scholarly journals A Comparison of Light Acclimatization Methods for Reduction of Interior Leaf Drop in Ficus spp.

1987 ◽  
Vol 5 (3) ◽  
pp. 102-104
Author(s):  
Melanie A. Turner ◽  
David Wm. Reed ◽  
David L. Morgan
Keyword(s):  
Photosynthetically Active Radiation ◽  
Poor Correlation ◽  
Active Radiation ◽  
Ficus Benjamina ◽  
Light Intensities ◽  
Constant Rate ◽  
Leaf Drop ◽  
Post Production ◽  
Interior Environment

Two acclimatization methods at 5 light intensities were investigated for indoor maintenance of Ficus benjamina and F. stricta. Plants were either grown at 5 production shade levels of full-sun (1685 μEm−2s−1) to 80% shade (340 μEm−2s−1) for 8 wks then placed directly into a simulated interior environment for 12 wks, or were grown in full-sun for 8 wks then acclimatized for 6 wks at 5 post-production shade levels prior to placement indoors. Photosynthetically active radiation (PAR) in the interior was set at 10.5 μEm−2s−1 (78 ft-c). For F. benjamina, the full-sun treatment caused the highest degree of defoliation and as production or post-production shade level increased, defoliation decreased. F. stricta showed similar effects under post-production shade, but under production shade levels there was a poor correlation between percent shade and leaf drop. There appeared to be two or three periods of leaf drop after placement indoors as opposed to a constant rate of defoliation.

scholarly journals Phototaxis of Fungus Gnat, Bradysia sp. nr coprophila (Lintner) (Diptera: Sciaridae), Adults to Different Light Intensities

HortScience ◽  
2007 ◽  
Vol 42 (5) ◽  
pp. 1217-1220 ◽  
Author(s):  
Raymond A. Cloyd ◽  
Amy Dickinson ◽  
Richard A. Larson ◽  
Karen A. Marley
Keyword(s):  
Light Intensity ◽  
Light Source ◽  
Photosynthetically Active Radiation ◽  
Management Strategy ◽  
Detection Threshold ◽  
Multiple Choice ◽  
Active Radiation ◽  
Light Intensities ◽  
Fungus Gnats ◽  
Fungus Gnat

Multiple-choice experimental arenas, with sample compartments, were used to assess the response of fungus gnat, Bradysia sp. nr. coprophila (Lintner) (Diptera: Sciaridae), adults to varying light intensities in environmentally controlled walk-in chambers. Each sample compartment contained a yellow sticky card (2.5 × 2.5 cm) to capture fungus gnat adults. Under conditions of darkness, fungus gnat adults migrated randomly with no significant differences among the six sample compartments. Fungus gnat adults were observed to positively respond to light intensities less than 0.08374 μmol·m−2·s−1. In addition, adults responded to light intensities that were below the detection threshold of a photosynthetically active radiation light sensor. A higher percentage of fungus gnat adults (22% to 39%) were captured on yellow sticky cards in the sample compartments that were closest to a directional light source compared with sample compartments that were located further away from the light source (2% to 9%). Fungus gnat adults exhibited a significant response when exposed to two distinct ranges of light intensities (0.12 to 0.26 versus 0.87 to 1.02 μmol·m−2·s−1) with adults significantly more attracted to the highest light intensities (0.87 to 1.02 μmol·m−2·s−1). The results obtained in this study indicate that fungus gnat adults are positively phototactic, and as light intensity increases, they display a preference for those higher light intensities. It is possible that modifications in light intensity may be a feasible management strategy for alleviating problems with fungus gnats in greenhouses.

scholarly journals A microbiota–root–shoot circuit favours Arabidopsis growth over defence under suboptimal light

Nature Plants ◽  
2021 ◽  
Author(s):  
Shiji Hou ◽  
Thorsten Thiergart ◽  
Nathan Vannier ◽  
Fantin Mesny ◽  
Jörg Ziegler ◽  
...  
Keyword(s):  
Stress Responses ◽  
Photosynthetically Active Radiation ◽  
Bacterial Community Composition ◽  
Light Condition ◽  
Long Distance ◽  
Active Radiation ◽  
Light Manipulation ◽  
Growth Deficiency ◽  
Dependent Growth ◽  
Control Light

AbstractBidirectional root–shoot signalling is probably key in orchestrating stress responses and ensuring plant survival. Here, we show that Arabidopsis thaliana responses to microbial root commensals and light are interconnected along a microbiota–root–shoot axis. Microbiota and light manipulation experiments in a gnotobiotic plant system reveal that low photosynthetically active radiation perceived by leaves induces long-distance modulation of root bacterial communities but not fungal or oomycete communities. Reciprocally, microbial commensals alleviate plant growth deficiency under low photosynthetically active radiation. This growth rescue was associated with reduced microbiota-induced aboveground defence responses and altered resistance to foliar pathogens compared with the control light condition. Inspection of a set of A. thaliana mutants reveals that this microbiota- and light-dependent growth–defence trade-off is directly explained by belowground bacterial community composition and requires the host transcriptional regulator MYC2. Our work indicates that aboveground stress responses in plants can be modulated by signals from microbial root commensals.

scholarly journals Intercepted Photosynthetically Active Radiation (PAR) and Spatial and Temporal Distribution of Transmitted PAR under High-Density and Super High-Density Olive Orchards

Agriculture ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 351
Author(s):  
Adolfo Rosati ◽  
Damiano Marchionni ◽  
Dario Mantovani ◽  
Luigi Ponti ◽  
Franco Famiani
Keyword(s):  
Spatial Variability ◽  
Photosynthetically Active Radiation ◽  
Temporal Distribution ◽  
High Density ◽  
Radiation Use Efficiency ◽  
Spatial And Temporal Distribution ◽  
Active Radiation ◽  
Use Efficiency ◽  
And Performance ◽  
Radiation Use

We quantified the photosynthetically active radiation (PAR) interception in a high-density (HD) and a super high-density (SHD) or hedgerow olive system, by measuring the PAR transmitted under the canopy along transects at increasing distance from the tree rows. Transmitted PAR was measured every minute, then cumulated over the day and the season. The frequencies of the different PAR levels occurring during the day were calculated. SHD intercepted significantly but slightly less overall PAR than HD (0.57 ± 0.002 vs. 0.62 ± 0.03 of the PAR incident above the canopy) but had a much greater spatial variability of transmitted PAR (0.21 under the tree row, up to 0.59 in the alley center), compared to HD (range: 0.34–0.43). This corresponded to greater variability in the frequencies of daily PAR values, with the more shaded positions receiving greater frequencies of low PAR values. The much lower PAR level under the tree row in SHD, compared to any position in HD, implies greater self-shading in lower-canopy layers, despite similar overall interception. Therefore, knowing overall PAR interception does not allow an understanding of differences in PAR distribution on the ground and within the canopy and their possible effects on canopy radiation use efficiency (RUE) and performance, between different architectural systems.

scholarly journals Estimation of Incident Photosynthetically Active Radiation from GOES Visible Imagery

2008 ◽  
Vol 47 (3) ◽  
pp. 853-868 ◽  
Author(s):  
Tao Zheng ◽  
Shunlin Liang ◽  
Kaicun Wang
Keyword(s):  
Photosynthetically Active Radiation ◽  
Terrestrial Ecosystem ◽  
New Method ◽  
High Temporal Resolution ◽  
Atmospheric Conditions ◽  
Ecosystem Models ◽  
Surface Conditions ◽  
Active Radiation ◽  
Ground Measurement ◽  
Visible Imagery

Abstract Incident photosynthetically active radiation (PAR) is an important parameter for terrestrial ecosystem models. Because of its high temporal resolution, the Geostationary Operational Environmental Satellite (GOES) observations are very suited to catch the diurnal variation of PAR. In this paper, a new method is developed to derive PAR using GOES data. What makes this new method distinct from the existing method is that it does not need external knowledge of atmospheric conditions. The new method retrieves both atmospheric and surface conditions using only at-sensor radiance through interpolation of time series of observations. Validations against ground measurement are carried out at four “FLUXNET” sites. The values of RMSE of estimated and ground-measured instantaneous PAR at the four sites are 130.71, 131.44, 141.16, and 190.22 μmol m−2 s−1, respectively. At the four validation sites, the RMSE as the percentage of estimated mean PAR value are 9.52%, 13.01%, 13.92%, and 24.09%, respectively; the biases are −101.54, 16.56, 11.09, and 53.64 μmol m−2 s−1, respectively. The independence of external atmospheric information enables this method to be applicable to many situations in which external atmospheric information is not available. In addition, topographic impacts on surface PAR are examined at the 1-km resolution at which PAR is retrieved using the GOES visible band data.

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