INVESTIGATIONS OF AIR CONTENT IN ROOT MEDIUM AND ROOT QUALITY IN THE OVERWINTERING OF CONTAINER PLANTS AT DIFFERENT DRAINAGES IN OPEN FRAME

2 – 3 years old container grown Juniperus virginiana ‘Sky Rocket’ potted in a mixture of coarse peat and rockwool (4:1) were placed on 3 different drainages: Plastic, vatex and sand in an open frame in the autumn 1976.

Following measurements were carried out during the period October 1976 to April 1977: Precipitation, temperature, available air content – and oxygen content in the containers and vitality in the root system were determined by TTC test (triphenyl tetrazolium chloride).

An obvious relation was found between rainfall and air content in the containers.
The air content was higher in the containers placed on vatex and sand than in those on plastic, when soil temperature was above 0°C. But at temperatures below 0°C the air content was the same for all treatments.

The lowest air content of approx. 5% was recorded during a short period with abundant precipitation and a temperature about 0°C. In the same period the oxygen content was found to be 7% 0₂.

TTC-test was carried out monthly on root samples taken 1 cm and 5 cm above the bottom of the containers.
The root activity decreased during the period November to February and then increased in March and April.
The root activity was lowest for plants placed on plastic and highest on sand and vatex.

The temperature was the same for all plants and therefore it was not possible to explain the difference in root activity between the drainages by temperature alone.
On the other hand, rainfall was considerably more abundant than normal.
From this point of view it is possible to explain the low root activity in plants on plastic by lower air content during winter.

Symposium on Propagation and Raising of Nursery Stock

P.E. Jørgensen, E. Nymann Eriksen

https://doi.org/10.17660/ActaHortic.1978.79.17