The Effect of Short Term Alkalinity on Photosynthesis Apparatus in Soil Cyanobacterium Fischerella sp. FS 18 - Ecophysiological Approach

Abstract

The possibility of change in the phycobilisome status, photosynthetic pigments, ratios and light parameters of soil cyanobacteria <i>Fischerella</i> sp. FS 18 has been investigated by two pre-treatment factors, with neutral and extreme alkaline pH (7 and 9) over a short period. After purification, cyanobacteria were subjected to extreme alkaline treatment for under one hour at 20 min intervals (20, 40 and 60 min). A sample was selected as a control without pre-treatment. Colorimetric assays (phycocyanin, alophycocyanin, phycoerythrin, chlorophyll) and a comparison of the combined effect of time and alkalinity on photosystemic ratios were performed through photophysiology. The photosynthesis - light curves were compared with direct measurements. The results showed that the combination of time and alkalinity after 20 min of inoculation significantly increased the performance of the photosystem and stability of the phycobilin system. The 40 min time interval, under both neutral and alkaline conditions, significantly increased the yield of photosystem II, increased the production of the first photosystem compared to the second system, increased the linear fraction of the photosynthesis-light curve, and reduced the energy needed to achieve maximum photosynthesis. Maximal photosynthesis was entirely different at 40 min pretreatment conditions versus without pretreatment. Concerning the 20 and 60 min time intervals, the results show no specific regularity or trend. Production of light collecting antennas is influenced by both time and alkalinity. Two important conclusions from this study include: applying pre-treatment times, even at 60 min or less, cause a significant change in the structure and performance of the photosynthetic apparatus; as well as,-using simple alkaline pretreatments in a very short time period, saving energy whilst, photosynthesis and cyanobacterial materialization can be significantly increased.