Comparison on light-response models of actual photochemical efficiency in photosystem II

The rosewood (Aniba rosaeodora Ducke) is a native tree species of Amazon rainforest growing naturally in acidic forest soils with reduced redox potential. However, this species can also been found growing in forest gaps containing oxide soils. Variations in the forms of mineral nitrogen (NO3- or NH4+) may be predicted in these different edaphic conditions. Considering that possibility, an experiment was carried out to analyze the effects of different NO3-:NH4+ ratios on the growth performance, mineral composition, chloroplastid pigment contents, photochemical efficiency photosystem II (PSII), and nitrate redutase activity (RN, E.C.1.6.6.1) on A. rosaeodora seedlings. Nine-month-old seedlings were grown in pots with a washed sand capacity of 7.5 kg and submitted to different NO3-:NH4+ ratios (T1 = 0:100%, T2 = 25:75%, T3 = 50:50%, T4 = 75:25%, and T5 = 100:0%). The lowest relative growth rate was observed when the NO3-:NH4+ ratio was equal to 0:100%. In general, high concentrations of NO3- rather than NH4+ favored a greater nutrient accumulation in different parts of the plant. For the chloroplastid pigment, the highest Chl a, Chl b, Chl tot, Chl a/b and Chl tot/Cx+c contents were found in the treatment with 75:25% of NO3-:NH4+, and for Chl b and Cx+c it was observed no difference. In addition, there was a higher photochemical efficiency of PSII (Fv/Fm) when high NO3- concentrations were used. A linear and positive response for the nitrate reductase activity was recorded when the nitrate content increased on the culture substrate. Our results suggest that A. rosaeodora seedlings have a better growth performance when the NO3- concentrations in the culture substrate were higher than the NH4+ concentrations.

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Response of common buckwheat and Tartary buckwheat from different elevations to selenium treatment

Fagopyrum ◽

10.3986/fag0019 ◽

2021 ◽

Vol 38 (1) ◽

pp. 15-23

Author(s):

Aleksandra Golob ◽

Neja Luzar ◽

Mateja Germ

Keyword(s):

Photosystem Ii ◽

Photochemical Efficiency ◽

Morphological Characteristics ◽

Tartary Buckwheat ◽

Control Group ◽

Common Buckwheat ◽

Biochemical Characteristics ◽

Selenium Treatment ◽

Uv Absorbing Compounds ◽

Effective Photochemical Efficiency

Common buckwheat and Tartary buckwheat were grown in Slovenia outdoors at different elevations – 300 m, 600 m and 1180 m a.s.l. Both species were foliarly treated with selenium twice (in the vegetative phase and in the flowering phase). The effects of Se treatment and different growing locations on selected biochemical, physiological and anatomical traits were monitored. In Se treated common buckwheat, amount of chlorophylls was higher in plants from Ljubljana (the lowest elevation – 300 m a.s.l.) than in plants grown in Podbeže (600 m a.s.l.), whereas in control group, plants grown in Ljubljana contained more chlorophylls than plants from Javorje (the highest elevation – 1180 m a.s.l.). In both buckwheat species, Se alone did not affect amount of chlorophylls in any of location. In Se treated common buckwheat plants, the amount of UV absorbing compounds was the highest in plants, grown at the highest elevation. In common buckwheat, Se lowered the number of CaOx in plants, grown in Javorje. Conditions at different elevations, as well as treatments with Se, did not affect potential and effective photochemical efficiency of Photosystem II. Keywords: common buckwheat, Tartary buckwheat, elevation, selenium, morphological characteristics, biochemical characteristics

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Light response of D1 turnover and photosystem II efficiency in the seagrassZostera capricorni

Planta ◽

10.1007/bf00620046 ◽

1996 ◽

Vol 198 (3) ◽

pp. 319-323 ◽

Cited By ~ 23

Author(s):

Yvette S. Flanigan ◽

Christa Critchley

Keyword(s):

Photosystem Ii ◽

Light Response ◽

Photosystem Ii Efficiency ◽

D1 Turnover

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Analysis of the effects of the spotted tentiform leafminer (Phyllonorycter blancardella) on the photosynthetic characteristics of apple leaves

Canadian Journal of Botany ◽

10.1139/b82-334 ◽

1982 ◽

Vol 60 (12) ◽

pp. 2734-2740 ◽

Cited By ~ 15

Author(s):

J. T. A. Proctor ◽

J. M. Bodnar ◽

W. J. Blackburn ◽

R. L. Watson

Keyword(s):

Photosynthetic Rate ◽

Dark Respiration ◽

Photochemical Efficiency ◽

Photosynthetic Apparatus ◽

Light Response ◽

Apple Leaves ◽

Economic Thresholds ◽

Fluorescence Reading ◽

Use Efficiency ◽

High Fluorescence

Infestation of apple leaves with the spotted tentiform leafminer (STLM) reduced their net photosynthetic rate (Pn) over a range of light intensities. At a saturating irradiance level of 1240 μE∙m−2∙s−1 and 20 mines per leaf, 32.9% of the leaf area was injured but Pn was decreased by only 23.2%. Examination of parameters in a model for leaf photosynthesis showed a reduction in maximum photosynthetic rate (asymptotic value of the light-response curve) and mesophyll conductance but not in photochemical efficiency or dark respiration. The STLM injury had no effect on transpiration, stomatal conductance, and a slight effect on internal CO2 concentration and water-use efficiency. Mining reduced chlorophyll content of the leaves and this reduced the chlorophyll fluorescence of the mined areas. Tissue around the mines had a relatively high fluorescence reading confirming the Pn measurements and suggesting that this technique was suitable for these and similar studies. Mining by the STLM disrupts the photosynthetic apparatus of the leaf and affects a number of mechanisms in the photosynthetic process. Correlating these effects with field observations will help in determining economic thresholds for this insect.

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Temperature response of photosynthesis and its interaction with light intensity in sweet orange leaf discs under non-photorespiratory condition

Ciência e Agrotecnologia ◽

10.1590/s1413-70542006000400012 ◽

2006 ◽

Vol 30 (4) ◽

pp. 670-678 ◽

Cited By ~ 15

Author(s):

Rafael Vasconcelos Ribeiro ◽

Eduardo Caruso Machado ◽

Ricardo Ferraz de Oliveira

Keyword(s):

Sweet Orange ◽

Photochemical Efficiency ◽

Temperature Response ◽

Light Response ◽

Photon Flux ◽

O2 Evolution ◽

Response Curves ◽

Leaf Discs ◽

Light Response Curves ◽

Heat Effects

This study aimed to evaluate the response of photosynthesis (A), given by photosynthetic O2 evolution, to increasing temperature from 25 to 50ºC in sweet orange (Citrus sinensis (L.) Osbeck) leaf discs under non-photorespiring conditions. In order to evaluate the response of gross photosynthesis to temperature and the balance between photosynthetic and respiratory activities, respiration (Rd) rates were also measured, i.e. the O2 uptake in each temperature. In addition, light response curves of photosynthesis were performed by varying the photosynthetic photon flux density (PPFD) from 0 to 1160 µmol m-2 s-1 at 25 and 40ºC. The highest A values were observed at 35 and 40ºC, whereas the highest Rd values were noticed at 50ºC. A higher relationship A/Rd was found at 30 and 35ºC, suggesting an optimum temperature of 35ºC when considering the balance between photosynthesis and respiration under non-photorespiring condition. Overall, heat effects on plant metabolism were more evident when evaluating the relationship A/Rd. In light response curves, higher A values were also found at 40ºC under PPFD higher than 300 µmol m-2 s-1. Light saturation point of photosynthesis was increased at 40ºC, without significant change of quantum efficiency under low PPFD. Respiration was also enhanced at 40ºC, and as a consequence, the light compensation point increased. The better photosynthetic performance at 35-40ºC was supported by higher photochemical efficiency in both light and temperature response curves. The temperature-dependence of photosynthesis was affected by growth temperature, i.e. a high air temperature during plant growth is a probable factor leading to a higher photosynthetic tolerance to heat stress.

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