Keywords: 
• Cannabis sativa ‘Yunma No.1’ /
• growth stage /
• plant sex /
• cell layers /
• relative crystallinity /
• crystal cell size /

Abstract: To know the growth status, the physical properties of cellulose in hemp stalk better and provide more information for use it. Wide angle X-ray diffraction and a microscope were used to study the influence of growth stage and plant sex on cambium generation activity and the physical structure of cellulose in the industrial hemp stalk of Cannabis sativa Yunma No. 1with 4 strains of hemp samples. Samples from healthy, no rot, no breaking of industrial hemp, close to the ground for the collection. Results over the whole hemp stalk fiber growth period showed that relative crystallinity of the hemp fiber exhibited a greatly change （P-value was 0.039 0）. For the growth period of 19－35 d, cell size was 0.230－0.245 nm, and from 42－186 d, cell size was basically unchanged （P-value was 0.086 2） with a decline of about 0.137 nm. For the same growing time, slightly more （P-value was 0.000 1） female plant cell layers than male were noted. From 77－91 d, the degree of relative crystallinity in male plants was higher （P-value was ＜ 0.05） than female plants, but from 98－186 d it was higher （P-value was 0.058 8） in female plants. Cell size of male and female plants from 77－186 d was 0.136－0.150 nm. Thus, there was no strong relationship for cell size among growth period, cell layers, and relative crystallinity （The correlation coefficients between those were －0.518 0, －0.551 7, and －0.829 1 respectively）. ［Ch, 1 fig. 3 tab. 13 ref.］