Comparison of the Photosynthetic Characteristics of Two Developmental Stages in Nostoc sphaeroides Kutzing （Cyanophyta）

The photosynthetic activities between two main developmental stages, colony and hormogonium, of the edible cyanobacterium Nostoc sphaeroides Kutzing, were compared. Hormogonia have a higher content of chlorophyll than that of colonies. It showed that the ratios of phycocyain （PC）, allophycocyain （APC） and phycoerythrocyanin （PEC） in hormogonia and colonies were different. The room temperature chlorophyll fluorescence, 77 K chlorophyll fluorescence, measurements of PSⅠand PS Ⅱ activities all showed that colony has higher photosynthetic competence than hormogonia. Hormogonia had a higher respiration rate than colony, while their maximum photosynthetic oxygen evolution rates were very close. The responses of hormogonia and colonies to high light illuminations also were different. Both of their oxygen evolution rates decreased quickly with the prolonged high light illumination, but hormogonia can keep relatively higher PSⅡ activity （Fv/Fm） than that of colonies. The results suggested that colony was photosynthetically more competent than hormogonia, while the ability of hormogonia to tolerate high light illumination was higher than that of colony.

Comparison of the photosynthetic characteristics of two developmental stages inNostoc sphaeroides Kützing (cyanophyta)

The photosynthetic activities between two main developmental stages, colony and hormogonium, of the edible cyanobacteriumNostoc sphaeroides Kützing, were compared. Hormogonia have a higher content of chlorophyll than that of colonies. It showed that the ratios of phycocyain (PC), allophycocyain (APC) and phycoerythrocyanin (PEC) in hormogonia and colonies were different. The room temperature chlorophyll fluorescence, 77 K chlorophyll fluorescence, measurements of PS I and PS II activities all showed that colony has higher photosynthetic competence than hormogonia. Hormogonia had a higher respiration rate were very close. The responses of hormogonia and colonies to high light illuminations also were different. Both of their oxygen evolution rates decreased quickly with the prolonged high light illumination, but hormogonia can keep relatively higher PS II activity (F _v/F _m) than that of colonies. The results suggested that colony was photosynthetically more competent than hormogonia, while the ability of hormogonia to tolerate high light illumination was higher than that of colony. Foundation item: Supported by the Key Project of the Chinese Academy of Sciences (KZCX1-SW-12), the 973 Project (2002CB412306) and the Frontier Sciences Projects Program of the Institute of Hydrobiology, Chinese Academy of Sciences (220316) Biography: LI Dun-hai (1971-), male, Ph.D., Associate professor, research direction: algal biology and ecosystem restoration.