Growth and development of tomato [Lycopersicon esculentum] seedlings under constant light-dark period with random light periods
2003
Toida, H. (Chiba Univ., Matsudo (Japan). Faculty of Horticulture) | Omura, Y. | Kubota, C. | Kozai, T.
Tomato (cv. Momotaro) seedlings with cotyledons were grown under three different alternation of light and dark periods for 14 days. In each treatment, the light period began at the same time of day every day. In the periodic alternation treatment (P), both the light and dark periods were 12 h for each day. In one of two non-periodic alternation treatments examined in the present study (ND-1), the number of hours in the light period was a random integer between 6 and 18 subject to the provision that the average light period per day during the experiment was 12 h. The dark period was adjusted to make the period 24 h. The other non-periodic alternation treatment, ND-2, was similar to ND-1 except that the random integer was between 1 and 23. The standard deviations of the light periods (SD) were O h in P, 4 h in ND-1, and 6 h in ND-2. At the end of the experiment, dry mass and leaf area per seedling were greater in P than in ND-1 and ND-2, while stem length was shortest in P, followed by ND-1 and ND-2. Flower-bud initiation was earliest in ND-2 and the number of leaves preceding the first flower truss differentiation was lowest in ND-2, followed by ND-1 and P. When SD is used as the independent variable, stem length increased and leaf area and the number of leaves preceding the first flower truss differentiation decreased with increasing SD. In this study, plant growth and development were not necessarily better when the alternation of light and dark periods was periodic than when it was non-periodic.
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