ABSTRACT
<p><b>OBJECTIVE</b>To study the effect of water stress on the growth and accumulation of active components of Isatis indigotica.</p><p><b>METHOD</b>By pot culture experiment,the characteristic indexes of water requirement, chlorophyll content, transpiration rate, photosynthesis, biomass and effective ingredient indirubin were studied under normal and water stress conditions, respectively.</p><p><b>RESULT</b>With the increase of the extent and duration of water stress, the quantity of water requirement, chlorophyll content, respiration rate, photosynthesis and biomass of I. indigotica were decreased, while water use efficiency increased.</p><p><b>CONCLUSION</b>It is a critical period of water requirement in July, high water content in soil and extreme water stress are not propitious to the accumulation of indirubin, appropriate water stress can stimulate indirubin accumulatio. The harvest of leaves of I. indigotica is optimal in July, while the harvest of root is appropriate in October. Yield and quantity of I. indigotica are improved when the field capacity is between 45% and 70%.</p>