Abstract

Cotton productivity depends on solar radiation reaching to the ground. Therefore, the present laboratory and field experiments were conducted during 2018-2019 growing seasons at the experimental station of Tashkent State Agrarian University, Uzbekistan to study UVA supplementations on growth parameters of cotton indoor and open field cultivations. Cotton (Gossipium hirsutum L. cv. “S-6524”) seeds were exposed to different doses of UV-A radiation at 340-350 nm wavelengths under a constant irradiance of 1.6 W/m2. The highest germination value (86.3%) was observed in the UVA treatment for 10 minutes. In the field condition, 10 μmol/m2/s UVA radiation intensities were given to the seeds before planting and at the true leaf formation, budding, and flowering stages of cotton, coded as UVA-2 toUVA-5 treatments. The seed germination rate was increased by 15.5% in the UVA-2 treatmentcompared to the untreated control. Furthermore, the supplemental UV-A radiation increasedoverall biomass production by 6.3 (UVA-2); 8.9 (UVA-3) and 15.1% (UVA-4), which correlated with 3.7%; 5.6% and 7.4% greater photosynthetic efficiency than those in control. All these positive changes due to the UVA intensities reflected to the cotton yields as indicated by greater values up to 10.9%, 12.3% and 15.1% in the UVA-2, UVA-3 and UVA-4 treatments, respectively. Taken together, the tested UVA supplementations enhanced the seed germination of indoor cultivation and stimulated cotton development processes of in the field condition.