scholarly journals Intensitas Cahaya dan Efisiensi Fotosintesis pada Tanaman Naungan dan Tanaman Terpapar Cahaya Langsung

2019 ◽  
Vol 4 (2) ◽  
pp. 44-49
Author(s):  
Maria Yustiningsih
Keyword(s):  
Carbon Fixation ◽  
Calvin Cycle ◽  
High Ratio ◽  
Photon Absorption ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Adaptation Mechanism ◽  
Ps Ii ◽  
Light Harvesting Complex ◽  
Shade Plants

Plant growth and productivity influenced by light. Sunlight activates light-dependent reactions or LDR and Calvin cycle or LIR in plant. Different light intensity induce change of LDR and LIR. Adaptation through efficiency of photon absorption, regulation of photosystem II - photosystem I, and carbon fixation can make photosynthesis efficiently. This paper aims to review research on photosynthesis mechanism in sun and shade plants. Alteration of light absorption in plants produce morphological and physiological adaptations. Plant adaptation mechanism use sieve effect, light channeling, and acclimatization. Distribution of chlorophyll in both types of plants changed the photosynthesis photon flux density. Propagation and distribution of light needed through vacuoles to minimize the distance on electron transport chain. Physiological acclimatization accelerates by changing the composition of chlorophyll and PSII / PSI ratio. Shade plants have a high ratio PS II / PSI and high ratio chlorophyll a / b to increase the light-harvesting complex and make photosynthesis efficiently.

scholarly journals Morphological and physiological responses of Cedrela Fissilis Vellozo (Meliaceae) seedlings to light

2006 ◽  
Vol 49 (1) ◽  
pp. 171-182 ◽  
Author(s):  
Débora Leonardo dos Santos ◽  
Miroslava Rakocevic ◽  
Massanori Takaki ◽  
Jorge Ribaski
Keyword(s):  
Photosynthetic Rate ◽  
Dry Mass ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Light Radiation ◽  
Aerial Parts ◽  
Young Leaves ◽  
Number Of Leaves ◽  
Shade Plants

Seeds of Cedrela fissilis Vellozo were planted and maintained under two distinct conditions: at east border of a forest with red: far-red ratio of 1.15 and under canopy with photosynthetic photon flux density of 0.22-7% of full sun radiation and red: far-red ratio of 0.21-0.36. Seedling growth (height and stem diameter) was faster under sun, the development of roots more continuous and the number of leaves almost twice of that of shade plants. The leaf area was 10 times greater in sun plants with 15-25 leaflets per leaf while under shade only 5 to 10 leaflets were found per leaf. In shade plants, a higher proportion of dry mass was found in aerial parts. Leaves of sun plants had the capacity of gas exchange to respond to high light radiation, but leaves adapted to shade presented a lower response to light changes. When shade plants were transferred and maintained under the sun for 15 days, only the young leaves were adapted to increased light radiation, reaching the same photosynthetic rate as sun plants, while old leaves were shed. Sun plants transferred to shade conditions did not lose leaves, but did not reach the same photosynthetic rate attained by shade plants.

Stomatal Metabolism: CO2 Fixation and Respiration

1977 ◽  
Vol 4 (4) ◽  
pp. 611
Author(s):  
N Thorpe ◽  
F.L Milthorpe
Keyword(s):  
Flux Density ◽  
Co2 Fixation ◽  
Calvin Cycle ◽  
Co2 Concentration ◽  
High Rate ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Initial Fixation ◽  
Sugar Phosphates ◽  
Early Fixation

The rate of fixation of CO2 by epidermis attached to the leaf of Commelina cyanea was linear with photon flux density up to 1.08 mE m-� s-� and with CO2 concentration from 0 to 355 ppm. Detached epidermis, on the other hand, showed no response to photon flux density and had rates in the light which were only twice those in the dark. There was substantial leakage of all labelled methanol-soluble substances from isolated epidermis. Its apparent reduced functioning may well be associated with this leakage rather than reflecting transport from the mesophyll. The early fixation products in light and dark were similar in attached and detached epidermis. These were mainly aspartate and malate in contrast to the Calvin cycle intermediates formed in mesophyll in the light. It seems likely that phosphoenolpyruvate carboxylase is closely implicated in the initial fixation of CO2 by stomata and is responsible for the much higher rates of fixation per unit of chlorophyll by epidermis than by mesophyll. Although aspartate and malate are the major products detectable after 2 min feeding with 14CO2 and remain as a high proportion of labelled products during a subsequent 12CO2 chase, amino acids, sugars and sugar phosphates together with polysaccharides and other methanol-insoluble products are eventually labelled. Attempts to measure respiration rates of attached epidermis were unsuccessful due to fixation of mesophyll-respired CO2; the rate in detached epidermis was high, suggesting a high rate of turnover of carbon products by stomata, but we were unable to relate this to rates in attached epidermis. Rates were higher in CO2-free than in CO2-containing environments, indicating a possible explanation of the CO2 effect on stomata.

scholarly journals An evaluation of the potential triggers of photoinactivation of photosystem II in the context of a Stern–Volmer model for downregulation and the reversible radical pair equilibrium model

2000 ◽  
Vol 355 (1402) ◽  
pp. 1489-1498 ◽  
Author(s):  
Kevin Oxborough ◽  
Neil R. Baker
Keyword(s):  
Photosystem Ii ◽  
Flux Density ◽  
Equilibrium Model ◽  
Radical Pair ◽  
Charge Recombination ◽  
Maximum Efficiency ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Intersystem Crossing ◽  
Ps Ii

Photoinactivation of photosystem II (PS II) is a light–dependent process that frequently leads to breakdown and replacement of the D1 polypeptide. Photoinhibition occurs when the rate of photoinactivation is greater than the rate at which D1 is replaced and results in a decrease in the maximum efficiency of PS II photochemistry. Down regulation, which increases non–radiative decay within PS II, also decreases the maximum efficiency of PS II photochemistry and plays an important role in protecting against photoinhibition by reducing the yield of photoinactivation. The yield of photoinactivation has been shown to be relatively insensitive to photosynthetically active photon flux density (PPFD). Formation of the P680 radical (P680 + ), through charge separation at PS II, generation of triplet–state P680 ( 3 P680*), through intersystem crossing and charge recombination, and double reduction of the primary stable electron acceptor of PS II (the plastoquinone, Q A ) are all potentially critical steps in the triggering of photoinactivation. In this paper, these processes are assessed using fluorescence data from attached leaves of higher plant species, in the context of a Stern–Volmer model for downregulation and the reversible radical pair equilibrium model. It is shown that the yield of P680 + is very sensitive to PPFD and that downregulation has very little effect on its production. Consequently, it is unlikely to be the trigger for photoinactivation. The yields of 3 P680* generated through charge recombination or intersystem crossing are both less sensitive to PPFD than the yield of P680 + and are both decreased by downregulation. The yield of doubly reduced Q A increases with incident photon flux density at low levels, but is relatively insensitive at moderate to high levels, and is greatly decreased by downregulation. Consequently, 3 P680* and doubly reduced Q A are both viable as triggers of photoinactivation.

Photosynthetic Characteristics of Sun Versus Shade Plants of Encelia farinosa as Affected by Photosynthetic Photon Flux Density, Intercellular CO2 Concentration, Leaf Water Potential, and Leaf Temperature

1995 ◽  
Vol 22 (5) ◽  
pp. 833 ◽  
Author(s):  
Hehui Zhang ◽  
MR Sharifi ◽  
PS Nobel
Keyword(s):  
Electron Transport ◽  
Intercellular Co2 Concentration ◽  
Co2 Concentration ◽  
Photosynthetic Photon Flux Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Photosynthetic Photon Flux ◽  
Sun And Shade ◽  
Shade Plants ◽  
Intercellular Co2

Limitations to photosynthesis were examined for Encelia farinosa Toney et A.Gray, a common C3 sub-shrub in arid regions of south-westem United States, for plants grown in full sunlight and those shaded to 40% of full sunlight. The initial slopes of CO2 assimilation (A) versus intercellular CO2 concentration curves were similar for sun and shade plants at low photosynthetic photon flux density (PPFD) but higher for sun plants as the PPFD increased, indicating a greater limitation by carboxylation capacity in shade plants. Sun plants had higher electron transport rates but a lower ratio of electron transport capacity to carboxylation capacity (Vmax); the ratio was inversely proportional to mesophyll conductance for both sun and shade plants. Dark respiration decreased with decreasing leaf water potential (Ψ1) in sun plants but remained unchanged in shade plants; day respiration was little affected by PPFD for both sun and shade plants. Stomatal conductance (gs) was similar for sun and shade plants under high soil-moisture conditions but higher in sun plants as Ψ1 decreased; for all data considered together, changes in the leaf-air vapour pressure difference accounted for 71% of the variation in gs. The lower A for shade plants of E. farinosa apparently resulted from a lower Vmax, as well as a lower gs when plants were under water stress.

scholarly journals Effect of Pre-Harvest Supplemental UV-A/Blue and Red/Blue LED Lighting on Lettuce Growth and Nutritional Quality

Horticulturae ◽  
2021 ◽  
Vol 7 (4) ◽  
pp. 80
Author(s):  
Triston Hooks ◽  
Joseph Masabni ◽  
Ling Sun ◽  
Genhua Niu
Keyword(s):  
Blue Light ◽  
Nutritional Quality ◽  
Uv Light ◽  
Ultra Violet ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Daily Light Integral ◽  
Lettuce Growth ◽  
Supplemental Lighting

Blue light and ultra-violet (UV) light have been shown to influence plant growth, morphology, and quality. In this study, we investigated the effects of pre-harvest supplemental lighting using UV-A and blue (UV-A/Blue) light and red and blue (RB) light on growth and nutritional quality of lettuce grown hydroponically in two greenhouse experiments. The RB spectrum was applied pre-harvest for two days or nights, while the UV-A/Blue spectrum was applied pre-harvest for two or four days or nights. All pre-harvest supplemental lighting treatments had a same duration of 12 h with a photon flux density (PFD) of 171 μmol m−2 s−1. Results of both experiments showed that pre-harvest supplemental lighting using UV A/Blue or RB light can increase the growth and nutritional quality of lettuce grown hydroponically. The enhancement of lettuce growth and nutritional quality by the pre-harvest supplemental lighting was more effective under low daily light integral (DLI) compared to a high DLI and tended to be more effective when applied during the night, regardless of spectrum.

scholarly journals Light Quality Affects Water Use of Sweet Basil by Changing Its Stomatal Development

Agronomy ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 303
Author(s):  
Sungeun Lim ◽  
Jongyun Kim
Keyword(s):  
Stomatal Conductance ◽  
Blue Light ◽  
Water Use ◽  
Growth Parameters ◽  
Stomatal Density ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Stomatal Development ◽  
Sweet Basil ◽  
Stomatal Responses

Different light qualities affect plant growth and physiological responses, including stomatal openings. However, most researchers have focused on stomatal responses to red and blue light only, and the direct measurement of evapotranspiration has not been examined. Therefore, we quantified the evapotranspiration of sweet basil under various red (R), green (G), and blue (B) combinations using light-emitting diodes (LEDs) and investigated its stomatal responses. Seedlings were subjected to five different spectral treatments for two weeks at a photosynthetic photon flux density of 200 µmol m−2 s−1. The ratios of the RGB light intensities were as follows: R 100% (R100), R:G = 75:25 (R75G25), R:B = 75:25 (R75B25), R:G:B = 60:20:20 (R60G20B20), and R:G:B = 31:42:27 (R31G42B27). During the experiment, the evapotranspiration of the plants was measured using load cells. Although there were no significant differences in growth parameters among the treatments, the photosynthetic rate and stomatal conductance were higher in plants grown under blue LEDs (R75B25, R60G20B20, and R31G42B27) than in the R100 treatment. The amount of water used was different among the treatments (663.5, 726.5, 728.7, 778.0, and 782.1 mL for the R100, R75G25, R60G20B20, R75B25, and R31G42B27 treatments, respectively). The stomatal density was correlated with the blue light intensity (p = 0.0024) and with the combined intensity of green and blue light (p = 0.0029); therefore, green light was considered to promote the stomatal development of plants together with blue light. Overall, different light qualities affected the water use of plants by regulating stomatal conductance, including changes in stomatal density.

scholarly journals LED Illumination Spectrum Manipulation for Increasing the Yield of Sweet Basil (Ocimum basilicum L.)

Plants ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 344
Author(s):  
Md Momtazur Rahman ◽  
Mikhail Vasiliev ◽  
Kamal Alameh
Keyword(s):  
Growth Rate ◽  
Fold Increase ◽  
Photosynthetic Photon Flux Density ◽  
Ocimum Basilicum ◽  
Photon Flux ◽  
Photon Flux Density ◽  
White Led ◽  
Experimental Conditions ◽  
Sweet Basil ◽  
Optimal Illumination

Manipulation of the LED illumination spectrum can enhance plant growth rate and development in grow tents. We report on the identification of the illumination spectrum required to significantly enhance the growth rate of sweet basil (Ocimum basilicum L.) plants in grow tent environments by controlling the LED wavebands illuminating the plants. Since the optimal illumination spectrum depends on the plant type, this work focuses on identifying the illumination spectrum that achieves significant basil biomass improvement compared to improvements reported in prior studies. To be able to optimize the illumination spectrum, several steps must be achieved, namely, understanding plant biology, conducting several trial-and-error experiments, iteratively refining experimental conditions, and undertaking accurate statistical analyses. In this study, basil plants are grown in three grow tents with three LED illumination treatments, namely, only white LED illumination (denoted W*), the combination of red (R) and blue (B) LED illumination (denoted BR*) (relative red (R) and blue (B) intensities are 84% and 16%, respectively) and a combination of red (R), blue (B) and far-red (F) LED illumination (denoted BRF*) (relative red (R), blue (B) and far-red (F) intensities are 79%, 11%, and 10%, respectively). The photosynthetic photon flux density (PPFD) was set at 155 µmol m−2 s−1 for all illumination treatments, and the photoperiod was 20 h per day. Experimental results show that a combination of blue (B), red (R), and far-red (F) LED illumination leads to a one-fold increase in the yield of a sweet basil plant in comparison with only white LED illumination (W*). On the other hand, the use of blue (B) and red (R) LED illumination results in a half-fold increase in plant yield. Understanding the effects of LED illumination spectrum on the growth of plant sweet basil plants through basic horticulture research enables farmers to significantly improve their production yield, thus food security and profitability.

Effect of leaf age on photosynthesis and transpiration of cassava (Manihot esculenta)

1977 ◽  
Vol 55 (17) ◽  
pp. 2288-2295 ◽  
Author(s):  
M. Aslam ◽  
S. B. Lowe ◽  
L. A. Hunt
Keyword(s):  
Chlorophyll Content ◽  
Manihot Esculenta ◽  
Leaf Age ◽  
Gas Analysis ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Genotypic Differences ◽  
Specific Leaf Weight ◽  
Manihot Esculenta Crantz ◽  
Leaf Weight

The effect of plant and leaf age on CO2-exchange rates (CER) and transpiration rates in 15 genotypes of cassava (Manihot esculenta Crantz) was measured in situ by infrared gas analysis. The plants were grown in a controlled-environment room with a 14-h photoperiod, day–night temperatures of 29–24 °C, and 60–70% relative humidity.Plant age had no effect on leaf CER, whereas transpiration rates in 14-week-old plants were significantly greater than those in 7-week-old plants. Both CER and transpiration rates decreased with leaf age. The decline was negligible when measured at low photosynthetic photon flux density. At saturating light, however, both CER and transpiration rates decreased significantly in most of the genotypes. Significant genotypic differences were observed in the pattern of decline. Both stomatal (rs) and residual (rr) resistances to the diffusion of CO2 increased with leafage in all the genotypes. The relative increase in rr was much greater than the increase in rs. In all the genotypes the ratio rr:rs was greater than unity, suggesting that rr is the major component of the total resistance to photosynthesis. Chlorophyll content and specific leaf weight also varied significantly among the genotypes. However, chlorophyll content decreased and specific leaf weight increased with leaf age.

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