INFLUENCE OF TEMPERATURE, PHOTOPERIOD AND CONTAINER SIZE ON THE GROWTH RATE AND DEVELOPMENT OF TOMATO PLANTS IN GROWING-ROOMS

1. photoperiod - 12 hours versus 16 hours,
2. temperature - a constant 21°C versus a differential day/night regime with a mean of 21°C, and
3. container size - use of a 10.8 cm container continuously versus a 3.5 cm container for the first ten days and thereafter a 10.8 cm container.

Growth curves based on dry weight samples at 3–4 day intervals showed an overall increase of 43% with the 16-hour photoperiod after 20 days. There were smaller increases in favour of the constant temperature and the 10.8 cm container.

The longer photoperiod substantially increased leaf area (15%), dry weight per unit leaf area (25%), plant height (21%), dry weight per unit height (12%), plant spread (10%) and flower-bud numbers. The larger container and the constant temperature regime induced smaller increases in most of the above traits.

In spite of the 16-hour photoperiod improving all growth parameters analysed and reducing the time to anthesis by 3.7 days, evidence is presented to indicate that a 12-hour photoperiod is more economical and easier to operate.

The efficency of space utilisation afforded by the use of the 3.5 cm container enhances the economics of a growing-room venture.

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