Effects of Combinations of Different Day-length Conditions during the Growth of Flax Plants (Linum usitatissium L.) on Their Growth and Development : II. The Effects of Transfer from Short Day to Natural Long Day

Abstract

Flax plants (var. Saginaw No. 1) were grown in pots under conditions of combinations of various day-lengths as follows: transfer from natural day (14h : 20m-14h : 40m) to short day (8h : 00m) was conducted at the third week (CS1 plot), the fourth week (CS2 plot), and the fifth week (CS3 plot) after germination. The control plot grown in the natural day (C plot) and also the one grown in the short day (S plot) were provided. The results obtained are summarized as follows : 1) In the case of the flax plants which were transferred from the long natural day to the short day, the effects of the short day were not recognized in both the date of anthesis and growth of the basal branches from dicotyledonal axilla, on account of the after effects of long natural day during 3∼5 weeks after germination; though the date of anthesis was delayed and basal branches of the plant became larger in the short day than in the long natural day. 2) In the case of the plants which were transferred from the long natural day to the short day at the later time during the 3∼5 weeks, the after effects of the long natural day were recognized in the growth of length of the plants, the contents of crude fibers in dry stems, the diameter of the fiber-cells and the contents of crude-cellulose, but in the case of the plants which were transferred to the short day at the earlier time during these weeks, the after effects were not recognized. These values in the short day plot became smaller than those of the long natural day, while in the case of the plants which were transferred to the short day at the earlier time, these values became just the same as those of the plants of the short day plot. 3) In the case of the plants which were transferred from the long natural day to the short day, the effects of the short day were recognized in the dry weight of the bolls, the diameter of the fiber-cells and the contents of lignin. The dry weight of the bolls and the diameter of the fiber-cells in the short day plot became smaller than those of the long natural day, while in the case of the plants which were transferred to the short day at the later time these values became smaller than those of the plants of the long natural day. The contents of lignin became larger in the plants of both the short day plot and the plots transferred from the long natural day to the short day than in the plants of the long natural day. 4) Growth in the diameter of the stems, the dry weight of the above-ground parts and the contents of α-cellulose in the flax plants which were transferred from the long natural day to the short day became smaller than those grown in the long natural day. These facts seem to depend upon the decrease of photosynthetic products owing to the transfer to the short day, because in the short day the hours of the sunshine per day were shorter than in the long natural day.