Effect of artificial chilling on the depth of endodormancy and vegetative and flower budbreak of peach and nectarine cultivars using excised shoots

Stem cuttings were obtained from 12 peach and nectarine cultivars during leaf fall, placed in plastic bags at 3.0 ± 0.1 °C to simulate 0–800 h of chilling and forced to budbreak at 20.0 ± 1.0 °C for a period of 6 weeks. Some cultivars showed high blooming and leafing without exposure to chilling; chilling enhances leafing and blooming but the percentage increment was higher in leaf buds. In general, maximum budbreak was reached with less chilling accumulation (<100–200 h) in flower buds compared with leaf buds; excessive chilling caused a reduction of the percentage budbreak in flower but not in leaf buds. Additionally, chilling modified the proportion of blooming that occurred before leafing. In non-chilled shoots, blooming occurred earlier than leafing, except in cv. ‘San Pedro 16–33’ but the proportion of blooming before leafing decreased significantly with chilling in most cases. By studying the mean time to budbreak, we conclude that the flower bud generally has a lower intensity of rest; the intensity of rest declines at a slower rate in flower than in leaf buds with chilling; flower buds had greater heat requirements than leaf buds when the chilling requirement had been covered, so that each peach cultivar had a point of critical chilling accumulation below which blooming tended to occur earlier, and above which leafing tends to occur first. Flower and leaf buds had different depths of endodormancy but similar chilling requirements in the majority of peach and nectarine cultivars studied. Finally, different varieties with similar chilling requirements showed different responses to chilling. Therefore, the cutting test measuring the response of vegetative and floral buds provides considerable information on the characterisation of the variety, compared with the sole and traditional data of chilling requirements.     

The effect of chilling,defoliation and hydrogen cyanamide on dormancy release,bud break and fruiting of Anna apple cultivar

The effect of defoliation (DEF) alone or combined with hydrogen cyanamide (HC) on dormancy state, fruit quality and yield of Anna apple cultivar was studied. Trees were manually defoliated on three successive dates, November 15th, December 1st and December 15th. The flower buds (FB) entered the endodormancy synchronized with vegetative buds (VB) for most of the treatments. Most of the treatments terminated endodormancy between January 27th and February 8th during the season 2004/2005 and between January 18th and February 8th during the season 2005/2006. The treatments were effective in dormancy release of FB and somewhat with VB. Defoliation on November 15th + HC recorded the lowest chilling accumulation needed to reach 50% bud break. All the treatments exceeded the control considering the percentage of flower (FBB) and vegetative bud break (VBB) either in the lab or at the field. Growing degree hours and the number of days required to reach each stage of fruiting were differed between the two studied seasons. The control and DEF on December 15th exceeded all the treatments regarding initial fruit set percentage (IFS). The defoliation treatments alone gave the highest yield (kg/tree). Defoliation + HC treatments gave the best fruit quality, while the control gave the least values.     

Pistachio Production Management in Iran by Rest-breaking Treatment and Comparison of Dynamic vs Chill Hour Model for Chill Accumulation

Shortage of winter chill has reduced pistachio (Pistacia vera L.) fruit yield and quality from 2015 to 2018 in Iran. In this study accumulated chilling was determined by the chill hour (CH) and the dynamic (DM) model in five regions near Shahrebabak County, Kerman Province, Iran, for dormant season 2017–2018. The CH model has been routinely used in Iran for reporting chilling accumulation for pistachios. This study suggested that the DM better differentiated regional chill accumulations, the impact of chilling on phenological indices of growth and production between cultivars ‘Owhadi’ and ‘Akbari’, with and without rest-breaking (RB) treatments of Volk dormant oil. Volk oil treatment significantly improved vegetative and reproductive development, offset lack of chilling effects on pollination and nut filling, and may have advanced budbreak in some instances.

     

Effect of climatic conditions on the overcoming of dormancy in apricot flower buds in two Mediterranean areas: Murcia (Spain) and Tuscany (Italy)

For temperate-zone fruit species such as apricot, when winter cold requirements are not adequately satisfied, negative repercussions on productivity occur. The aim of this research was to study the effect of, mainly temperature on the overcoming of dormancy in different apricot cultivars growing in two areas (Italy, Tuscany: lat. 43°02′N, long. 10°36′E; Spain, Murcia: lat. 38°16′N, long. 1°16′W) representative of the Mediterranean climate. Trials were conducted for two consecutive years on the same genotypes: ‘Currot’, ‘San Castrese’, ‘Goldrich’, ‘Stark Early Orange’ and ‘Orange Red’. These genotypes cover the range of chilling requirements (CR) in the apricot species in these Mediterranean areas. The CR (measured by chill units, CU and portions) for breaking of dormancy, heat requirements, flowering date and flowering and fruit-set percentages were measured. Temperatures were recorded and transformed into the corresponding CU and portions by the Utah Model and the Dynamic model, respectively. The winter climatic conditions determined a dissimilar chill unit accumulation in Tuscany (Italy) and Murcia (Spain) as well as an important effect of the year in both areas. While all cultivars with the exception of Stark Early Orange overcame dormancy, significant differences regarding the CR of cultivars for two different years and growing in two environments were observed, depending also on the cultivar. The results showed that both the Utah Model and Dynamic Model were not completely accurate with regard to establishing the CR for dormancy release under a Mediterranean climate. Temperature should be analysed together with other climatic factors in order to improve the CR assessment.     

Biochemical changes in dormant grapevine shoot tissues in response to chilling: Possible role in dormancy release

At leaf fall, one-year-old shoots of cv. Superior Seedless table grape were collected and cut into single-node sections. These cuttings were subjected to 0, 100, 200, 300, 400 or 500 h of chilling at 5 °C to simulate natural chilling accumulation. After each treatment, one group of cuttings was forced to break buds while a second group was used to study biochemical changes taking place in the bud and underlying internode tissues. Carbohydrates, free polyamines and proline concentrations were determined and amylolitic and invertase (EC 3.2.1.26) activities were estimated. Low temperature treatment caused a hydrolysis of starch concomitant with an accumulation of sucrose. There was also a rapid build-up of proline, putrescine (Put) and spermidine (Spd) which reached their maximum levels at 300 positive chill units (PCU). Afterwards, as buds approached chilling satisfaction (400 and 500 PCU), hexoses accumulated in the buds while sucrose concentration increased considerably in both structures. Proline and Put, however, decreased in both tissues. Spd level remained high, while spermine (Spm) increased slightly. Changes in starch concentration seem to be controlled by α-amylase (EC 3.2.1.1). Sucrolytic activity, consisting mainly in the acid invertase form, changed inversely to sucrose concentrations. Nevertheless, at chilling satisfaction both sucrose content and invertase activity remained high in the buds implying a possible import of sucrose into the bud which acted as a strong utilizing sink. Our data suggest that limited budbreak due to a lack of chilling may be due to low hexoses availability. However, as buds approached chilling satisfaction, a high acid invertase activity, high soluble sugars concentration and a decrease in Put to Spd plus Spm ratio appear to be correlated with bud dormancy release and improve budbreak. Furthermore, endodormancy can be divided into two phases: the first one (from 0 to 300 PCU) is an acclimation period; the second (from 300 to 500 PCU) is a beginning of growth resumption.     

Mehr Chilling f��r Obstb?ume in w?rmeren Wintern?

The objective of this study was the calculation of winter chill for fruit trees in the Meckenheim fruit growing region for all winters since 1958 and the evaluation of long-term trends in response to global warming. A further objective was the comparison of three winter chill models, the Chilling Hours Model (Chilling Hours??CH), the Utah Model (Chill Units??CU) and the Dynamic Model (Chill Portions??CP) with respect to temporal trends and seasonal variation in chilling intensity. To meet these objectives, about 120,000 hourly temperature measurements from Klein-Altendorf were correlated with daily temperature extremes. From this relationship, a long-term record of 466,000 hourly temperature data was constructed and used to calculate winter chill between 1st October of each year and three dates of the following year for all winters since 1958/1959. On average over all years, 955 CH, 1160 CU and 58.0 CP had accumulated in the Meckenheim fruit growing region by 1st January, 1356 CH, 1527 CU and 77.3 CP by 1st February, and 1727 CH, 1883 CU and 96.1 CP by 1st March. Coefficients of variation varied between 14 and 16% for the Chilling Hours Model, between 18 and 19% for the Utah Model and between 9 and 10% for the Dynamic Model. In spite of significant warming of the site, no clear long-term trends were detected. Due to the structure of the winter chill models, which do not consider freezing temperatures as chilling-effective, the highest chilling was not registered in the coldest winters, but rather when average temperatures between early December and late February were between 2 and 6°C. The coldest winter on record (1963/1964; mean winter temperature of ??4°C) had by far the lowest winter chill total, and chilling during the more recent cold winters 2009/2010 and 2010/2011 was also below average. Only very pronounced warming reduced winter chill, with the warmest winter on record (2006/2007; mean winter temperature of 7.1°C) accumulating less winter chill than slightly cooler winters. As long as such extreme temperatures remain exceptional, fulfilment of chilling requirements of local apple and cherry cultivars should not become critical. It is important to note, however, that substantial knowledge gaps exist in the field of fruit tree dormancy, which will have to be closed, before more reliable projections of future fulfilment of chilling requirements can be made.     

High temperatures and time to budbreak in low chill apricot ‘Palsteyn’. Towards a better understanding of chill and heat requirements fulfilment

The efficiency of different temperature cycles in inducing budburst of one-year-old shoots of the apricot cultivar ‘Palsteyn’ from dormancy was evaluated. Three replications of shoots were collected during two consecutive years from adult trees, following the accumulation of different amounts of chilling in the field. Thereafter, shoots were exposed to different temperature cycles in growth chambers, for 60 days. The temperature treatments included a continuous temperature of 5 °C; daily temperature cycles of 19/5 h at 5/15 °C, at 5/20 °C, and at 5/25 °C; and the same temperature cycles for the remainder of the 60-day period, after pretreatment at 5 °C for 30 or 45 days. After the temperature treatments, shoots were forced at 25 °C until budburst. The mean time to budburst (MTB) (in days) of lateral vegetative, terminal vegetative and reproductive buds was evaluated. The efficiency of the different treatments was greatly influenced by the date on which shoots were cut. High temperatures had a more positive effect on the reduction of MTB when chilling accumulation had occurred in the field instead of the growth chamber. After partial chilling accumulation in the field, high temperatures (25 °C) combined with low temperatures are more efficient than cycles of moderate temperatures (15 or 20 °C) to induce an earlier budburst. In view of these results, a parallel accumulation of both chilling and heat requirements after partial chilling accumulation is suggested. The application of these results could assist in the development of more accurate models for the prediction of the overcoming of dormancy and blooming.     

Auswirkungen des Klimawandels auf die Verfügbarkeit von Kältewirkung (Chilling) für Obstgehölze in Deutschland

To quantify the effects of climate change on fruit production in Germany, this study aimed at determining long-term trends in winter chill, as calculated with the Chilling Hours and Dynamic Models (Chill Portions). An idealized daily temperature curve was used to convert daily temperature records from 43 weather stations, taken throughout the twentieth and late nineteenth centuries, into an hourly dataset, which was then converted to units of winter chill. Besides exposing temporal trends in winter chill, the data could be spatially interpolated, yielding contiguous maps of typical winter chill in Germany around 2010, as well as chilling losses since 1950. Throughout Germany, winter chill varied between 1700 and 3000 Chilling Hours or 125 and 150 Chill Portions. The areas of highest winter chill were located in the northern parts of the country. For the whole of Germany, there were no significant temporal trends. The extent of interregional variation in winter chill depended on the chilling model used. While the Chilling Hours Model showed strong declines in winter chill for the areas around Dresden and Leipzig, as well as for the Lake Constance region, the Dynamic Model did not detect such dramatic changes. More than a decline in winter chill, increased heat during the winter months might become a challenge to German fruit growers. As already experienced during the extraordinarily warm winter of 2006/07, warm temperatures during the winter can cause fruit trees that fulfill their chilling requirements relatively early to bloom prematurely. This can then lead to elevated risk of frost damage and hamper the homogeneity of flowering.     

Simultaneous down-regulation of DORMANCY-ASSOCIATED MADS-box6 and SOC1 during dormancy release in Japanese apricot (Prunus mume) flower buds

In temperate deciduous fruit crops such as Prunus spp., bud endodormancy is an important physiological phase affecting the timing of blooming and subsequent fruit development. Japanese apricot (Prunus mume) bears unmixed flower buds, separate from vegetative buds, that bloom slightly more than a month before vegetative bud burst. Seasonal expression of Prunus mume DORMANCY ASSOCIATED MADS-box genes (PmDAMs) has previously been analyzed only in vegetative buds, with an association between these genes and flower bud endodormancy release not yet confirmed. In this study, we performed a seasonal expression analysis of PmDAM1–6 genes in flower buds of two Japanese apricot genotypes – namely, high-chill and low-chill cultivars. The analysis revealed that PmDAM3, PmDAM5, and PmDAM6 expressions are closely associated with dormancy release in both flower and vegetative buds. In addition, a yeast two-hybrid screening demonstrated that PmDAM6 can interact in yeast with the homolog of Arabidopsis SOC1 (PmSOC1). Synchronized expression patterns were detected in PmDAM6 and PmSOC1 during dormancy release in flower buds of the two genotypes. Taken together, these results suggest that the dimer of PmDAM6 and PmSOC1 may play a role in the regulation of dormancy transition and blooming time in Japanese apricot flower buds.     

Flower morphologic anatomy and embryological characteristics in Chrysanthemum multicaule (Asteraceae)

Chrysanthemum multicaule is an annual herbaceous ornamental species. The inflorescence is gynomonoecious and consists of bisexual tubular florets and female ray florets. The pistils consist of two stigmas which are of the open type with a hollow stylar canal. At the base of the tubular floret style, the pistil is surrounded by oil gland cells. The anthers are tetrasporangiate and the young anther wall is composed of epidermis, endothecium, middle layer and tapetum. The mature anther wall comprises only thickened endothecium after the release of the pollens. In the tubular florets, simultaneous microsporocyte meiotic cytokinesis results in mostly tetrahedral with a small proportion of decussate tetrads. The mature pollen grain is tricellular. The ovules are unitegmic and tenuinucellate, and the nucellus degenerates during the development of the megasporocyte. The development of the embryo sac follows the Polygonum type. At 4–6 days after blooming, the embryos reached the globular stage, thereafter passing through the heart- and torpedo-shape stages before maturing into the cotyledon embryos. From blooming to seed maturity, it takes about 3–4 weeks under our conditions.     

Self-fertilization in homozygous and heterozygous self-compatible almonds

In homozygous self-compatible genotypes 100% of the pollen grains are potentially able to grow through their own pistil, and thus the rate of self-fertilization could be higher than in heterozygous self-compatible genotypes. To evaluate the advantages of growing homozygous self-compatible almonds, pollen tube growth along the pistil at different times following self-pollination, and fruit set were studied in four homozygous and four heterozygous self-compatible seedlings. The results showed important differences between homozygous and heterozygous individuals for the percentages of pollen tubes in the third section of the style at 24 and 48 h, the pollen tube growth rate being higher in the homozygous. Twenty-four hours following self-pollination only the homozygous individuals showed pollen tubes in the ovary. However, at 72 and 96 h those values were similar for both genotypes, suggesting that space and availability of nutrients become the main limiting factors, overcoming the genetic interactions between pollen and pistil. In general, fruit set was similar in homozygous and heterozygous individuals. Interestingly, one of the homozygous individuals showed problems of fruit development, which might be explained by its inbred origin.     

Effect of high temperatures in the pre-blooming and blooming periods on ovule formation,pollen grains and yield of ‘Granada’ peach

The aim of this work was to evaluate the effects of high temperatures in the pre-blooming and blooming periods on the growth of sexual gametes and yield of ‘Granada’ peach. The experiment was carried out in the commercial orchard of Charqueadas, under the subtropical conditions of the Central Depression at Rio Grande do Sul State, Brazil (28°57′S; 51°37′W; 30 m alt.). Two treatments were tested: (1) trees in the greenhouse with partial ventilation and (2) trees in the orchard. The phenology, morphologic constitutions of the pollen grains, ovule growth, yield and germination (%) of pollen grains and fruit set were evaluated. High temperatures in the pre-blooming and blooming periods anticipated the break of dormancy and blooming. These conditions also delayed the female gametophytes (embryo sac) and promoted anomalies in the formation of male gametophytes. Those factors promoted low pollen viability and a lack of synchrony in fertilization, thereby generating low fruit set percentages and yield.     

Developmental problems in over-winter off-season longan fruit. I: Effect of temperatures

Fruit development was investigated in the field in over-winter off-season (bloomed in late November) and on-season (bloomed in mid April) longans (Dimocarpus longan Lour. cv. Chuliang) in 2004–2005 and 2007–2008 crops, and in potted trees grown in phytotrons set at cold (15/10 °C, day/night, simulating winter) or warm temperatures (28/23 °C, day/night) in 2008. Development of fruit in both on-season and off-season longans could be divided into two stages based on the pattern of fresh weight increase. Stage I was characterized by the slow fruit growth, and Stage II by rapid fruit growth with aril expansion. Off-season longan had a longer period of fruit development than on-season longan, chiefly due to a longer Stage I. The development of off-season fruit, especially in Stage I, was exposed to low and abruptly fluctuating temperatures. In contrast, the temperatures during on-season fruit growth were warmer and less fluctuating. Off-season fruit were smaller with a significantly higher fruit drop. Intensive fruit drop did not occur during cold period until temperature had risen. Fruit cracking in off-season longan was severe (27.6%) in 2004–2005 with a dry and cold winter, but negligible in 2007–2008 with a wet and cold winter. In phytotron experiment, trees exposed to the cold temperature regime during early fruit development produced significantly smaller fruit compared to those exposed to the warm temperature regime (6.2 g vs 7.3 g), while there was no significant difference in fruit drop rate and cracking incidence. The results suggested temperatures lower than 15 °C were stressful for the growth of young fruit and reduced the growth potential and thus fruit size. Severe fruit drop in over-winter off-season longan might be associated with stressful cold plus abrupt temperature fluctuations, while severe fruit cracking in over-winter off-season longan might be related to cold and dry weather in the winter.     

Bioindikatoren für den Dormanzstatus bei Obstgehölzen

This contribution is part of a bachelor thesis, which reviews the literature about suitable bio-indicators for the current dormancy status of a (fruit) tree in the winter. This is part of an on-going chilling research project and evaluation of the three chilling models as to their suitability for fruit growing in temperate zone regions with cool winters. The aim is to provide information on the dormancy status of a tree for the application of cultivation techniques to overcome dormancy.     

遮阴对日光温室柑橘生长及生理特性的影响

以4年生枳砧砂糖橘为试材,研究不同遮阴处理对温室柑橘树冠微环境、柑橘生长及叶片生理特性的影响。结果表明:未遮阴的日光温室条件下,中午光合有效辐射强、温度高、相对湿度低,柑橘叶片净光合速率日变化呈"双峰型",有明显的光合"午休"。遮阴可显著降低光合有效辐射,降低柑橘树冠温度,增加树冠相对湿度,柑橘叶片净光合速率日变化表现为"单峰型"。遮阴处理对新萌发夏梢生长表现出抑制作用,随着透光率的降低,柑橘枝长、枝粗、枝条数降低。遮阴处理使柑橘叶片单叶面积增大,叶片变薄。遮阴使叶绿素b含量增加,随着透光率的降低,叶绿素a/b值变小。一层遮阴柑橘幼果坐果率比对照提高了16.44%,二层遮阴处理坐果率为0。     

Growth and its partitioning in Prunus rootstocks in response to root zone temperature

Rootstocks for stone fruit varieties differentially influence tree physiology and one possible explanation for these differences is that varieties vary in their response to root zone temperature (RZT). To examine the effects of RZT, two trials using actively growing plants of five different Prunus rootstocks with chill requirements between 100 and 1100 h were undertaken. Plants were grown at RZTs of 5, 13 and 19 °C for 6 weeks after which total dry matter accumulation and its partitioning amongst roots, stems and leaves was determined. In general, the magnitude of total dry matter and its component parts positively correlated with RZT and significant differences were found among varieties in the magnitude of total dry matter accumulation. Individual varieties ranked differently at the three RZTs with respect to total dry matter: in general, the same ranking was also seen in the ranking of each growth component. RZT significantly influenced partitioning causing differences in leaf, stem and root mass ratios. These differences were greatest at low RZTs and became less as RZT increased. Several patterns of partitioning were found. Firstly, the low chill varieties (Okinawa and Flordagold) were little affected by RZT with similar partitioning occurring at each RZT. Secondly, the higher chill varieties, Green Leaf Nemaguard (GL), Golden Queen (GQ) and Fay Elberta (FE), reacted more strongly to RZT and were particularly affected by the lowest RZT. For these varieties, the root mass ratio rose and stem mass ratio fell as RZT increased. However, with respect to leaf mass ratio, two different trends were found: the leaf mass ratio for FE and GQ positively correlated with RZT whilst the relationship for GL was negative. These findings suggest that the response to RZT is related to a variety's chill requirement; offer an explanation for differences in performance of rootstock–scion combinations at different locations; and will aid the development of more accurate tree performance models by taking RZT into account.     

Chill unit models for blackcurrant (Ribes nigrum L.) cultivars ‘Ben Gairn’, ‘Ben Hope’ and ‘Ben Tirran’

Temperate-zone crops require a period of winter chilling to terminate dormancy and ensure adequate bud break the following spring. The exact chilling requirement of blackcurrant (Ribes nigrum), a commercially important crop in northern Europe, is relatively unknown. Chill unit models have been successfully utilized to determine the optimum chilling temperature of a range of crops, with one chill unit equating to 1 h exposure to the optimum temperature for chill satisfaction. Two-year-old R. nigrum plants of the cultivars ‘Ben Gairn’, ‘Ben Hope’ and ‘Ben Tirran’ were exposed to temperatures of −10.1 °C, −3.4 °C, 0.1 °C, 1.5 °C, 2.1 °C, 3.4 °C or 8.9 °C (±0.7 °C) for durations of 0, 2, 4, 6, 8 or 10 weeks and multiple regression analyses used to determine the optimum temperature for chill satisfaction.     

Phenolic content and free radical scavenging activities in rambutan during fruit maturation

The 1,1-diphenyl-2-picrylhydrazyl (DPPH^•) scavenging activity, changes and accumulation of phenolic content were studied in the peel, seed and pulp of rambutan, Nephelium lappaceum L. (Rongrien and Seeechompoo cultivars) during fruit maturation. The IC₅₀ values of the radical scavenging activity of the peels, in both cultivars remained low through fruit development (1.42–4.75 μg/mL) but the values of the seed and pulps were low at the beginning and increased markedly toward fruit development until harvest (4.87 to >1000 μg/mL). The accumulation of phenolic compounds in rambutan peels of Rongrien and Seechompoo cultivars increased continuously until reaching a maximum of 1653 and 733 mg per fruit at the time of being harvested, at 112 and 98 days after full bloom (DAFB), respectively. Ellagic acid, corilagin and geraniin in the peels of both cultivars were observed and quantified. The major component in the peels of the two cultivars was geraniin. The accumulation of ellagic acid, corilagin and geraniin in the peels increased and reached the maximum at the harvest stage, especially the major constituent of geraniin (1011 and 444 mg/fruit for Rongrien and Seechompoo, respectively). The free radical scavenging property was observed to have a relationship with the phenolic content quantified in different parts of the rambutan fruit. This research demonstrates potential data on phenolic constituents through fruit development, especially in the peels at the time of harvest.     

几种适宜设施栽培果树需冷量的研究

 1996～1999 年, 采用Utah 加权模型, 先后对5 个树种、65 个常见设施栽培果树品种的需冷量及相关特性进行了研究。结果表明: 不同树种、品种的需冷量差异显著, 葡萄、西洋樱桃的需冷量最高, 桃最低, 李、杏居中, 而且年际间有较大差异, 说明作为一种遗传特性, 需冷量亦受环境因素的调节; 同一树种不同品种的需冷量高低与本品种果实的成熟期无明显关系, 果实成熟期早而需冷量较高的情况普遍存在; 同一品种其需冷量基本趋势是花芽高于叶芽; 根系在低温需求进程中起调控作用, 与地上低温同步的根际高温减少了花芽的需冷量, 而根系低温则没有效果。晚秋根外喷布6-BA 降低了油桃和杏的低温需求量, GA₃ 则有增加低温需求量的趋势, 而ABA 无明显效果。     

Pistil abortion is related to ovary mass in olive (Olea europaea L.)

Pistil abortion is considered to be an evolutionary adaptation to save resources in andromonoecious species, balancing the number of pistils with the resources available. It follows that large-fruited species/cultivars should have greater levels of pistil abortion. Working in olive, we found that pistil abortion, expressed as percentage of staminate flowers, was positively correlated to the average ovary mass at bloom, across cultivars with different ovary/fruit mass. Since ovary mass correlated with fruit mass, pistil abortion also correlated with fruit mass. The absolute number of perfect flowers per inflorescence was negatively correlated with both ovary mass and pistil abortion, while the number of staminate flowers per inflorescence increased with both parameters. The total number of flowers (i.e. staminate + perfect) was not correlated to ovary mass or pistil abortion, suggesting that male function was not affected. The results support the hypothesis that pistil abortion is related to competition for resources among ovaries, and suggest that genetic differences in pistil abortion among olive cultivars may be explained by their different pistil mass and sink strength.