BOTANY!!! (de Juan, Gamboa, Manalaysay, Matundan, Sebastian)
-
Upload
doms-gamboa -
Category
Documents
-
view
11 -
download
2
Transcript of BOTANY!!! (de Juan, Gamboa, Manalaysay, Matundan, Sebastian)
Detoxification of Dissolved SO2 (Bisulfite) by Terricolous Mosses
Group 1De Juan, Michelle Ligaya E.
Gamboa, Domina Flor L.Manalaysay, Jessica Alba G.Matundan, Celine Marie C.
*Sulfur dioxide exists in these forms: SO2, SO3-2
and HSO3- (bisulfite)
*Terricolous: Land-dwelling
INTRODUCTION
Pleurozium schreberi- calcifuge moss- moderately tolerant of SO2
Rhytidiadelphus triquetrus
- calcareous or calcicole moss- strongly affected by SO2 pollution in the 20th century
Pleurozium schreberi
Source: http://commons.wikimedia.org/wiki/File:Rhytidiadelphus_triquetrus.JPG
Rhytidiadelphus triquetrus
Source: http://commons.wikimedia.org/wiki/File:Pleurozium.schreberi.jpg
⇨ Tolerance of SO2 is seen on the metabolic
detoxification of dissolved bisulfite by these mosses
Bryophytes (as well as Lichens) are sensitive to atmospheric pollution, particularly SO2
- Limited cuticle- High surface area- Low metabolic activities- Modest innate growth rates
* Detoxification ⇨ Resistant bryophytes: relatively high growth rates: which means that they have the ability to detoxify
* In higher vascular plants: tolerance on SO2 is by detoxification mechanisms (excluding tolerance by cuticle and stomata)
oxidized to sulfate ion (SO4-) ORreduced to sulfide
*SO2 Phytotoxicity
Intracellular O2-
production as cause of SO2 phytotoxicity
*Photo-oxidation: oxidation in the presence of radiant energy (light)
*SO2 Phytotoxicity
Intracellular O2-
production as cause of SO2 phytotoxicity
Superoxide dismutase- Active in SO2 tolerant plants
- Catalyses decomposition of O2-
- Inhibits photo-oxidation of SO2
*Photo-oxidation: oxidation in the presence of radiant energy (light)
*SO2 Phytotoxicity
Intracellular O2-
production as cause of SO2 phytotoxicity
Superoxide dismutase- Active in SO2 tolerant plants
- Catalyses decomposition of O2-
- Inhibits photo-oxidation of SO2
Diethyl dithiocarbamate (DETC)- Controls activity of superoxide
dismutase
*Photo-oxidation: oxidation in the presence of radiant energy (light)
* Detoxification like higher vascular plants in bryophytes: Sphagnum- Higher tolerance for plants in more polluted areas- Oxidation of bisulfite: brought about by metal cations (Fe3+, Mn2+ and Cu2+)
*Focus of the studyPleurozium schreberiRhytidiadelphus triquetrus
⇨ In dilute bisulfite solutions: Photosynthesis in these mosses was strongly inhibited by short (2-hour) incubations with bisulfite ⇨ Longer incubations: no effect → Shoots have a high capacity to detoxify dissolved SO2
*Hypotheses(a) tolerance of bisulfite by P. schreberi and R.
triquetrus depends primarily on detoxification (oxidation) of the pollutant
(b) bisulfite detoxification involves metabolic energy
(c) Ca2+ and Fe3+ stimulate the detoxification process
(d) SOD is involved in bisulfite detoxification
MATERIALS AND METHODS
(1) Pleurozium schreberi: collected from an acid, sandy loam soil under grassland and scrub
(2) Rhytidiaelphus triquetrus: was collected from chalk grassland on a rendzina soil
(1) Incubation treatmentsShort-term incubation experimentLong-term incubation experiment
* Reagent used: NaHSO3
(2) Bisulfite disappearance in relation to initial concentration
(3) DCMU experiment (3-( 30,40-dichlorophenyl)-1,1-dimethylurea)- Inhibits photosynthetic electron transport and oxygen evolution
(4) DETC experiment (diethyldithiocarbamate)- Inhibitor of superoxide dismutase- To see if the enzyme plays a role in bisulfite oxidation
(5) Bisulfite oxidation: influence of Ca2+ and Fe3+
(6) Bisulfite and sulfate determinations- Spectrophotometric methods
(7) Statistical analyses- One-way ANOVA- Duncan’s multiple range test
RESULTS
* Disappearance of bisulfite during short-term incubations with moss shoots
- Decay of bisulfite greater in the presence of light for both species
- Rhytidiadelphus triquetrus: has a greater capacity in catalyzing disappearance of bisulfite
*Disappearance of bisulfite during long-term incubations
- Absence of mosses: 28% remaining at the end of the fifth day of incubation
- Presence of mosses: ≈ 95% of bisulfite had disappeared after a three day incubation
*Disappearance of bisulfite in relation to initial concentration
- Disappearance of bisulfite: dependent on initial concentration and presence of light
(1) Pleurozium schreberi: initial concentration of bisulfite is roughly proportional to the final; no significant effect of light
(2) Rhytidiadelphus triquetrus: total bisulfite lost increased in the presence of light
*Disappearance of bisulfite in relation to acidity
- pH 3 to 5: small reduction in final volume of bisulfite for both species* Much greater reduction at pH 6
*Effects of DCMU on disappearance of bisulfite
- Presence of DCMU in both light and dark: great bisulfite persistence
- Twice as much bisulfite remained in the incubation solutions of Pleurozium schreberi as in those of Rhytidiadelphus triquetrus
*Effects of DETC on disappearance of bisulfite
- inhibited bisulfite loss from the incubation medium in both species
- Pleurozium schreberi: doubling of the concentration of bisulfite remaining
- Rhytidiadelphus triquetrus: even greater increase in concentration of bisulfite remaining
*Evidence for extracellular oxidation of bisulfite to sulfate: influence of Ca and Fe
- Pleurozium schreberiFe: no differenceCa: more sulfate was detectedEDTA: no change or small increase in sulfate
- Rhytidiadelphus triquetrusFe: small but significant increase in sulfateCa: reduction in sulfate productionEDTA: reduction in sulfate
DISCUSSION
- Addition of bisulfiteRapid cessation of photosynthesisIncreasing incubation periods: photosynthesis restored→ Due to oxidation of bisulfite
- Presence of the two mossesGreatly accelerates decrease in amount of bisulfite in incubation solutions
- Rate of bisulfite loss depends on:(1) Presence or absence of light(2) Application of metabolic inhibitors(3) Acidity(4) Nature and concentrations of adsorbed metal cations(5) Species of moss
- Light significantly stimulated bisulfite loss from the external solution
- Differences in the degree of photoprotection between the two mosses might also explain their different abilities to detoxify bisulfite solutions
- DCMU inhibits photosynthetic electron transport and oxygen evolution. It caused a substantially reduced rate of bisulfite loss from the incubation solution, especially in R. triquetrus
- Experiment with DETC, an inhibitor of SOD, led to a very significant reduction in the rate of bisulfite loss from the incubation solution with both mosses
- Fe(III) catalysed extracellular oxidation of bisulfite as the pretreatment was accompanied by an increase in the sulfate concentration of the external solution.
- The reduced extracellular sulfate observed could indicate that Ca(II) enhances cellular uptake of bisulfite (indirect effect). - Ca(II) functions for stabilizing cell membranes or
embedded portein channels against loss of permeability control
- EDTA pretreatement did not cause lowered bisulfite disappearance
- Possibly, EDTA was relatively ineffective in chelating metals such as Fe(III) from the moss shoots.
- Alternatively, the EDTA may have disrupted normal membrane function so that bisulfite uptake or retention rates were modified
CONCLUSION
*Loss of bisulfite(1) External oxidation of bisulfite using metabolic (including photooxidative) energy
(2) ‘passive’ external oxidation of bisulfite catalysed by adsorbed Fe3+ ions
(3) cellular uptake and metabolic detoxification of bisulfite
AuthorsBhagawan Bharali
Jeffrey Bates
Department of Crop Physiology, Assam Agricultural University, Jorhat-785013, Assam, India and 2Division of Biology, Imperial College
London, Silwood Park Campus, Ascot, Berkshire SL5 7PY, UK