Abstract:No presente estudo, comparou-se o curso diário de fluxo de seiva, condutância estomática e potencial hídrico (psi) de duas espécies sempre-verdes, Rapanea guianensis e Roupala montana. Os dados foram obtidos no final da estação seca, quando os efeitos do déficit hídrico seriam mais acentuados. As medidas foram realizadas no campo sujo, onde predomina gramíneas com sistemas radiculares superficiais, e no cerradão, em que a maior densidade de elementos lenhosos com sistemas radiculares profundos poderia levar a … Show more
“…The positive relationship of variables A and E in comparison with gs, in J. curcas specimens subjected to drought and flooding treatments indicates that stomatal closure may be the major limiting factor of these variables (Cornic, 2000;Sapeta et al, 2013;Silva et al, 2010). This interaction between gs and E, shows the importance of controlling stomatal movement (opening and closing), in plants adapted to stress condition, as occured in J. curcas plants under water deficit, allowing the plant to maintain a high WUE (Naves- Barbiero et al, 2000;Yang et al, 2005).…”
With the purpose of assessing the physiological responses of J. curcas young plants to drought and flooding, plants were subjected to three watering regimes: Control, drought and flooding. In the same period, five plants were submitted to drought (irrigation suspension), five to flooding and five were maintained near the field capacity (control). Measurements of leaf gas exchange, chlorophyll content, biomass of each organ (leaf, stem and root), biomass ratios, as well as the root:shoot ratio were made. When compared to control, drought and flooding treatments led to significant reductions (P≤.05) of gas exchange rates at 14 and 7 days after imposition treatments (DAIT), respectively. At the 16 th DAIT, significant reductions of leaf, root, stem and total biomass were observed, which resulted in changes of biomass partitioning of each organ. Significant reduction of leaf dry biomass (LDB) was observed in water deficit plants. Moreover, no significant effects of water deficit were observed in root dry biomass. Such response has led to a higher root:shoot ratio, suggesting an improved ability for water and nutrients uptake. In turn, flooding has induced a significant decrease in the dry biomass of all organs. Stem dry biomass ratio of flooded plants (0.67 g g -1 ) was significantly higher than that of control plants (0.41 g g -1 ), which, was seemingly due to leaf senescence and root system rotting of flooded plants. Altogether, present results reinforce the susceptibility of the studied genotype of J. curcas to flooding, as well as highlight some characteristics of drought tolerance in this species.
“…The positive relationship of variables A and E in comparison with gs, in J. curcas specimens subjected to drought and flooding treatments indicates that stomatal closure may be the major limiting factor of these variables (Cornic, 2000;Sapeta et al, 2013;Silva et al, 2010). This interaction between gs and E, shows the importance of controlling stomatal movement (opening and closing), in plants adapted to stress condition, as occured in J. curcas plants under water deficit, allowing the plant to maintain a high WUE (Naves- Barbiero et al, 2000;Yang et al, 2005).…”
With the purpose of assessing the physiological responses of J. curcas young plants to drought and flooding, plants were subjected to three watering regimes: Control, drought and flooding. In the same period, five plants were submitted to drought (irrigation suspension), five to flooding and five were maintained near the field capacity (control). Measurements of leaf gas exchange, chlorophyll content, biomass of each organ (leaf, stem and root), biomass ratios, as well as the root:shoot ratio were made. When compared to control, drought and flooding treatments led to significant reductions (P≤.05) of gas exchange rates at 14 and 7 days after imposition treatments (DAIT), respectively. At the 16 th DAIT, significant reductions of leaf, root, stem and total biomass were observed, which resulted in changes of biomass partitioning of each organ. Significant reduction of leaf dry biomass (LDB) was observed in water deficit plants. Moreover, no significant effects of water deficit were observed in root dry biomass. Such response has led to a higher root:shoot ratio, suggesting an improved ability for water and nutrients uptake. In turn, flooding has induced a significant decrease in the dry biomass of all organs. Stem dry biomass ratio of flooded plants (0.67 g g -1 ) was significantly higher than that of control plants (0.41 g g -1 ), which, was seemingly due to leaf senescence and root system rotting of flooded plants. Altogether, present results reinforce the susceptibility of the studied genotype of J. curcas to flooding, as well as highlight some characteristics of drought tolerance in this species.
“…A variação diurna do potencial hídrico observado neste estudo é similar à relatada por outros pesquisadores (Perez & Morais, 1991;Naves-Barbiero et al, 2000;Jadoski et al, 2005). Por exemplo, em Erytroxylum suberosum (St.) os valores de Ψdiminuem até atingir um mínimo próximo das 14:00 h, observando-se reidratação da folha ao final da tarde (Perez & Morais, 1991).…”
Section: Resultsunclassified
“…e Roupala montana (Aubl.) o potencial hídrico da folha é máximo pela manhã, mas diminui até atingir valores mínimos entre 13:00 e 15:00 h, aumentando a turgidez da folha ao final da tarde (Naves-Barbiero et al, 2000).…”
RESUMOO potencial hídrico da folha é um dos fatores mais importantes que afetam o funcionamento dos estômatos. O objetivo deste trabalho foi avaliar o efeito da variação diurna na irradiância e déficit de pressão de vapor (DPV) na fotossíntese (A), condutância estomática (g s ) e potencial hídrico da folha (Ψ) em Carapa guianensis (Aubl.). Os dados foram coletados de 07:00 às 17:00 h. A taxa fotossintética atingiu um valor máximo (2,5 µmol m -2 s -1 ) às 10:00 h, depois declinou até atingir um mínimo de 1 µmolm -2 s -1 às 16:00 h. A condutância estomática oscilou durante o dia, de 0,04 molm -2 s -1 (ao meio dia) para 0,02 molm -2 s -1 no final da tarde. O potencial hídrico da folha foi máximo nas primeiras horas do dia (-0,3 MPa) e mínimo (-0,75 MPa) no meio da tarde (14:30 a 15:00 h). Após ter alcançado um mínimo, o Ψ aumentou até -0,64 MPa no fim da tarde. A taxa fotossintética aumentou linearmente em função do g s (P < 0,01). Também houve uma relação positiva entre Ψ e g s (P < 0,01). A taxa fotossintética declinou durante o dia após ter alcançado um pico no início da manhã, demonstrando que os fatores ambientais que afetam o Ψ têm efeito significativo na assimilação do carbono de C. guianensis.
PALAVRAS-CHAVEDéficit de pressão de vapor, potencial hídrico foliar, transpiração, trocas gasosas da folha. and lower . After reaching a minimum, MPa at sunset. Photosynthetic rates increased linearly as a function of g s (P < 0.01). Also there was a positive relationship between Ψ and g s (P< 0.01). Photosynthetic rates declined during the day after reaching a peak early in the morning, which makes clear that environmental factors that influence Ψ greatly affect carbon assimilation of C. guianensis.
Photosynthesis, stomatal conductance and leaf water potential in crabwood (Carapa guianensis)
ABSTRACT
Leaf water potential is one of the most important factors affecting stomatal functioning. The aim of this study was to assess the effect of variation in diurnal irradiance and vapour pressure deficit on photosynthesis (A), stomatal conductance (g s ) and leaf water potential (Ψ) in
KEYWORDSLeaf gas exchange, leaf water potential, transpiration, vapour pressure deficit.
“…The increase in leaf blade area, reduction in internal temperature, and anatomic alterations observed in these organs may enhance the photosynthetic rate in N. wightii cultivated in shaded environments. The photosynthetic rate is largely influenced by radiation (Naves-Barbiero et al 2000), which is often altered by shading. Plants generally have specific light needs, predominantly in the red and blue wavelengths (Messinger et al 2006).…”
Plants have the ability to undergo morphophysiological changes based on availability of light. The present study evaluated biomass accumulation, leaf morphoanatomy and physiology of Neonotonia wightii and Pueraria phaseoloides grown in full sunlight, as well as in 30% and 50% shade. Two assays were performed, one for each species, using a randomized block design with 10 replicates. A higher accumulation of fresh mass in the shoot of the plants was observed for both species under cultivation in 50% shade, while no differences were detected between the full sunlight and 30% shade. N. wightii and P. phaseoloides showed increase in area and reduction in thickness leaf when cultivated in 50% shade. There were no changes in photosynthetic rate, stomatal conductance, water use efficiency and evapotranspiration of P. phaseoloides plants because growth environment. However, the shade treatments caused alterations in physiological parameters of N. wightii. In both species, structural changes in the mesophyll occurred depending on the availability of light; however, the amount of leaf blade tissue remained unaltered. Despite the influence of light intensity variation on the morphophysiological plasticity of N. wightii and P. phaseoloides, no effects on biomass accumulation were observed in response to light.
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