depleted (Yusron and Januwati, 2004). However, it is widely cultivated in India, Sri Lanka, Malaya Peninsula, China and Thailand, but a proper cultivation method is required. The need for kalmegh plant as a raw material for traditional medicine continues to increase, but the supply of kalmegh harvested from farms is still unpredictable (Purwanto et al., 2011). Environmental conditions such as shading strongly affect its growth (Kosma et al., 2013). Solar radiation with a proper intensity, quality and duration of exposure is an important factor for its growth. When the received light intensity is low, the amount of light received by the surface area of each leaf within a specified period of time will be low as well. Lack of light leads to metabolism disorder and decreases in photosynthesis and carbohydrate synthesis rates. Conversely, if the light intensity is too high, the plant may suffer from high temperature stress and drought stress (Parwanto et al., 2011). Therefore, the objective of this study was to determine the effects of 20% shading at different growth stages on the growth, yield and quality of harvested kalmegh. This study was also meant to identify the optimum period for shading, in terms of days after planting till harvest, and inform farmers so as to enhance their kalmegh production. Materials and Methods A field experiment was conducted at an experimental plot in the area of the Faculty of Agricultural Technology, King Mongkut’s Institute of Technology Ladkrabang, Bangkok, Thailand, during January to April, 2018. Seeds of kalmegh (Prachinburi, Phisanulok 5-4 and Phichit 4-4