Changes in the Levels of Ribulose-1,5-bisphosphate Carboxylase/Oxygenase (Rubisco) in Tetraedron minimum (Chlorophyla) during Light and Shade Adaptation

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Exponentially growing cultures of the chlorophyta Tetraedron minimum were allowed to photoadapt to low (50 μmole quanta・m^<-2>・s^<-1>) and high (500 μmole quanta・m^<-2>・s^<-1>) irradiance levels. In these cultures, various aspects of the organization of the photosynthetic apparatus and related differences in its performance were studied. In this organism, the observed five-fold increase in pigmentation of low-light adapted cells was due to increases in the numbers of PSU's, while their sizes remained constant. Using radioimmunoassay technique, we found that high-light adapted algae had over five times more Rubisco per PSU than their low-light adapted counterparts. The high-light adapted algae also exhibited far higher (×2.3) light saturated photosynthetic rates per chl α. This increase was the result of a reduction of tau, τ, the turnover time of PS II reaction centers. We propose that the increase in Rubisco per PSU in high-light adapted algae explains the reduction in τ, which results in the higher P_<max>, rates per chl αin these algae. The relationship is non linear, since the increase in Rubisco per PSU was x 5.3 whereas that in P_<max> per chl αwas only ×2.3.
日本植物生理学会の論文