scholarly journals Fluorescence characteristics and photoinhibition in saplings of manwood on clear days and under overcast conditions

2007 ◽  
Vol 64 (6) ◽  
pp. 595-600 ◽  
Author(s):  
Daniela Pereira Dias ◽  
Ricardo Antonio Marenco
Keyword(s):  
Leaf Surface ◽  
High Irradiance ◽  
Photoinhibition Of Photosynthesis ◽  
Low Light ◽  
Sharp Rise ◽  
Tropical Plants ◽  
Fluorescence Characteristics ◽  
Photon Fluence ◽  
Plant Exposure ◽  
Quantum Yield Of Psii

High irradiance may reduce the productivity of tropical plants by exacerbating photoinhibition of photosynthesis, particularly in the case of shade-adapted plants. The aim of this study was to determine the effect of cloud cover on the fluorescence characteristics and photoinhibition on saplings of manwood (Minquartia guianensis Aubl.). Three-year-old saplings were exposed to full irradiance either on clear days (10, 45 and 90 min) or under overcast conditions (120, 180, and 420 min). Changes in the population of functional photosystem II (PSII), the initial (Fo) and maximum fluorescences (Fm), and the Fv/Fm ratio (maximum potential quantum yield of PSII) were monitored after plant exposure to full irradiance and during recovery (within 48 h) at low light intensity. Although photoinhibition of PSII (Fv/Fm) was determined by the number of photons reaching the leaf surface (photon fluence), cloudiness tended to reduce the photoinhibitory effect of irradiance. Fo increased with fluence on cloudy days and was unaffected by irradiance on clear days, except for a sharp rise during the first 10 min of exposure to full sunlight. For a given photon fluence, Fm was lower on clear days. Recovery from photoinhibition was similar in both light environments. Although photon fluence is the preponderant factor determining the extent of photoinhibition, cloudiness might alleviate the photoinhibitory effect of irradiance.

Photoinhibition of Photosynthesis in situ in Six Species of Eucalyptus

1992 ◽  
Vol 19 (3) ◽  
pp. 223 ◽  
Author(s):  
E Ogren ◽  
JR Evans
Keyword(s):  
Quantum Yield ◽  
Time Course ◽  
O2 Evolution ◽  
Photoinhibition Of Photosynthesis ◽  
Low Light ◽  
First Order ◽  
Psii Photochemistry ◽  
Kinetics Of ◽  
Quantum Yield Of Psii

Photoinhibition of photosynthesis was investigated in horizontally and vertically restrained leaves of Eucalyptus plants growing outdoors. This was done by measuring the quantum yield of PSII photochemistry, assayed by the ratio of variable to maximal fluorescence (FV/FM) after 15 min of dark adaptation, and the quantum yield of O2 evolution. On clear days, a time-dependent depression in both parameters was observed. Though horizontal leaves showed stronger photoinhibition (max. 40%) than did vertical leaves (max. 30%), this difference was smaller than the threefold difference in light interception. Since the inherent susceptibility to photoinhibition was the same in vertical and horizontal leaves, a non-linear light dependence of photoinhibition was assumed. The time course of recovery from photoinhibition under low light followed the kinetics of a first order reaction, with 50% recovery after 45 min. When watering was restricted on a hot and clear day a more severe photoinhibition developed in horizontal leaves, which took several days of low light to overcome. This photoinhibition state was triggered by high leaf temperatures, resulting from decreased stomatal conductance and transpiration, which sensitised the leaf to light.

Does Astaxanthin Protect Haematococcus against Light Damage?

1998 ◽  
Vol 53 (1-2) ◽  
pp. 93-100 ◽  
Author(s):  
Lu Fan ◽  
Avigad Vonshak ◽  
Aliza Zarka ◽  
Sammy Boussiba
Keyword(s):  
Light Intensity ◽  
Light Stress ◽  
Phosphate Starvation ◽  
High Light Intensity ◽  
High Irradiance ◽  
High Light ◽  
Protective Agent ◽  
Light Damage ◽  
Low Light ◽  
Very High

Abstract The photoprotective function of the ketocarotenoid astaxanthin in Haematococcus was questioned. When exposed to high irradiance and/or nutritional stress, green Haematococcus cells turned red due to accumulation of an immense quantity of the red pigment astaxanthin. Our results demonstrate that: 1) The addition of diphenylamine, an inhibitor of astaxanthin biosynthesis, causes cell death under high light intensity; 2) Red cells are susceptible to high light stress to the same extent or even higher then green ones upon exposure to a very high light intensity (4000 μmol photon m-2 s-1); 3) Addition of 1O2 generators (methylene blue, rose bengal) under noninductive conditions (low light of 100 (μmol photon m-2 s-1) induced astaxanthin accumulation. This can be reversed by an exogenous 1O2 quencher (histidine); 4) Histidine can prevent the accumulation of astaxanthin induced by phosphate starvation. We suggest that: 1) Astaxanthin is the result of the photoprotection process rather than the protective agent; 2) 1O2 is involved indirectly in astaxanthin accumulation process.

scholarly journals Apex structures enhance water drainage on leaves

2020 ◽  
Vol 117 (4) ◽  
pp. 1890-1894 ◽  
Author(s):  
Ting Wang ◽  
Yifan Si ◽  
Haoyu Dai ◽  
Chuxin Li ◽  
Can Gao ◽  
...  
Keyword(s):  
Leaf Surface ◽  
Control Mechanisms ◽  
Water Drainage ◽  
Tropical Plants ◽  
Leaf Apex ◽  
Drainage Rate ◽  
Retention Volumes ◽  
Rapid Removal ◽  
Shape Changes ◽  
Surface Changes

The rapid removal of rain droplets at the leaf apex is critical for leaves to avoid damage under rainfall conditions, but the general water drainage principle remains unclear. We demonstrate that the apex structure enhances water drainage on the leaf by employing a curvature-controlled mechanism that is based on shaping a balance between reduced capillarity and enhanced gravity components. The leaf apex shape changes from round to triangle to acuminate, and the leaf surface changes from flat to bent, resulting in the increase of the water drainage rate, high-dripping frequencies, and the reduction of retention volumes. For wet tropical plants, such as Alocasia macrorrhiza, Gaussian curvature reconfiguration at the drip tip leads to the capillarity transition from resistance to actuation, further enhancing water drainage to the largest degree possible. The phenomenon is distinct from the widely researched liquid motion control mechanisms, and it offers a specific parametric approach that can be applied to achieve the desired fluidic behavior in a well-controlled way.

scholarly journals Cell Cycle Regulation by Light inProchlorococcus Strains

2001 ◽  
Vol 67 (2) ◽  
pp. 782-790 ◽  
Author(s):  
Stéphan Jacquet ◽  
Frédéric Partensky ◽  
Dominique Marie ◽  
Raffaella Casotti ◽  
Daniel Vaulot
Keyword(s):  
Cell Cycle ◽  
High Irradiance ◽  
S Phase ◽  
Low Light ◽  
Close Coupling ◽  
Cell Cycles ◽  
Flow Cytometric ◽  
Initiation Of Dna Replication ◽  
Cell Cycling ◽  
Cycle Regulation

ABSTRACT The effect of light on the synchronization of cell cycling was investigated in several strains of the oceanic photosynthetic prokaryote Prochlorococcus using flow cytometry. When exposed to a light-dark (L-D) cycle with an irradiance of 25 μmol of quanta · m−2 s−1, the low-light-adapted strain SS 120 appeared to be better synchronized than the high-light-adapted strain PCC 9511. Submitting L-D-entrained populations to shifts (advances or delays) in the timing of the “light on” signal translated to corresponding shifts in the initiation of the S phase, suggesting that this signal is a key parameter for the synchronization of population cell cycles. Cultures that were shifted from an L-D cycle to continuous irradiance showed persistent diel oscillations of flow-cytometric signals (light scatter and chlorophyll fluorescence) but with significantly reduced amplitudes and a phase shift. Complete darkness arrested most of the cells in the G1 phase of the cell cycle, indicating that light is required to trigger the initiation of DNA replication and cell division. However, some cells also arrested in the S phase, suggesting that cell cycle controls in Prochlorococcus spp. are not as strict as in marine Synechococcus spp. ShiftingProchlorococcus cells from low to high irradiance translated quasi-instantaneously into an increase of cells in both the S and G2 phases of the cell cycle and then into faster growth, whereas the inverse shift induced rapid slowing of the population growth rate. These data suggest a close coupling between irradiance levels and cell cycling in Prochlorococcus spp.

Distinction and characterisation of submergence tolerant and sensitive rice cultivars, probed by the fluorescence OJIP rise kinetics

2009 ◽  
Vol 36 (3) ◽  
pp. 222 ◽  
Author(s):  
Ramani Kumar Sarkar ◽  
Debabrata Panda
Keyword(s):  
Photosynthetic Rate ◽  
Oryza Sativa L ◽  
Indica Rice ◽  
Light Stress ◽  
Elongation Growth ◽  
Rice Cultivars ◽  
Low Light ◽  
Test Parameters ◽  
Fluorescence Characteristics ◽  
Low Light Stress

Rice (Oryza sativa L.) plants experience multiple abiotic stresses when they are submerged. In addition to the effects of submergence on gas exchange, water also creates shading of submerged plants. It is believed that responses to submergence are actually responses to low light stress, although during complete submergence in addition to low light other environmental factors like reduce movement of gases affect the plant growth, and therefore, the consequences of submergence are not always alike to shade. We monitored the extent to which shade and submergence change the plant height, chlorophyll a fluorescence characteristics and CO2 photosynthetic rate in three Indica rice cultivars, namely Sarala, Kalaputia and Khoda, which differed in submergence tolerance. There were both similarities and dissimilarities between the consequence of shade and submergence on rice plants. Under shade conditions, elongation growth was greater in submergence tolerant cultivars than the sensitive cultivar, whereas elongation growth was greater under submergence in sensitive cultivar. The reduction in chlorophyll content, damage to PSII, and decrease in CO2 photosynthetic rate was more notable under submergence than the shade conditions. Our results show that several JIP-test parameters clearly distinguish between submergence tolerant and sensitive cultivars, and responses to submergence among different rice cultivars differ depending on their sensitivity to submergence. There were different interactions between cultivar and shade (~low light) and cultivar and submergence.

PHOTOACCLIMATION IN PHOTOSYNTHETIC MICROORGANISMS: AN ULTRASTRUCTURAL RESPONSE

1998 ◽  
Vol 46 (2) ◽  
pp. 141-146 ◽  
Author(s):  
Tamar Berner ◽  
Assaf Sukenik
Keyword(s):  
Light Intensity ◽  
Light Harvesting ◽  
Photosynthetic Apparatus ◽  
Typical Feature ◽  
Optimal Operation ◽  
High Irradiance ◽  
High Rate ◽  
Low Light ◽  
Low Light Intensity ◽  
Photosynthetic Microorganisms

Photosynthetic microorganisms are able to modify their chemical composition, cellular structure, and organization of their chloroplasts in response to the level of irradiance. The photosynthetic apparatus adjusts itself to any new light regime by changing the ultrastructural properties of the chloroplast to provide space and area needed to match other biochemical changes in order to optimize light harvesting and utilization. Acclimation to low light intensity is characterized by an increase in thylakoid number in cyanobacteria, and in the chloroplast volume in eukaryotic plants. In the Eukaryota, these changes allow the packaging of more thylakoids within this organelle to harbor the addition of photosynthetic complexes, i.e., light harvesting antennae, reaction centers, and electron transport components. These changes are essential for optimal operation of the photosynthetic apparatus at low light intensity, mainly to increase the absorption of light energy. Acclimation to high irradiance is characterized by a reduction of the surface density of thylakoid membranes and reduction in the specific volume of the chloroplast. The accumulation of storage bodies containing starch and lipids is yet another typical feature of high light acclimated cells in response to the high rate of photosynthetic activity.

scholarly journals 763 PB 307 ENVIRONMENTAL CONTROL ON FLOWERING AND GROWTH OF LYSIMACHIA CONGESTIFLORA

HortScience ◽  
1994 ◽  
Vol 29 (5) ◽  
pp. 542c-542
Author(s):  
Donglin Zhang ◽  
Allan M. Armitage ◽  
James M. Affolter ◽  
Michael A. Dirr
Keyword(s):  
Environmental Control ◽  
Day Treatment ◽  
Dry Weight ◽  
High Irradiance ◽  
Flower Initiation ◽  
Low Light ◽  
The North ◽  
Long Day ◽  
Total Plant ◽  
Lower Temperature

Lysimachia congestiflora Wils. (Primulaceae) is a new crop for American nurseries and may be used as an annual in the north and a half-hardy perennial in the south. The purpose of this study was to investigate the influence of photoperiod, temperature, and irradiance on its flowering and growth. Three experiments were conducted with photoperiod of 8, 12, 16 hrs day-1, temperature of 10, 18, 26C, and irradiance of 100, 200, 300 μmol m-2s-1, respectively. Plant.9 given long day photoperiod (16 hours) flowered 21 and 34 days earlier, respectively, than plants at 12 sad 8 hour photoperiods. Plants under long day treatment produced more flowers than those at 8 and 12 hours. Plant dry weight did not differ between treatments, but plants grown in the long day treatment produced fewer but larger leaves. Total plant growth increased as temperature increased, but lower temperature (10C) decreased flower initiation and prevented flower development, while high temperature (26C) reduced the longevity of the open flowers. Flowering was accelerated and dry weight increased as plants were subjected to high irradiance levels. The results suggest that Lysimachia congestiflora is a quantitative long day plant. It should be grown under a photoperiod of at least 12 hours at a temperature of approximately 20C. Low light areas should be avoided and supplemental lighting to provide the long days may improve the plant quality.

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.  

Éléments pour une approche morphométrique de la croissance végétale et de la floraison : le cas d'espèces tropicales du modèle de Leeuwenberg

1991 ◽  
Vol 69 (10) ◽  
pp. 2095-2112 ◽  
Author(s):  
P. E. Lauri ◽  
E. Terouanne
Keyword(s):  
Plant Growth ◽  
Differential Evolution ◽  
Growth Process ◽  
Apical Meristem ◽  
Leaf Surface ◽  
Ricinus Communis ◽  
Quantitative Description ◽  
Tropical Plants ◽  
The Relationship ◽  
Surface Length

A quantitative description of primary growth from the apical meristem activity is proposed for four tropical plants: Alstonia vieillardii var. vieillardii (Apocynaceae), Miconia ciliata (Melastomaceae), Ricinus communis (Euphorbiaceae), and Solanum rugosum (Solanaceae). The development of these four plants corresponds to Leeuwenberg's model. Three parameters were measured at different stages of plant growth: leaf surface, length of the underlying internode, and the surface of the internode section. Two other parameters were derived from these three: parameter T, which summarizes the first three parameters and corresponds to the overall dimension of the leaf–internode system, and parameter D, showing the differential evolution of the leaf surface and the corresponding axial volume. The higher the D value, the higher the predominance shown by the twig over the leaf component. This phenomenon is named axialization. The reciprocal situation is called foliarization. For parameter T, the observed variations are present in all four species and showed an increase followed by a decrease in dimensions during the growth process. From the evolution of parameter D, two processses can be recognized. In A. vieillardii var. vieillardii and Solanum rugosum, the amplitude of variation is wide and can be compared with that of parameter T. In M. ciliata and R. communis, the amplitude of variation is significantly reduced. A link can be established between this morphometric evolution and flowering. The results obtained for these four species are compared with those obtained by other researchers and bring new elements to the study of the relationship between the vegetative evolution of the plant and its flowering. Key words: architecture, morphometry, Leeuwenberg's model, ontogeny. [Journal translation]

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