PHYSIOLOGICAL ASPECTS OF CARBON DIOXIDE ENRICHMENT TO CUCUMBER PLANTS GROWN IN GREENHOUSES

The present investigation was carried out to determine the response of cucumber plants to elevated CO₂ level in combination with increased air temperatures.
A glasshouse with three compartments was used for each treatment.
Treatment I; A CO₂ concentration of 1300 vpm was applied after sunrise until air temperature reached 28°C. Treatment II; CO₂ of 1300 vpm was applied below 28°C. Between 28 and 33°C the concentration varied from 400 to 1000 vpm.
Treatment III; No CO₂ was added.

CO₂ enrichment resulted in an increased yield for the first 45 days of harvest.
The treatment II had the highest yield in the first 45 day period.
During the second 45 day period, the control was higher yielding than treatment II. Plant grown in the enriched air had marked increases in the rate of photosynthesis, and had considerable increases in a leaf temperature and in a leaf resistance to water vapour diffusion over control plants which recieved no additional CO₂. Afterward, marked decreases in net photosynthetic rate were observed in the CO₂ enriched plants.
CO₂ enriched plants from treatment I showed that a higher proportion of the ¹⁴C-assimilates was tranported to the roots.
Treatment II had the smallest amount of downward translocation.

A sharp decline in K level was found in the enriched plants from upper to lower leaves.
High starch content in leaves of plants grown in CO₂ enriched air was associated with low water contents in the leaf.

Symposium on Potential Productivity in Protected Cultivation

T. Ito

https://doi.org/10.17660/ActaHortic.1978.87.13