scholarly journals Effects of Light, N and Defoliation on Biomass Allocation in Poa annua

Plants ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1783
Author(s):  
Louis John Irving ◽  
Sayuki Mori
Keyword(s):  
Biomass Allocation ◽  
Light Level ◽  
Poa Annua ◽  
Root Mass ◽  
Light Conditions ◽  
Low Light ◽  
Light Levels ◽  
Below Ground ◽  
Shoot Mass

Plants allocate biomass to above- and below-ground organs in response to environmental conditions. While the broad patterns are well-understood, the mechanisms by which plants allocate new growth remain unclear. Modeling approaches to biomass allocation broadly split into functional equilibrium type models and more mechanistically based transport resistance type models. We grew Poa annua plants in split root boxes under high and low light levels, high and low N supplies, with N supplied equally or unequally. Our data suggest that light level had the strongest effect on root mass, with N level being more important in controlling shoot mass. Allocation of growth within the root system was compatible with phloem partitioning models. The root mass fraction was affected by both light and N levels, although within light levels the changes were primarily due to changes in shoot growth, with root mass remaining relatively invariant. Under low light conditions, plants exhibited increased specific leaf area, presumably to compensate for low light levels. In a follow-up experiment, we showed that differential root growth could be suppressed by defoliation under low light conditions. Our data were more compatible with transport resistance type models.

scholarly journals Interactive effects of temperature and light on reattachment success in the brown alga Fucus radicans

2019 ◽  
Vol 62 (1) ◽  
pp. 43-50
Author(s):  
Ellen Schagerström ◽  
Tiina Salo
Keyword(s):  
High Temperature ◽  
Water Temperature ◽  
Asexual Reproduction ◽  
Net Primary Production ◽  
Light Level ◽  
Interactive Effects ◽  
Low Light ◽  
Dispersal Capacity ◽  
Light Levels ◽  
The Baltic

Abstract Fucus radicans is an endemic habitat-forming brown macroalga in the Baltic Sea that commonly complements its sexual reproduction with asexual reproduction. Asexual reproduction in F. radicans takes place through formation of adventitious branches (hereafter fragments), but the exact mechanisms behind it remain unknown. We assessed experimentally the importance of two environmental factors determining the re-attachment success of F. radicans fragments. By combining different light conditions (daylength and irradiance; high or low light) and water temperature (+14°C and +4°C), we mimicked ambient light and temperature conditions of winter, spring/autumn and summer for F. radicans. Fragments were able to re-attach in all tested conditions. Temperature and light had an interactive impact on re-attachment: the combination of high temperature and high light level resulted in the highest re-attachment success, while light level had no effects on re-attachment success in cooler water temperature and the re-attachment success in high temperature under low light levels was very low. The results suggest that rhizoid formation, and thus re-attachment success, may depend on the net primary production (metabolic balance) of the fragment. However, whether the re-attachment and asexual reproduction success simply depends on photosynthetic capacity warrants further mechanistic studies. Understanding the mechanisms of asexual reproduction in F. radicans is important in order to assess the dispersal capacity of this foundation species.

scholarly journals Response time of an avian prey to a simulated hawk attack is slower in darker conditions, but is independent of hawk colour morph

2019 ◽  
Vol 6 (8) ◽  
pp. 190677 ◽  
Author(s):  
Carina Nebel ◽  
Petra Sumasgutner ◽  
Adrien Pajot ◽  
Arjun Amar
Keyword(s):  
Response Time ◽  
Response Times ◽  
Bright Light ◽  
Light Level ◽  
White Background ◽  
Light Conditions ◽  
Dark Light ◽  
Light Levels ◽  
Columbia Livia ◽  
Colour Morphs

To avoid predation, many species rely on vision to detect predators and initiate an escape response. The ability to detect predators may be lower in darker light conditions or with darker backgrounds. For birds, however, this has never been experimentally tested. We test the hypothesis that the response time of avian prey (feral pigeon Columbia livia f. domestica ) to a simulated hawk attack (taxidermy mounted colour-polymorphic black sparrowhawk Accipiter melanoleucus ) will differ depending on light levels or background colour. We predict that response will be slower under darker conditions, which would translate into higher predation risk. The speed of response of prey in relation to light level or background colour may also interact with the colour of the predator, and this idea underpins a key hypothesis proposed for the maintenance of different colour morphs in polymorphic raptors. We therefore test whether the speed of reaction is influenced by the morph of the hawk (dark/light) in combination with light conditions (dull/bright), or background colours (black/white). We predict slowest responses to morphs under conditions that less contrast with the plumage of the hawk (e.g. light morph under bright light or white background). In support of our first hypothesis, pigeons reacted slower under duller light and with a black background. However, we found no support for the second hypothesis, with response times observed between the hawk-morphs being irrespective of light levels or background colour. Our findings experimentally confirm that birds detect avian predators less efficiently under darker conditions. These conditions, for example, might occur during early mornings or in dense forests, which could lead to changes in anti-predator behaviours. However, our results provide no support that different morphs may be maintained in a population due to differential selective advantages linked to improved hunting efficiencies in different conditions due to crypsis.

Phenotypic flexibility and genetic adaptation along a gradient of secondary forest succession in the grass Danthonia spicata

1986 ◽  
Vol 64 (4) ◽  
pp. 739-747 ◽  
Author(s):  
Samuel M. Scheiner ◽  
James A. Teeri
Keyword(s):  
Forest Succession ◽  
Secondary Forest ◽  
Moisture Gradient ◽  
Pine Forests ◽  
Genetic Adaptation ◽  
Phenotypic Flexibility ◽  
Light Conditions ◽  
Low Light ◽  
Light Levels ◽  
Danthonia Spicata

Populations of Danthonia spicata were studied from sites of ages 0, 26, 32, 44, and 69 years after fire in the aspen–pine forests of northern lower Michigan. Along this gradient the environment changes from unshaded and dry to a shaded, moist pine and hardwood forest. Greenhouse treatments and transplant gardens were used to investigate the extent to which phenotypic flexibility and genetic adaptation were responsible for the persistence of D. spicata across this light and soil moisture gradient. With regard to phenotypic flexibility, we found that individual plants of D. spicata can grow and reproduce in light levels lower than those found at any site in the field. The populations were genetically distinct from each other but the differences were small relative to the range of phenotypic flexibility. Some populations and individuals performed better under high light conditions and all individuals performed equally poorly under low light conditions. A multivariate analysis suggests that genetic drift may have been more important than selection in differentiating the populations. Phenotypic flexibility was shown to be more important than genetic adaptation in explaining the persistence of D. spicata along the successional gradient.

scholarly journals Adjustable light source for low light level with nearly constant correlated color temperature

2022 ◽  
Vol 2149 (1) ◽  
pp. 012016
Author(s):  
Z F Wu ◽  
L Li ◽  
C H Dai ◽  
Y F Wang ◽  
Q T Cheng ◽  
...  
Keyword(s):  
Light Source ◽  
Spectral Distribution ◽  
Light Level ◽  
Color Temperature ◽  
Spectral Radiance ◽  
Integrating Sphere ◽  
Spectral Difference ◽  
Low Light ◽  
Light Levels ◽  
Variable Aperture

Abstract Low light level (LLL) calibration becomes more and more important since the rapid growth of remote sensing. The spectral radiance at normal higher light levels can be calibrated with good accuracy, while LLL spectral radiance cannot. If an adjustable light source can be designed at nearly constant correlated color temperature (CCT) covering several orders of magnitude, low light level spectral radiance can be obtained with the help of a photodetector. Whether or not the spectral distribution of an integrating sphere based light source is nearly constant is investigated. By adjusting the diameter of the variable aperture between the integrating sphere and tungsten lamp, the spectral radiance can be varied over 6 orders of magnitude. However, the relative spectrum in the red region increases notably when the spectral radiance is decreased to 1/100000. If the spectral radiance is decreased further, the spectral difference can be more than 300% and CCT decreases more than 250 K. By using baffles and another integrating sphere, low light level radiation source at nearly constant spectral distribution is obtained. The variation of CCT is less than 50 K over 6 orders of magnitude.

scholarly journals Biomass allocation of chestnut oak (Quercus castaneifolia C.A. Mey) seedlings: effects of provenance and light gradient

2014 ◽  
Vol 60 (No. 11) ◽  
pp. 443-450 ◽  
Author(s):  
F. Babaei Sustani ◽  
S.G. Jalali ◽  
H. Sohrabi ◽  
A. Shirvani
Keyword(s):  
Biomass Allocation ◽  
Leaf Size ◽  
Growth Conditions ◽  
High Irradiance ◽  
Growth Strategies ◽  
Low Light ◽  
Rainfall Gradient ◽  
Light Levels ◽  
Light Gradient ◽  
Precipitation Regimes

Patterns of biomass allocation were determined for seedlings of five provenances of Quercus castaneifolia from west to east of the Hyrcanian forest along a rainfall gradient. Experimental design was executed under controlled conditions at seven different light levels (10, 20, 30, 40, 50, 60, 70 and 100% full light). We quantified the biomass allocation patterns to leaves, stems and roots. For all provenances total mass increased with irradiance at low light levels, reaching an optimum at an intermediate level but decreasing at a high irradiance level. As results show, in drier provenances and at high light levels, the seedlings invest more biomass into root mass to facilitate water uptake and to alter their leaf size to prevent overheating. In contrast, at wetter provenances and low light levels, towards increased light interception, more biomass is allocated proportionally to leaves and the stems but, accordingly, less to roots. The leaf to root ratio (L/R) was negatively correlated with light, with high correlation at wetter provenances compared to drier ones. In contrast, the relationship between the root to shoot (R/Sh) ratio and light was positively correlated with light, but it was weak at drier provenances and became gradually stronger at wetter ones. Such relationships indicated that chestnut oak seedling growth strategies are different along a rainfall gradient to irradiance levels. Despite similar growth conditions in the greenhouse, different growth strategies may be the result of genetic adaptation to the ecological conditions, especially when precipitation regimes prevail in the native habitat.  

An Evaluative Study of Three Photographic Focusing Screens under Two Levels of Illumination

1980 ◽  
Vol 9 (1) ◽  
pp. 37-44
Author(s):  
John B. Bunch
Keyword(s):  
Light Level ◽  
Illumination Level ◽  
Low Light ◽  
Evaluative Study ◽  
Light Levels ◽  
High Illumination ◽  
Significant Difference ◽  
Low Illumination ◽  
Post Hoc

The purpose of this experiment was to evaluate the ability of photography students to focus a camera accurately under two levels of illumination (high/low) with three types of focusing screens (plain groundglass, split-image and microprism). The participants were required to focus each screen three times under each light level; scores were focus errors in feet. A 2 × 3 MANOVA design was used, and post hoc comparisons were made for plain vs. split-image, plain vs. microprism, and plain vs. microprism and split-image combined. There was significantly less focus error (p < .05) under the low illumination level, but no significant difference between screen types across both light levels. The screen type X light level interaction was much higher than the p .05 required in this study. Plain groundglass produced the least overall error; microprism yielded the least error under low illumination and the highest error under high illumination; and split-image was the most accurate under high illumination and the least accurate for the low light level condition.

scholarly journals Morphological and Photosynthetic Response to High and Low Irradiance ofAeschynanthus longicaulis

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Qiansheng Li ◽  
Min Deng ◽  
Yanshi Xiong ◽  
Allen Coombes ◽  
Wei Zhao
Keyword(s):  
Light Stress ◽  
High Irradiance ◽  
Anthocyanin Content ◽  
Light Conditions ◽  
Leaf Color ◽  
Low Light ◽  
Light Levels ◽  
Chlorophyll Fluorescence Parameter ◽  
Fluorescence Parameter ◽  
Length Width

Aeschynanthus longicaulisplants are understory plants in the forest, adapting to low light conditions in their native habitats. To observe the effects of the high irradiance on growth and physiology, plants were grown under two different light levels, PPFD 650 μmol·m–2·s–1and 150 μmol·m–2·s–1for 6 months. Plants under high irradiance had significantly thicker leaves with smaller leaf area, length, width, and perimeter compared to the plants grown under low irradiance. Under high irradiance, the leaf color turned yellowish and the total chlorophyll decreased from 5.081 mg·dm−2to 3.367 mg·dm−2. The anthocyanin content of high irradiance leaves was double that of those under low irradiance. The plants under high irradiance had significantly lower Amax(5.69 μmol·m–2·s–1) and LSP (367 μmol·m–2·s–1) and higher LCP (21.9 μmol·m–2·s–1). The chlorophyll fluorescence parameterFv/Fmwas significantly lower and NPQ was significantly higher in high irradiance plants. RLCs showed significantly lowerETRmax⁡andEkin plants under high irradiance. It can be concluded that the maximum PPFD of 650 μmol·m–2·s–1led to significant light stress and photoinhibition ofA. longicaulis.

scholarly journals Plastic responses in the coral Pocillopora acuta to extreme low-light conditions with and without food provision

2021 ◽  
Vol 168 (7) ◽  
Author(s):  
Jenny Fong ◽  
Rosa Celia Poquita-Du ◽  
Peter A. Todd
Keyword(s):  
Species Differences ◽  
Light Level ◽  
Ambient Light ◽  
Light Conditions ◽  
Feeding Rates ◽  
Low Light ◽  
Reef Environment ◽  
Ambient Light Level ◽  
Related Stress ◽  
Plastic Responses

AbstractThis study examines phenotypically plastic responses in Pocillopora acuta collected from a highly urbanized reef environment to extreme low-light conditions. While among-species differences in how corals cope with low light are well documented, much less is known about within-species responses. It also remains unclear how extreme low light and provision of food may interact and influence coral physiology. Clonal fragments from six colonies (genotypes) of P. acuta were subjected to two light treatments with mean midday irradiances of 4 and 40 μmol photons m−2 s−1 photosynthetically active radiation (PAR), representing just 0.5 and 5% ambient light level, and were either fed with zooplankton or not fed for nine days. Corals maintained in 4 PAR had lower endosymbiont density but higher cellular chlorophyll a concentration than those in 40 PAR. Feeding rates were similar in both light treatments and had no significant effects on endosymbiont density and chlorophyll a concentrations. While genotypes varied in the level of phenotypic plasticity expressed for both photoacclimation and heterotrophy, most displayed similar directions in their responses, indicating photoacclimation in P. acuta is broadly predictable. Our study demonstrates that P. acuta from Singapore is able to acclimate to very low-light conditions by adjusting their photophysiology, providing additional evidence that this species is resilient to urbanization-related stress.

scholarly journals Learning to feed in the dark: how light level influences feeding in the hawkmoth Manduca sexta

2021 ◽  
Vol 17 (9) ◽  
pp. 20210320
Author(s):  
Tanvi Deora ◽  
Mahad A. Ahmed ◽  
Bingni W. Brunton ◽  
Thomas L. Daniel
Keyword(s):  
Motor Control ◽  
Manduca Sexta ◽  
Three Dimensional ◽  
Light Level ◽  
Artificial Light ◽  
Motion Sensors ◽  
Light Conditions ◽  
Light At Night ◽  
Light Levels ◽  
Artificial Flowers

Nocturnal insects like moths are essential for pollination, providing resilience to the diurnal pollination networks. Moths use both vision and mechanosensation to locate the nectary opening in the flowers with their proboscis. However, increased light levels due to artificial light at night (ALAN) pose a serious threat to nocturnal insects. Here, we examined how light levels influence the efficacy by which the crepuscular hawkmoth Manduca sexta locates the nectary. We used three-dimensional-printed artificial flowers fitted with motion sensors in the nectary and machine vision to track the motion of hovering moths under two light levels: 0.1 lux (moonlight) and 50 lux (dawn/dusk). We found that moths in higher light conditions took significantly longer to find the nectary, even with repeated visits to the same flower. In addition to taking longer, moths in higher light conditions hovered further from the flower during feeding. Increased light levels adversely affect learning and motor control in these animals.

scholarly journals Postharvest Handling of Cut Campanula medium Flowers

HortScience ◽  
2002 ◽  
Vol 37 (6) ◽  
pp. 954-958 ◽  
Author(s):  
Theresa Bosma ◽  
John M. Dole
Keyword(s):  
Sucrose Concentration ◽  
High Light ◽  
Deionized Water ◽  
Vase Life ◽  
Light Conditions ◽  
Low Light ◽  
Storage Duration ◽  
Light Levels ◽  
Postharvest Handling

Various postharvest treatments were evaluated for effect on longevity and quality of cut Campanula medium L. `Champion Blue' and `Champion Pink' stems. Stems stored at 2 °C either wet or dry had no difference in vase life or percent flowers opened; however, flowers stored dry had a slightly greater percentage of senesced flowers at termination. Increasing storage duration from 1 to 3 weeks decreased vase life. Stems pretreated for 4 hours with 38 °C floral solution (deionized water amended to pH 3.5 with citric acid and 200 mg·L-1 8-HQC) or a 1-MCP pulse followed by a 5% sucrose pulse solution produced the longest vase life (10.3 or 10.4 days, respectively). Flowers opening after treatments commenced were paler than those flowers already opened and a 24-hour pretreatment with 5% or 10% sucrose did not prevent this color reduction. Stems had an average vase life of only 3.3 days when placed in floral vase foam but lasted 10.0 days without foam. Optimum sucrose concentration was 1.0% to 2.0% for stems placed in 22 °C floral vase solution without foam and 4% for stems placed in foam. High (110 μmol·m-2·s-1) or low (10 μmol·m-2·s-1) light levels did not affect postharvest parameters, but the most recently opened flowers were paler under low light conditions than under high light conditions. Chemical names used: 8-hydroxyquinoline citrate (8-HQC); 1-methylcyclopropene (1-MCP).

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