Heat and cold resistance of Eucalyptus occidentalis Endl. leaves and its relationship to soil water conditions*


  • *

    Contribution from the Agricultural Research Organization, Bet Dagan, Israel.


A direct correlation was found between soil water stress and resistance of E. occidentalis leaves to extreme temperatures. A distinct seasonal rhythm of heat and cold resistance of the leaves was recorded. Maximal tolerance was observed towards the end of the dry season, when the resistance value, that is, the temperature injuring 50% of the leaf area at Ilanot was –5.8°C for cold resistance and 51.0°C for heat resistance. The minimal tolerance to extreme temperatures was recorded in the middle of the rainy (winter) season.

Irrigation of the trees during the summer reduced both heat and cold resistance.