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.

Variation in Chlorophyll a and b in the Seagrass Halodule in Central Visayas, Philippines

2014 ◽  
Vol 8 (1) ◽  
Author(s):  
BILLY THEODORUS WAGEY
Keyword(s):  
Chlorophyll Content ◽  
Chlorophyll A ◽  
Photosynthetic Activity ◽  
Light Availability ◽  
Experimental Manipulation ◽  
Marine Ecology ◽  
Chlorophyll A And B ◽  
Photosynthetic Performances ◽  
Plastic Responses ◽  
One Way Anova

Chlorophyll content of seagrass leaves varies among species and habitats byat least a factor of five, and shows plastic responses to seasonal variations in light availability as well as direct experimental manipulation. This study generally attempted to observe the relative amount of chlorophyll a, b content of Haloduleuninervis and Halodule pinifolia in Central Visayas, Philippines in relation tothese environmental factors which are: exposure, density, temperature, and lightintensity. Chlorophyll was determined using the equation of Jeffrey and Humprey(1975) whereas data gathered went through one way ANOVA followed byTukey’s Test. Significant variations were found in most photosynthetic parametersmeasured in this study. Overall, H. uninervis and H. pinifolia seems to obtainoptimal photosynthetic performances over a broad range of irradiances. Mainly,genus Halodule can be seen as a highlight species, which has also the ability to acclimate to low irradiances. in general, the result indicated that seagrasses tend to decrease the ratio of chlorophyll a:b by increasing the amount of chlorophyllb to compensate for the decline in light intensity in subtidal areas. Therefore, H.uninervis and H. pinifolia seem to have the ability of adjusting their chlorophyllcontent in performing optimal photosynthetic activity over a broad range of irradiance regimes.Keywords: Marine Ecology, chlorophyll content, seagrass, Halodule, experimental design,Philippines

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 Effect of foliar or soil application of selenium on some morphological and physiological traits of garden pansy (Viola x wittrockiana Gams) grown under salinity stress

2020 ◽  
Vol 115 (2) ◽  
pp. 357
Author(s):  
Farima JAVADI ◽  
Sepideh KALATEJARI ◽  
Marjan DIYANAT
Keyword(s):  
Chlorophyll A ◽  
Salinity Stress ◽  
Morphological Traits ◽  
Foliar Application ◽  
Dry Mass ◽  
Sodium Selenate ◽  
Viola X Wittrockiana ◽  
Chlorophyll A And B ◽  
Morphological And Physiological Traits ◽  
Fresh And Dry Mass

<p>Salinity stress is one of the most important plant stresses in Iran. In this regard, a factorial experiment was conducted to investigate the effects of salinity stress on the garden pansy. The investigated factors were containing sodium selenate (0, 2, 4 and 8 mg l<sup>-1</sup>), its method of application (foliar and soil applications) and salinity stress (0, 3 and 6 dS m<sup>-1</sup>). The obtained results indicated that salinity leads to the significant reduction in morphological traits, chlorophyll a and b contents. Under the salinity of 6 dS m<sup>-1</sup>, when sodium selenate was used in the soil, the fresh and dry mass of flower increased by 11.34 and 10.39 %, respectively, compared to the control. However, the use of sodium selenate by foliar application led to the increasing fresh and dry mass of garden pansy’s flower by 25.10 and 25.41 %, respectively. Also, the content of chlorophyll a increased by 12.93 % under the salinity of 6 dS m-1 with applying 8 mg l<sup>-1</sup>sodium selenate compared to the case of non-application. The superoxide dismutase activity decreased by 26.13 % compared to the non-sodium selenate usage treatment. In conclusion the foliar application of sodium selenate at the concentraion of 8 mg l<sup>-1</sup> resulted in the garden pansy’s growth improvement.</p>

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 Changes in the chlorophyll a and b content in different-aged leaves of Spergula vernalis Willd.

2015 ◽  
Vol 43 (2) ◽  
pp. 235-241
Author(s):  
Ewa Symonides
Keyword(s):  
Organic Matter ◽  
Chlorophyll A ◽  
Seasonal Variations ◽  
Habitat Conditions ◽  
Chlorophyll A And B ◽  
Green Pigments

The result are reported of investigations on the seasonal variations in the chlorophyll a and b content in the successive leaf tiers of <i>Spergula vernalis</i> Willd. growing in two different dune habitats. It was endeavoured to determine the influence of habitat conditions on the concentration of green pigments. The eventual relationship between their amount and the production of organic matter by the plants is discussed.

STEROID HORMONE METABOLISM IN RESPONSIVE TISSUES IN VITRO

1971 ◽  
Vol 68 (1_Suppl) ◽  
pp. S279-S294 ◽  
Author(s):  
Paul Robel
Keyword(s):  
Steroid Hormone ◽  
Physiological Activity ◽  
Physiological State ◽  
Target Cells ◽  
Target Tissue ◽  
Hormone Metabolism ◽  
Metabolizing Enzymes ◽  
Relationship Of

ABSTRACT Of the information available on steroid hormone metabolism in responsive tissues, only that relating hormone metabolism to physiological activity is reviewed, i. e. metabolite activity in isolated in vitro systems, binding of metabolites to target tissue receptors, specific steroid hormone metabolizing enzymes and relationship of hormone metabolism to target organ physiological state. Further, evidence is presented in the androgen field, demonstrating 5α-reduced metabolites, formed inside the target cells, as active compounds. This has led to a consideration of testosterone as a »prehormone«. The possibility that similar events take place in tissues responding to progesterone is discussed. Finally, the role of hormone metabolism in the regulation of hormone availability and/or renewal in target cells is discussed. In this context, reference is made to the potential role of plasma binding proteins and cytosol receptors.

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