A pot experiments were carried out during 2003 and 2004 summer seasons in the greenhouse of the National Research Center, Dokki, Giza, Egypt to determine the effect of sitosterol on root formation of cotton cuttings, growth, yield and its components as well as biochemical constituents of two cotton cultivars. Cuttings of two Egyptian cotton (Gossypium barbadense L.) cultivars Giza 85 and Giza 89
... [Show full abstract] were taken from the previous growing season during the activity stage of buds containing two nodes. Cotton cuttings were soaked in sitosterol concentrations (100, 150 and 200 ppm) for 1 h at laboratory conditions as well as control treatment (distilled water). Cotton cuttings were grown in pots N. 30 filled with loamy soil at March 27 and 31 of 2003 and 2004 seasons, respectively. The results indicated that in both cotton cultivars root length was significantly and gradually increased with increasing sitosterol from zero to 150 or 200 ppm. Data also showed that sitosterol application significantly increased boll weight and seed cotton yield per plant with increasing sitosterol up to 200 ppm. Application of 200 ppm sitosterol in Giza 85 produced the highest values in all yield traits in comparison with untreated plants or with plants received 100 or 150 ppm sitosterol. On contrary, in Giza 89 application of 200 ppm sitosterol decreased number of bolls per plant, number of seeds per boll and seed weight per boll in comparison with control plants or with low sitosterol concentrations. Total indoles in stem of Giza 85 was increased by using 100 or 150 ppm sitosterol, while total soluble sugars was increased in roots of Giza 85 at high concentration in both cotton cultivars. Application of 200 ppm sitosterol increased total carbohydrates in root, stem and leaves of Giza 85 while in Giza 89 an opposite trend was noticed by using the highest sitosterol concentration. In general, it could be concluded that application of sitosterol to cotton cuttings lead to encourage the root formation and enhancing the growth and yield of cotton plants.