Photosynthetic Utilisation of Lightflecks by Understory Plants

1988 ◽  
Vol 15 (2) ◽  
pp. 223 ◽  
Author(s):  
RW Pearcy
Keyword(s):  
Photosynthetically Active Radiation ◽  
Co2 Fixation ◽  
Photosynthetic Apparatus ◽  
Continuous Light ◽  
Stomatal Opening ◽  
Carbon Gain ◽  
Light Activation ◽  
Low Light ◽  
Active Radiation ◽  
Induction State

The light environment in forest understories is highly dynamic because the weak shade light is period- ically punctuated by lightflecks lasting from a second or less to tens of minutes. Although present for only a small fraction of the day, these lightflecks can contribute more than two-thirds of the photosynthetically active radiation. Several factots are of importance in determining the capacity of a leaf to utilise lightflecks. Following long low-light periods the induction state of the photosynthetic apparatus is limiting. During induction, 20-60 min may be required before maximum assimilation rates are reached due first to a light activation requirement. of ribulose-1,5-bisphosphate carboxylasel oxygenase and later to the light-induced stomatal opening. Continuous light is not required and induction occurring during a series of lightflecks results in higher carbon gain for later as compared to earlier lightflecks. Post-illumination CO2 fixation resulting from utilisation of metabolite pools built up during the lightfleck can significantly enhance carbon gain during short (5-20 s) lightflecks. The carbon gain of a leaf in response to a lightfleck is a consequence of the limitations imposed by induction state plus the enhancements due to post-illumination CO2 fixation. In the field, this will depend on the frequency and duration of the lightflecks and the duration of the intervening low-light periods.

Physiological performance of a foliose macrolichen Umbilicaria antarctica as affected by supplemental UV-B treatment

2015 ◽  
Vol 5 (2) ◽  
pp. 222-229 ◽  
Author(s):  
Mariana Gonzalez Medina ◽  
Roxana Avalos-Chacon
Keyword(s):  
Chlorophyll Fluorescence ◽  
High Resistance ◽  
Photosynthetically Active Radiation ◽  
High Intensity ◽  
Photosynthetic Efficiency ◽  
Photosynthetic Apparatus ◽  
Ps Ii ◽  
Fluorescence Kinetics ◽  
Active Radiation ◽  
High Doses

To date, a limited knowledge is available about Umbilicaria antarctica responses when it is exposed high doses of UV-B radiation. It is well established that resistance of Antarctic lichens to natural UV-B levels including increased doses during ozone hole period is high, thanks to numerous photoprotective mechanism. Capacity of the photoprotective processes, however, is not well known This study attempts to determine changes on the photosynthetic efficiency and on the synthesis of UV-B absorbing compounds of U. antarctica when exposed to low photosynthetically active radiation and extremely high intensity of UV-B light: 3.0 W m-2, of UV-B for 3 hours, 6 hours and 7 days. During the experiment, chlorophyll fluorescence was measured to evaluate changes in photosynthetic apparatus of intrathalline alga. After 7 d exposition, amount of UV-B absorbing compounds was evaluated in U. antarctica. Heavy UV-B stress let to an increase in chlorophyll fluorescence kinetics (OJIPs), however, majority of parameters related to functioning of PS II remained unchanged indicating high resistance of U. antarctica to UV-B stress. Potential (FV/FM) and actual (ФPSII) yields of PS II were not affected by the UV-B treatment as well. In majority of cases, heavy UV-B treatment led to a decrease in the amount of UV-B absorbing compounds extracted from treated thalli.

Photosynthetically active radiation and carbon gain drives the southern orientation ofMyrtillocactus geometrizansfruits

Plant Biology ◽  
2017 ◽  
Vol 19 (2) ◽  
pp. 279-285 ◽  
Author(s):  
A. Ponce-Bautista ◽  
P. L. Valverde ◽  
J. Flores ◽  
A. Zavala-Hurtado ◽  
F. Vite ◽  
...  
Keyword(s):  
Photosynthetically Active Radiation ◽  
Carbon Gain ◽  
Active Radiation

Pathways of CO2 Fixation in the Cam Plant Kalanchoe daigremontiana. III. Correlation With δ13C Value During Growth and Water Stress

1976 ◽  
Vol 3 (6) ◽  
pp. 787 ◽  
Author(s):  
CB Osmond ◽  
MM Bender ◽  
RH Burris
Keyword(s):  
Co2 Fixation ◽  
Acid Synthesis ◽  
Co2 Assimilation ◽  
Stomatal Opening ◽  
Total Carbon ◽  
Controlled Environment ◽  
Low Light ◽  
Light Regimes ◽  
Light Levels ◽  
Δ13c Value

Seedlings of K. daigremontiana were grown in the same controlled-environment room under nine different day temperature and light regimes. In each treatment, irrigated plants maintained dawn water potentials of approximately -5 bar whereas droughted plants ranged to -22 bar. Irrigated plants showed a characteristic stomatal opening on illumination, closure during deacidification and partial stomatal opening following deacidification. Stomata of droughted plants remained closed throughout the light period. Irrigated and droughted plants showed comparable dark acid synthesis. Low light levels and low day temperature resulted in lower dark acid synthesis and more protracted deacidification in the light. The δ13C value (total carbon) of old as well as newly formed leaves of irrigated plants tended to become less negative throughout the experiment except in low-light, low-day-temperature treatments. This trend was accentuated in the δ13C value (total carbon) of whole shoots of droughted plants. These data are consistent with an increase, with age, in the proportion of CO2 assimilated in the dark during growth of irrigated plants, and with the greater dependence on dark CO2 assimilation during the slower growth of droughted plants. Differences in the δ13C value of soluble and insoluble carbon from irrigated and droughted plants assayed at dawn appear to be consistent with the established starch to acid relationships in crassulacean plants.

scholarly journals Evidence for a Regulatory Link of Nitrogen Fixation and Photosynthesis in Rhodobacter capsulatus via HvrA

1998 ◽  
Vol 180 (7) ◽  
pp. 1965-1969 ◽  
Author(s):  
Monika Kern ◽  
Paul-Bertram Kamp ◽  
Annette Paschen ◽  
Bernd Masepohl ◽  
Werner Klipp
Keyword(s):  
Nitrogen Fixation ◽  
Gene Fusion ◽  
Rhodobacter Capsulatus ◽  
Photosynthetic Apparatus ◽  
Light Activation ◽  
Reporter Strain ◽  
Nitrogen Fixing ◽  
Oxygen Control ◽  
Low Light ◽  
Regulatory Link

ABSTRACT A Rhodobacter capsulatus reporter strain, carrying a constitutively expressed nifA gene and anifH-lacZ gene fusion, was used for random transposon Tn5 mutagenesis to search for genes required for the NtrC-independent ammonium repression of NifA activity. A mutation inhvrA, which is known to be involved in low-light activation of the photosynthetic apparatus, released both ammonium and oxygen control of nifH expression in this reporter strain, demonstrating a regulatory link of nitrogen fixation and photosynthesis via HvrA. In addition, a significant increase in bacteriochlorophyll a (BChla) content was found in cells under nitrogen-fixing conditions. HvrA was not involved in this up-regulation of BChla. Instead, the presence of active nitrogenase seemed to be sufficient for this process, since no increase in BChla content was observed in different nif mutants.

scholarly journals Compensation Mechanism of the Photosynthetic Apparatus in Arabidopsis thaliana ch1 Mutants

2020 ◽  
Vol 22 (1) ◽  
pp. 221
Author(s):  
Joanna Wójtowicz ◽  
Adam K. Jagielski ◽  
Agnieszka Mostowska ◽  
Katarzyna B. Gieczewska
Keyword(s):  
Light Stress ◽  
Photosynthetic Apparatus ◽  
Protein Composition ◽  
Mrna Levels ◽  
Chlorophyll B ◽  
Low Light ◽  
Plant Acclimation ◽  
Chlorophyll B Deficiency ◽  
Composition Changes

The origin of chlorophyll b deficiency is a mutation (ch1) in chlorophyllide a oxygenase (CAO), the enzyme responsible for Chl b synthesis. Regulation of Chl b synthesis is essential for understanding the mechanism of plant acclimation to various conditions. Therefore, the main aim of this study was to find the strategy in plants for compensation of low chlorophyll content by characterizing and comparing the performance and spectral properties of the photosynthetic apparatus related to the lipid and protein composition in four selected Arabidopsis ch1 mutants and two Arabidopsis ecotypes. Mutation in different loci of the CAO gene, viz., NW41, ch1.1, ch1.2 and ch1.3, manifested itself in a distinct chlorina phenotype, pigment and photosynthetic protein composition. Changes in the CAO mRNA levels and chlorophyllide a (Chlide a) content in ecotypes and ch1 mutants indicated their significant role in the adjustment mechanism of the photosynthetic apparatus to low-light conditions. Exposure of mutants with a lower chlorophyll b content to short-term (1LL) and long-term low-light stress (10LL) enabled showing a shift in the structure of the PSI and PSII complexes via spectral analysis and the thylakoid composition studies. We demonstrated that both ecotypes, Col-1 and Ler-0, reacted to high-light (HL) conditions in a way remarkably resembling the response of ch1 mutants to normal (NL) conditions. We also presented possible ways of regulating the conversion of chlorophyll a to b depending on the type of light stress conditions.

Changes in the Stoichiometry of Photosystem II Components as an Adaptive Response to High-Light and Low-Light Conditions during Growth

1986 ◽  
Vol 41 (5-6) ◽  
pp. 597-603 ◽  
Author(s):  
Aloysius Wild ◽  
Matthias Höpfner ◽  
Wolfgang Rühle ◽  
Michael Richter
Keyword(s):  
Photosystem Ii ◽  
Functional Organization ◽  
Photosynthetic Apparatus ◽  
High Light ◽  
Molar Ratio ◽  
Light Conditions ◽  
Low Light ◽  
Pigment System ◽  
Transport Chain ◽  
The One

The effect of different growth light intensities (60 W·m-2, 6 W·m-2) on the performance of the photosynthetic apparatus of mustard plants (Sinapis alba L.) was studied. A distinct decrease in photosystem II content per chlorophyll under low-light conditions compared to high-light conditions was found. For P-680 as well as for Oᴀ and Oв protein the molar ratio between high-light and low-light plants was 1.4 whereas the respective concentrations per chlorophyll showed some variations for P-680 and Oᴀ on the one and Oв protein on the other hand.In addition to the study of photosystem II components, the concentrations of PQ, Cyt f, and P-700 were measured. The light regime during growth had no effect on the amount of P-700 per chlorophyll but there were large differences with respect to PQ and Cyt f. The molar ratio for Cyt f and PQ between high- and low-light leaves was 2.2 and 1.9, respectively.Two models are proposed, showing the functional organization of the pigment system and the electron transport chain in thylakoids of high-light and low-light leaves of mustard plants.

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.

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