Biology of the Fruit Tree Red Spider Mite Metatetranychus Ulmi (Koch) in South-East England

Measurements of the rate of fruit drop and the hormone content of the seeds, made at weekly intervals on three varieties of apple, have shown that periods of very active hormone production are invariably associated with periods of low fruit drop. On the basis of these and other observations, an hypothesis is proposed to account for the periodicity of fruit drop. It is suggested that, throughout its development, the fruit possesses an inherent tendency to separate from the spur but that, at certain periods, it is prevented from doing so by hormonal stimuli emanating from the developing seeds. Two such stimuli have been demonstrated, at 3–4 weeks and 7–10 weeks after petal-fall respectively, both of which are associated with particular developmental stages of the endosperm. In addition the existence of a third, as yet undetected stimulus at the time of fertilization, is postulated.     

A Method For the Quantitative Estimation of Growth Substances Based on the Response of Tomato Ovaries to Known Amounts of 2-Naphthoxy-Acetic Acid

Unpollinated tomato ovaries treated with certain synthetic growth substances can be stimulated to develop into seedless fruits, and the rate of development during the first six days is shown to be related to the amount of growth substance with which the ovary is treated. The details of this relationship have been worked out in a series of experiments in which ovaries were treated with known amounts of 2-naphthoxy-acetic acid (BNOA). With this as a basis, a quantitative test method has been evolved by which the activity of different growth substances and natural hormone extracts can be measured relative to that of BNOA. The method, as is described in the next article in this number (see p. 32), has been used to follow the changes in the hormone content of apple seeds throughout the season.     

不同授粉处理对沙田柚果实发育中内源激素水平变化的影响

沙田柚自花授粉果实的重量和体积均低于异花授粉处理。与未授粉子房相比,授粉子房迅速膨大。授粉处理可使子房内源激素(ＩＡＡ)、赤霉素(ＧＡ１＋３)、细胞分裂素(ＣＴＫｓ)和脱落酸(ＡＢＡ)水平急剧上升,异花授粉处理更明显。未授粉的子房内源生长促进类激素含量保持低水平,生长抑制类激素(ＡＢＡ)水平上升,这种激素水平的失衡最终造成未授粉子房的迅速凋落。果实生长发育初期,自花授粉幼果内源激素促进类激素含量低于异花授粉处理,ＡＢＡ水平明显高出后者,果实迅速增长期间,内源ＩＡＡ和ＧＡ１＋３有两个明显的高峰期,显示ＩＡＡ和ＧＡ１＋３含量与果实迅速膨大有密切关系。果实发育后期直至成熟,内源ＡＢＡ水平逐渐升高。测定果实发育整个过程的ＡＢＡ/(ＩＡＡ＋ＧＡ１＋３＋ＣＴＫｓ),未发现规律性的变化。     

荔枝三种结实类型内源激素的平衡与坐果机理

首次引入内源激素平衡[(1AA+GAs+CTK)/ABA]概念,比较分析了荔枝三种类型果实(大核、小核、无核)内源激素平衡的动态变化;揭示了无核果在花后3d相对高水平的生长促进类激素(IAA+GAs+CTK)及花后ABA水平的持续下降是其具有单性结实能力的主要原因;同时,揭示了坐果期低水平的IAA、GAs及相对较低的(IAA+GAs+CTK)/ABA值是小核品种严重生理落果的主要原因;并比较了荔枝果实各组成部分(果皮、假种皮、种子)内源激素平衡的差异,认为胚的正常发育对维持荔枝果实后期的生长发育有重要意义,是大核品种后期生理落果较少的内部生理基础。     

Seed-sprouting in tomato fruits

Although tomato juice possesses properties which are inhibitory to seed germination, sprouting of seeds has been observed frequently in ripe tomatoes of mechanical harvest cultivars ‘VF 145’ and ‘VF 13L’. Juice from these cultivars was less inhibitory to tomato seed germination, as determined by bioassays, than that of other cultivars. There was no difference in the inhibition between juice from the pulp and that from the locular gel. Soluble solids accounted for 44% of the inhibition, osmotic concentration 2%, and pH only 0.2%; and the remainder came from other constituents in the juice. Abscisic acid and 2 unidentified substances in the juice isolated by extraction and chromatography were shown to inhibit seed germination; the degree varied with maturity and cultivar.Injection of abscisic acid into the vascular tissue of the stem scar inhibited sprouting within the fruit. Gibberellic acid and kinetin gave variable results, depending upon harvest dates. Fruits from plants grown in low potassium nutrient culture solutions had increased sprouting of seeds.Presented at the XXth International Horticultural Congress, Sydney, Australia, August 1978, Abstract 1189     

赤霉素和脱落酸对番茄种子发芽的生理调控──文献综述

介绍番茄种子发育过程中，种子发芽力和抗脱水力形成，浅休眠和胎萌等现象的基础上，着重讨论了ＧＡ与ＡＢＡ在番茄种子浅休眠形成、抑制胎萌方面的作用以及对渗控处理和发芽过程中种子水分关系、种胚生长、ＤＮＡ复制、胚乳弱化等的生理调控机制。     

The Strawberry Aphid,Pentatrichopus Fragariae (Theob.), in North Wales,with Special Reference to the Maintenance of Healthy Strawberry Stocks in Non-Fruit-Growing Areas

Summary

Excessive premature abscission of developing fruitlets in UK cherry orchards often results in low fruit yields. An improvement in our understanding of the underlying causes of embryo abortion and fruitlet abscission will help rationalize effective remedies to this problem. The aim of this study was to determine the effects of limiting the availability of leaf-derived assimilates, during critical stages of fruitlet development, on the severity of fruitlet abscission. Experimentally, this was achieved by isolating individual “spur units” (short shoots (<10 cm) with leaves and fruit) from the tree by girdling (severing the phloem connections) branches on either side of the unit. In this way, the developing fruitlets within the associated spur would be able to derive their assimilates only from the associated spur leaves. Spur units with different total leaf areas and variable numbers of developing fruitlets were chosen to achieve a wide range of potential source and sink strengths. The spurs analysed varied in leaf number from 4–9 leaves as spur leaf area increased. The largest variability in the spur leaf area number relationship occurred in spurs with 6–7 leaves. When initially determining the total leaf area per spur in May, there was no obvious relationship with fruit number per spur. Subsequent analysis of the relationship between spur leaf area and fruit number per cluster showed that fruit had been lost from spurs with the smallest leaf areas. Spurs girdled later in the season in June also showed no obvious relationship between spur leaf area and fruit number. As with spurs girdled in May, those manipulated in June lost fruit from spurs with small leaf areas. By July, there was a positive curvilinear relationship between spur leaf area and fruit number for girdled spurs. Neither total nor average fruit fresh weight per spur, at harvest, could be related to spur leaf area. The average individual fresh weight of fruit in a spur was, however, limited by the number of fruit within that spur. When spurs were girdled, fruit loss was shown to take place preferentially where the spur leaf area per fruit was low. From this analysis, it was possible to predict which girdled spurs would lose fruit, using the calculated ratio of spur leaf area per fruit. It is concluded that fruit retention, not size, appears to be limited by the availability of leaf-derived assimilates.     

Studies of Fruit Development in Relation to Plant Hormones: II. The Effect of Naphthalene Acetic Acid on Fruit Set and Fruit Development in Apples

The experiments described in this paper were designed. (1) to investigate the mechanism whereby α-naphthalene acetic acid (NAA), applied as a spray to apple trees between full bloom and two to four weeks after petal-fall, reduces the crop ; and (2) to assess the possible value of this substance as a blossom- and fruit-thinning agent.

Spraying open flowers with NAA before pollination was found to induce incompatibility between the pollen tubes and the stylar tissue, and it is considered that this may account for the reduction in set which results from spraying trees at full bloom with NAA. Applied after petal- fall, the spray caused the abortion of a large proportion of the developing seeds and this, in turn, led to an abnormally large drop of young fruitlets. The seeds appeared to be susceptible to damage by NAA only as long as the endosperm was in the free nuclear stage, a condition which, in most varieties of apple, persists until about the third week after petal-fall. As a thinning agent, NAA has the disadvantage that it tends to retard fruit growth. This effect is particularly marked when the spray is applied later than two weeks after petal-fall, and frequently offsets any increase in fruit size which might have resulted from thinning. Earlier application of the spray may, in certain varieties, cause a permanent stunting of the foliage. In the strongly biennial Miller’s Seedling, none of the thinning treatments, using NAA on individual branches, resulted in the differentiation of fruit buds in the " on ” year.     

Sensitive stages of fruit and seed development of chili pepper (Capsicum annuum L. var. Shishito) exposed to high-temperature stress

The sensitivity of developmental stages to high temperature was investigated in chili pepper (Capsicum annuum L. var. Shishito). Plants were subjected to heat stress (38/30 °C day/night) immediately after anthesis for 5 or 10 days, or from 10 to 30 days after anthesis (DAA), from 30 DAA until harvest of the seeds, or immediately after anthesis until harvest of the seeds. Control plants were grown at 30/22 °C (day/night). Exposure to high temperature (heat stress) during different periods of development after anthesis adversely affected fruit growth, seed yield, and seed quality in chili pepper. Heat stress for the whole period after anthesis, and from 30 DAA until harvest reduced the growth period of chili fruits by 15 and 10 days, respectively. Heat stress from 10 to 30 DAA reduced fruit width and fruit weight. The early stage of seed development from anthesis until 10 DAA was sensitive to high temperature, which affected fruit length, fruit weight and seed set. Applying high temperatures to plants for 10 DAA increased the proportion of abnormal seeds per fruit. High temperatures from 10 DAA until 30 DAA inhibited carbohydrate accumulation and adversely affected seed germinability and vigor. These results suggest that the stage of development at which chili peppers are exposed to high temperatures is an important factor in fruit and seed growth and in seed quality.     

Gibberellins and Other Growth Hormones in Apple Seeds

New methods for the complete extraction of gibberellins and other hormones from freeze-dried seeds, and for the partial purification and resolution of the extracts on cellulose columns, are described.

The presence of gibberellins A₄ and A₇ in developing apple seeds has been confirmed by thin-layer and gas-liquid chromatography. Bioassay of partially purified extracts in the lettuce hypocotyl test showed that gibberellins first appeared in the seeds about 5 weeks after full bloom, increased to a maximum concentration at 9 weeks and subsequently decreased again, disappearing completely by the time the seed was mature.

The rapid build-up of gibberellins was preceded by the appearance of an unidentified hormone, highly active in the Avena mesocotyl assay, which reached its peak concentration 6 weeks after bloom. A second unidentified hormone with similar biological properties reached its highest concentration 13 weeks after bloom, at the time when gibberellins were fast disappearing.

It is pointed out that the sequence of hormone production in the apple seed is linked with well-defined stages of embryo and endosperm development and the possible functional significance of the hormones is discussed.     

夏金脐橙落花落果规律研究

脐橙落花落果严重,着果率较低,保花保果的成败是脐橙高产的关键。对夏金脐橙的落花落果进行了观察。结果表明,不同年份夏金脐橙落蕾落花的开始时间和高峰期不同,落蕾落花高峰期一般出现在落蕾落花开始后的4~5天,2008年集中在4月中旬初,2009年在3月下旬末;4月21日开始第一次生理落果,持续35天左右,于5月底结束,4月底至5月初出现落果高峰;落花结束后15~16天,于5月上旬出现第二次生理落果,5月中旬出现落果高峰期,不同年份落果持续时间有别;落蕾落花数量超过生理落花落果总数的60%,第一次生理落果所占比例也较高,第二次生理落果所占比例最小,稳定在3.0%左右;夏金脐橙着果率1.65%,脐黄率29.4%,裂果率2.4%。     

去雄时间对番茄杂交种种子产量的影响

摘要：为了提高番茄杂种种子的纯度和产量,需要确定适宜的去雄时间。以番茄杂交组合SD-26-38的父母 本为材料,分别在日光温室内和露地设置开花前2 d上午、开花前2 d下午、开花前1 d上午、开花前1 d下午4个 去雄时间,在开花当天上午9：00—10：00进行授粉,研究不同去雄时间对坐果率及单果种子数的影响。结果 表明：无论是日光温室内还是露地条件下,在开花前1 d下午去雄的番茄坐果率、平均单果种子数均最高,温 室条件下分别为96.0%和134.9粒,露地条件下分别为60.7%和88.7粒。各处理杂种种子纯度均为100%,满足生 产需求。综合得出,在番茄开花前1 d下午人工去雄的制种效果最好。     

植物生长调节剂TDZ 对‘索邦’百合果实生长发育的影响

 以东方百合‘索邦’（Lilium Oriental Hybrids‘Sorbonne’）为试材,开花初期用不同浓度的 植物生长调节剂噻重氮苯基脲（thidiazuron,TDZ）对植株喷洒处理,观测其对坐果率、果实生长及种子 发育的影响;对百合幼果胞壁转化酶（cell wall-bound invertase）活性、叶片叶绿素含量及净光合速率进 行了测定。结果表明：外源TDZ 对百合果实生长发育及种子形成有显著促进作用;能够显著提高幼果细 胞壁转化酶活性、叶片叶绿素含量及净光合速率,对百合果实生长发育有促进作用。与对照相比,TDZ 各处理在早期（10 d）时对果实膨大影响的差异表现较小,到30 d 时差异达到最大;以200 μmol · L-1 TDZ 处理效果最佳,其果实横、纵径分别是对照的1.75 和1.23 倍,坐果率比对照提高75.22 个百分点,有胚 种子率比对照提高65.31 个百分点,单果有胚种子数为对照的12.89 倍,单果种子质量为对照的21.87 倍。     

Studies on endogenous cytokinins in Citrus

Cytokinin amounts were determined in the ovaries of flowers and fruitlets on leafy and leafless inflorescences of seeded and seedless cultivars of Citrus sinensis, C. reshni and C. clementine. Flowers were sampled over a 65 day period from before anthesis to after fruit set, during the period from fructification to fruitlet expansion. Cytokinin activity appeared in both organic and aqueous phases obtained in the extraction process. Generally, the maximum activity in the organic phase occurred at anthesis, except in ‘Navelate’ orange, and decreased sharply following petal fall, whereas the aqueous phase had more cytokinins later, when the fruitlets had reached 1-2 cm diameter. The effect of pollination on cytokinin-like compounds was studied in seeded cultivars. The pollinated ovaries showed a peak in cytokinin activity at anthesis, in contrast to unpollinated ovaries. Partition chromatography of the organic phase on Sephadex LH-20 indicated five zones of cytokinin activity, four of which had the same elution volumes as ribosyl zeatin, zeatin, isopentenyl adenosine and isopentenyl adenine.     

Analysis of the Phenylpropanoid Enzyme Activities and Products in the Soft- and Hard-Seeded Pomegranate Genotypes During Fruit Development

To find out more about the biochemical aspects of seed-softness trait in pomegranate (Punica granatum L.), some of the phenylpropanoid pathway enzymes as well as their products were evaluated in the various soft- and hard-seeded genotypes during fruit development. Results showed that peroxidase (POD) activity decreased in all studied genotypes during fruit growth, while increasing at the last stages only in the hard-seeded genotypes. Although laccase (LAC) activity did not show high differences during fruit ripening and in different genotypes, but its general trend was increasing. Phenylalanine ammonia-lyase (PAL) activity decreased during the fruit development and approximately diminished for the hard-seeded genotypes. All genotypes had lignin components in their seeds and amount of lignin increased during the growth season. Total phenolic decreased drastically and antioxidant capacity increased gradually showing an opposite trend and probable competitive effect for the same substrate during fruit development. Considerable differences that were observed in the POD activity at the last sampling stage, and higher activity that was observed in POD than LAC, may indicate that POD is more important for polymerization of lignin in the pomegranate seed and this enzyme might have some role in the development of seed softness trait in pomegranate. Also, this is the first report about lignin detection in the seeds of soft-seeded pomegranate genotypes, and represents a different mechanism (such as monolignol conformation in the final polymer) from lignin content for development of the soft-seeded pomegranate genotype.     

番茄生长素响应因子基因SlARF12在果实发育过程中的功能分析

以番茄‘Micro-Tom’为材料,研究了生长素响应因子基因SlARF12 （序列号：HM565127.1）在果实发育过程的生物学功能。实时定量PCR 检测表明,SlARF12在花蕾中表达量逐渐降低,而在授粉后的子房中显著高于去雄后未授粉的子房。利用RNA干扰（RNAi）技术抑制SlARF12表达,对番茄植株营养生长与花的发育没有显著影响,但SlARF12 RNAi果实显著大于野生型与空载转化植株的果实,且开花前去雄未授粉不能形成单性结实的果实。利用半薄切片观察转基因番茄果实早期发育细胞学特性发现,转化植株的果实果皮细胞显著大于对照果实细胞,但是两者果皮细胞层数没有显著差异。基因表达分析发现在SlARF12 RNAi的子房与幼果中细胞分化相关基因CycB1.1和CDKB2.1等的表达水平同对照相比下降,而SlPEC等细胞膨大基因表达量显著高于对照。所以抑制SlARF12可增强果实中细胞膨大相关基因的表达,从而促进果实膨大。以上结果表明,SlARF12可负调控番茄果实膨大但不参与坐果启动调控过程,显示了生长素通过ARF信号精细调控果实发育的各个阶段。     

Non-structural carbohydrate status and CO2 exchange rate of apple fruitlets at the time of abscission influenced by shade,NAA or BA

Four days of 90% shading at the time of fruit setting (1–5 days after petal fall, DAPF) of mature ‘Jonagold’/M.9 apple trees was combined with the application of thinning agents to establish the possible interaction of both main treatments on fruit retention, and the effects of the main treatments on fruitlets CO₂ exchange and their carbohydrate concentration. Shading alone reduced yield by up to 35%. When shading was followed by the application of 15 ppm 1-naphthaleneacetic acid (NAA) or 50 ppm 6-benzyladenine (BA), the interaction between shading and chemical thinners was on the border of significance. Following the assumption that abscission was induced by shading before the application of chemical thinning agents, the same process of diminished dark respiration rate (R_d) was found on fruitlets sampled 3 days after the end of shading and 7 days after NAA and BA spraying, i.e. in the fruitlets that were considered prone to drop. A week after the end of shading the abscission of fruitlets due to shading was completed and on the remaining fruitlets that were not prone to abscission any more, larger negative net CO₂ assimilation rates (A) and enhanced R_d were recorded. Fruitlets prone to abscission sampled 2 days after the end of shading showed a lower concentration of glucose and ascorbic acid and a higher concentration of starch. Eight days after the end of shading, the fruitlets from shaded trees that were not prone to abscission any more contained less fructose while the fruitlets from NAA and BA sprayed trees had a higher concentration of fructose a week after application. The results do not support the hypothesis that a good assimilate supply is needed for the retention of apple fruitlets, because the fruitlets retained on trees expressed even stronger CO₂ loss and because the concentration of non-structural carbohydrates did not decrease in fruitlets prone to drop with the exception of glucose.     

糯米糍荔枝果实内源激素与落果的关系

以糯米糍荔枝生理落果期的田间调查和胚胎发育研究为基础,探讨了内源激素与生理落果的关系.结果表明,糯米糍生理落果高峰的主要原因是:第1次因授粉受精不良导致的生长促进类激素尤其是CTK水平过低;第2次与胚乳为胚的发育所利用而消失、IAA和GAs急剧降低有关;第3次与胚的败育造成CTK、GAs和IAA的全面下降有关;第4次发生在假种皮(果肉)迅速生长期,与种皮和假种皮ABA升至高水平有关.此外,还探讨了ABA /(IAA+GAs+CTK)与生理落果的相关性,以及胚囊、珠被和假种皮等果实内部组分内源激素的变化特点.     

疏果剂敌百虫在‘金冠’苹果短果枝内的分布和对光合强度及产物分配的影响

‘金冠’苹果盛花后14天喷施1200ppm敌百虫可以引发落果,在短期内抑制幼果的生长。根据幼果在短果枝上的发育与坐果特征的不同,可分为三类:中心果、初生边果和次生边果。~(14)C-敌百虫示踪实验表明,敌百虫在维管束和幼果中含量高。敌百虫喷施48小时后,短果枝莲座叶的光合作用显著地受抑制,同时运向幼果的~(14)C-同化物显著减少,光合作用在8至18天内恢复正常。作者认为,敌百虫疏果的机制是减弱“源”、“库”的强度,加剧短果枝内碳水化合物短暂缺乏,使较小的幼果因碳水化合物缺乏而减缓生长,直至脱落,达到疏果的目的。     

超干贮存对番茄种子活力的影响

 研究了超干含水量、贮存温度对番茄种子生活力和活力的影响, 结果表明: 含水量为4. 6 %、2. 4 %的番茄种子在20 ℃下密封贮存13 年后, 发芽率、苗长、脱氢酶活性、SOD 活性与对照(0 ℃、6. 2 %)相比均无明显差异, 但含水量为1. 9 %的种子上述指标却显著下降, 说明含水量为4. 6 %、2. 4 %的超干番茄种子在常温下具有良好的耐藏性, 含水量过低(1. 9 %) 不利于长期贮存, 但上述三种含水量(4. 6 %、2. 4 %、1. 9 %) 的番茄种子在0 ℃下密封贮存13 年后, 均有着较高的种子活力、生活力和酶活性。