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Gas exchange in young plants of Tabebuia aurea (Bignoniaceae juss.) subjected to flooding stress

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Ademir Kleber Morbeck Oliveira
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The paratudo, Tabebuia aurea, is a common Brazilian tree from the Pantanal wetland from Miranda, Mato Grosso do Sul, an area with hydric seasonality. To evaluate the effects of water stress on CO2 exchange, ten-month-old T. aurea seedlings cultivated in planting bags were subjected to water stress by suppressing irrigation for 23 days. Stomatal conductance, transpiration rate, and photosynthetic rate were measured during the stress and recovery period, totaling 28 days, using an infrared portable analyzer. After 23 days without irrigation, the transpiration, stomatal conductance, and net photosynthesis rates in leaflets were zero, while the leaflets water potential reached -2.6 MPa. After this point, daily irrigation was resumed, and the values of the measured variables recovered to the initial levels after 96 hours (transpiration rate from 2.0 to 2.6 mmol m⁻² s⁻¹; stomatal conductance rate from 0.12 to 0.18 mol m⁻² s⁻¹ and photosynthesis rate from 8.1 to 9.5 µmol m⁻² s⁻¹). Furthermore, the hydric potential values were similar to those observed at the beginning of the experiment (-0.5 MPa). The results showed that T. aurea has tolerance to drought, allowing their survival in areas subjected to periodic water stress. © 2017, Universidade Federal de Uberlandia. All rights reserved.
O paratudo, Tabebuia aurea, é uma árvore típica do Pantanal de Miranda, Mato Grosso do Sul, Brasil, sendo esse local, uma área de inundação sazonal. Para avaliar as trocas gasosas de Tabebuia aurea sob estresse hídrico por alagamento, grupos de plantas com oito meses de idade foram mantidas em vasos com o solo coberto por uma lâmina de 2 a 3 cm de água. As taxas de condutância estomática, transpiração e fotossíntese foram determinadas durante o período de experimento (115 dias), através de um analisador portátil de gás infravermelho. Os valores de condutância estomática no início do experimento estavam em torno de 0,22 mol m-2 s-1 e foram decrescendo até 0,02 mol m-2 s-1. Em relação à fotossíntese líquida, o valor máximo inicial foi de 8,0 mmol m-2 s-1, atingindo zero no 108º dia. Após redução em 100% da fotossíntese líquida, as plantas foram retiradas da condição de alagamento e avaliadas (8 dias). Os valores obtidos ao final do processo de recuperação para condutância estomática foram: 0,21 mol m-2 s-1 e fotossíntese = 8,0 mmol m-2 s-1. O alagamento do solo reduziu a fotossíntese, a condutância estomática e afetou o crescimento da parte aérea, induzindo o aparecimento de sintomas característicos de estresse por inundação, como a hipertrofia das lenticelas. Porém, a espécie apresenta tolerância ao estresse, indicando adaptabilidade a áreas sujeitas a alagamento periódico.
Ademir Kleber Morbeck Oliveira
added a research item
The Paratudo (Tabebuia aurea) is a species occurring in the Pantanal of Miranda, Mato Grosso do Sul, Brazil, an area characterized by seasonal flooding. To evaluate the tolerance of this plant to flooding, plants aged four months were grown in flooded soil and in non-flooded soil (control group). Stomatal conductance, transpiration and CO2 assimilation were measured during the stress (48 days) and recovery (11 days) period, totalling 59 days. The values of stomatal conductance of the control group and stressed plants at the beginning of the flooded were 0.33 mol m-2 s-1 and reached 0.02 mol m-2 s-1 (46th day) at the end of this event. For the transpiration parameter, the initial rate was 3.1 mol m-2 s-1, and the final rate reached 0.2 or 0.3 mol m-2 s-1 (47/48th day). The initial photosynthesis rate was 8.9 mmol m-2s-1 and oscillated after the sixth day, and the rate reached zero on the 48th day. When the photosynthesis rate reached zero, the potted plants were dried, and the rate was analyzed (11th day). The following values were obtained for dried plants: stomatal conductance = 0.26 mol m-2 s-1, transpiration rate = 2.5 mol m-2 s-1 and photosynthesis rate = 7.8 mmol m-2 s-1. Flooded soil reduced photosynthesis and stomatal conductance, leading to the hypertrophy of the lenticels. These parameters recovered and after this period, and plants exhibited tolerance to flooding stress by reducing their physiological activities. © 2016, Sociedade de Investigacoes Florestais. All rights reserved.