Effect of soil water stress on the development of stone cells in pear (Pyrus pyrifolia cv. ‘Niitaka’) flesh

This study was carried out to investigate the cause of stone cell formation in pear (Pyrus pyrifolia cv. ‘Niitaka’) flesh. Potted plants grown in a glass house were subjected to water stress conditions without irrigation for 30 days from 30 days before full bloom (BFB treatment), full bloom (FB treatment) and 30 days after full bloom (AFB treatment). Control plants were drip-irrigated daily maintaining a soil matrix potential around −40 ± 5 kPa. The formation of stone cells in pear flesh increased in the FB treatment and AFB treatment plants and this tendency was sustained until the harvest season. Root activity was investigated 60 days after full bloom (DAFB) and the triphenyltetrazolium chloride (TTC) reduction potential, the formazan content and leaf water potential were investigated 30, 45, and 60 DAFB. Root activity decreased progressively due to the effect of water stress. Also, the Ca content in leaf and flesh was lower. The peroxidase activity was high in the flesh at the early stages of fruit growth and decreased at the late stages of fruit growth, and then a higher increase of peroxidase activity was observed in water-stressed fruit. The reduction in calcium content of leaf and fruit in plants under water stress may be related to the reduction of root activity and leaf water potential. The increase in peroxidase activity under water stress may be due to limited calcium absorption. Higher peroxidase activity may induce the accumulation of lignin in the cell wall and promote the formation of stone cells in pear flesh. We conclude that water stress condition during the early stages of fruit growth is one of several factors that determine the formation of stone cells in pear flesh.     

Effects of different crop loads and thinning times on yield,fruit quality,and return bloom in Malus × domestica Borkh. ‘Elstar’

Summary

‘Elstar’ is the latest-maturing commercial apple cultivar grown in Norway, with high fruit quality when properly managed. In May 2006, an experiment with four different crop loads [2, 4 ,6, or 8 flowers or fruitlets cm^–2 trunk cross-sectional area (TCSA), respectively] was established at two different stages [first bloom (FB), or 20-mm diameter fruitlets] and compared to unthinned control trees. Fruit growth was measured on individual fruit for each treatment throughout the season at weekly intervals. Thinning at FB gave a significantly lower final percentage fruit set than thinning to the same cropping level at the 20-mm fruitlet stage. However, fruit weights and soluble solids contents (SSC) were significantly higher, and the background fruit colour improved when trees were thinned at FB. The final number of fruit at harvest was less than the amount established at FB, or at the 20-mm fruitlet stage. There were significant differences between treatments in final fruit numbers per TCSA, which reflected the different crop loads. Fruit weights and SSC values were highest with the lowest crop load, and decreased with increasing crop loads. There was also a strong crop-load effect on the extent of return bloom per tree in the subsequent year. Trees thinned at FB had significantly more flower clusters than those thinned at the 20-mm fruitlet stage of. Untreated control trees had the lowest number of flower clusters. The amount of return bloom declined with increasing crop load. Second year crop loads and fruit weights were highest when trees were thinned at FB to two or four apples cm^?2 TCSA in the previous year. Trees with the highest crop load had the lowest crop load in the following year. Fruit quality was generally high for all treatments.     

Flower bud thinning in ‘Rojo Liso’ cactus pear

Summary

The export of cactus pear fruit from Mexico has increased over the last decade, with growing consumer demand for larger and higher quality fruit. Growers are concerned that yields decrease when fruit thinning is used to increase fruit size. Our objective was to assess the effects of flower bud (FB) thinning on the pre-harvest and post-harvest attributes and yields of ‘Rojo Liso’ cactus pear (Opuntia ficus-indica) fruit. The experiments were conducted in 2005 and 2006. The treatments used were: 1) no thinning, considered as the control; 2) thinning every second bud (T1); or 3) thinning two out of every three buds (T2). Marketable fruit (having an equatorial diameter > 5 cm) in the thinned treatments increased compared to the unthinned controls in both seasons. Thinning did not reduce fruit yield. Fruit quality was similar among treatments, both at harvest and after storage, except for the soluble solids concentrations which were higher in both the T1 and T2 treatments in 2005. Fruit weight loss in storage was similar among treatments. Flower bud thinning can therefore be recommended for commercial use.     

Effects of inflorescence removal on the fruit set of the remaining inflorescences and development of the laterals on one year old apple (Malus domestica Borkh.) branches

Summary

Inflorescences are known to be important physiological sinks especially when they set fruit. The effect, over two successive years, of inflorescence removal on one year old wood was investigated on apple (Malus domestica Borkh.). The study was carried out on medium vigour (around 30 cm) branches of cv. Granny Smith. On one set of branches (control) the inflorescences were untreated, while on two other sets, one-third and two-thirds of inflorescences (spur leaves, bourse-shoot and flower cluster) were removed at full bloom. The first analysis investigated the fruit setting ability of remaining inflorescences. The results generally confirmed previous results on the positive correlation between the number of leaves and flowers of the inflorescence and fruit set, and also the higher fruit set on two year old wood as compared with one year old wood. On one year old wood, inflorescence removal treatments tended to increase the fruit set of inflorescences with a low number of leaves and flowers leading to a level of fruit set similar to that of inflorescences with a larger number of leaves and flowers. On two year old wood, in the following year, only the two-thirds treatment increased fruit set consistently compared with the control. A second analysis investigated the effect of inflorescence removal on lateral shoot development. It was shown that the treatments had a little effect on quantitative growth (length, diameter) of the laterals per se. On the other hand, the removal of two-thirds of the inflorescence significantly stimulated the development of fruitful inflorescences the following year. Results are discussed in relation to the local versus global physiological integration at the branch level.     

梨子花发育对果实品质的影响

选择梨主栽品种‘丰水’、‘黄金’、‘新高’、‘鸭梨’、‘茌梨’和‘绿宝石’等为试材,对梨子花发育状况以及对果实品质的影响进行了调查研究。结果显示：梨不同品种子花发生率差异明显,‘丰水’、‘黄金’、‘新高’等砂梨系统品种子花发生率比‘鸭梨’、‘茌梨’和‘绿宝石’等白梨系统品种高;在结果枝类型上,短果枝的子花发生率比长果枝高;在结果母枝类型及生长势的强弱上,1年生弱枝的子花发生率比强枝高,2年生枝比3年生枝高;在同一花枝上中部子花发生率高;子花的开花期比母花晚 1 ~ 2 d,小花数在3 ~ 6朵之间,开花顺序与母花相反,为中心花先开,中心果发育最快。子花所结果实比母花果实小,商品价值低。因此,梨生产上子花的及早摘除有利于果品质量的提高。     

Thinning time during stage I and fruit spacing influences fruit size of ‘Contender’ peach

Early peach thinning during stage I was done at 0, 10, 20, 30, and 40 days after full bloom (DAFB). At each thinning time, trees were hand-thinned to achieve different crop loads by spacing flowers or fruits 10, 15, or 25 cm along the shoot on whole tree canopies. In 2001 and 2002, fruit weight decreased quadratically with increasing time to hand-thin and increased linearly with increasing spacing. In both years, fruit diameter decreased linearly with increasing time to thin and increased linearly with increased fruit spacing. In both years, number of fruits harvested and yield per tree decreased linearly with increased spacing. Hand-thinning at 0 or 10 DAFB resulted in fewer fruit and lower yield; therefore, thinning at 20 DAFB was better. The effect of time of thinning on soluble solids was not consistent. In both years spacing (i.e., crop load) did not affect soluble solids.     

Fruit growth and chemical properties of Ribes magellanicum “parrilla”

The aim of this work was to study the time course and pattern of fruit growth and the evolution of some of the chemical attributes such as soluble solids, acidity, and anthocyanin content in Ribes magellanicum plants growing in a natural environment near Ushuaia city, Tierra del Fuego (Argentina). Fruit growth and composition presented significant changes along the days from the full bloom phase. Fresh and dry fruit weight exhibited a typical double sigmoid curve. The first period of rapid fresh fruit growth was from full bloom phase until 28 days after, followed by a lag period until 42 days from the full bloom phase, and then by a second period of rapid increase until 56 days from the full bloom phase. Then, fresh fruit weight increased slowly (days 70–98 from the full bloom phase), reaching its maximum. Afterwards, fresh fruit weight decreased significantly until the end of the summer, and the fruiting period approximately ended 112 days from full bloom phase. On a dry weight basis the maximum fruit biomass was reached 98 days from the full bloom phase. Evolution of fruit growth was related with the compositional changes evaluated. By day 98 from the full bloom phase, soluble solids (17.5°Brix) and anthocyanin content (240.1 mg/100 g fruit fresh weight) were at their maximum, while at this time the total titratable acidity was at a minimum (0.4%). The results obtained not only contribute to the knowledge of the quantitative content of anthocyanin, a metabolite with nutraceutical value, but also give some tools for the definition of the optimal harvest time of R. magellanicum fruits, which it is important for fruit destination.     

早熟梨套袋技术研究

通过开展早熟梨果实套袋试验表明：对早熟梨实施套袋,可以显著地改善果实品质,尤以对外观品质的作用显著。套袋果实的果面都较对照的果实光滑,果点较小,锈斑面积小。可见,套袋是提高果实的商品性、生产无公害梨产品的有效途径。但套袋果可溶性固形物含量稍低于对照果,风味稍变淡,内在品质不如对照果,在生产上可采取多施有机肥、根外追肥、适当晚采、采前去袋等措施弥补这一缺陷。同时,套袋纸质的选择应根据品种而确定：‘翠冠’梨选择以台湾好果袋、山东爱农果袋等质量较好的双层纸袋为好。梨套袋时间也应根据不同品种特性确定：果点大而密、颜色深、锈斑严重的应该尽早套袋;果点小、颜色淡、锈斑轻的品种套袋时期可适当晚一些。‘翠冠’梨适宜的套袋时期一般以谢花后30 d为宜。     

‘砀山酥梨’褐皮芽变木质素含量及相关酶活性与CCoAOMT 表达量分析

 为了探讨‘砀山酥梨’芽变品系‘锈酥’果皮褐色形成机理,采用分光光度法测定盛花后25、50、75、100、125、150和175 d果皮中木质素含量和相关酶活性变化;从构建的‘锈酥’正向SSH-cDNA文库中筛选出与木质素生物合成密切相关的CCoAOMT-EST,通过实时荧光定量PCR测定了‘砀山酥梨’和‘锈酥’果皮中CCoAOMT的相对表达量。结果表明：‘锈酥’果皮发育前期木质素增量较大,且木质素增量累计比‘砀山酥梨’高12.2%;‘砀山酥梨’和‘锈酥’果皮中PAL、4CL、CAD酶活性均在花后75 d达到最大值,而POD酶活性则在花后125 d出现高峰;二者果皮中4种酶活性变化趋势基本一致,但‘锈酥’果皮中均相对较高;‘锈酥’果皮中的PAL和4CL酶活性与木质素增量变化均呈显著正相关,而‘砀山酥梨’则未呈现出此规律;在果实生长发育各个时期,‘锈酥’果皮中CCoAOMT相对表达量均高于‘砀山酥梨’。因此推测,‘锈酥’果皮褐色形成与果皮中木质素积累及相关酶活性提高有关,果皮中CCoAOMT的增量表达是‘锈酥’果实褐皮形成的重要原因之一。     

Timing of fruit removal affects concurrent vegetative growth and subsequent return bloom and yield in olive (Olea europaea L.)

Olive (Olea europaea) demonstrates a high tendency toward alternate fruit production, with significant negative consequences on the industry. Fruit load is one of the main cause-and-effect factors in the phenomenon of biennial bearing, often disrupting the balance between reproductive and vegetative processes. The objectives of the present study were to identify the time range during which heavy fruit load reversibly interrupts the reproductive processes of the following year. The linkage between timing of fruit removal, vegetative growth, return bloom, and fruit yield was studied. Complete fruit removal in cv. Coratina until about 120 days after full bloom (August 15) caused an immediate resumption of vegetative growth. The new shoots grew to twice the length of those on trees that underwent later fruit removal. Moreover, a full return bloom, corresponding with high subsequent yields, was obtained by early fruit removal, while poor or no bloom developed on late-defruited or control trees. Thus, the critical time to affect flowering and subsequent fruiting in the following year by fruit thinning occurs in olive trees even weeks after pit hardening—much later than previously suggested. Furthermore, the data indicate that flowering-site limitation, due to insufficient or immature vegetative growth during the On-year, is a primary factor inducing alternate bearing in olive.     

Fruit set and June drop in Cox's Orange Pippin apple as affected by pollination and treatment with a mixture of gibberellins A4 and A7

Single spray applications of 100 ppm of a mixture of the gibberellins A₄ and A₇ (GA_{4 + 7}) were made on fruiting spurs of the apple cultivar Cox's Orange Pippin to investigate the effect on set, June drop and growth of fruits, as well as on shoot development and flower-bud formation on the bourses. Applications were made from 1 to 50 days after full bloom following partial hand-pollination of flowers, i.e. two stigmas per flower pollinated. In another experiment applications were made from 1 to 20 days after full bloom following complete (five stigmas per flower) or partial (two stigmas per flower) hand-pollination, after open pollination, or on emasculated flowers.GA_{4 + 7} only temporarily increased fruit set after open pollination or after effemination of flowers, and then only after application 1 day after full bloom. GA_{4 + 7} did not affect the very high fruit set after complete or partial hand-pollination. Both latter pollination treatments induced an equally high fruit set.GA_{4 + 7} reduced June drop significantly whenever fruits were left after first drop, except after early applications following open pollination. GA_{4 + 7} was effective in June-drop reduction up to 40 days after full bloom, i.e. until the onset of the June drop.Fruit size was not clearly affected by GA_{4 + 7}. The smaller fruits obtained in some cases after GA treatment could be explained by assuming that maturity was reached by fruits that would have abscised without an exogenous GA_{4 + 7} supply. GA_{4 + 7} also increased seed abortion. Fruit length was increased by GA_{4 + 7} only for applications made up to 20 days after full bloom.GA_{4 + 7} stimulated bourse-shoot development to some extent. Flower-bud formation on the bourses was not clearly affected by GA_{4 + 7}, but was markedly influenced by the presence of fruits.That GA_{4 + 7} reduced June drop so much in spite of a slight promotive effect on bourse-shoot growth and a slight abortive action on seeds suggests that these gibberellins may be specific stimuli for apple-fruit growth after actual fruit set is achieved.     

Fruit cracking in Cereus peruvianus,a new cactus crop

Summary

Fruit of Cereus peruvianus (L.) Miller, a newly developed cactus crop, is subject to cracking. Fruit growth follows a double sigmoid curve, with a significant size increase in the first and third stages and moderate increase in the middle stage. Peel and seed grow in the first two stages, while pulp growth and maturation (e.g. peel colour change and stretching, sugar accumulation, fruit softening) occur in the final stage. Sensitive, moderately sensitive, and tolerant clones are subject to 100, 50–60 and 6–9% cracking, respectively, correlated to relative growth rate of the pulp in the third stage. Fruit cracking, lengthwise splitting of the peel, and exposure of the pulp occurred in fully mature fruits towards the end of their growth. Continuous monitoring of fruit growth revealed expansion and cracking during the day and shrinkage during the night, as expected for CAM plants. Cracking was not correlated with the threshold cracking turgor, which declined during ripening in all clones. GA₃ sprays during colour break reduced cracking in the two most susceptible clones to 20% and 60%, while paclobutrazol increased cracking. Cracking rates were the same in two ecozones differing in salinity, temperatures and relative humidity. It is suggested that breeding and hormone treatments could reduce cracking significantly.     

‘糯米糍’荔枝碳素营养储备动态与坐果的关系

 以10～12年生的‘糯米糍’荔枝(Litchi chinensis Sonn. ) 为材料, 研究了高产树(60～65 kg·株^{- 1} ) 和低产树(5～10 kg·株^{- 1} ) 不同部位(叶片、各级枝条和主干) 碳素营养储备(淀粉) 的差异及季节动态; 分析了不同果实发育阶段树体碳素营养水平与坐果率的关系。结果表明, 果实成熟时高产树各部位的淀粉含量均低于低产树, 而可溶性糖含量高于低产树。果实采收后, 低产树早于高产树抽发新梢。入冬季前(11月底前) , 低产树和高产树分别抽发了3次和2次秋梢。7～11月秋梢生长发育期间, 高产树和低产树均无显著淀粉积累, 11月中旬以后枝梢生长停滞期间, 各部位, 尤其是4 cm直径以内的枝条大量积累淀粉, 在花穗发育前达到高峰。之后, 随花穗发育、开花及坐果而持续降低。高产树和低产树各部位淀粉高峰并无明显差异, 表明坐果量对树体碳素营养储备的累积并无明显的长期影响。叶片、主枝和主干积累的淀粉含量较低, 总体相对稳定; 而4 cm直径以下的枝梢淀粉含量变化剧烈, 说明这些枝梢是更为活跃的碳素储备库。本研究还表明, 坐果早期(花后3周内) 枝条(2 cm直径) 的淀粉含量与该枝条上最终坐果率呈显著正相关, 而果实发育中期(花后8周) 枝条淀粉含量与坐果率无关, 说明早期果实发 育一定程度依赖树体碳素营养储备, 而中后期果实发育几乎不依赖树体储备。     

Quantitative and qualitative aspects of peroxidases extracted from cladodes of Opuntia ficus indica

Peroxidases (EC 1.11.1.7) were extracted from fresh cladodes harvested from nine ecotypes of the cactus species Opuntia ficus indica Mill. growing as a collection, in Marrakech (South Morocco). Two enzyme fractions were obtained by a progressive solubility method leading to soluble peroxidases (S) and ionically wall-bound peroxidases (I). The preferred substrate for cladode peroxidases was determined to be o-dianisidine over 4-chloro-1-naphtol and guaiacol. Contrarily to roots, no guaiacol-based activity was found in cladodes. The late ecotypes 1‘Haddaouia’ and ‘Moussa’ showed a relatively high peroxidase ratio S/I (units g⁻¹ fresh weight). When subjected to electrophoresis on polyacrylamide gels, S and I peroxidase fractions each exhibited two enzyme forms based on their electric charges in basic and acidic gel media. Acidic peroxidase forms, well separated on basic gels, showed two principal migration zones with great differences in their enzyme activities depending on the fraction types S and I. Acidic ionically wall-bound peroxidases exhibited fast, highly active isoforms with R_f values 0.42–0.58. Basic forms, represented essentially in fractions S and resolved on acidic gels, were typified by slow and fast isoforms with a double banded pattern in most ecotypes. Opuntia ecotypes collected from localities surrounding Marrakech exhibited fast basic soluble isoforms, while distant ecotypes from Marrakech, including late ones, were typified by a fast acidic ionically bound isoperoxidase of R_f 0.58. Possible roles of O. f. indica peroxidases in growth and their evaluation as markers in this cactus species are discussed in this study.     

Wood age and leaf area influence fruit size and mineral composition of apple fruit

Summary

The influence of wood age, fruiting position and leaf area within the tree canopy on fruit mineral content and quality for several apple (Malus domestica Borkh.) cultivars was investigated. Size and Ca, Mg and K content of individual fruit on one-year (lateral and terminal positions), two-year and older than three-year wood were compared for cvs Royal Gala, Braeburn, Granny Smith and Fuji. Fruit on two-year spurs and one-year terminals was generally larger at commercial harvest than that on one-year laterals and spurs older than three years. Flower receptacles at full bloom were larger and fruit growth rates were greater from 60 to 100 d after full bloom on two-year spurs than on one-year laterals. Fruit Ca and Mg concentrations and contents at commercial harvest were highest for terminal fruit, but there was no consistent difference between fruit from other positions. One-year terminals had the greatest primary and bourse leaf areas, two-year spurs were intermediate and one-year laterals had the lowest areas of both leaf types. Removal of 50% of primary leaves and/or removal of bourse shoots from clusters at bloom reduced fruit Ca content at commercial harvest for two-year spurs, one-year laterals and one-year terminals. Bourse shoot removal also reduced Mg content for all positions. However there was no effect of leaf removal on fruit size or K content. Ca content of individual fruit increased curvilinearly with increasing total spur leaf area for fruit on two-year spurs and one-year terminals but not for fruit on one-year lateral clusters. Terminal fruit with total spur leaf areas and fruit size similar to those on two-year spur fruit had higher Ca content.     

‘早熟红李’在黔北地区的生物学特性及栽培技术

历经7年（2005--2012）对黔北地区‘早熟红李’进行引种观察和栽培试验，结果表明：（1）‘早熟红李’具有结果早，果实成熟早，果大，紫红色，甜酸适口等优点；（2）该品种定植后第2年部分植株开花结果，第3年大部分植株开花结果，第4年植株普遍开花结果，第5年以后进入盘果期；（5）该品种植株抗病、抗虫性较强，同时抗低温、抗旱、抗裂果较强。在海拔800～1200m，平地、山地和坡地栽植生长结果均良好。提出高标准建园、配方施肥、合理修剪、合理管理花果、有效防治病虫害和适时采收等配套栽培措施。     

Individual and combined effects of shading and thinning chemicals on abscission and dry-matter accumulation of ‘Royal Gala’ apple fruit

Summary

Shade and chemical thinning treatments were applied to mature ‘Royal Gala’/M.26 apple trees either alone or in combination to study their effects on the pattern of abscission and growth of spur fruit. Natural fruit drop occurred in two distinct waves in both years; the first wave peaked 20 d after bloom (DAB) at a weekly abscission rate of c 15% in both years. The second wave of fruit drop in 2001 occurred earlier and was more intense than in the previous season. Application of NAA as a bloom thinner increased the maximum weekly abscission rate during the first wave of fruit drop in both years. Chemical fruit thinning treatments (Carbaryl in 2000, BA or delayed lime sulphur in 2001) had no effect on abscission or growth of spur fruit. Covering trees with 80% shade cloth for 3 d (2000) or 5 d (2001) stimulated a wave of fruit abscission that peaked c 10–15 d after removal of the cloth. Shade during the period from 20–25 DAB stimulated more fruit drop than earlier shade treatments, resulting in weekly abscission rates as high as 70%.There were no additive effects of combining thinning chemicals and shade treatments on abscission of fruit from spurs. However, additive effects of shade and thinning treatments were observed when measured as whole-tree crop density values, indicating that abscission of fruit from one-year wood was stimulated when low light conditions preceded application of (fruit) thinning chemicals. Shading trees from 34–39 DAB in 2000 resulted in a transient reduction and subsequent increase in the rate of dry-matter accumulation in fruit that were retained. Considerable challenges lie ahead in developing models of fruit growth that can account for the inter-dependent effects of light and crop load on fruit abscission and development that exist within an orchard environment.     

晚熟桃新品种‘中桃21号’

‘中桃21号’是通过人工杂交选育而成的晚熟大果桃品种。果实圆形,平均单果质量265 g,大果510 g。果皮底色浅绿白色,成熟时50%以上果面着深红色。果肉白色,溶质,风味甜香,可溶性固形物12.6% ~ 13.9%,总糖11.2%,总酸0.37%,维生素C 0.127 mg ? g-1,品质优良。果核长椭圆形,粘核。在郑州地区3月下旬开花,8月中旬成熟,果实发育期约140 d。花蔷薇型,花药白色,无花粉。3年生树产量约16.7 t ? hm-2,5年生树32.2 t ? hm-2。     

Flowering and fruiting phenology,and physico-chemical characteristics of 2-year-old plants of six species of Opuntia from eight regions of Morocco

SUMMARY

We have described the flowering and fruiting phenology of 14 accessions of six Opuntia species grown in Morocco: O. ficus-indica, O. robusta, O. aequatorialis, O. dillenii, O. leucotricha, and O. stricta. We also determined the physicochemical characteristics of their cladodes. For each accession, we used four-to-20 plants. Two systems were used to measure phenology: the extended Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie (BBCH)-scale and the National Phenology Monitoring System. Five principal stages were described: the development of vegetatively-propagated organs (vegetative buds), the development of flower buds, flowering, fruit development, and fruit maturity. The number of vegetative buds varied significantly among the 14 accessions, while only four accessions produced flower buds. After reaching their final size, fruit lengths varied from 3.40–6.40 cm, while fruit diameters varied from 1.93–3.90 cm. The average cladode number differed significantly among genotypes and varied from 1.75–7.75. There were also significant differences in cladode length (13.75–30.63 cm), width (6.25–17.33 cm), thickness (0.65–1.38 cm), fresh weight (FW; 67.50–766.00 g), and dry weight (DW; 8.75–67.15 g) between species. Water content and ash content, as well as total protein and total sugar concentrations, showed significant differences and were within the ranges of 86.67–92.04% (w/w), 12.97–22.08g 100 g^?1 DW, 4.64–11.56g 100 g^?1 DW, and 3.22–12.51 g 100 g^?1 DW, respectively. Our results will help in the development of agronomic management practices and improve the characterisation, valorisation, and use of cactus pear species grown in Morocco.     

The Influence of Shoot Competition on Fruit Retention and Cropping of Apple Trees

Fruit set was increased by removing all shoots 5 days after full bloom and at weekly intervals thereafter from trees of Sunset and Laxton’s Fortune, but removing shoots from Fortune trees 25 days after full bloom produced no beneficial effect on fruit retention. All treatments resulted in a heavier rate of fruit shedding during the ‘June drop’ period than occurred from control trees, and at harvest the trees without shoots had fewer fruits, and lower yields, than the controls. In a comparison of shoot removal and shoot tip removal starting 15 days after full bloom on Fortune trees, both treatments improved set, but whereas shoot removal caused a heavier ‘June drop’ compared with untreated trees, shoot tip removal increased the number of fruits retained to harvest and produced a yield increase. The difference between the two treatments in their influence on fruit retention, during and after the ‘June drop’, is accounted for by the beneficial effect of a relatively small number of leaves on each tipped shoot. Studies on the pattern of distribution of photosynthates, using ¹⁴CO₂ and autoradiography, produced results supporting the concept of competition between fruits and shoots and also showed changes in the pattern of assimilate movement brought about by shoot tip removal. It is concluded that competition between fruits and shoots, occurring during blossoming and the following 2–3 weeks, may limit fruit set, but the presence of shoot leaves is beneficial to fruit retention in the later part of the season, particularly during the ‘June drop’ period.