CO_2 photoassimilation, chlorophyll fluorescence, lipid peroxidation and yield in cotton (Gossypium hirsutum L. cv Giza 65) in response to O_3

摘要

Over the recent years, convincing evidence has emerged of both a decrease in stratospheric ozone (O_3) and an increase in tropospheric O_3 concentration. There is an intimate relationship between O_3 and photosynthesis (A), which is ultimately linked to plant growth and yield. Photosynthetic response, chlorophyll fluorescence, Rubisco activity, lipid peroxidation and yield of an Egyptian cultivar of cotton (Gossypium hirsutum L. Cv. Giza 65) in response to fumigation with 70 nl l~(-1) O_3 for 14 days, 10 hd~(-1) (8:00-18:00 local time) were investigated. Photosynthetic rate (A), stomatal conductance (g_s), the ratio between variable and maximum fluorescence (F_v/F_m) and total Rubisco activity were reduced by 18%, 23%, 11% and 34%, respectively, and chlorophyll content, growth and yield of the plant were also reduced substantially by O_3 exposure. O_3-induced reductions in A were related to declines in growth and yield. Since exposure to O_3 concentration typical of level of the pollutant recorded in Egypt reduced A, growth and yield of the species under investigation, reductions in A may be occurring in other important crops in Egypt.