CO₂ AND NIGHT TEMPERATURE ON GROWTH AND DEVELOPMENT OF CHRYSANTHEMUM

In this experiment it was the aim to study the effect of night temperature, CO₂-concentration during day hours and plant density.

All compartments were planted with three varieties, and all three were planted on two dates.

During the growing period with three week intervals a number of plants were harvested from each plot for analyses of growth and development. Fresh and dry weight of leaves and stems, plant height and number of leaves were determined. Moreover, flower bud development, time of harvest and, during harvest, the number of buds, open flowers and branches were counted. From these observations a large number of combinations of data can be calculated like for instance the quality of the main stem. Some of the major results are presented in the following.

The effect of the night temperature on plant fresh weight, number of leaves, stem length and quality is presented. Independent of cultivar, planting date, and density the fresh weight of the plants is equal for the night temperatures applied (22&rarrow;13°C). The number of leaves decreases with 4%, plant weight decreases with 11%, while quality of the main stem (weight/height) increases with 24%. Thus, at low night temperature a shorter and firmer plant is produced than at 22°C; fresh weight, however, remains unaltered.

The effect of increased CO₂-concentration (900 versus 300 ppm) is that fresh weight increases with 9%, number of leaves with 2%, plant weight with 7% and quality of the stem with 10%.

Thus, CO₂ favours both plant height and firmness of the stem. Increasing plant density, from 51 to 64 plants per m² results in decreased plant fresh weight with 12%, the number of leaves with 2%, plant height with 5% and quality with 8%.

Evidently, from these data it can be concluded that a threefold CO₂ concentration roughly compensated for some 20% density.

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