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 (Ww) 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 Ww = 0.97 MPa) increased rapidly and reached the greatest final size, that from the most stressed (average Ww = 2.81 MPa) grew most slowly and were smallest. In general, equatorial transverse areas of the mesocarp increased with increasing Ww, 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 Ww. 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-toendocarp ratio were found with Ww 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 Ww 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 Ww 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

Interaction of crop load and water status on growth of olive fruit tissues and mesocarp cells

Trabajo presentado en el XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Plant Physiology from Cell to Fruit Production System, celebrado en Lisboa (Portugal) del 22 al 27 de agosto de 2010.Field-grown olive trees (Olea europaea L. ‘Leccino’) were hand-thinned at 5-6 weeks after full bloom (AFB) to establish heavy or low crop loads, and then were subjected to three irrigation regimes: a) FI, fully-irrigated with pre-dawn leaf water potential (LPWP) greater than -1.1 MPa; b) DI, deficit irrigated (LPWP between -1 and -3.3 MPa; c) SI, water stressed (LPWP higher than -4.2 MPa). Fruits were sampled at pit hardening and harvest, the mesocarp separated from the endocarp, and their fresh weight and dry weight determined. Additional fruits were fixed in FAE for anatomical studies, their mesocarp and endocarp area measured on transverse slices with an image analysis system connected to a stereo microscope. Mesocarp cell size and number were then determined by microscope after standard paraffin processing. The effect of crop load on the growth of fruit tissues was significantly influenced by the irrigation regime. Within the FI or DI treatments the mesocarp dry weight was higher at low than at high crop load. In the SI treatment, mesocarp dry and fresh weights were 180 and 200% respectively those for trees bearing high crop loads. The pulp-pit ratio was decreased by high cropping for both DI and SI treatments, but was unaffected for the fully-irrigated trees. Overall, there was a notable interaction of crop load and water status on fruit growth processes at multiple morphogenetic levels, including the absolute and relative growth of pulp and pit, mesocarp cell division and enlargement.Peer reviewe

The effect of water deficit during early fruit development on olive fruit morphogenesis

A field experiment was conducted over two growing seasons to determine the combined effect of crop load and irrigation on yield components of olive trees (Olea europaea L. ‘Leccino’) planted at 6 m 3.8 m in a sandy-clay soil. Different crop loads were established by manual thinning of fruits. Drip irrigation was managed to maintain pre-dawn leaf water-potentials (PLWP) within the following ranges: (i) higher than –1.1 MPa (FI; fully irrigated); (ii) between –1.0 and –3.3 MPa (DI; deficit irrigated); or (iii) below –1.2 MPa, but not lower than –4.2 MPa (SI; severe deficit irrigated).The irrigation period lasted from 6 – 16 weeks after full bloom (AFB) in 2003, and from 5 – 19 weeks AFB in 2004. In 2003, full bloom was on 26 May; in 2004, it was on 3 June. Neither irrigation regime nor crop load affected flowering or flower quality the following Spring. The combined fruit yields [on a fresh weight (FW) basis] over both years in SI and DI trees were 49.0% and 81.6% of FI trees, respectively.The oil yields of SI and DI trees were 52.5% and 81.2% of FI trees, respectively. Fruit FWs in FI trees were greater than those of DI or SI trees at 8 weeks AFB.At harvest, FI trees bore the largest fruits, and SI trees the smallest fruits. The FWs of individual fruits at harvest in the FI and DI treatments decreased as crop load increased, but no such relationship was apparent for SI trees. The oil content of the mesocarp increased as PLWP increased from approx. –3.5 MPa to –1.5 MPa.The oil content of FI trees at harvest decreased from 53.1% to 45.7% dry weight as fresh fruit yield increased from 5 – 25 kg dm–2 trunk crosssectional area. However, crop load did not have any effect on the oil content of the mesocarp in DI trees. Fruit maturation was delayed by irrigation. Maturation index also decreased (indicating delayed maturation) as the crop load on FI or DI trees increased, but did not vary with crop level in SI trees

O papel das folhas na entrada e saída da dormência dos gomos de oliveira

Estaquinhas sub-apicais com três nós, obtidas a partir de ramos do ano, foram forçadas, com e sem folhas, em câmaras de crescimento a 20°C, ou armazenadas a 5°C antes do período de forçagem, com o objectivo de determinar o papel das folhas na entrada e quebra da dormência dos gomos da oliveira. Os resultados dos ensaios realizados com estaquinhas forçadas imediatamente após a sua colheita no campo mostram um efeito inibidor das folhas no abrolhamento dos gomos localizados nas respectivas axilas (paradormência) até meados de Fevereiro, com algumas diferenças entre as árvores com (safra) e sem (contra-safra) frutos. Nas árvores sem frutos, o abrolhamento dos gomos axilares das estacas sem folhas vai diminuindo progressivamente ao longo do período outonal, enquanto nas árvores com frutos o abrolhamento é irregular, mas mais uniforme durante todo o período de observação. Em meados de Fevereiro, nas estacas colhidas nas árvores sem frutos no ano anterior, as folhas perdem o seu efeito inibidor, justamente no momento em que todos os gomos abrolhados passam a dar origem a inflorescências. Os resultados dos ensaios com armazenamento prévio a 5°C das estacas colhidas em árvores sem frutos confinam o papel inibidor das folhas sobre o abrolhamento, quer o momento da desfoliacao tenha sido antes ou depois do armazenamento. Contudo, apenas nas estacas armazenadas com folhas se notou uma redução no abrolhamento dos gomos axilares e a produção de inflorescências. Estes resultados sugerem um importante papel das folhas na imposição progressiva de um certo estado de dormência dos gomos reprodutivos da oliveira e que esse papel se mantém até à completa satisfação das necessidades em frio