Enrico Maria Lodolini

Water deficit-induced changes in mesocarp cellular processes and the relationship between mesocarp and endocarp during olive fruit development

A field experiment was conducted during two consecutive growing seasons to determine and quantify the growth response of the olive (Olea europaea L. cv. Leccino) fruit and of its component tissues to tree water status. Pre-dawn leaf water potential (Psi(w)) and fruit volume were measured at about weekly intervals, and fresh weight (FW) and dry weight (DW) of the fruit tissues at 15, 20 and 21 weeks after full bloom (AFB). Fruit anatomical sections were prepared at 8, 15 and 21 weeks AFB for area determinations and cell counts. Fruit volume of the well-watered trees (average Psi(w) = -0.97 MPa) increased rapidly and reached the greatest final size, that from the most stressed (average Psi(w) = -2.81 MPa) grew most slowly and were smallest. In general, equatorial transverse areas of the mesocarp increased with increasing Psi(w), and this response was more evident at 21 than at 15 weeks AFB. By 21 weeks AFB, the mesocarp of the well-watered trees reached values more than three times higher than those measured at 8 weeks AFB. The endocarp FW and DW did not increase between 15 and 21 weeks AFB. Within each sampling date the endocarp area, FW and DW responded weakly to Psi(w). The mesocarp-to-endocarp ratio (FW and DW) increased from 15 to 21 weeks AFB regardless of water status, mainly due to the mesocarp growth. In both years at 20 and 21 weeks AFB, low values of the mesocarp-to-endocarp ratio were found with Psi(w) below -2.5 MPa. Within the mesocarp, cell size was more responsive to water deficit than to cell number. At 8 weeks AFB, the number of cells in the mesocarp was unaffected by tree water deficit, whereas cell size decreased, although slightly, in fruits sampled from trees in which Psi(w) was < -3.0 MPa. At 21 weeks AFB, cell size showed a linear decrease with increasing level of water deficit, whereas the number of cells at 21 weeks AFB decreased as the Psi(w) decreased below -2.5 MPa and seemed unaffected above that range. Overall, the results clarify the complexity of the water-induced response of mesocarp and endocarp growth and cellular processes of olive fruits.

Olive (Olea europaea L.) Root Growth in Soil Sectors with Olive Husks and Hay Residues

ABSTRACT Olive oil by-products have an important fertilizing value due to their high organic matter and nutrient content; however, they also possess a phytotoxic effect. Therefore, it is necessary to study the reaction of plants and, more specifically, the roots of olive trees to the presence of husks used as amendment in olive orchards. In this experimental work olive plants were grown in split-pots in which the roots were divided in four sectors and grown in different substrates. Husks, hay, and a mixture of the two was added to a soil substrate to simulate growing conditions in an olive orchard with green mulching. Results showed that olive roots performed differently in the different substrates. Husk substrates were avoided if a husk-free section was present. If not, the plants stopped growing and half of them perished. If hay was added with husks the toxic effect was reduced. It can be argued that in the field, olive plants, thanks to their great transmigration capacity, may be able to avoid the patches amended with husks, but repeated treatments with husks could cause shoot growth problems because it would be more difficult for roots to find optimal substrate to continue their growth.

Oil Characteristics of Four Palestinian Olive Varieties

Olive oil represents an important source of income for Palestinian farmers in local, national and international markets. Sometimes, olive oil produced in local climatic conditions, does not achieve the International Olive Council (IOC) trade standards so that international markets are precluded. The oil chemical composition and sensory profile of four Palestinian olive varieties (Nabali Baladi, Nabali Mohassan, Souri and K18) were characterized in 2010 throughout an in situ evaluation. Most of the physicchemical characteristics and the fatty acid composition of the varieties met the International Olive Council trade standards (IOC-TS) for extra virgin olive oils. Values of K270 for Nabali Baladi and linolenic acid for Souri slightly exceeded the limit. Eicosanoic acid exceeded the IOC-TS limits in the oils of all considered varieties. Among the sterols, the Δ-7-stigmastenol resulted too high for Nabali Baladi and Souri. Sensory profile for the tested varieties showed a reminiscence of tomato or artichoke and light to medium bitter and pungent sensations. Results represent an important baseline reference for further studies about oil composition and quality of the main Palestinian olive germplasm and provide indication of potential critical points to be controlled in order to ensure the full achievement of IOC-TS and access international markets.