Studying the composition of olive oil requires cold-press olive oil extraction. One of the most common laboratorial mills is the Abencor system. However, its operation protocol was formulated decades ago for Spanish olive varieties from traditionally rain-fed orchards. We modified this protocol for use with ''Barnea'' and ''Picual'' olives from irrigated orchards that are characterized by high water content. Independent effects of malaxation time, temperature, water addition and talc addition on extraction efficiency, and major quality indices of virgin olive oil were studied. Overall, addition of talc to the fruit paste was the most significant treatment in terms of yield and quality of the oil although its effect was cultivar dependent. Improved oil yield was particularly significant for ''Picual.'' Extended malaxation time was also effective in improving oil extractability. Addition of talc generally improved oil-quality parameters, while water addition had the opposite effect. Yet, quality parameters remained within the extra virgin level. Temperature increments reduced oil quality. The need to adapt a modified protocol for use with fruits from irrigated orchards that will facilitate critical comparison of results obtained from different agronomic theses and different laboratories is highlighted. It is recommended that each laboratory develops an appropriate protocol for the operation of the Abencor system in accordance to the characteristics of the olive fruit they are working with.Practical applications: Abencor system serves as the major laboratorial mill world-wide. Those mills allow the researchers to characterize olive oil in accordance to the treatments received by the trees. This cannot be done in commercial mills. The system operation protocol was established decades ago for fruits from rain-fed orchards. In the past decade there was a rapid increase in the use of irrigation in olive orchards and therefore it is crucial to optimize the operation protocol for fruit with relatively high water content. In the current work we have evaluated the influence of a series of technological parameters (i.e., talc and water addition, malaxation time, and temperature) on the extraction efficiency and quality indices of olive oil. This allowed us to present a modified protocol for the Abencor system operation suitable for olive fruit of irrigated orchards that will facilitate a reliable representation of the influence of different treatments on the yield and characteristics of the olive oil.

Olive (Olea europaea) has a very high tendency for year-to-year deviation in yield (alternate bearing), which has a negative economic impact on the olive oil industry. Among possible reasons for alternate bearing, depletion of stored carbohydrates (CHO) during the On-year (high yield) has often been mentioned. The objective of the present study was to verify the role of CHO reserves, as a cause or effect, in the alternate bearing of intensively cultivated olives. A monthly survey of soluble sugar and starch concentrations in the leaves, branches, bark and roots of On- and Off-trees (cv. Barnea) was carried out during a complete reproductive cycle from November 2005 to October 2006. Carbohydrate concentration in the sapwood was determined in January, as well as an estimate of whole-tree biomass. The trunk and limbs possess the largest portion of CHO reserves. The influence of reduced fruit load on CHO reserves was also investigated. Starch, mannitol and sucrose concentrations increased from December to March in all tissues, and then declined along with fruit development. Leaves, branches and bark have a significant role in CHO storage, whereas roots accumulated the lowest CHO concentrations. However, fluctuations in reserve content suggested considerable involvement of roots in the CHO budget. Nevertheless, there were no meaningful differences in the annual pattern of CHO concentration between On- and Off-trees. Even a 75-100% reduction in fruit number brought about only a minor, sluggish increase in CHO content, though this was more pronounced in the roots. Carbohydrate reserves were not depleted, even under maximum demands for fruit and oil production. It is concluded that in olives, the status of CHO reserves is not a yield determinant. However, they may play a significant role in the olive's survival strategy, ensuring tree recovery in the unpredictable semiarid Mediterranean environment. This suggests that CHO reserves in olive act like an active sink, challenging the common concept regarding the regulation of CHO reserves in plants.

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The objective of the present study is to evaluate a Citrus tree's investment in the flowering process in relation to its photoassimilate resources, as a part of its annual reproductive effort. The overall requirement for carbohydrate of a single flower of grapefruit (Citrus paradisi Macf. cv. 'Marsh seedless') is evaluated as 8·33 × 10 -3 mol C over 3 weeks. The direct cost of production of a single flower is estimated to be 5·75 × 10 -3 mol C, most of which is allocated to the petals, anthers and style -organs designated to abscise. About 2·58 × 10 -3 mol C is consumed by respiration not associated with growth processes. Growth respiration (R g ) occurs mostly during early stages of flower growth and development. However, the total respiration rate increases sharply during anthesis, when growth processes have almost ceased. Ethylene evolution also reaches remarkably high rates during anthesis. High temperatures increase the rate of flower respiration (Q 10 = 2·12) but shorten the duration of flowering. A grapefruit tree may bear each year 20 000-50 000 flowers, only 0·5-2·5% of which develop into mature fruit. The amount of carbohydrate invested each year in bloom at the whole-tree level is 166-400 mol C per tree (depending on the number of flowers), amounting to 10-20% of the carbohydrate consumed for fruit growth. The overall daily demand for carbohydrate by the flowers of a grapefruit tree during anthesis may exceed the daily carbohydrate production by the leaves. High temperatures lead to a further increase in the daily demand for carbohydrate. In such cases, the management of flowering must rely on carbohydrate reserves recruited from other tree organs. The ecophysiological and evolutionary aspects of Citrus flowering are discussed.Key-words: Citrus paradisi; alternative pathway of respiration; carbohydrate demand; flowering; growth respiration; maintenance respiration; reproductive effort; sink; source. INTRODUCTIONA single Citrus tree (e.g. C. sinensis) may bear a large number of flowers (up to 250 000) during each blooming season, depending on the cultivar, tree size and environmental conditions (Monselise 1986). Only a small proportion of the flowers develop into mature fruit (0·1-3·5%) (Monselise 1986); most of the reproductive units abscise as flowers or fruitlets within 2 months of blooming. A grapefruit (C. paradisi) tree bears a relatively modest number of flowers, 20 000-50 000, only 400-600 of which will be harvested as fruit.Citrus flower development lasts about 3-5 weeks and may be characterized by several stages (Goldschmidt & Huberman 1974), as illustrated in Fig. 1. At anthesis, growth (in terms of dry weight) of all flower organs except the ovary has already terminated. Petals, anthers and style, which comprise the larger portion of the flower, drop after anthesis. Considerable nectar production (Monselise 1985) and respiratory losses must also be taken into account in the metabolic cost of flowering.Weather conditions during bloom, mainly temperature, have major effects on Citrus ...