Abstract: Using the Zhejiang Province leading varieties of Nongsang 14， Qiangsang 1 and Heyebai as the subjects， this experiment was conducted to investigate the difference of 1\|deoxynojirimycin（DNJ） concentration in different mulberry leaves at different time， and the effect of light on DNJ concentration in mulberry tree. The results showed that the DNJ content in these three varieties of mulberry leaf was significantly different in different periods， and within the same variety， leaf DNJ content also had significant difference. In spring， DNJ content in these three varieties was as high as 0432%， 0467% and 0649%， respectively. The highest average concentration of DNJ in the first 10 pieces of mature leaves was on May 1st， thereafter with leaf aging, it gradually decreased to below 02%. After cutting in summer， the average concentration of DNJ in the first 10 pieces of mature leaves in these three varieties was the highest on July 1st. Followed with the leaf senescence， the content of DNJ was decreased gradually. But with temperature and light intensity increased， the content of DNJ increased again， and reached to the peak on September 1st for Nongsang 14， September 16th for Qiangsang 1 and August 16th for Heyebai. Thereafter， with leaf aging， the DNJ concentration gradually decreased to below 01%. The effect of light intensity on the DNJ content of NongSang 14 plantlets was studied， and the result showed that with 5 h and 16 h light per day， not only the mulberry growth morphology was significantly affected， but the DNJ content was also evidently increased from （0389±0029）% to（0689±0024）% in leaf and enhanced from（0449±0026）% to（0859±0037）% in trunk. These results indicated that the concentration of the DNJ was the highest in mulberry bud， and with the leaf senescence， its concentration reduced gradually. But the DNJ content in mulberry leaf could significantly increase under longer light condition. These results provided a consult for selecting the cultivation areas and harvest period of medicinal used mulberry trees.

Key words: mulberry leaf, 1\, deoxynojirimycin, growth law, light