Abstract
Under controlled environmental conditions, the authors studied the effect of extendedlight/dark cycles of 24/12, 48/24, 96/48, and 120/60 h and continuous lighting on the content and ratio ofphotosynthetic and nonphotosynthetic pigments in a number of Solanaceae (eggplant (Solanum melongena L.),sweet pepper (Capsicum annuum L.), tobacco (Nicotiana tabacum L.), and tomato (Solanum lycopersicum L.))and Brassicaceae (broccoli (Brassica oleracea var. italica Plenck), mizuna (Brassica rapa ssp nipposinica(L.H. Bailey) Hanelt), arugula (Eruca vesicaria sp. sativa Mill.), and cauliflower (Brassica oleracea L. var.botrytis L.)) plants. Plants were grown in controlled-climate chambers at 23°С and light intencity of270 μmol/(m2s) PAR. Control plants were grown under photoperiod of 16/8 h. Continuous lightingdecreased the content of chlorophyll, its share in light-harvesting complex and chlorophyll to carotenoidsratio, but increased chlorophyll a/b ratio and the content of anthocyanins and flavonoids; these effects weredifferently manifested depending on plant species. At all other examined light/dark cycles (24/12, 48/24,96/48, and 120/60 h) where average daily light integral did not differ from such under common photoperiod(16/8 h), changes in pigment complex were often observed similar to photoprotective reactions occurringupon exposure of plants to excess illumination (a decrease in the content of photosynthetic pigments, modification of their ratios, and accumulation of protective, nonphotosynthetic pigments). At the same time,plant responses were species-specific. On the whole, the obtained results have shown that changes within theplant pigment complex may be induced not only by excessive light energy coming to plants, but also by distribution of daily light integral in time as it occurs in response to abnormal light/dark cycles that, in theauthors’ opinion, cause a circadian asynchrony
Published Version
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