Effect of Altering Diurnal Fluctuations of Day and Night Temperatures at the Seedling Stage on the Subsequent Growth of Flowering Anuual

Abstract

The effects of diurnal fluctuations between day and night temperature (DIF) during the early seedling stage of Matthiola incana (stock), Antirrhinum mains (snapdragon), Viola × wittrokiana (pansy) and Impatiens walleriana (Impatiens), were investigated to test whether they persisted.Under positive DIF, seedling height, internode length, and the 1st leaf petiole length were longer than in plants grown under negative DIF. Although positive DIF tended to favor leaf elongation and leaf unfolding rate, in that the leaves during the rapid extension (13 days after treatment started) were always longer than those grown under negative DIF, no significant difference was observed in the final measurement.The elongation response to DIF alteration during the rapid elongation was reflected in plant height, internode length, and leaf petiole length in all plant species. After DIF was altered, a significant difference on the final length was observed between the corresponding treatments (i. e. between positive DIF and alteration from positive to negative DIF, and between negative DIF and alteration from negative to positive DIF treatment). The response to DIF alteration from negative to positive was greater than that from positive to negative. The elongation after DIF alteration was greater in seedlings which were smaller at the time of DIF alteration than in the larger seedlings; the former were under the negative DIF until the alteration while the latter were under the positive DIF. This result could be summarized that the DIF during early nursery stage had a small effect on the growth after the treatment. We concluded that DIF could be applied in seedling production.