1. OVERALL CONTEXT RESULTS MATERIAL AND METHODS CONCLUSION
Photosynthetic parameters and Eucalyptus clones growth under different climatic conditions in Brazil Aline Regina Vergani1, Arthur Vrechi1, Sérgio Ricardo Silva1, Marina Shinkai Gentil2, Antonio Natal Gonçalves2, José Luiz Stape3 1Veracel Celulose S.A, Brazil. 2 ESALQ, University of São Paulo, Brazil. 3 NCSU, North Carolina State University, USA.
OVERALL CONTEXT
RESULTS
The Eucalyptus cultivated area in the world increased rapidly over the last two decades, exceeding 19 million hectares.
As plantations have been moving to dry sites causing less productive land availability it is necessary to evaluate the Eucalyptus ecophysiological responses to different water regimes.
This study aims to evaluate the physiological behavior and growth of different Eucalyptus clones under different climatic conditions.
The photosynthetic rate average along the day was much higher (13.5 mol CO2 m-2 s-1) in all genetic material planted in the wet climate area when compared to the dry climate area (3.4 mol CO2 m-2 s-1). The plants presented a linear decline of the stomatal conductance due to the VPD increase. On the dry climate area, plants have kept their stomata almost closed due to the low soil moisture and high VPD (Figure 2).
The volume growth was 67% higher on the wet climate. Transpiration and stomatal conductance values were significantly higher on wet climate considering all evaluated clones, especially for clone D, which had a different behavior from other genetic material on both areas. This clone, when compared to the other materials, showed a lower volume growth in the wet climate area with transpiration and stomatal conductance values below the other clones averages and a higher volume growth in the dry climate area (Table 1), presenting to be more adapted to drier conditions.
MATERIAL AND METHODS
Four clones of Eucalyptus grandis x urophylla named A, B, C and D were planted in two different locations: a wet climate area, and a dry climate area, with average annual precipitation of 1200 mm and 900 mm, respectively. 
Wet climate
Dry climate
Figure 3. Stomatal conductance and VPD on wet area (A) and dry area (B).
Figure 1. Precipitation and temperature throughout the year for both areas of study.
Table 1. Transpiration, Stomatal Conductance and Volume averages of the clones A, B, C and D in the highest and lowest rainfall area.
The photosynthetic measurements occurred in 2010, when the forests were aged 22 months, and were performed through and equipment IRGA model Li-6400.
* Values followed by different letters differ at P = 0,05. Capital letters compare different areas, and lower case letters compare different clones.
CONCLUSION
Transpiration, stomatal conductance and volume growth values were significantly higher on wet climate conditions, wich shows the effect of water on the physiological behavior of Eucalyptus clones.
Different responses between clones were observed in both areas, what represents the importance of understanding the physiological behavior for the genetic material selection.
Figure 2: Details of the equipment IRGA Li-6400, and tower used for photosynthetic measurements.