FROST RESISTANCE OF SOME OLIVE CULTIVARS DURING THE WINTER
Frost resistance, expressed as the lethal temperature for 50% of the tissues (LT 50) of leaves, buds and shoots, was periodically evaluated on shoots collected from adult plants in the field and submitted to different temperatures in a growth chamber.
At collecting time, water and carbohydrate contents of leaves and shoots and leaf water potential were recorded.
The LT 50 showed a trend correlated to temperature, with lower values occurring during colder periods and corresponding on an average to -12°, -13° and -18°C for leaves, buds and shoots, respectively. No varietal differences were found for the LT 50 of leaves, whereas shoots and, in particular, the buds of cv. "Nostrale di Rigali" showed a greater frost resistance primarily at the beginning and at the end of the cold period.
On all cultivars soluble solids of leaves and shoots increased with decreasing temperature, whereas water content and leaf water potential were lower in the colder periods. The differences recorded for these parameters do not seem to explain the higher frost resistance of the cv. Nostrale di Rigali.