Agostino Tombesi

Gas Exchange in Olive Fruit

Dry matter (DM) of olive fruit (cv. Leccino) constantly increased from fruit-set (mid-June) to the end of October. The oil content increased rapidly from the beginning of August, about 40-50 d after full bloom (AFB), to the end of October. As the oil content increased, the saccharide content decreased. On a DM basis, fruit dark respiration rate (RD) and stomatal conductance (Gs) were high soon after fruit-set, then strongly decreased. Gross photosynthetic rate (PG) in full sunlight was high in the first 3 weeks after fruit-set, when the chlorophyll (Chl) content and the ratio between fruit surface area and volume were high, then it progressively decreased. The fruit intercellular CO2 concentration (Ci) was always relatively high, particularly from September onwards. The PG increased following the increase of irradiance (I). The daily PG trend was similar to the I and temperature trends, showing the maximum values at 14:00 h. For a large part of the fruit growing period, during daylight, the CO2 intake by a fruit permitted the reassimilation of a large part (40-80%) of the CO2 produced by RD. The stomata in the first stages of fruit growth were oval and surrounded by guard cells, two months later they lost their shape and were covered by wax. The reduction in fruit PG during fruit growth could be connected to the reduction of the ratio between fruit surface area and fruit volume and the cellular differentiation, whereas the constant high Ci seems to exclude the influence of Gs decrease. Even if olive fruit is highly heterotrophic organ, its photosynthesis can considerably reduce the use of assimilates for respiration and favour fruit maintenance and growth.

Effects of gibberellic acid, asparagine and glutamine on flower bud induction in olive

SummaryIn 1992, the following treatments were applied to olive trees, cv. Maurino, which had average flowering: removal of 50% and 100% of the flowers in mid-June, leaf treatment with gibberellic acid (GA3) at 60 ppm in mid-July, at the end of August, in mid-October and in July, August and October, leaf treatment with paclobutrazol (PP333) at 1000 ppm at the end of October, treatment of the soil with asparagine (10–5M) and glutamine (10–5M) at the end of December. Thinning and complete removal of the blossoms stimulated vegetative activity. Treatments with GA3 in July slightly increased vegetative growth in both the treatment year and the following year, while the later treatments and those with asparagine and glutamine stimulated growth only in the following year. PP333 reduced plant growth in the year following treatment. The complete or partial removal of the olive blossoms strongly increased flowering and fruit production in the year following treatment. Treatment with GA3 and PP333 did not significan...