Maximum crop evapotranspiration (ETc) represents the evapotranspiration rate for a crop with little or no reduction in transpiration due to a water limitation. However, ETc is dependent on the irrigation method and management because of the influence on soil evaporation. When the soil surface evaporation is minimal, differences between actual evapotranspiration (ETa) and crop evapotranspiration (ETc) result from plant control of transpiration, which depends mainly on environmental conditions. Therefore, the ratio of ETa to ETc may provide a good measure of water stress when there is minimal soil evaporation. To investigate this idea, experiments were conducted over grapevines near Villasor, Italy. ETc was calculated as the product of ETo calculated using the Penman-Monteith equation and crop coefficient (Kc) values from FAO Irrigation and Drainage Paper 56. Big changes in the ratio ETa/ETc occurred following an irrigation, but the ratio tended to stabilize once the soil surface had dried. Typically, ETa and ETc rates were similar until just before noon when the ETa dropped below the ETc rate For the remainder of the day. The hourly and daily differences between ETa and ETc were attributed to both soil evaporation and physiological responses of the plants to water deficit.

Uses of myrtle as aromatic plant are related to essential oil extraction from leaves (for perfume and food industry) and to liqueur production by cold infusion of fruit. Myrtle uses are largely dependent on harvest from wild plants, although this seems not sufficient to support a further increase of liqueur production. To develop myrtle cultivation as an aromatic crop, investigations on germplasm variability were made. Morphological and biometric characters of ecotypes selected from spontaneous populations have been recorded to obtain a preliminary database for a further clone selection. Useful characters for the selection of good clones may be indicated in fruit mean weight, peduncle length and pulp/seed ratio.

Woody plants of Mediterranean maquis play an ecological role of fundamental importance. From ancient times they have been used: to protect lands from the risks of desertification or to increase forestry development; to produce wood or fodder; to prepare food, spices? essential oils, and folk remedies; as ornamental plants. Today, interest in these plants is rapidly increasing with three goals in mind: a) to enhance their use in ecological and sustainable forestry; b) to develop food, aromatic and medicinal uses of some species; c) to increase and improve their use as ornamental plants through specific breeding programs.In accordance with these objectives by 1994 five species were studied to facilitate their domestication: lentisk (Pistacia lentiscus L.); strawberry tree (Arbutus unedo L.); myrtle (Myrtus communis L.); rosemary (Rosmarinus officinalis L.); wild olive (Olea europaea L. var. oleaster). All species were analysed from the biological and ecological viewpoint. Lentisk was studied for the selection of female ecotypes characterised by high reproductive efficiency for the colonisation of lands with a desertification risk. Strawberry tree was evaluate as a potential small fruit tree. In this case, the aims of the ecotype selection program were focused on fruit characteristics, such as pulp fibre, acid and sugar content. A mass selection program was carried out on myrtle to select clones for intensive growth and fruit yield for the liqueur industry, as a seasoning crop, and for essential oil extraction. Eleven ecotypes were selected from spontaneous population of rosemary for evaluation as seasoning and essential oil crop.Olive wild ecotypes were studied for sustainable forestry purpose.

Weekly phenology and fruit quality data were taken over four years on two Sardinian areas covering the geographical and climatic range of the region. Accumulated Degree-Days were calculated using the single sine method in order to check the response of kiwifruit to different environmental conditions. The accuracy of the Degree-Day (degrees D) model was tested in terms of variability of accumulated heat and occurrence of phenological stages. The analysis of the degrees D model results showed that 10 degrees C threshold provides a better prediction of phenological stage occurrence in comparison to the 8 degrees C threshold. Regression of the dates of phenological stage occurrence and number of accumulated degrees D showed that the model accounted for 96% of the variance in the two sites. Fruit quality data showed the effect of different air temperature range on acid and soluble solids content during the ripening stage.

The biochemical characteristic of adaptation to drought in Opuntia ficus-indica has been investigated in the present study. The research was conducted on young self-rooted plants of cactus pear cv "Gialla", irrigated or droughted from May 1993 to May 1994. Cladode size, fresh and dry weight, osmotic pressure, pH and titratable acidity, polyamines (PA(s)), and abscissic acid (ABA) levels were recorded in tissues sampled in February and in May 1994, at different hours of the day. All the plants survived after a prolonged water stress, but drought affected cladode morphology and the new cladode production. Typical day-night fluctuation in tissue pH and titratable acidity was observed in irrigated and water stressed plants both in winter (February) and in the growth season (May), but CAM activity decreased as the stress proceeded. ABA content increased as the season advanced and the highest levels of this hormone were observed in the droughted plants. Pa-s levels were higher in irrigated plants and increased during night, together with the greatest accumulation of malic acid. Among Pa-s putrescine was the main represented polyamine, followed by spermidine and spermine. Only these two polyamines increased their concentrations in water stressed plant tissues.

In order to test the sensitivity of colorimetric technique in phytodiagnostics, with particular regard to color variations caused by water stress, an d to verify the potential for use in irrigation timing of horticultural crops, water stress was induced o n two-year-old, container-grown Citrus macrophylla an d Citrus paradisi cv. Star Ruby plants in the third year after grafting. Measurements on plant leaves were preceded by a test of the colorimeter with the ai m of evaluating the accuracy of the instruments an d to poi n t out possible drift effects due to prolonged use. The trend of colorimetric an d xylematic pressure potential values over ti me w ere measured o n leaf samples. Color of well-watered plant leaves showed very small variations while unwatered plant leaves presented a wide change in color. In addition water stress determined an increase in both the dominant wavelength and the saturation. The chromaticity co-ordinates y and z and the index (x+y)lz showed the best sensitivity in discriminating color variations. Moreover, clear correlations between xylematic pressure potential and chromaticity co-ordinates were found. Use of colorimetric technique may improve the possibilities for irrigation management, with particular regards to irrigation timing.

Polyamines have been related to the "Crassulacean Acid Metabolism" (CAM) in higher plants. Such relationship was however observed in plants where CAM activity is inducible by external factors. Results presented here indicate that, inOpuntia F. indica, cladodes where onset of CAM is dependent on internal conditions, i.e. leaf age, the concentration of putrescine increases in parallel to the acidity of the cytoplasm. The parallel increase of putrescine concentration and acidity (malic acid concentration) can be best evaluated during the onset of CAM (young cladodes), while such correlation is not observed in mature cladodes where CAM is already in it's full function. Spermidine and spermine show no correlation with CAM activity neither during the onset of CAM nor during it's full function. However, spermidine levels correlate negatively to CAM activity when cladodes attain > 30 days of age. The results suggest that putrescine in free form could possibly counteract the increase of cellular acidity during onset of CAM inOpuntia F. indica; the possible roles of spermidine are discussed.

SUMMARY Five Citrus varieties ("Washington nave1", "Tarocco", "Biondo comune", "Valencia" sweet oranges, and "Avana" mandarin) on different rootstocks (sour orange, "Troyer" citrange, citremon 1449, Poncirus trifoliata "Rubidoux", "Orlando" tange1o), and at two planting distances (4x4 m, 5x5 m) were evaluated for 3 years in a factorial experiment, with a completely randomized design. Observations were made on growth, productivity and fruit quality. T ree growth, productivity and fruit quality were affected both by variety and by rootstock and planting distance. "Valencia" and "Biondo comune" showed the best growth and yie1d, and "Avana" mandarin the poorest. Severa! differences in fruit quality were observed in the different varieties, mostly concerning fruit weight, rind thickness, juice, TSS and T A. The rootstock also affected growth, yie1d and fruit characteristics. The growth was decreased by "Rubidoux" trifoliate orange, while the yield was slightly increased by "Troyer", "Rubidoux" and "Orlando". "Rubidoux" and citremon improved several fruit characteristics, such as rind thickness, juice, and TSS contento As the trees were still young, planting distance did not affect growth, but some small differences were found in fruit quality. The yie1d/tree and the efficiency were increased by 5x5 m treatment, while the yie1d/ha was, on the contrary, higher in 4x4 m treatment. Finally, some interactions were found between variety and rootstock.