A study was carried out at Embrapa Semi-Árido, Petrolina-PE, Brazil, aiming to understand the gas exchange process of the umbu tree (Spondias tuberosa Arr. Cam.) in the dry and rainy seasons. Stomatal conductance, transpiration, photosynthesis and internal CO2 concentration were obtained with a portable infrared gas analyzer (IRGA). During the dry season the umbu tree showed a much lower stomatal conductance early in the morning, as soon as the vapor pressure deficit increased, apparently affecting CO2 assimilation more than transpiration. The highest values were detected around 6:00 am but decreased to the lowest points between 10:00 am and 2:00 pm. During the rainy season, however, stomatal conductance, transpiration and photosynthesis were significantly higher, reaching the highest values between 8:00 and 10:00 am and the lowest around 2:00 pm. It was also observed at 4:00 pm, mainly during the rainy season, an increase on these variables indicating that the umbu tree exhibits a two-picked daily course of gas exchange.
-The experiment was carried out at the Embrapa Semi-Árido, Petrolina-PE, Brazil, in order to study the physiological responses of umbu plants propagated by seeds and by stem cuttings under water stress conditions, based on leaf water potential and gas exchange measurements. Data were collected in one-year plants established in pots containing 30 kg of a sandy soil and submitted to twenty-day progressive soil water deficit. The evaluations were based on leaf water potential and gas exchange data collection using psychrometric chambers and a portable infra-red gas analyzer, respectively. Plants propagated by seeds maintained a significantly higher water potential, stomatal conductance, transpiration and photosynthesis under decreasing soil water availability. However, plants propagated by stem cuttings were unable to maintain a favorable internal water balance, reflecting negatively on stomatal conductance and leaf gas exchange. This fact is probably because umbu plants propagated by stem cuttings are not prone to formation of root tubers which are reservoirs for water and solutes. Thus, the establishing of umbu plants propagated by stem cuttings must be avoided in areas subjected to soil water deficit. Index terms: water potential, stomatal conductance, transpiration, photosynthesis, root tubers. ESTADO HÍDRICO E TROCAS GASOSAS DE UMBUZEIROS (Spondias tuberosa Arr. Cam.) PROPAGADOS POR SEMENTES E ESTAQUIARESUMO-O experimento foi realizado na Embrapa Semi-Árido, Petrolina-PE, Brasil, objetivando estudar as respostas fisiológicas de umbuzeiros propagados por sementes e por estaquia, sob condições de deficiência hídrica. Os dados foram coletados em plantas com aproximadamente um ano de idade, estabelecidas em vasos contendo 30 kg de solo de textura arenosa e submetidas a déficit progressivo de água, durante 20 dias. As avaliações foram realizadas, tomando-se como base o potencial hídrico foliar e as trocas gasosas, monitorados com auxílio de câmaras psicrométricas e um analisador portátil de gás por infravermelho, respectivamente. As plantas propagandas por sementes mantiveram valores de potencial hídrico, condutância estomática, transpiração e fotossíntese significativamente maiores, sob condições decrescentes de disponibilidade de água no solo. Entretanto, plantas propagadas por estaquia foram incapazes de manter um balanço hídrico favorável, refletindo negativamente na condutância estomática e trocas gasosas. Estes resultados estão provavelmente associados ao fato de que o umbuzeiro propagado por estaquia dificilmente apresenta túberas em suas raízes, as quais são reservatórios de água e solutos. Dessa forma, o plantio de umbuzeiros propagados por estaquia deve ser evitado em áreas sujeitas à deficiência hídrica. Termos para indexação: potencial hídrico, condutância estomática, transpiração, fotossíntese, túberas.
-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...
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.