CARBON-DIOXIDE EFFECTS ON POTATO GROWTH UNDER DIFFERENT PHOTOPERIODS AND IRRADIANCE

Carbon dioxide concentration can exert a strong influence on plant growth, but this influence can vary depending on irradiance. To study this, potato plants (Solanum tuberosum L.) cultivars 'Norland'. 'Russet Burbank', and 'Denali' were grown in controlled-environment rooms at different levels of CO2 and irradiance. Carbon dioxide levels were maintained either at 350 or 100-mu-mol mol-1 and applied in combination with 12- or 24-h photoperiods at 400 or 800-mu-mol m-2 s-1 photosynthetic photon flux. Air temperatures and relative humidity were held constant at 16-degrees-C and 70%, respectively, and plants were harvested 90 d after planting. When averaged across all cultivars, CO2 enrichment increased tuber yield and total plant dry weight by 39 and 34%, respectively, under a 12-h photoperiod at 400-mu-mol m-2 s-1; 27 and 19% under 12 h at 800-mu-mol m-2 s-1; 9 and 9% under 24 h at 400-mu-mol m-2 s-1. It decreased dry weights by 9 and 9% under 24 h at 800-mu-mol m-2 s-1. Tuber yield of Denali showed the greatest increase (21%) in response to increased CO2 across all irradiance treatments, while tuber yields of Russet Burbank and Norland were increased 18 and 9%, respectively. The results show a pattern of greater plant growth from CO2 enrichment under lower PPF and a short photoperiod.