Chlorophylls are degraded and flavonoids synthesized during autumn senescence of deciduous trees. In the present study, chlorophyll and flavonol contents of individual leaves were monitored non-destructively throughout the autumn. Loss of chlorophyll and synthesis of flavonols were not gradual. Instead, each leaf maintained steady chlorophyll content until rapid chlorophyll degradation, accompanied by flavonol synthesis, was triggered. In ~1 week, the leaf turns yellow and falls. The pattern was similar in birch (Betula pendula), maple (Acer platanoides) and bird cherry (Prunus padus); in rowan (Sorbus aucuparia), very slow gradual chlorophyll degradation occurred on top of the main pattern.

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The volumetric productivity of the highlight tolerant strain hit2 of Chlamydomonas reinhardtii was found to be higher than that of the parental strain CC124 during continuous growth at PPFD from 200 to 1,500 µmol m-2 s-1. At PPFD of 1,250 µmol m-2 s-1 , hit2 produced 2.53 ± 0.18 and CC124 produced 2.05 ± 0.12 g(biomass) dm-3 d-1. The rate constant of photoinhibition of hit2 was less than half of that of CC124, suggesting that hit2 produces more biomass than CC124 because hit2 does not need to allocate as much resources for PSII repair as CC124. Growth in high light triggered similar loss of chlorophyll, increase in the carotenoid-to-chlorophyll ratio, and decrease in PSI fluorescence in both strains. Thermoluminescence B band was shifted toward the Q band in hit2, suggesting that low redox potential of the QB/QBpair contributes to the photoinhibition tolerance of hit2.

The potential of a wastewater treatment and biomass production process with the green microalgae Neochloris oleoabundans in a 45-L tubular photobioreactor was tested. In a stable and reliable alga-based process, wastewaters should undergo pre-treatment to remove colored substances. Our data show that further optimization steps may be required, such as adjustment of the N:P ratio and addition of essential metals. As a final result, parameters were established for a continuous-mode photobioreactor run with optimized wastewater for five times the hydraulic retention time (157 h) at the dry biomass concentration of 0.47 ± 0.03 g L −1 . During that period, 75% and 99.6% removal efficiencies for NH 4 + and PO 4 3− , respectively, were achieved.