Exponentially growing cultures of the chlorophyta Tetraedron minimum were allowed to photoadapt to low (50μmole quanta m−2s−1) and high (500μmole quanta m−2−1) 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 a. 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 Pmax rates per chl a in these algae. The relationship is non linear, since the increase in Rubisco per PSU was ×5.3 whereas that in PmM per chl a was only ×2.3.
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Fisher et al. (1989) studied this question.