INVESTIGADORES
VILLAFAÑE Virginia Estela
artículos
Título:
Differential responses of Nostoc sphaeroides and Arthrospira platensis to solar ultraviolet radiation exposure: Importance of long-term acclimation
Autor/es:
WALTER HELBLING, E; KUNSHAN GAO,; H AI,; Z MA,; VIRGINIA ESTELA VILLAFAÑE
Revista:
JOURNAL OF APPLIED PHYCOLOGY
Referencias:
Año: 2006 vol. 18 p. 57 - 66
ISSN:
0921-8971
Resumen:
During October to December 2003 we carried out experiments to assess the impact of high solar radiation levels (asnormally occurring in a tropical region of Southern China) on the cyanobacteria Nostoc sphaeroides and Arthrospira(Spirulina) platensis. Two types of experiments were done: a) Short-term (i.e., 20 min) oxygen production ofsamples exposed to two radiation treatments (i.e., PAR+UVR—280–700 nm, and PAR only—400–700 nm, PABand P treatments, respectively), and b) Long-term (i.e., 12 days) evaluation of photosynthetic quantum yield (Y)of samples exposed to three radiation treatments (i.e., PAB; PA (PAR+UV-A, 320–700 nm) and P treatments,respectively). N. sphaeroides was resistant to UVR, with no significant differences (P > 0.05) in oxygen productionwithin 20 min of exposure, but with a slight inhibition of Y within hours. A fast recovery of Y was observed afterone day even in samples exposed to full solar radiation. A. platensis, on the other hand, was very sensitive to solarradiation (mainly to UV-B), as determined by oxygen production and Y measurements. A. platensis had a circadianrhythm of photosynthetic inhibition, and during the first six days of exposure to solar radiation, it varied between 80and 100% at local noon, but cells recovered significantly during afternoon hours. There was a significant decreasein photosynthetic inhibition after the first week of exposure with values less than 50% at local noon in samplesreceiving full solar radiation. Samples exposed to PA and P treatments recovered much faster (within 2–3 days),and there were no significant differences in Y between the three radiation treatments when irradiance was low (lateafternoon to early morning). Long-term acclimation seems to be important in A. platensis to cope with high UVRlevels however, it is not attained through the synthesis of UV-absorbing compounds but it seems to be mostly relatedto adaptive morphological changes.