Increase of atmosphere co2 concentration and its effects on weeds/soybeans interaction

Author(s)

Jucileia Irian dos Santos

• Document type: Doctoral Thesis
• Press: Jaboticabal. 2018-10-31.
• Institution: Universidade Estadual Paulista (Unesp). Faculdade de Ciências Agrárias e Veterinárias. Jaboticabal
• Defense date: 2018-07-13
• Advisor: Pedro Luis da Costa Aguiar Alves; Carlos Alberto Martinezam Hua

Abstract

By the end of the 21st century, climate change projections based on the emission of greenhouse effect gases suggest an increase in the concentration of atmospheric carbon dioxide, in up to 750 ppm. In this scenario, we have significant changes in plant development, and consequently, in agricultural systems, thus altering the interactions between crops and weeds. Based on that, the aims of this work were to evaluated the effect of increasing of atmospheric CO2 concentration on the interaction between weeds (Euphorbia heterophylla and Amaranthus viridis) and soybeans (Glycine max), and the physiological and biochemical characteristics of these plants at two concentrations of CO2. Two experiments were carried out in open-top chambers (OTCs), in a completely randomized experimental design in a 5x2 factorial scheme: five coexistence conditions (monoculture of soybean, Slender Amaranth and wild poinsettia, and coexistence of soybean with Slender Amaranth and soybean with wild poinsettia) and two concentrations of CO2: 400 and 800 ppm. In the first experiment, the results showed that the increase of CO2 was different on the three species, and the intraspecific interference of soybean and slender amaranth was higher in 800 ppm, while in wild poinsettia the intraspecific interference was higher in 400 ppm. The coexistence of soybeans with slender amaranth and soybeans with wild poinsettia resulted in mutual injury, for both soybean and for weeds, however, when soybean was developed in coexistence with wild poinsettia, interspecific interference was higher in 800 ppm. In the second experiment, increase of CO2 resulted in greater carbon assimilation by photosynthesis only in soybeans, however, there was increase in the water use efficiency and in the carotenoid content, for the three species. In general, the increase of atmospheric CO2 reduced the lipid peroxidation in soybean, slender amaranth and wild poinsettia, but a greater activity of the SOD enzyme was observed in these three species. The metabolic profile was changed by the higher CO2 concentration, wherein at 400 ppm presented higher sucrose content, while plants 800 ppm presented higher glucose content. The secondary metabolism of soybean and wild poinsettia presented a higher synthesis of flavonoid compounds at 800 ppm, while slender amaranth showed decrease of flavonoid rutin. (AU)

• FAPESP's process: 15/22748-2 - Increase in the atmospheric CO2 and the effects on the interactions between weed and soybeans
• Grantee: Juciléia Irian dos Santos
• Support Opportunities: Scholarships in Brazil - Doctorate