Different Light Radiation Intensities on Cotton: A Physiological Approach
Lucas Aparecido Manzani Lisboa *
Integrated College Stella Maris (FISMA) and Educational Fundation of Andradina (FEA), Andradina, São Paulo, Brazil and São Paulo State University (Unesp), College of Agricultural and Technological Sciences, Dracena, Brazil.
Fernando Takayuki Nakayama
Paulista Agribusiness Technology Agency (APTA), Alta Paulista Regional Camp, Adamantina, Brazil.
Edivaldo Cia
Agronomic Institute of Campinas (IAC), Campinas, Brazil.
Paulo Alexandre Monteiro de Figueiredo
São Paulo State University (Unesp), College of Agricultural and Technological Sciences, Dracena, Brazil.
Sérgio Bispo Ramos
São Paulo State University (Unesp), College of Agricultural and Technological Sciences, Dracena, Brazil.
Ronaldo da Silva Viana
São Paulo State University (Unesp), College of Agricultural and Technological Sciences, Dracena, Brazil.
Rodrigo Vitorino
Paulista Agribusiness Technology Agency (APTA), Alta Paulista Regional Camp, Adamantina, Brazil.
Thiago de Souza Celestrino
São Paulo State University (Unesp), School of Natural Sciences and Engineering, Ilha Solteira, Brazil.
Samuel Ferrari
São Paulo State University (Unesp), College of Agricultural and Technological Sciences, Dracena, Brazil.
*Author to whom correspondence should be addressed.
Abstract
The luminosity and the temperature are factors that act directly in the photosynthetic process, where an elevation of the luminous intensity can cause a reduction of the assimilation of carbon, which consequently lowers the development of the cotton. The objective of this work was to assess the response of physiological parameters of cotton when subjected to different artificial light intensities. Two varieties of cotton IMA5801B2RF and IACRDN, were interacting with five artificial light intensities: 0 (control); 500; 1000; 1500 and 2000 μmol m−2 s−1 of photosynthetically active radiation provided by LED bulbs. The experiment was set in a randomized complete block design using a 2x5 factorial scheme. The variables measured were the rate of CO2 assimilation, transpiration, stomatal conductance, inner CO2 concentration in the substomatic chamber, and efficient use of water (for which a portable device of gas exchange was used). The cotton varieties responded positively to different luminous intensities until reaching the point of maximum saturation between 1400 and 1600 µmol m-1 s-1 of light, which provided a better rate of CO2 assimilation, concentration of CO2 in the substomatic chamber, and efficient use of water. Leaf transpiration and stomatal conductance showed a positive linear response with increasing light intensity. The ideal luminous intensity for the use of Infra-Red Gas Analyzer - IRGA was 1500 µmol m-1 s-1 for the tested cotton varieties.
Keywords: Gossypium L., brightness, CO2 assimilation, photosynthesis rate