Emergência e Crescimento Inicial de Plântulas de Cebola Sob o Aumento da Temperatura e Concentração de CO2 (Onion Seedlings Emergence and Initial Growth Under Increased Temperature and CO2)

Abstract

As mudanças climáticas, especialmente o aumento da temperatura e da concentração de gases de efeito estufa na atmosfera , afetarão o crescimento e desenvolvimento das plantas. O objetivo deste trabalho foi avaliar o efeito de aumento da temperatura e da concentração de CO2 na emergência de plântulas de cebola das cultivares Alfa São Francisco, Franciscana IPA 10, Vale Ouro IPA 11 e Serena .O experimento foi conduzido em câmaras de crescimento, com controle de umidade, luminosidade, temperatura e CO2, durante 12 dias. O delineamento experimental utilizado foi o inteiramente casualizado, em esquema fatorial 4x4x2, com quatro cultivares de cebola, quatro temperaturas (25 ºC; 28 ºC; 31 ºC e 34 ºC) e duas concentrações de CO2 (380 e 770 ppm) e , com quatro repetições e 36 sementes por tratamento. Sementes de cebola das cultivares Alfa São Francisco, Franciscana IPA 10, Vale Ouro IPA 11 e Serena foram semeadas em bandejas de polietileno com 36 células contendo substrato comercial e mantido nas diferentes concentrações de CO2 e temperatura. Foram avaliados a porcentagem de emergência, tempo médio de emergência, velocidade de emergência, índice de velocidade de emergência, comprimento da parte aérea e comprimento da raiz principal. Os dados foram submetidos à análise de variância e as médias comparadas pelo teste de Scott Knott a 5% de probabilidade. As concentrações de CO2 e as diferentes temperaturas proporcionaram efeitos significativos entre as cultivares para a maioria das variáveis analisadas. O aumento de CO2 e temperatura influenciaram no processo de emergência de plântulas de cebola. Climate change, especially atmosphere temperature and concentration of greenhouse gases increase, will affect plant growth and development . The aim of this study was to evaluate the effect of increased temperature and CO2 concentration in emergence of seedlings of onion cultivars Alfa San Francisco, Franciscan IPA 10, Valley IPA 11 Gold and Serena. The experiment was conducted in growth chambers with humidity, light, temperature and CO2 control during 12 days. The experimental design was completely randomized in a 4x4x2 factorial scheme, with four onion cultivars , four temperatures (25 °C; 28 °C, 31 °C and 34 °C and two concentrations of CO2 (380 to 770 ppm), with four replications and 36 seeds per treatment. Seeds of onion cultivars Alfa São Francisco, Franciscana IPA 10, Vale Ouro IPA 11 and Serena were sown in plastic trays with 36 cells containing commercial substrate and placed in different CO2 concentrations and temperature. Emergence percentage, average time of emergence, emergence speed, emergence speed index, shoot length and root length was evaluated. The data were submitted to variance analysis and the averages compared by Scott Knott test at 5% probability. The CO2 concentrations and different temperatures produced different effects among cultivars for most of the variables. The increase of CO2 and temperature influence the emergence onion seedlings process. Key-words: climate change, impacts, agriculture

Growth of Vernonia ferruginea Seedlings Submitted to Thermal Stress

“…The leaf number variable indicates that this accession is more adapted to air temperatures ranging between 20 and 30 o C. It was also observed that the lowest tested temperature (10 o C) provided the least number of leaves, differing significantly from the other treatments. In the photosynthetic process, CO 2 fixation and reduction occurs slowly at low temperatures, increasing with heating, until reaching the optimum temperature (Costa et al, 2015).…”

“…At temperatures above the optimum one, the carboxylation of ribulose 1,5-bisphosphate (RuBP) decreases considerably, due to the temperature increase, and the O:CO 2 ratio is modified; the solubility of CO 2 decreases in relation to that of O 2 and, thus, photorespiration is favored, reducing the photosynthetic yield. There is also an unbalance promotion in the input and output of CO 2 by plants (Costa et al, 2015).…”

“…Thermal stress is one of the primordial factors that restrict the development and adaptation of some species (Silva et al, 2000), and it may limit them to certain regions according to the temperature. An increase in air temperature promotes the reduction of the metabolic activity and the increased respiration of many species, directly affecting their growth and development (Costa et al, 2015).…”

“…A higher air temperature can directly affect the metabolism of young plants and seedlings, modifying the speed of chemical reactions and the activity of the enzymes that participate in these processes, as well as increasing soil temperature, which can compromise the development of plants (Costa et al, 2015).…”