lower-bud formation in pome fruits as affected by fruit thinning

Fruit thinning is commonly practiced in many fruit bearing woodyperennials to improve fruit quality and to prevent biennial bearing, thesevere alternation of fruit load in successive on and off years. Biennialbearing has its origin in the negative effect of the presence of fruits onflower production (return bloom), and, thus, the yield for next year. Forreasons of labour cost, fruit thinning is usually done by using chemicalcompounds such as ethephon and ammonium thiosulphate at the blossomingstage, and for fruit thinning NAA, NAAm, carbaryl, and a few cytokinins.Apart from indirect effects of the various chemicals on return bloom viareduction of fruit load, they may also influence flower formation directly.In view of the supposedly negative relationship between flowering andshoot growth, chemical thinners may even affect bloom via interference withthe vegetative development of the tree. In the present paper, in additionto a short discussion of the essentials of the flower-formation process inpome fruits, the effect of a number of chemical thinners on flower formationis reviewed. It is argued that in most experimental studies the data on theeffect of thinning on return bloom is insufficiently detailed, and a betterunderstanding especially of the early phases of the flower-formationprocess is badly needed.     

Blühfördernde Wirkung von 2-Chloräthylphosphonsäure bei Apfelbäumen

Experiments with the growth regulator ethephon (2-chloroethylphosphonic acid) were made to stimulate the flower differentiation in the ‘Carola’ and ‘Golden Delicious’ apple cultivars in Pillnitz (GDR) and ‘Jonathan’ and ‘Golden Delicious’ in Ujfehértó (Hungaria). A twofold application of 150 ppm ethephon in June proved most effective. Our results indicate that it is possible to promote flower differentiation in apple trees without growth retardation and fruit thinning.     

Effect of Acid treatment of plant cuticles on sorption of selected auxins

Sorption characteristics of 2-(1-naphthyl)acetic acid (NAA), 2-(1-naphthyl)acetamide (NAAm), and 2,4-dichlorophenoxyacetic acid (2,4-D) were determined for cuticles enzymically isolated from mature tomato (Lycopersicon esculentum Mill. cv Sprinter) and pepper (Capsicum annuum L.) fruit. Sorption equilibrium for NAA and 2,4-D by tomato cuticular membranes (CM) and dewaxed cuticular membranes (DCM) was achieved within 24 hours at 25°C. The average K (partition coefficient) values for NAA in tomato CM and DCM were 166 and 204, respectively, whereas the corresponding K values for 2,4-D were 292 and 383, respectively. Sorption equilibrium for 2,4-D and NAA in pepper cuticles was not achieved after 18 and 63 days, respectively. Sorption equilibrium for NAAm in tomato and pepper CM and DCM was attained within 48 hours. Acid pretreatment (2.0 n HCl, 10 minutes) had no effect on NAA, 2,4-D, or NAAm sorption by tomato CM and DCM, or on NAAm sorption by pepper CM and DCM. Acid pretreatment of pepper CM and DCM led to slightly lower K^pH (apparent partition coefficient) values for both NAA and 2,4-D. More significantly, sorption equilibrium for NAA and 2,4-D in pepper CM and DCM was achieved within 24 hours after acid treatment.     

疏花对富士苹果光合同化物分配的外部调节和生理表现

在盛花期,利用对树冠不同部位疏除花序的试验。对富士苹果树体内同化物的调配及其生理表现进行了研究。结果表明,苹果平均单果重和平均单果叶面积之间关系呈线性正相关。该相关关系在不同处理之间无差异（r=0.91),充分说明在苹果树体内存在一个可自由流动的碳水化合物库或者说树体对结果具有光合调节作用,疏花可以从外部调节光合同化物分配的方向。对每株苹果树未结果部位和结果部位短枝及延长枝叶片净光合速率测定表明。结果和未结果部位光合速率没有显著差异。虽然疏花没有显著影响苹果单株枝条生长量和叶面积,但是,苹果树树冠全部疏除花序的一侧 或主枝的平均枝条生长量和叶面积去比该树其它结果部位分别平均高出153.5cm和8900cm^2,差异极为显著。苹果树疏除花序1/2或3/4的数量使苹果平均单果重比不疏花分别显著增加了33g或79g。而果实钙浓度每百克鲜重分别降低了1.62mg或2.66mg,充分说明当疏花显著地影响果实大小时,果实内钙浓度也会明显地发生相应的变化,虽然在疏花处理之间不同部位疏除花序没有影响单株花芽总数量,但是,每株树前一年春季疏花的部位比未疏花,结果的部位极显著地增加了花芽数量（SED=11.6)。     

In vitro genotoxicity assessment of the synthetic plant growth regulator, 1-naphthaleneacetamide

1-Naphthaleneacetamide (NAAm) is a synthetic plant growth regulator in the auxin family that is widely used in agriculture to promote the growth of numerous fruits, for root cuttings and as a fruit thinning agent. The potential genotoxic effects of NAAm were investigated in vitro by the chromosome aberrations (CAs), and cytokinesis-block micronucleus assays in human peripheral blood lymphocytes (PBLs) for the first time. The human PBLs were treated with 20, 40, 80, and 160 µg/mL of NAAm for 24 and 48 h. The results of this study showed that NAAm significantly induced the formation of structural CA and MN for all concentrations (20, 40, 80 and 160 µg/mL) and treatment periods (24 and 48 h) when compared with the negative and the solvent control. In addition, the higher concentrations of NAAm (80 and 160 µg/mL) caused a statistically significant increase in nuclear bud (NBUD) formation for both 24 and 48 h treatment times. With regard to the cell cycle kinetics, at all the tested concentrations, NAAm caused a statistically significant reduction in the mitotic index (MI) only for 48 h treatment period and also in the nuclear division index (NDI) for both 24 and 48 h treatment periods as compared to the control groups. The reductions in the MI and NDI occured in a concentration-dependent manner for both treatment times. In conclusion, the present results indicate that in the tested experimental conditions, NAAm was genotoxic and cytotoxic on human PBLs in vitro.     

胡桃楸个体有性生殖过程研究

胡桃楸是东北东部山地阔叶红松林的重要组成树种。以胡桃楸个体有性生殖过程为研究对象,通过定株定枝调查,研究了胡桃楸芽种群分化、物候及散粉规律、颗粒生长发育过程及环境影响因子。结果表明：１．胡桃楸壮龄树芽种群分化简单。２．胡桃楸个体间花期物候差异很大,并具有典型的雌雄异熟现象。３．胡桃幼果期生长速度快,生长分化现象严重,疏果率高;进入果实生长后期之后,生长速度及疏果率均显著降低。     

Fruit thinning of peach trees

The present review deals with the importance of fruit thinning in peach.The date of treatment, the severity and the criteria underlying the practiceare discussed. Methods of fruit thinning are described, with particularemphasis on the use of chemical treatment as an alternative to handthinning. Strategies for chemical thinning are advanced.     

DEVELOPMENT OF THE INFLORESCENCE AND “CROWN” OF ANANAS COMOSUS AFTER TREATMENT WITH ACETYLENE,NAA, AND ETHEPHON

The vegetative apex of the Masmerah cultivar of pineapple, Ananas comosus (L.) Merr., is dome-shaped and has the typical tunica-corpus organization. Treating the plant with acetylene, NAA or ethephon transforms the vegetative apex to a reproductive one. As early as two days after treatment the apical height and width increase, attaining maximum dimensions in 8–14 days, after which they progressively decrease. During 4–6 weeks, when the full complement of florets has been initiated, the dimensions of the apex are again increased and leaves that form the fruit crown are initiated. A cambium-like zone at the base of the corpus is noticed 2–4 days after the application of acetylene and ethephon. Acetylene and NAA result in a more pointed apex initially, while ethephon results in a more broadened apex. The largest increase in apical height and width is seen when NAA is used. The development of the inflorescence from the time the full complement of florets is formed to fruit maturity is described. Cell multiplication is the main cause of peduncle elongation and inflorescence head enlargement, although towards the later stages of growth, cell enlargement contributes more to the increase in size of the organs.     

Rates of cuticular penetration of 1-naphthylacetic acid (NAA) as affected by adjuvants, temperature, humidity and water quality

When NAA is used for fruit thinning, results can be unpredictable. Problemswith foliar penetration of NAA can contribute to this variability. Usingisolated pear leaf cuticles we have investigated effects of humidity,temperature, hard water and selected adjvants on rates of cuticularpenetration of NAA. If NAA was dissolved in deionised water about 40% ofthe applied dose penetrated in 8 h, while water having a pH > 7 practicallyeliminated cuticular penetration of NAA, even at high humidity (100%) andmoderate temperatures (20°C). Rates of penetration were much lowerat 10°C and 55% humidity. Adding urea, ammonium sulphate or Tween20 increased rates of penetration but not to a great extent. Highest rates ofpenetration were obtained when solutions were buffered at pH 4 with DL-lactic acid and the accelerator adjuvant Genapol C-100 was added. Withthis combination, about 70% of the applied NAA dose penetrated within 8 hat 20°C and 40% at 10°C, respectively, even at low humidity(55 to 60%) and when hard water was used as carrier. It is argued thatpoor performance of NAA as chemical thinner must be expected when hardwater is used for spraying and when the pH of the spray liquid is notadjusted to values around 4, such that a significant proportion of the NAAis non-ionised. Only non-ionised NAA can penetrate cuticles. Rates of foliarpenetration of NAA can be greatly increased, especially at low temperatures,by adding 0.2 to 2.0 g l^–1 Genapol C-100. Since NAA is destroyed byUV light, spraying should be done in the evening. High humidity during thenight is favourable for foliar penetration, but low temperatures aredetrimental and addition of an accelerator adjuvant (i.e. Genapol C-100) isnecessary. If NAA must be sprayed during cold weather (5–10°C),higher NAA concentrations may be used because rates of penetrationduring the night are proportional to dose and excess NAA left on the foliagewill be destroyed by UV light after sunrise.     

Effects of fruit thinning agents on apple tree canopy photosynthesis and dark respiration

Effects on photosynthesis of the fruit thinning agents naphthaleneaceticacid (NAA) and three commercial plant growth regulator formulations,naphthaleneacetic acid ('Rhodofix') and naphthaleneacetamide('Amidthin') and 2-chloroethylphosphonic acid('Ethrel')were evaluated with respect to the stress they impose on the fruit tree, usingthe alternate-bearing sensitive apple cv. 'Elstar'. This work wasbased on the hypothesis that plant stress in the form of large reductions inleaf photosynthesis are a pre-requisite for successful fruit thinning. A newtechnology was employed for continuous recording of tree canopyphotosynthesis, dark respiration and carbon balance of apple trees. This wasbased on six canopy chambers, which enclosed apple trees under naturalconditions in the field, with on-line measurements and continuous analysis ofCO₂ exchange and automated data acquisition. All employed thinningagents reduced whole tree canopy photosynthesis consistently by3–34% on the five days following their application, withphotosynthesis still declining thereafter in the case of the NAA and'Amid-thin' application. The reduction after application of either'Rhodofix' or 'Ethrel', declined within five days, suchthat most of the original photosynthetic potential was restored, indicatingacceptable phytotoxicity of these three plant growth regulators at theconcentrations used. The effects on dark respiration differed markedly. NAA and'Ethrel' increased dark respirationover-proportionally by up to 106%, whereas 'Amid-thin' and'Rhodofix' decreased it by up to 46%inthe first night after application, thereby drastically affecting the carbonbalance of the tree in opposite ways. These results are integrated into ahypothesis linking basipetal auxin transport, phloem loading, translocation anddeficiency of photoassimilates.     

Cell division and cell enlargement in fruit of Lagenaria leucantha as influenced by pollination and plant growth substances

The effects of NAA (naphthaleneacetic acid), GA₃ (gibberellic acid), CPPU (N-(2-chloro-4-pyridyl)-N'-phenylurea) and pollination on fruit set, cell division and enlargement were studied in Lagenaria leucantha, an important vegetable. NAA and GA₃ were ineffective in inducing parthenocarpy, whereas CPPU induced parthenocarpic fruit significantly larger than fruit that resulted from pollination. Cell division, which occurred during the first 4 days after pollination was not reactivated by NAA or GA₃, but was effectively reactivated by CPPU. The cell number of the total cross-section of CPPU-treated fruit was 117.4% of that of pollinated fruit and 154.4% of that of unpollinated at 12 DAA (days after anthesis) respectively. The CPPU-induced parthenocarpic fruit had the largest cell cross-sectional area followed, successively, by pollinated fruit, NAA-treated fruit, GA₃-treated fruit and unpollinated fruit. These results indicate that CPPU induced parthenocarpic fruit growth by directly reactivating cell division and expansion.     

Abscission and thinning of young fruit and thier regulation by plant hormones and bioregulators

Natural abscission of young fruit and its regulation by plant hormones isconsidered and compared to the generally accepted model of senescencetriggered abscission of, for example, leaves or mature fruit. It isconcluded that abscission of young fruit cannot be explained by this model.Alternatively, it is suggested that the senescence triggered initial step inthe classical abscission model should be replaced by a correlativelytriggered step. Polar basipetal IAA transport with its autostimulation andautoinhibition components is the main regulating signal in this correlativeacting system and replaces ethylene as the initial driving force from thesenescence triggered model.Results supporting this model are presented and tested against existingresults from the literature. Finally, this hypothesis is tested as a possibleexplanation of the mode of action of some thinning chemicals orbioregulators. It is speculated how a thinning chemical should be designedto function in a more reliable way, at least as far as its interference with the endogenous hormone system is concerned.     

Regulation of source: sink relationship,fruit set,fruit growth and fruit quality in European plum (<Emphasis Type="Italic">Prunus domestica</Emphasis> L.)—using thinning for crop load management

Demand for large fruit of uniform size is increasing in the market; thinning is a means to achieve consistently large fruit and to overcome possible alternate (biennial) bearing for the small-fruited European plum (Prunus domestica L.). However, chemical thinning agents for stone fruits are scarce and/or often ineffective. Hence, the objective of this work was to study possibilities of enhancing fruit growth and to improve fruit quality, viz size using plum as a model crop. Nine-year-old ‘Ortenauer’ plum trees, trained to spindles, with maximum flowering intensity (score value 9) near Bonn, Germany were mechanically, chemically or hand-thinned. Un-thinned plum trees in the same rows served as control. Trees were either mechanically thinned at full bloom on 20 April 2009 with a rotor speed of either 300, 400 or 500 rpm, and half of those trees additionally treated with ATS (15 L/ha) and an ethylene releasing compound 35 days after full bloom or manually thinned. The objective of 1/3 flower removal was successfully achieved even with the slowest rotor speed of 300 rpm. The number of fruit per branch was significantly reduced from 152 to 67–76, equivalent to a (source: sink) leaf: fruit ratio of 5:1. Mechanical thinning significantly enlarged fruit mass from 28 g in the un-thinned control to 30–32 g with rotor speeds of 400 or 500 rpm. Additional chemical thinning with ATS and an ethylene-releasing compound resulted in no further increase in fruit mass. Inner fruit quality (sugar) of the plums appeared unaffected by either mechanical or chemical thinning, except for fruit firmness: Plums thinned with an ethylene releasing compound were softer and ripened earlier than respective control fruit. The most efficient method of flower removal and fruit mass enlargement was mechanical blossom thinning with 400 rpm, which may provide a suitable replacement for chemical and/or manual thinning. Alternatively, the mechanical thinning can be combined with either of those options. Mechanical blossom thinning was as effective to overcome or avoid alternate/biennial bearing as the ethylene releasing compound in the previous year. The results are discussed with respect to stone fruit being more difficult to thin than pome fruit, because the former do not exhibit leaves at the time of blossom thinning. Stone fruits develop within a shorter time and a larger number of (smaller) leaves (source) are required for the same fruit growth and final fruit size (sink). A lower threshold of fruit removal has to be exceeded before the remaining stone fruit grow faster and final fruit mass and sugar (and possibly fruit firmness) increase, while acidity remains unaffected by fruit set. An upper saturation threshold is reached fairly quickly without further effects.     

Auxin modification of the incompatibility response in Theobroma cacao

The time course and control of floral abscission and fruit set in Theobroma cacao were studied after spray application of growth regulators. 1-Naphthaleneacetic acid (NAA) prevented flower abscission in a concentration dependent manner and induced the early stages of fruit development. The cytokinin benzylaminopurine (BAP) counteracted NAA but resulted in longer fruit retention. Measurements of endogenous levels of indole-3-acetic acid showed an inverse correlation between the number of flowers per plant and auxin content. The results suggest that the genetic control of self-incompatibility in T. cacao may be modulated by the hormonal content of the flower.     

厦门地区冬季观果与观花植物及其园林应用分析

通过实地调查,对厦门地区冬季观果和观花园林植物进行统计,分析其生活型、观赏特征、色彩和应用频度。结果表明,厦门冬季具有观赏价值的观果植物有20科22属25种(含种下等级),观花植物有33科51属63种(含种下等级)。厦门冬季观果植物以常绿乔木、灌木为主,果色以红色系为主,高应用频率的观果植物优势不明显;观花植物以乔木为主,花色以红色系、黄色系为主,高应用频率的观花植物优势明显,开花呈衬式花相的种类占多数。厦门冬季观果与观花植物资源较为丰富,但冬季表现较好的观果种类较少,而一些表现较好的植物未普遍应用,植物景观营造不合理,针对此问题提出改善厦门冬季植物配置的建议。     

Significance of flower and fruit thinning on fruit quality

The effects of mechanical or chemical flower and fruit thinning on fruitquality were primarily by altering crop load. However, there were alsodirect effects of thinning agents. Fruit size was directly related tothinning intensity. In addition to crop load, age of wood, flower budquality, competition within clusters and canopy were important factorsaffecting the response to thinning. Short- and long-term thinningstudies identified two groups of quality components: Group 1characteristics include size, colour, skin performance, firmness andsugar and acid content of the fruit. Group 2 characteristics wererepresented by inorganic components, especially calcium and potassiumwhich are implicated in the susceptibility of fruit to physiologicaldisorders. While group 1 characteristics were improved by increasingthinning intensity, storability of the fruit was better at high than atlow crop loads. Therefore, a compromise between all quality requirementsmust be found for a good economic return. Establishing the trends ofthinning on the different quality parameters can help to select athinning strategy for local or regional conditions typically beingdetermined by growing and market conditions.     

Quantification of ethephon requirements for abscission in olive fruits

Ethepon is used commercially in Israel to facilitate mechanical harvesting or hand picking of olive fruits, but the results are often not satisfactory, due to insufficient reduction of the fruit removal force. Studies with ¹⁴C-ethephon were carried out to follow the fate of the applied ethephon from treatment until fruit harvest and to determine the actual uptake and efficiency of the sprayed compound.Only a small portion (less than 3%) of the applied ethephon actually penetrated the target tissue i.e. the pedicels, and released the ethylene responsible for promoting fruit loosening. There was almost no translocation of ethephon from other organs (leaves, fruits) to the fruit pedicels. Extended imbibition in the ethephon solution increased ethephon uptake, which was also enhanced by higher ambient temperatures. Penetration of ethephon varied among different tissues (leaves, fruits and pedicels). Field applications enabled some calculations of the relationship between the amount of ethephon applied and that actually required to achieve proper fruit loosening.     

Contrasting responses of plants and pollinators to woodland disturbance

Preserving species diversity is critical to ensure ecosystem functioning; however, different components of diversity might respond to human disturbance in different ways. Similarly, trophic levels might have uncoupled responses to the same disturbance, thus ameliorating or aggravating the persistence of ecological communities. In this study, we analysed how the density, richness and evenness of flowers and pollinators respond to four levels of woodland thinning intensity (0, 30, 50 and 70% of woodland basal area removed) over 2 years in three contrasting sites. We found a mismatch in the response of flowers and pollinators to thinning. Flower density and richness had disparate responses, depending on the site and year, while evenness did not change with thinning. In contrast, pollinator density and richness, but not evenness, consistently increased with thinning among years and sites. These results suggest that thinning has a great influence on pollinators through changes in abiotic conditions and, perhaps, flower attractiveness rather than through small‐scale changes in flower density and richness. At the site where tree flowers were absent, bee pollinator community composition was impoverished, suggesting that trees provide important floral resources to pollinators. Our findings indicate that disturbance may diminish local plant abundance and richness, but pollinator abundance and richness are enhanced after intense thinning at small scales.     

间伐强度对黄桥林区辽东栎生殖构件的影响

为了阐明抚育间伐强度对辽东栎生殖构件的影响,以黄土高原南部黄龙和桥山林区辽东栎中龄林为研究对象,对不同间伐强度(对照、10%、20%、30%)下近自然经营抚育间伐5年后的辽东栎平均单株个体大小、生殖构件产量、比率及空间分布格局特征等进行研究.结果表明: 间伐强度对辽东栎林分平均树高、胸径影响不显著,而与冠幅面积、冠幅体积呈显著正相关;辽东栎标准株的生殖枝、幼果、成熟果实产量随间伐强度的增大而增大,而营养枝、雄花序、雄花、雌花的产量变化不大.当间伐强度达到20%时,生殖枝、幼果、成熟果实产量显著提高,30%间伐下达到最大.生殖枝比例和座果率随间伐强度增大而增大,在20%、30%间伐强度时与对照的差异达到显著水平.约3/4的生殖枝、雌花、雄花集中分布于树冠上层,1/4分布于下层;树冠阳面生殖构件数量占65%,树冠阴面占35%.树冠下层、阴面生殖枝、雌花、雄花序的空间分布比例随着间伐强度的增大而增大;树冠上层、阳面生殖枝、雌花、雄花序分布比例随间伐强度的增大呈递减趋势.因此,选择30%间伐强度(保留郁闭度0.6)最佳,可以大幅提高辽东栎的座果率和成熟率,有效提高结实量和品质,为辽东栎林的采种及天然更新提供保证.