INFLUENCE OF CHANGES IN DAYLENGTH AND CARBON-DIOXIDE ON THE GROWTH OFPOTATO

Potatoes (Solanum tuberosum L.) are highly productive in mid- to high- latitude areas where photoperiods change significantly throughout the growing season. To study the effects of changes in photoperiod on grow th and tuber development of potato cv. Denali, plants were grown for 1 12 d with 400 mu mol m(-2) s(-1) photosynthetic photon flux (PPF) unde r a 12-h photoperiod (short days, SD), a 24-h photoperiod (long days, LD), and combinations where plants were moved between the two photoper iods 28, 56, or 84 d after planting. Plants given LD throughout growth received the greatest total daily PPF and produced the greatest tuber yields. At similar levels of total PPF, plants given SD followed by L D yielded greater tuber dry mass (DM) than plants given IID followed b y SD. Stem DM per plant, leaf DM, and total plant DM all increased wit h an increasing proportion of LD and increasing daily PPF, regardless of the daylength sequence. When studies were repeated, but at an enric hed (1000 mu mol mol(-1)) CO2 concentration, overall growth trends wer e similar, with high CO2 resulting in greater stem length, stem DM, le af DM, and total plant DM; but high CO2 did not increase tuber DM. (C) 1997 Annals of Botany Company.