Relações Hídricas Internas Do Umbuzeiro Sob Condições Semi-Áridas

Abstract

-A study was conducted at the Embrapa Semi-Árido, Petrolina-PE, Brazil, with the aim of understanding the mechanism by which the umbu tree (Spondias tuberosa Arr. Cam.) maintains its diurnal internal water balance in dry and wet seasons. The results obtained were based on the measuring of leaf water potential and its components using the pressure chamber and hygrometric chambers / microvoltmeter. Under dry conditions, the lowest values on water potential and osmotic potential were observed around 8:00 h, reaching, respectively, -0. 97 MPa and -1.17 MPa, resulting a turgor pressure of 0.2 MPa. The lowest turgor pressure occurred at 16:00 h when 0.16 MPa was detected but full recovery was not observed by the end of the light period. During the raining season, however, the lowest water potential was -1.55 MPa at 14:00h and -1.57 MPa at 14:00 h giving a turgor pressure of 0.02 MPa. Recovery was fast and, by the end of the day, plant water status was similar to the value observed at predawn. These results suggest the umbu tree presents two strategies for maintaining a favorable internal water balance, regarding the environmental situations studied. Under dry conditions the diurnal balance would be maintained at the expenses of water stored in the tubers and by restricted transpiration. During the rainy season, the diurnal water balance may have been mediated by a short term osmotic adjustment as judged by the observed afternoon range between water potential and osmotic potential.Index terms: water potential, osmotic potential, turgor pressure, osmotic adjustment, Spondias tuberosa. 1 RELAÇÕES HÍDRICAS INTERNAS DO UMBUZEIRO SOB CONDIÇÕES SEMI-ÁRIDASRESUMO -Realizou-se um estudo na Embrapa-Centro de Pesquisa Agropecuária do Trópico Semi-Árido (CPATSA), Petrolina-PE, objetivando identificar os mecanismos, através dos quais o umbuzeiro (Spondias tuberosa Arr. Cam.) mantém o balanço hídrico interno durante as estações de seca e chuvosa. Os resultados obtidos basearam-se em observações do potencial hídrico e de seus componentes, utilizando-se da câmara de pressão e câmaras higrométricas / microvoltímetro. Sob condições de seca, os valores mais baixos de potencial hídrico e potencial osmótico foram observados em torno das 8 h, atingindo, respectivamente -0,97 MPa e -1,17 MPa, resultando em uma pressão de turgor de 0,2 MPa. A pressão mais baixa ocorreu às 16 h, atingindo 0,16 MPa. Entretanto, a recuperação hídrica não foi observada, até o final dia. Durante a estação chuvosa, os valores de mais baixos de potencial hídrico foram obtidos às 14 h , quando foram detectados, respectivamente -1,55 MPa. Neste momento, o potencial osmótico atingiu -1,57 MPa , culminando com uma pressão de turgor de 0,02 MPa. Entretanto, até o final do dia, a condição hídrica da planta foi similar à observada no início do dia. Estes resultados sugerem que o umbuzeiro apresenta duas estratégias para manter, durante o dia, um balanço hídrico interno favorável, dentro das condições ambientais estudadas. Sob condições de sequeiro, o balanço seri...

<i>Spondias tuberosa</i> trees grown in tropical, wet environments are more susceptible to drought than those grown in arid environments

“…In this study, we showed that, during the period when the water stress was most severe, i.e., November, the photosynthetic rates of the tropical arid plants were significantly higher than the rates in the tropical wet plants, an effect that was strongly shifted at the beginning of the rainy season, which is the opposite to what should be expected for trees growing in a wet environment. Some investigators previously reported that S. tuberosa can maintain its Ψpd at a relatively constant level during the beginning of the dry season (Lima Filho, 2001;Lima Filho, 2004;Lima Filho, 2007;Lins Neto et al, 2012). A possible explanation for this result is that the umbu tree reduces its stomatal conductance in response to drought early in the morning, resulting in a dramatic decline in plant water loss and assuring (Lima Filho and Silva, 1988).…”

“…Old plants growing in their native fields can have more than 1,000 xylopodia, and their fresh weight can exceed 2,000 kg. These resources are used during the dry season to maintain normal plant metabolism (Cavalcanti and Resende, 2006;Lima Filho, 2001;Lima Filho, 2004).…”

“…These investigators suggested that the root tubers may act as an important source of water under stress conditions. However, the aforementioned studies (Lima Filho, 2001;Lima Filho, 2004;Lima Filho, 2007) only describe the gas exchange of umbu trees under semiarid conditions and the importance of tubers in helping plants avoid stress.…”

Plant functional types broadly describe water use strategies in the Caatinga, a seasonally dry tropical forest in northeast Brazil

“…leptophloeos has the lowest wood density, greatest diameter, and therefore the greatest stem water storage capacity. S. tuberosa likely has the greatest root water storage capacity, given the presences of a significant number and size of xylopodia (Antunes et al, 2016;Filho, 2001). Xylopodia are large root tubers that store water and carbohydrates.…”

Estrategias de enriquecimento do Umbuzeiro (Spondias tuberosa Arruda Cam.) em áreas de caatinga no semiarido paraibano.

“…A recuperação de áreas degradadas requer a utilização de princípios ecológicos e práticas silviculturais oriundos do conhecimento básico do ecossistema que se vai trabalhar, com descrição das espécies a serem utilizadas na aplicação de modelos de recuperação, todavia, para se alcançar pleno êxito nesta tarefa, além do conhecimento das causas da degradação e formas de recuperação, é preciso, também, conhecer as necessidades sociais, econômicas e os aspectos culturais da comunidade humana local (LIMA FILHO, 2004).…”