Gas exchange in olive fruit

摘要

Studies in a 30-year-old non-irrigated orchard of olives cv. Leccino in Foligno, Italy, between full bloom (mid-June) and harvest (end of November) showed that fruit dry matter (DM) increased from fruit set (mid-June) to the end of October. The oilcontent increased rapidly from the beginning of August, about 40-50 days after full bloom, 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 rapidly decreased. Gross photosynthetic rate (PG) in full sunlight was high in the first 3 weeks after fruit set, when the chlorophyll 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 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 had 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 cellular differentiation, whereas the constant high Ci seems to exclude the influence of Gs decrease.