Interactions between UV-B exposure and phosphorus nutrition. II. Effects on rates of damage and repair

The interactive effects of P starvation and exposure to UV radiation (UVR) on rates of damage (k) and repair (r), modeled from exposure response curves (ERCs), in the chlorophyte microalga Dunaliella tertiolecta Butcher were investigated. When nutrient-replete cells were exposed to the UVR during growth, k and r both increased by approximately 62% and 100%, respectively. However, when cells were starved of phosphorus, k increased by a similar amount as observed in replete cells, but r decreased by about 70%, explaining the increased susceptibility of cells to UVR-induced inhibition of photosynthesis under P starvation. Although not specifically investigated in this study, it is argued that the decreased repair capacity under P starvation is due to a decline in nucleotides such as ATP and GTP, which are necessary for protein repair.