| Physiological activities of fourteen grapevine cultivars were evaluated in the field under prevailing environmental conditions in 1979 and 1980. The field vines were grown at the Campbell Avenue Farm in Tucson, Arizona at an elevation of 720 meters.; No significant differences were found in 1979 between the mean apparent photosynthetic rates of Cabernet Sauvignon, Chardonnay, Petite Sirah, Sauvignon blanc, Tinta Madeira and White Reisling grown in the field.; Statistical comparisons between the mean apparent photosynthetic rates of Cabernet Sauvignon, Carignane, Grey Reisling and Tinta Madeira in 1980 indicated all cultivars were significantly different from each other at the 5% level. However, no significant differences between the means of their dark respiration rates were found.; Significant differences between the mean apparent photosynthetic rates of Alden, De Chaunac, Himrod, Malvasia bianca, Petite Sirah, Sauvignon blanc, Sylvaner and Seyval Blanc were found. However, dark respiration rates were not significantly different.; Comparisons of apparent photosynthesis and dark respiration rates between and within field grown Grey Riesling vines showed only days had a significant effect on apparent photosynthesis, while vines, shoots and interaction between vines and shoots had no significant effect. However, none of these factors had a significant effect on dark respiration rates of Grey Riesling.; Diurnal patterns of apparent photosynthesis and dark respiration rates of Tinta Madeira cultivar were investigated under field conditions and the results showed that apparent photosynthesis was minimal at sunrise, then sharply increased to reach a peak value at 7:00 a.m. in May and at 8:00 a.m in June, then showed a low rate for the rest of the day, reaching a minimum rate at 7:00 p.m. in both May and June. Dark respiration rates were low at sunrise, then increased to reach a peak at 10:00 a.m. and a second peak at midday in May. However, in June, the first and second peaks were reached at 11:00 a.m. and 3:00 p.m., respectively. Then they declined to reach a minimum rate at 7:00 p.m.; Diurnal changes in leaf water potentials of the investigated cultivars (Tinta Madeira, Sylvaner and Malvasia bianca) showed a similar pattern where high values were recorded at sunrise, followed by a sharp decline reaching minimum values about midday, when they levelled off for several hours and then increased late in the evening.; The relationship between apparent photosynthesis and leaf water potentials of Carignane using join point regression analysis indicated that apparent photosynthesis was maintained until the leaf water potential fell to about -9.3 bars; it then decreased rapidly, reaching its minimum rate at about -13.0 bars.; The effects of a series of cycles of alternating low and high soil moisture contents on the rates of apparent photosynthesis, true photosynthesis post-illumination carbon dioxide burst and dark respiration rates of three carbon dioxide burst and dark respiration rates of three container-grown grape vine cultivars (Carignane, Petite Sirah and Tinta Madeira) was investigated. The results indicated that before wilting was evident, there was a marked reduction in the measured physiological activities, with the severity of reduction depending upon the severity of drought stress. |
