ASSESSMENT OF WATER STATUS IN VARIOUS CITRUS SPECIES AND LINES

The research was carried out in two different pedoclimatic areas, namely a coastal and an inland area of Sicily, from 1983 to 1985.

The different potential values recorded in the same area show the different responses of the plants to various VPD, that is their ability to face various evaporative demands.

The differences between potentials of similar plants in the two areas when the VPD was equal could be attributed to different frequencies of irrigation which caused a different water potentials in the soil, and to different soil features.

The main findings of this research were:

• Nucellar lines exhibited a lower (more negative) potential than old lines.
• The potentials of the species were thus ordered: mandarins > oranges > grapefruits.
• Plants grafted on rootstocks Troyer citrange and sour orange showed lower potential values than plants on C. macrophylla Wester (Alemow).
• The values of foliar potential and VPD were closely related.
• The results achieved in 1983 during the day by measuring stomatic resistance with a porometer and differential temperature with an infrared thermometer paralleled and confirmed the results obtained with the pressure chamber.

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