Hava F. Rapoport

Productivity of olive trees with different water status and crop load

SUMMARY 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 cross-sectional 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.

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.

Long-term evaluation of yield components of young olive trees during the onset of fruit production under different irrigation regimes

A four-year study was conducted on young Olea europaea L. trees to investigate the effect of deficit irrigation starting from the onset of fruit production. Subsurface drip irrigation was used to supply 100% (FI), 46–52% (DI), or 2–6% (SI) of tree water needs. Tree growth was reduced by deficit irrigation, whereas, return bloom was not. Per tree fruit yield of DI trees was 68% that of FI, but fruit yield efficiency based on tree size was similar between treatments. Fruit set and the number of fruits of FI trees were similar to those of DI trees and significantly higher than in SI trees. No significant differences in fruit fresh weight were found between FI and DI. The oil yield and oil yield efficiency of the DI treatment were 82 and 110% that of FI trees, respectively. A level of about 50% deficit proved sustainable to irrigate trees for oil production.

The floral biology of the olive: effect of flower number, type and distribution on fruitset

Abstract The effect of flower number and distribution on the fruiting behavior of various olive cultivars was studied over a period of 10 years. The number of staminate flowers within each cultivar had no significant effect on fruitset. Pre-bloom removal of up to 50% of the flowers did not affect fruitset. Variation in prebloom flower-removal position resulted in similar fruitset per inflorescence, whether flowers were removed along the inflorescence axis or from the distal half of each inflorescence. Removal of half of the inflorescences resulted in doubling the fruit set on the remaining ones, except in cv. Koronaiki which normally sets more than one fruit on most of its inflorescences. The distal fruitful inflorescence set more than one fruit (mostly two) on 70–80% of the shoots of various cultivars. In cv. Santa Caterina a clear increase in fruitset per shoot was observed when 80% of the flowers per inflorescence were removed. In this cultivar the lateral flowers were significantly more fruitful than the king flower. This however, was not the case with cv. Manzanillo.

Growth and development of fruits of olive ‘Frantoio’ under irrigated and rainfed conditions

Summary A field experiment was performed in Tuscany, Italy, whereby fruit growth and development of irrigated olive trees (Olea europaea L. ‘Frantoio’) were compared, at two stages of fruit development, with those of trees cultivated under rainfed conditions. The fresh weight of fruits from irrigated trees was significantly higher than that from rainfed trees at 21 weeks after full bloom (AFB), whereas there were no differences at 8 weeks AFB or in fruit dry weight at both dates. Mesocarp transverse equatorial areas were 15.6 and 13.5% greater for the irrigated treatment than rainfed cultivated trees at 8 and 21 weeks AFB, respectively. Endocarp transverse area did not increase between 8 and 21 weeks AFB, indicating that endocarp expansion had occurred completely by 8 weeks AFB. The endocarp transverse area of irrigated trees was greater than that of unirrigated trees. For both treatments, mesocarp transverse area increased about 2.5-fold from 8 to 21 weeks AFB. Growth of the mesocarp between sampling dates was mainly due to a more than two-fold increase in mesocarp cell size for both treatments, whereas cell number increased only slightly over the same period. Irrigation appeared to increase mesocarp cell size rather than mesocarp cell number on both sampling dates. There were no differences in mesocarp oil content between irrigated and rainfed trees either at 8 or at 21 weeks AFB.

Influence of temperature on the growth and development of olive (Olea europaea L.) trees

Summary Temperature is one of the most important factors controlling plant growth and development. Knowledge of the effects of temperature on plants is vital if crop management strategies are to be optimised and the best varieties chosen for local conditions. As the effects of global warming are now becoming patent, it is even more critical that we should understand how temperature affects crop growth. In this study, degree-day (DD) accumulation was used to establish the influence of temperature on flowering, vegetative growth, and fruit growth in olive. The results show that the timing of olive flowering in the study region can be predicted from mean April and May temperatures, although this can be improved by taking into account the maximum March, and even February, temperatures. With respect to heat accumulation and flowering, the lower threshold temperature (LTT) was 4.7ºC, with 890 ºCd necessary. The LTT for trunk growth was 7ºC, while that for shoot and crown volume growth was 13º – 14ºC. The LTT for fruit growth was 15ºC with respect to fresh weight, and 24º – 26ºC with respect to cross-sectional diameter. The increase in the longitudinal diameter of fruit was more rapid than the increase in the cross-sectional diameter, which was more dependent on temperature. Increasing temperatures in the study area would cause olive trees to flower earlier and their growth period to be lengthened.

Early growth and development of the olive fruit mesocarp

SUMMARY We examined growth and development of the ‘Manzanilla’ olive fruit mesocarp in transverse equatorial sections during the first 12 weeks after full bloom (AFB). Sequential sampling and quantitative data provided an integrated view of the formation of this tissue. The mesocarp, or fruit flesh, was formed by relatively isodiametric parenchyma cells with a small number of isolated sclereids. By four weeks AFB a gradient in cell size characteristic of mature olive fruits began to appear. Biweekly measurements of cell size and number indicated that, as in other drupes, both cell division and expansion contribute to initial mesocarp growth. From six weeks AFB, further mesocarp growth was determined solely by cell expansion. Transverse areas of mesocarp and endocarp, also measured biweekly, revealed that both tissues expand in a similar manner until eight weeks AFB, after which mesocarp growth predominated.

Tissue size and cell number in the olive (Olea europaea) ovary determine tissue growth and partitioning in the fruit

The relationship between tissue size and cell number in the ovary and tissue size in the fruit, was studied in eight olive (Olea europaea L.) cultivars with different fruit and ovary size. All tissues in the ovary increased in size with increasing ovary size. Tissue size in the fruits correlated with tissue size in the ovary for both mesocarp and endocarp, but with different correlations: the mesocarp grew about twice as much per unit of initial volume in the ovary. Tissue size in the fruit also correlated with tissue cell number in the ovary. In this case, a single regression fitted all data pooled for both endocarp and mesocarp, implying that a similar tissue mass was obtained in the fruit per initial cell in the ovary, independent of tissues and cultivars. Tissue relative growth from bloom to harvest (i.e. the ratio between final and initial tissue size) differed among cultivars and tissues, but correlated with tissue cell size at bloom, across cultivars and tissues. These results suggest that in olive, tissue growth and partitioning in the fruit is largely determined by the characteristics of the ovary tissues at bloom, providing important information for plant breeding and crop management.

Morphological and anatomical evaluation of adult and juvenile leaves of olive plants

The olive tree (Olea europaea L.), like many other woody plants, has a long juvenile period in which the plant is not able to produce flowers. Knowledge of the moment when the plant is capable of flowering is important for breeding programs and also for determining the physiological basis for sexual reproductive behavior, but currently the only indicator of that moment is the actual flowering. In many species, the juvenile-to-adult phase shift includes changes in leaf structure known as heteroblasty, that is, varied form of successive leaves on the same plant. Some differences have been observed between juvenile and adult olive leaves, particularly in size and form, but to our knowledge, no complete systematic study has been carried out. In this research, we measured size, morphology and anatomy for juvenile and adult leaves of olive plants grown from seeds. Differences were found in most of the parameters studied, including leaf size, form, mesophyll thickness, layers of palisade parenchyma and quantity of peltate trichomes, which were generally significant but overlapping between the two leaf types. The most consistent and striking difference was the presence of an organized layer of subepidermal cells only in the abaxial mesophyll of adult leaves. This characteristic could be a simple and effective criterion of phase change in the olive tree.

FEASIBILITY AND ANATOMICAL DEVELOPMENT OF AN IN VITRO OLIVE CLEFT-GRAFT

SummaryThe feasibility and anatomical development of an in vitro olive cleft-graft method were studied. Grafting survival after 60.d in vitro was 85% which then dropped slightly to 67% after hardening. Three days after grafting, callus formation was observed along the cut surfaces of the rootstock and scion, after 6.d the first healing cellular unions were observed, and by 12.d after grafting a strong union developed. The first cellular differentiation to form vascular tissues was observed 12.d after grafting and continued rapidly until a total connection was reached 10.d later. Thus a complete graft union of the in vitro olive cleft-grafts was achieved in three weeks, and vigorous plants were established after 60.d of in vitro culture followed by 10.d of hardening. The in vitro olive cleft graft is suggested as an effective and useful method for germplasm multiplication.