Growth and photosynthesis of eucalyptus: effects of atmospheric CO2 concentration, water stress, and microclimates
Name: JOSÉ HAMILTON DE OLIVEIRA BRAGA
Publication date: 14/07/2016
Advisor:
Name |
Role |
|---|---|
| JOSÉ EDUARDO MACEDO PEZZOPANE | Advisor * |
Examining board:
| Name |
Role |
|---|---|
| JOSÉ EDUARDO MACEDO PEZZOPANE | Advisor * |
| SANDRO DAN TATAGIBA | Co advisor * |
| TALITA MIRANDA TEIXEIRA XAVIER | External Examiner * |
Summary: Eucalyptus shows its importance as being the forest species that covers the greatest areathroughout the Brazilian territory, thus being the essential economic component to the forestry sector. Beyond the financial benefits, its ecological importance is also evident; its cultivation decreases the pressure for timber products from native forests. This study sought to evaluate the gas exchange and growth of eucalyptus seedlings subjected to combinations of different concentrations of CO2, soil water availability, and evaporative demand of the atmosphere. The study was conducted in air-conditioned greenhouses located in the experimental area of the Department of Forest Sciences and Wood in Agricultural Sciences Center of the Federal University of Espírito Santo, located in the town of Jerônimo Monteiro - ES, with the geographic coordinates 20º 47 ' 22 '' S and 41º 23 '42' 'W. In each room, six OTC (open top chambers) were placed, each having four plants. The treatments were submitted to two evaporative demands of the atmosphere (low and high atmospheric demand), two concentrations of CO2 (± 450 and ± 850 ppm) and two water treatments (50% and 100% of available water in the soil) with six replications during a trial period of 96 days. At the end of the experiment, growth analysis of the plants was carried out by obtaining the total dry mass, leaf area, specific leaf area, biomass partition, leaf area ratio and efficiency of the use of water productivity. The water status of the plant, performed at the end of the experimental period, was obtained from the observation of the relative water content in the leaves. The measurement of gas exchange was performed throughout the 88-day experiment at the times of 8:00, 10:00, 12:00, 14:00 and 16:00 in order to obtain the diurnal courses of photosynthesis, stomatal conductance and transpiration. Also measurements of gas exchange were made for curve fitting A/FPAP and A/C for the time period of 9:00 to 12:00 to obtain photosynthetic parameters and eventually the quantification of the levels of photosynthetic pigments. The experiment was conducted using a completely randomized design using a factorial arrangement of 2x2x2. The data was submitted to an analysis of variance, and, when significant, the means were compared by the Tukey test at 5% probability. The three treatments of higher concentrations of CO2, high atmospheric demand, and 100% of available water all contributed to the eucalyptus seedlings having higher amounts of total dry mass and efficiency of water usage. The root mass fraction had higher values at high atmospheric demands and less soil water availability. The shoot mass fraction values were higher under high atmospheric demand and higher amount of water available in the soil. The leaf area ratio values were lower under conditions of greater water availability, high CO2 concentration, and microclimates of high atmospheric demand, indicating that these conditions are the ones that most favor the production of total dry mass. The relative water content in leaves was higher in plants in treatments with 100% water availablility in the soil. The diurnal courses of net CO2 assimilation had higher values in high atmospheric demands, greater water levels of water availabiity, and higher concentrations of CO2. It can be observed that treatments of low water availability in the soil in high atmospheric demands had greater growth performance and gas exchange while under conditions of high CO2 concentration, compared to treatments of low atmospheric concentrations of CO2. The outcomes of growth and gas exchange of the plants subjected to low atmospheric demand proved indifferent to higher concentrations of CO2, showing diferences only to the different water levels in the soil.
