J.E. Hårdh
Experiments on CO2 enrichment in greenhouses sometimes give positive results, sometimes the benefit of using CO2 proves to be doubtful. It is clear that, not only the CO2-concentration, but also other factors in the greenhouse influence the effect of CO2 enrichment. Tests, therefore in controlled environment chambers were performed in order to check the reactions of plants to different conditions of CO2, temperature and light.

Cucumber plants grown in a fluctuating temperature, (35°C for 15 hours and 12° for 9 hours) without CO2 enrichment, were twice as tall as in a constant temperature of 23°. In 0.2% CO2 the plant height in the fluctuating temperature was about three to four times that in the constant 23° and the number of leaves was 8.2 compared with 4.7 in the constant temperature (table 1).

In a former test it was shown, too, that CO2 enrichment associated with a fluctuating temperature gives the best and sturdiest plants.

The plant heights 29 days after transplanting in 0.2% CO2 combined with a fluctuating temperature of 12° to 30°C, in 0.2% CO2 and a constant temperature of 19° and in 0.05% CO2 and 19°, were respectively 25.2, 6.3 and 4.1 cm, the plant weights 30.3, 12.7 and 3.3 g and the number of leaves 9.8, 5.0 and 3.3.

From these results it is obvious, that a fluctuating temperature from 12° by night to '30° or 35° by day promotes plant growth. This difference is still more striking in an atmosphere with CO2 enrichment. The usual method of raising cucumber plants consists of continuous illumination of the plants in an approximately constant temperature. In an atmosphere with

Hårdh, J.E. (1966). CO2 ENRICHMENT IN RAISING YOUNG VEGETABLE PLANTS. Acta Hortic. 4, 126-128
DOI: 10.17660/ActaHortic.1966.4.24

Acta Horticulturae