UENF - Teses
URI permanente para esta coleçãohttps://thoth.dti.ufv.br/handle/123456789/12099
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Item Effect of high temperatures and CO2 concentration on physiological, biochemical and growth traits in Coffea sp.: aspects related to the single leaf and whole canopy(Universidade Estadual do Norte Fluminense Darcy Ribeiro, 2017-02-21) Rodrigues, Weverton Pereira; Campostrini, EliemarThe tropical coffee crop has been predicted to be threatened by future climate changes and global warming. However, the real biological effects of such changes remained unknown at both leaf and whole-canopy level. Therefore, we designed a set of experiments in Coffea sp. under both controlled and non-controlled (seasonal fluctuations) conditions. The experiments were related to single and combined effects of the increase in the atmospheric CO2 concentration and temperature on photosynthesis at leaf–scale, as well as related to impacts of rising temperatures on gas exchanges at whole-canopy scale. The first experiment aimed at to evaluate changes at stomatal and photochemical levels in Coffea arabica (cv. Catuaí Amarelo 65) and C. canephora (cv. Emcapa 8111 Clone 02) under mild temperature (spring) and high temperature (summer) exposure. Potted plants were maintained in a greenhouse, watered to field capacity and subject to the natural variations of light, temperature and relative humidity (Chapter 1). In the second experiment, cropped genotypes of C. arabica L. (cv. Icatú and IPR108) and C. canephora cv. Conilon Clone 153 (CL153) were grown for ca. 10 months at 25/20 °C (day/night) and 380 or 700 μL CO2 L-1 . After that they were subjected to a gradual temperature increase (0.5 °C day -1 ) up to 42/34 °C. Leaf impacts related to stomatal traits, gas exchanges, C-isotope composition, chlorophyll a fluorescence parameters, thylakoid electron transport rates and enzyme activities were assessed at 25/20, 31/25, 37/30 and 42/34 °C (Chapter 2). The third experiment evaluated whole-canopy gas exchanges on genotypes from the two main coffee producing species (C.arabica cv. Catuaí Amarelo 65 and C. canephora cv. Emcapa 8111 Clone 02) during two different seasons varying in temperature. Six plants with ca. 1-year-old of each species were grown in a greenhouse and kept well-watered. Data were continuously collected for 10 days during spring (September 2014 - moderate temperature) and summer (February 2015 -high temperature) and micrometeorological variables were monitored inside the greenhouse (Chapter 3). Overall, our results showed under controlled conditions, both coffee genotypes were tolerant up to 37/30 oC, whereas declines in photosynthetic rates were observed at 42/34 oC mainly associated with higher heat sensibility of the photosynthetic enzymes, namely ribulose-1,5-bisphosphate carboxylase/oxygenase (RuBisCO) and ribulose 5-phosphate kinase (RuB5PK). However, enhanced [CO2] strongly alleviated the impacts of high temperatures, particularly at 42/34oC, modifying the response of coffee plants to supra-optimal temperatures. Additionally, coffee genotypes grown under elevated [CO2] did not show an acclimation of photosynthesis so that photosynthetic rates and photochemical and biochemical activities were all improved at all temperatures. On the other hand, under a fluctuating environment conditions, supra-optimal temperatures lead to increases in air DPV affecting both leaf and whole-canopy photosynthetic rates in C. arabica plants. Decreases in photosynthetic rates in this specie during summer were linked to declines in both stomatal and canopy conductance, however without an apparent damage to the photochemical pathway. Finally, although C.canephora showed higher heat tolerance than C. arabica, maintaining similar both whole-canopy and leaf CO2 assimilation values in both seasons, its canopy architecture limited whole-canopy gas exchange due to poor light distribution within the canopy.