In recent years, the high market demand for products from planted forests has
led to the expansion of planting areas, with investors seeking the implantation of
crops with high production and low implantation costs, began to explore several parts
of the country, and found in the Tocantins ideal conditions for the implantation and
exploitation of planted forests, for having extensive areas and reduced land prices.
However, this activity has been expanding in the state without prior planning as to the
selection of the best material for each region. Since the state presents high
temperatures and low levels of precipitation during the year, studies are needed on
the species most adapted to the regional edaphoclimatic conditions, especially with
respect to the resistance of the materials to the water stress. The objective of this
study was to evaluate the physiological, biochemical and morphological responses in
three eucalypt clones subjected to water stress. The experiment was installed in
February 2017 at the Experimental Station of the Federal University of Tocantins,
Campus de Gurupi under greenhouse conditions. A completely randomized design
was used in a 3x3 factorial scheme, with three clones (Clone 1- Eucalyptus
urophylla, Clone 2- E. urophylla x E. grandis, Clone 3- E. urophylla x E.
camaldulensis) and three water manures (Irrigated, resumption of irrigation and
deficit). Ten plants of each species were used in each treatment, being six plants for
the evaluation of the biochemical variables and four plants for evaluations of the
physiological and morphological variables. The plants were evaluated for stomatal
conductance (gs), net carbon assimilation rate (A), transpiration rate (E),
carboxylation efficiency (A / Ci) and instant water use efficiency (USA), chlorophyll
content aeb, proline, enzyme activity of the antioxidant mechanism (superoxide
dismutase and catalase) and total dry matter. Different responses were obtained
from the evaluated materials in relation to water management. Clone 2 showed the
lowest values of stomatal conductance (0.005 mol.m-2.s-1), net assimilation rate
(7.08 μmol.m-2.s-1), carboxylation efficiency (0.028 μmol.m And water use efficiency
(2.12 μmol.mmol-1), and higher activity of catalase in irrigated management (7.90,
indicating greater sensitivity to the climatic conditions of the region). clone 3
presented results that showed good adaptability under optimal conditions of water
availability. The highest rates of net carbon assimilation (10.57 μmol.m-2.s-1) and
stomatal conductance (0.20 mol.m-2.s-1), presented in the regimen of irrigation
recovery show that the clone 1 exhibits rapid growth recovery. In the management of
water deficit, it can be observed that the highest values of stomatal conductance
(0.07 mol.m-2.s-1), net assimilation rate (8.05 μmol.m-2.s-1) , the efficiency of the
carboxylation (0.056 μmol.m-2.s-1) and water use efficiency (4.18 μmol.mmol-1)
were obtained by clone 3, showing to be the most suitable for planting in areas with
low water availability. On the other hand, the lower rates of net carbon assimilation
and the higher proline content presented by clones 1 and 2 indicate higher sensitivity
of these materials under water deficit conditions.
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