Assessing the role of light availability in the regeneration of Araucaria angustifolia (Araucariaceae)

2002 ◽  
Vol 50 (6) ◽  
pp. 741 ◽  
Author(s):  
L. S. Duarte ◽  
L. R. Dillenburg ◽  
L. M. G. Rosa
Keyword(s):  
Forest Succession ◽  
Light Availability ◽  
Canopy Cover ◽  
Native Forest ◽  
Araucaria Angustifolia ◽  
Light Conditions ◽  
Area Index ◽  
Species Tolerance ◽  
Role Of Light

The role of Brazilian pine (Araucaria angustifolia) in the process of forest succession is a topic of increasing controversy. While some authors consider the species to be pioneer, others consider it to be a climax species in relict temperate forests. We designed a field experiment to assess the role of light availability on the regeneration of A. angustifolia. The following three forests, with contrasting patterns of the species regeneration, were selected at a National Forest in southern Brazil: a Pinus plantation, an Araucaria plantation and a native araucarian forest. We analysed the population structure of Brazilian pine, the vegetation architecture, the light regime experienced by seedlings and the height growth of seedlings and sprouts. Brazilian pine colonisation and regeneration were observed in the Pinus and Araucaria plantations, respectively. No seedlings were found in the native forest. The greatest foliage area index and canopy cover were found in the native forest and the smallest in the Pinus plantation. In spite of the architectural differences, the native forest and the Araucaria plantation had similar light conditions and they both had lower levels of irradiances than the Pinus plantation. Seedlings and sprouts of Brazilian pine were found to occupy spots in the Araucaria plantation with canopy cover greater than the average forest conditions. Considering the similarity of understorey light conditions between the Araucaria plantation and the native forest (where no regeneration was taking place), we concluded that light availability was not limiting the regeneration of the species. Tolerance to shading and other aspects of the species indicate that Brazilian pine is not strictly heliophyllous and pioneer and is able to be established in the forest understorey.

scholarly journals The effect of light availability on leaf area index, biomass production and plant species composition of park grasslands in Warsaw  

2013 ◽  
Vol 59 (No. 12) ◽  
pp. 543-548 ◽  
Author(s):  
P. Dąbrowski ◽  
B. Pawluśkiewicz ◽  
Kalaji HM ◽  
Baczewska AH
Keyword(s):  
Solar Radiation ◽  
Leaf Area Index ◽  
Leaf Area ◽  
Light Availability ◽  
Vegetation Coverage ◽  
Light Conditions ◽  
Area Index ◽  
Sward Height ◽  
Poa Trivialis ◽  
Leaf Density

How light conditions affect development of park grasslands is a question that has not been satisfactory addressed. The aim of this study was therefore determination of the level to which unfavorable light conditions influence grassy parks area and relationships between parameters which determine state of turf grasses. Researches were conducted in two parks in Warsaw, in various light conditions and included measurement of: leaf density, sward height, leaf area index (LAI), and botanical composition of the communities. The leaf density of shaded areas did not exceed 70%. LAI value varied from 0.5 to 0.9-fold lower than in the areas in half-shade and in sun. The participation of basic lawn species at Skaryszewski Park was higher under shade, while at Łazienki Królewskie was higher in full-sunlight areas. The state of tested grassy areas in limited solar radiation does not satisfy the requirements of recreational and representational functions. The development processes of vegetation coverage were inhibited at the sites of lower solar radiation. LAI was influenced by both leaf coverage and sward height. Agrostis stolonifera and Poa trivialis may be recommended to create grass areas under limited solar radiation.

scholarly journals Spatial and temporal variability of canopy cover and understory light in a Cerrado of Southern Brazil

2010 ◽  
Vol 70 (1) ◽  
pp. 19-24 ◽  
Author(s):  
JP. Lemos-Filho ◽  
CFA. Barros ◽  
GPM. Dantas ◽  
LG. Dias ◽  
RS. Mendes
Keyword(s):  
Rainy Season ◽  
Light Availability ◽  
Canopy Cover ◽  
Dry Season ◽  
Photon Flux ◽  
Photon Flux Density ◽  
Spatial And Temporal Variability ◽  
Wet Season ◽  
Area Index ◽  
Understory Plants

Canopy cover has significant effects on the understory environment, including upon light availability for seedling growth. The aim of the present study was to verify spatial heterogeneity and seasonal changes in the canopy cover of a dense Cerrado area, and their relationship to understory photosynthetic active radiation availability. Leaf area index (LAI) values in the rainy season varied from 0.9 to 4.83, with 40% of the values ranging from 4.0 to 5.0, while in the dry season LAI varied from 0.74 to 3.3, with 53% of the values oscilating from 2.0 to 3.0. Understory light (Qi ) and the Lambert-Beer ratio (Qi/Qo) were taken around noon on sunny days (between 11:00 AM and 1:00 PM). They were also statistically different (p < 0.01) between the dry and wet seasons, with 72% of sampled points in the rainy season presenting photosynthetic photon flux density (PPFD) values lower than 250 μmol.m-2/s around noon, whereas in the dry season, most PPFD values varied from 1500 to 1817 μmol.m-2/s , thus providing high light availability for understory plants. In most of the studied sites, understory plants did not even receive enough light for 50% of their photosynthetic capacity in the wet season. In contrast during the dry season, Qi/Qo values of 0.8 to 1.0 were observed in more than 50% of the points, thereby allowing for photosynthetic light saturation. Thus, light variability around noon was higher during the dry season than in the wet season, its heterogeneity being related to spatial complexity in the canopy cover.

scholarly journals Antioxidant and Photoprotection Networking in the Coastal Diatom Skeletonema marinoi

Antioxidants ◽  
2019 ◽  
Vol 8 (6) ◽  
pp. 154 ◽  
Author(s):  
Arianna Smerilli ◽  
Sergio Balzano ◽  
Maira Maselli ◽  
Martina Blasio ◽  
Ida Orefice ◽  
...  
Keyword(s):  
External Forcing ◽  
Light Conditions ◽  
Cosmetic Products ◽  
Low Light ◽  
Physiological Regulation ◽  
Wave Distribution ◽  
Role Of Light ◽  
Antioxidant Molecule ◽  
Skeletonema Marinoi

Little is known on the antioxidant activity modulation in microalgae, even less in diatoms. Antioxidant molecule concentrations and their modulation in microalgae has received little attention and the interconnection between light, photosynthesis, photoprotection, and antioxidant network in microalgae is still unclear. To fill this gap, we selected light as external forcing to drive physiological regulation and acclimation in the costal diatom Skeletonema marinoi. We investigated the role of light regime on the concentration of ascorbic acid, phenolic compounds and among them flavonoids and their connection with photoprotective mechanisms. We compared three high light conditions, differing in either light intensity or wave distribution, with two low light conditions, differing in photoperiod, and a prolonged darkness. The change in light distribution, from sinusoidal to square wave distribution was also investigated. Results revealed a strong link between photoprotection, mainly relied on xanthophyll cycle operation, and the antioxidant molecules and activity modulation. This study paves the way for further investigation on the antioxidant capacity of diatoms, which resulted to be strongly forced by light conditions, also in the view of their potential utilization in nutraceuticals or new functional cosmetic products.

Biomass allocation in Aster acuminatus: variation within and among populations over 5 years

1985 ◽  
Vol 63 (11) ◽  
pp. 2035-2043 ◽  
Author(s):  
Jeffrey W. Ashmun ◽  
Robert L. Brown ◽  
Louis F. Pitelka
Keyword(s):  
Biomass Allocation ◽  
Clonal Growth ◽  
Standing Crop ◽  
Light Availability ◽  
Light Level ◽  
Light Regimes ◽  
Wide Range ◽  
Role Of Light ◽  
Growth And Allocation

Patterns of biomass allocation were analyzed over a 5-year period for 15 patches of the forest herb, Aster acuminatus Michx., on Kent Island, New Brunswick. The patches were distributed over a wide range of understory light regimes but otherwise occupied similar environments. In every year, light level was positively correlated with mean ramet size, ramet density, and plot standing crop (grams per square metre). This suggests that the patches were at or near their light-determined carrying capacities. There was significant variation in patterns of biomass allocation among plots in every year. This variation was always correlated with plot standing crop. In general, as standing crop increased, mean relative allocation to stems, flowers, and clonal growth increased, while allocation to leaves and rhizomes decreased. Patterns of allocation varied significantly between years for those plots sampled more than once, yet among-plot relationships with standing crop were maintained. Both thinning and shading of natural patches had pronounced effects on growth and allocation. Thinning resulted in larger plants and greater relative allocation to flowers and clonal growth, compared to controls. Shading resulted in generally opposite patterns. This study documents the important role of light availability, working directly and through intraspecific competition, in determining patterns of growth and biomass allocation in A. acuminatus.

scholarly journals The role of light in the adaptation of Thymus praecox Opiz subsp. praecox for diverse habitat conditions

2020 ◽  
Vol 48 (3) ◽  
pp. 1194-1209
Author(s):  
Beata BARABASZ-KRASNY ◽  
Katarzyna MOŻDŻEŃ ◽  
Anna SOŁTYS-LELEK ◽  
Ingrid TURISOVÁ
Keyword(s):  
Chlorophyll A ◽  
Cell Membranes ◽  
Physiological Activity ◽  
Light Availability ◽  
Dry Mass ◽  
Habitat Conditions ◽  
Partial Shade ◽  
Chlorophyll A And B ◽  
Role Of Light

The light decides about the course and efficiency of photochemical processes, being an important component of the surrounding environment shaping the plant composition in specific conditions. Thymus praecox subsp. praecox belongs to endangered taxa due to preferences for open habitats, which as a result of natural succession are exposed to overgrowth and shading with forest-scrub vegetation. In this study, an attempt was made to check the physiological activity of creeping thyme in changing environmental conditions prevailing on isolated stands in the Ojców National Park (Southern Poland). The increase in fresh and dry mass and the percentage of water in plants were determined, the content of chlorophyll a and b was measured, the intensity of chlorophyll a fluorescence was examined and the degree of electrolytes leakage through cell membranes was checked. The main aim was to determining the optimal habitat conditions for this taxon, which could help protect it. Based on the conducted research it was found, among others higher mass increase in plants from a sunny stand. Regardless of the measurement period, an increase in chlorophyll a and b content and a higher degree of cell membranes destabilisation in plants from a partially shaded stand was observed. The obtained results show, that T. praecox subsp. praecox characterises small habitat flexibility - even partial shade is not a convenient habitat for it. To optimal development, this subspecies requires conditions with high light availability. Creeping thyme is a heliophilic and thermophilic taxa and the sunny stands are optimal for it.

scholarly journals The Role of Selected Wavelengths of Light in the Activity of Photosystem II in Gloeobacter violaceus

2021 ◽  
Vol 22 (8) ◽  
pp. 4021
Author(s):  
Monika Kula-Maximenko ◽  
Kamil Jan Zieliński ◽  
Ireneusz Ślesak
Keyword(s):  
Photosystem Ii ◽  
Spectral Composition ◽  
Photosynthetic Electron Transport ◽  
Metabolic Energy ◽  
Light Conditions ◽  
Gloeobacter Violaceus ◽  
Transport Chain ◽  
Cyanobacterial Culture ◽  
Photosynthetic Antennas

Gloeobacter violaceus is a cyanobacteria species with a lack of thylakoids, while photosynthetic antennas, i.e., phycobilisomes (PBSs), photosystem II (PSII), and I (PSI), are located in the cytoplasmic membrane. We verified the hypothesis that blue–red (BR) light supplemented with a far-red (FR), ultraviolet A (UVA), and green (G) light can affect the photosynthetic electron transport chain in PSII and explain the differences in the growth of the G. violaceus culture. The cyanobacteria were cultured under different light conditions. The largest increase in G. violaceus biomass was observed only under BR + FR and BR + G light. Moreover, the shape of the G. violaceus cells was modified by the spectrum with the addition of G light. Furthermore, it was found that both the spectral composition of light and age of the cyanobacterial culture affect the different content of phycobiliproteins in the photosynthetic antennas (PBS). Most likely, in cells grown under light conditions with the addition of FR and G light, the average antenna size increased due to the inactivation of some reaction centers in PSII. Moreover, the role of PSI and gloeorhodopsin as supplementary sources of metabolic energy in the G. violaceus growth is discussed.

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