Photosynthetic behavior of Spanish Arbequina and Italian Maurino olive ( Olea europaea L.) cultivars under super-intensive grove conditions.

The study was carried out in a four-year-old super-high density olive grove in Central Italy to compare leaf gas exchanges of Spanish Arbequina and Italian Maurino olive cultivars. Overall, from mid July to mid November, Maurino had a slightly higher maximum light-saturated net photosynthetic rate ( P) than Arbequina. The lowest and the highest P values were recorded at the end of July and in mid November, respectively. Current-season leaves showed similar or slightly higher P values than one-year-old leaves. During the day Maurino always had slightly higher values or values similar to Arbequina, with the highest P being in the morning. Maurino had similar or higher dark respiration rate ( R) values compared to Arbequina. During the day, in both cultivars the R was lower at 9:00 than in the afternoon. The pattern of the photosynthetic irradiance-response curve was similar in the two genotypes, but the apparent quantum yield ( Y) was higher in Maurino. In both cultivars intercellular CO concentration ( C) tended to increase when P decreased. The increase in C corresponded to a decrease in stomatal conductance ( g). The transpiration rate ( E) increased from mid July to the beginning of August, then decreased in September and increased again in November. Particularly in the morning, the current-season leaves showed similar or slightly higher E values than the one-year-old leaves. During the day, in both cultivars and at both leaf ages, E was higher in the afternoon. No effects on leaf gas exchanges due to the presence or absence of fruit on the shoot were found. Overall, there was satisfactory physiological adaptation for Arbequina to the conditions of Central Italy and for Maurino to the superintensive grove conditions. [ABSTRACT FROM AUTHOR]