Responses of chlorophyll b-Free chlorina 3613 barley mutant to a prolonged decrease in illuminance: 1. Dynamics of chlorophyll content, growth, and productivity

Responses of plants deficient in chlorophyll b (Chl b) to a long-term (lasting for 7 days) decrease in illumination and subsequent restoration of normal illumination were investigated in chlorina 3613 mutant of barley (Hordeum vulgare L.). Efficiency of acclimation was estimated by productivity. Throughout the entire vegetation period, control chlorina 3613 plants growing under full natural illumination (PAR photon flux density of 2000-2200 mu mol/(m(2)s)) were notable for a low content of chlorophyll a (Chl a), slow growth, and low productivity as compared with Donaria parent genotype (wild type). In the experiments, mature chlorina 3613 plants were shaded for 1 week, so that radiant flux density of PAR came to 60 or 40% of that in full sunlight. In experimental chlorina 3613 plants subjected to shading for 7 days, accumulation of Chl a and the lack of Chl b were accompanied by activation of growth processes and rise in total biomass; in contrast, in Donaria 7-day-long shading negatively influenced the accumulation of biomass by the plants. After restoration of full natural illumination, growth and productivity characteristics of chlorina 3613 plants, which for 7 days received only 40% of full natural illumination, became close to the characteristics of wild-type plants. Thus, the lack of Chl b in chlorina 3613 plants did not affect growth and productivity after a 7-day-long shading (to 40% of full illumination).