Interactive effects of and light on growth rates and RUBISCO content of small and large centric diatoms

Abstract

<p><strong>Abstract.</strong> Among marine phytoplankton groups, diatoms span the widest range of cell size, with resulting effects upon their nitrogen uptake, photosynthesis and growth responses to light. We grew two strains of marine centric diatoms, the small <i>Thalassiosira pseudonana</i> and the larger <i>T. punctigera</i> in high and low nitrogen media, across a range of growth light levels. Nitrogen and total proteins per cell decreased with increasing growth light in both species when grown under low nitrogen media. Surprisingly, low nitrogen increased the cellular allocation to RUBISCO and the rate of electron transport away from Photosystem II for the smaller diatom under low growth light, and for the larger diatom across the range of growth lights. Low nitrogen decreased the growth rate of the smaller diatom, particularly under higher light, but stimulated the growth rate of the larger diatom. Our results show that the high nitrogen in common growth media favours the growth rate of a small diatom but inhibits growth of a larger species.</p>

Photoacclimation of the polar diatom Chaetoceros neogracilis at low temperature

“…Although the dark reactions of photosynthesis were probably limiting at high irradiance, cells did not compensate by increasing Rubisco content. Rubisco contents measured in this study (5-18% of total protein) are higher than the majority of the values reported for mesophilic diatoms [41][42][43] (see grey line in Fig 3) but accord well with those of psychrophilic diatoms (17% of total protein) [3].…”