The influence of polyamines on apricot ovary development and fruit set

Polyamine (PA) concentrations of ovaries of two apricot cultivars, ‘S405‐17’ and ‘Bergeron’, collected at three stages of floral development, were analysed. The relationships between PA profiles, ovule development and fruit load between the two apricot cultivars were also determined. We show that PA levels vary with ovary development, depending on the cultivar. Higher concentrations of putrescine (PUT), spermidine and spermine were found in S405‐17 cultivar at all phenological stages. In addition, S405‐17 cultivar had more developed ovules and a higher fruit load than Bergeron. Moreover, the exogenous application of 10 mM PUT in Bergeron increased the percentage of functional ovules from 17.1% (control) to 33.3%. These results prove the effects of PAs on ovary development and indicate the possible improvement of apricot ovule development by their exogenous application. All these results define the relationship between PA content and ovule development in apricot. Further studies would confirm the use of free endogenous PA concentrations as markers of the developmental stage of the ovary, because determination of PA contents is easier and faster than serial sectioning.     

Antibacterial activity and mechanism of action of chitosan solutions against apricot fruit rot pathogen Burkholderia seminalis

The in vitro antibacterial activity and mechanism of action of two kinds of acid-soluble chitosan and one water-soluble chitosan against apricot fruit rot pathogen Burkholderia seminalis was examined in this study. Results showed that water-soluble chitosan displayed limited antibacterial activity at four tested concentrations. However, two kinds of acid-soluble chitosan solution at 2.0 mg/mL had strong antibacterial activity against B. seminalis although weak antibacterial activity was observed at a concentration lower than 1 mg/mL. The antibacterial activity of acid-soluble chitosan may be due to membrane disruption, cell lysis, abnormal osmotic pressure, and additional chitosan coating around the bacteria based on integrity of cell membranes test, out membrane permeability assays and transmission electron microscopy observation. In addition, biofilm biomass were markedly reduced after treating with two kinds of acid-soluble chitosan at concentrations of 2.0 and 1.0 mg/mL for 3 and 12 h, indicating the importance of biofilm formation in the antibacterial mechanism of chitosan. Overall, the results clearly indicated that two kinds of acid-soluble chitosan had a potential to control the contamination of apricot fruits caused by B. seminalis.     

Overproduction and selective abortion of ovules based on the order of fertilization revisited

Given that seeds fertilized by slowly growing pollen are of low quality genetically, we theoretically reanalyzed the hypothesis that plants selectively abort ovules fertilized later to enhance the mean quality of resulting seeds. We assumed that both superior and inferior pollen exist, the superior pollen growing faster to fertilize ovules, resulting in seeds of higher quality than those of ovules fertilized by inferior pollen. We developed two models to determine the conditions under which selective abortion is favored. In the first model, ovules in one flower are fertilized by pollen grains that arrive at different times, with each visit bringing both fast- and slow-growing pollen. In the second model, ovules in two flowers are fertilized by all pollen grains that arrive at the same time. In the first model, we found that selective abortion based on the order of fertilization is never advantageous irrespective of the duration of the time lag between the two visits. Rather, random abortion is possibly favored. In the second model, although selective abortion based on the order of fertilization can be advantageous, the parameter region favoring it is rather restricted. This is because overproduction can be advantageous only if the quantity of the superior pollen is not limited in one flower but is limited in the other flower. In addition, the degree of overproduction was very low, implying that the merit of overproduction (increase in the number of superior seeds) is low compared to the cost of overproducing ovules. These results suggest that selective abortion of ovules based on the order of fertilization is not as advantageous as previously considered.     

Endogenous polyamines in apple and their relationship to fruit set and fruit growth

The distribution of free and bound polyamines was investigated from blooming until harvest on flower, fruitlets and fruits of Malus domestica Borkh cv. Golden Delicious, Relationships between polyamines and fruit set and growth were also investigated. The level of free polyamines was high only during the first weeks after full bloom and then decreased gradually. The amount of bound trichloroacetic acid-insoluble polyamines was much higher than free polyamines. Bound spermine in particular showed a high value for almost 40 days after full bloom, while spermidine and putrescine were no longer detectable even a few days after full bloom.
In relation to fruit set, it was possible to observe that abscission peaks took place when free polyamine levels were low or decreasing. Insofar as fruit growth is concerned, the most substantial variations in polyamine levels occurred very early in the season when fruit dry weight and protein amount were also changing rapidly and fruit diameter was almost impossible to measure.     

Detection and inheritance of stylar ribonucleases associated with incompatibility alleles in apricot

 Stylar proteins were surveyed by non-equilibrium pH gradient electrofocusing to identify S-RNases associated with gametophytic self-incompatibility in nine apricot cultivars. RNase activities associated with the alleles of incompatibility S ₁ , S ₂ , S ₅ , and S ₆ and with the allele of compatibility Sc were clearly identified. Two other bands that we considered related to the alleles S ₃ and S ₄ were unique to cultivars Sunglo and Harcot, respectively. Two generations of 17 seedlings from the cross Moniquí× Pepito and 38 from Gitano × Pepito were used to determine the inheritance of the S-RNases. Inheritance of these RNase bands followed the expected segregation ratios and the band combinations correlated perfectly with the known self-incompatibility status of the seedlings determined after self-pollination and observation of pollen tube growth. All evidence presented in this study strongly suggests that RNases are associated with gametophytic self-incompatibility of apricot and that RNases may be the S-gene products. This is the first report identifying S-RNases and describing the inheritance of these S-RNases in apricot. Received: 19 February 1998 / Revision accepted: 2 April 1998     

Effect of plant growth regulators on in vitro fiber development from unfertilized and fertilized Egyptian cotton ovules

Unfertilized and fertilized ovules of Gossypium barbadense Giza 45 (extra long staple variety) were used to study the effect of plant growth substances (auxins, gibberellins and cytokinins) on in vitro fiber initiation and development. Kinetin, alone did not increase total fiber unit (TFU) of unfertilized ovules, while an increase in TFU value occurred when a constant level of IAA and GA₃ were used either separately or in combination in the liquid medium. GA₃ used alone, produced a higher TFU value than that produced by IAA, whilst, IAA with a constant level of GA₃ (5 M) produced the highest value of TFU. GA₃ with a constant level of IAA (5 M) produced a lower TFU value. Kinetin reduced the stimulatory effect of IAA and GA₃ on TFU value when used in combination with either substance. In fertilized ovules, the highest level of TFU was reached when IAA, with a constant level of GA₃, was added to the medium, whilst its lowest level was obtained when IAA was used alone. Estimation of in vitro fiber production, as well as the effect of growth substances used in different concentrations on in vitro fiber initiation and development from unfertilized and fertilized ovules of Egyptian cotton varieties Gossypium barbadense Giza 45 are discussed.     

Production of seedlings from ovules excised at the zygote stage in Lilium spp.

The present study was undertaken to establish a culture system for ovules excised at the zygote stage in Lilium spp. Ovules of Lilium × `Connecticut King' and L. × `Enchantment' were excised together with placental tissue 3, 5, and 10 days after pollination (DAP) and cultured on B5 medium and half-strength B5 medium containing sucrose at different concentrations. In vitro embryo development in ovules cultured at 3 DAP was influenced by the basal media and the sucrose concentration. The half-strength B5 medium with 9% sucrose was the best condition, but only a few ovules isolated from placental tissue developed into seedlings. Application of embryo culture, in which embryos were excised from ovules after 14 weeks of ovule-with-plancetal-tissue culture, greatly improved the production of seedlings. The present study indicates that a two-step culture procedure, ovule-with-placental-tissue culture and embryo culture, make it possible to produce seedlings from ovules just after fertilization.     

A new hypothesis for the evolution of overproduction of ovules: an advantage of selective abortion for females not associated with variation in genetic quality of the resulting seeds

A new hypothesis for the evolution of overproduction of ovules within flowers is proposed: overproduction is a counter-strategy of female seed production in the conflict with males and/or offspring. It is advantageous for females to produce a uniform size of seeds, whereas it is advantageous for fertilized ovules to absorb more resources than this size. If there is a variance in resource absorption ability among fertilized ovules, nonuniform seeds are produced. Then, by overproducing ovules, females should select fertilized ovules with similar resource absorption rates, resulting in seeds of uniform size. A model analysis confirmed that this hypothesis works. In the model, the fertilized ovules of a plant consist of two genotypes that differ in resource absorption rate. I found that overproduction of ovules and selective abortion is advantageous if the difference in the resource absorption rates of the genotypes is large. The new hypothesis is different from the selective abortion hypothesis in that selecting ovules is advantageous even if there are no differences in the genetic quality of resulting seeds.     

膨大期果面喷施IAA对桃成熟期果实性状和相关基因表达的影响北大核心CSCD

为明确桃果实发育后期外源生长素对果实成熟的影响及更深入的认识生长素调控果实发育与成熟的机制,本研究以桃品种‘小白凤’为试材,采用不同浓度的外源IAA(200,10,0.1μmol/L)喷施第2次快速膨大期的桃果实,在处理后10,20,30 d分别取样,分析桃果实的硬度,糖组分(蔗糖、葡萄糖、果糖、山梨醇),果胶,纤维素含量以及乙烯释放量的变化,并对200μmol/LIAA处理后30 d及对照组的果实进行了转录组测序分析,深入认识生长素调控桃果实成熟的作用和机理。结果表明,(1)IAA处理后30 d时,200μmol/L处理组桃果实果肉硬度与对照组相比显著增加,成熟期平均延迟5 d,而10,0.1μmol/LIAA处理组与同期对照组间无显著差异。(2)果肉蔗糖含量在0.1,200μmol/LIAA处理后30 d显著低于同期对照组,在10μmol/LIAA处理后30 d时与对照组无显著差异;葡萄糖、果糖和山梨醇含量在各浓度IAA处理后30 d时多与对照组间无明显差异。(3)在处理30 d时,果肉中可溶性果胶含量在0.1μmol/L IAA处理组与对照组无显著差异,在10,200μmol/LIAA处理组均显著低于对照组,此时不同浓度IAA处理桃果肉中不可溶果胶和纤维素含量均与对照组之间无显著差异。(4)在IAA处理后10,20,30 d时,果实乙烯释放量均表现为0.1,10μmol/L处理与对照组无显著差异,200μmol/L处理组显著低于对照组。(5)转录组数据显示,200μmol/L IAA处理与对照组中共存在86个差异表达基因,KEGG分析发现其中有6个与果实发育成熟密切相关的代谢途径中多个基因的表达谱发生显著变化,且变化趋势与已测定的生理指标数据吻合。综合分析表明200μmol/L的外源IAA处理第2次快速膨大期的桃果实能够延缓果实成熟的进程。     

不同品种杏的性器官发育和结实性比较研究

通过对原产于不同地区的５１个杏品种的性器官发育和结实性的系统调查和测定,结果表明,１．花粉上和形状少数虽有一定差异,而大数色大多数品种相似,吕种间花粉萌发率尽管差异很大,但所有品种均为花粉可育型。２．大多数品种不完全花百分率很高,自然授粉率很,其主要原因是雌蕊败育。３．品种间不完全花百分率与花粉萌发率呈正相关;４．欧洲生态群品种与中国生态群品种比较芬粉大小和形态基本相似,而花粉萌发率和不安全花百分     

Calcium in the micropylar secretion and receptivity of explanted Crocus ovules to intra- and interspecific pollen

The micropylar secrete of the ovules of Crocus vernus ssp. vernus was analyzed for the Ca⁺² content by atomic absorption, and its capacity to germinate and attract pollen was tested by pollinating explanted ovules, and incubating in absence of culture medium. The results display a Ca⁺² concentration of 28.9 mM in the micropylar secrete. On this secrete both compatible- and incompatible pollen germinates with a mean percentage of 53.7%, and their pollen tubes enter the micropylar canal with percentages of 32.3% to 21.0%. In situ the ovules fail to attract tubes of incompatible pollen. The results are discussed in relation to the ovule receptivity and the guided growth of pollen tubes, substantiating the model of the tropic growth towards increasing calcium concentrations.     

三种蔷薇科果树小绿叶蝉及捕食性天敌种群动态的比较

对3种果树小绿叶蝉及其天敌数量进行t检验得出,樱桃园与梨园之间,小绿叶蝉、异色瓢虫、锥腹肖蛸差异显著、三突花蟹蛛差异极显著,均是樱桃园多于梨园;樱桃园与杏园之间,三突花蟹蛛、草间小黑蛛差异显著,异色瓢虫、锥腹肖蛸差异基本显著,均是樱桃园多于杏园,小绿叶蝉差异基本显著,杏园多于樱桃园;梨园与杏园之间,草间小黑蛛和小绿叶蝉均差异显著,杏园多于梨园。采用灰色系统分析方法研究樱桃小绿叶蝉数量与其天敌个体数量关联度,结果是,关联度较高的天敌依次是锥腹肖蛸、草间小黑蛛、八斑球腹蛛和中华草蛉,与理想优势种天敌数量关联度较高的天敌依次是三突花蟹蛛、异色瓢虫、草间小黑蛛和中华草蛉;利用生态位分析方法分析的结果是,与小绿叶蝉时间生态位和空间生态位重叠指数较大的天敌依次是异色瓢虫、草间小黑蛛、三突花蟹蛛和锥腹肖蛸;与小绿叶蝉两种生态位相似性比例指数较大的天敌依次是异色瓢虫、三突花蟹蛛、草间小黑蛛和锥腹肖蛸。综合排序分析,前4位的天敌依次是异色瓢虫、草间小黑蛛、三突花蟹蛛和锥腹肖蛸。     

Variability in the developmental toxicity of bropirimine with the day of administration

The aim of this study was to determine the mechanism by which bropirimine exerts its developmental toxicity. This drug is an immunomodulator and interferon inducer with antiviral and antitumor activities in experimental models. Timed-pregnant Upj:TUC(SD)spf (Sprague-Dawley) rats were given a single oral (gastric intubation) dose of bropirimine at 200 or 400 mg/kg (doses as high as 100 mg/kg/day have been employed in human cancer trials) on days 5, 6, 7, 8, 9, 10, 11, or 12 of gestation and in a second experiment on day 12, 13, 14, 15, 16, 17, 18, or 19 of gestation. The dams were killed 24 hours after dosing and their uterine contents examined. In a third experiment, bropirimine (400 mg/kg) was administered on day 4 of gestation and the uteri of different groups were examined on day 8, 9, 10, 11, or 12 of gestation. Serum progesterone levels were measured at sacrifice. In the first two experiments a battery of hematologic/clinical chemistry assays also were performed. In all three experiments, bropirimine-related maternal toxicity was observed; such toxicity was characterized by significant decreases in weight gain, relative to the concurrent vehicle controls, as well as significant differences in several blood parameters including platelets, white blood cells, alanine aminotransferase, and aspartate transaminase. In the first experiment, bropirimine treatment on day 11, but not day 12, resulted in significant decreases in the mean number of live embryos per litter. In the second experiment, significant decreases in the number of live fetuses per litter occurred 24 hours after dosing on day 18 (200 and 400 mg/kg groups) or day 19 (400 mg/kg group). Decreases in serum progesterone appeared to correlate well with the embryolethal effects seen after treatment between days 6 and 11 of gestation, but not with the fetal lethality seen when treatment was given on day 17 or 18. The decreases in serum progesterone levels found most likely were the result of a luteolytic effect, although it is unknown if bropirimine has a direct or indirect effect on the corpora lutea. In the third experiment, bropirimine treatment on day 4 of gestation resulted in only slight preimplantational losses, but significant decreases were found in mean number of live embryos per litter after day 9. Uterine decidual necrosis has been observed in the first experiment where bropirimine was given on day 11; however, treatment on day 4 resulted in an apparent decrease in decidual development but not necrosis.     

氮高效利用基因型水稻生育后期氮素分配与转运特性

选择前期筛选出的氮高效利用基因型水稻为试验材料,以低效利用基因型为对照,采用土培试验,在低氮(100 mg·kg^-1)和正常施氮(200 mg·kg^-1)下,研究了高效和低效基因型水稻生育后期不同器官的氮素分配量、转运量和转运效率差异.结果表明: 与低效基因型水稻相比,高效基因型在低氮条件下,仍能保持较高的产量和氮素利用效率,其产量为低效基因型的1.75倍,氮肥利用率高达50.9%,而低效基因型仅为36.4%.与正常施氮相比,低氮更有利于提高氮素在高效基因型穗部的分配量,穗部积累量在扬花期、灌浆期和成熟期分别增加了34.2%、2.5%和0.5%,而低效基因型在灌浆期和成熟期却分别降低了23.5%和15.6%.不同施氮水平下,氮素在高效基因型不同器官的分配比例为扬花期:叶＞茎鞘＞根＞穗,灌浆期:穗＞叶＞茎鞘＞根,成熟期:穗＞茎鞘＞叶＞根,随着生育期的推进,穗部的分配比例明显增加.在低氮和正常施氮下,高效基因型氮素转运量表现为叶＞茎鞘＞根,而低效基因型表现为茎鞘＞叶＞根;高效基因型氮素转运效率分别为60.8%、60.3%,分别为低效基因型的1.67、155倍.因此,高效基因型抽穗后叶片较高的转运效率为籽粒的灌浆结实奠定了良好基础.     

Fertilization-dependent auxin response in ovules triggers fruit development through the modulation of gibberellin metabolism in Arabidopsis

Fruit development is usually triggered by ovule fertilization, and it requires coordination between seed development and the growth and differentiation of the ovary to host the seeds. Hormones are known to synchronize these two processes, but the role of each hormone, and the mechanism by which they interact, are still unknown. Here we show that auxin and gibberellins (GAs) act in a hierarchical scheme. The synthetic reporter construct DR5:GFP showed that fertilization triggered an increase in auxin response in the ovules, which could be mimicked by blocking polar auxin transport. As the application of GAs did not affect auxin response, the most likely sequence of events after fertilization involves auxin-mediated activation of GA synthesis. We have confirmed this, and have shown that GA biosynthesis upon fertilization is localized specifically in the fertilized ovules. Furthermore, auxin treatment caused changes in the expression of GA biosynthetic genes similar to those triggered by fertilization, and also restricted to the ovules. Finally, GA signaling was activated in ovules and valves, as shown by the rapid downregulation of the fusion protein RGA-GFP after pollination and auxin treatment. Taken together, this evidence suggests a model in which fertilization would trigger an auxin-mediated promotion of GA synthesis specifically in the ovule. The GAs synthesized in the ovules would be then transported to the valves to promote GA signaling and thus coordinate growth of the silique.     

Competition and fruit set in the Washington navel orange

In the Washington navel orange [ Citrus sinensis (L.) Osbeck] an increase in the number of flowers results in a reduction of flower weight at anthesis and the initial fruit growth rate, and the number of developing fruitlets increases. Most of these fruitlets are shed during post-anthesis, and the final set of fruit is unrelated to the number of flowers and to the total amount of metabolites and mineral elements used up in fructification but appears to be controlled by the capacity of the tree to supply metabolites to the developing fruitlets during post-anthesis. When the number of flowers is too large, there is a reduction both in the number of initially developing fruitlets and in their growth rate. The final set of fruit is reduced through a different mechanism acting at anthesis and involving differences in mineral composition, which impairs the capacity of the fruit to act as a sink.     

Resistance to pathogens and host developmental stage: a multifaceted relationship within the plant kingdom

The induction of resistance to disease during plant development is widespread in the plant kingdom. Resistance appears at different stages of host development, varies with plant age or tissue maturity, may be specific or broad-spectrum and is driven by diverse mechanisms, depending on plantpathogen interactions. Studies of these forms of resistance may help us to evaluate more exhaustively the plethora of levels of regulation during development, the variability of the defense potential of developing hosts and may have practical applications, making it possible to reduce pesticide applications. Here, we review the various types of developmental resistance in plants and current knowledge of the molecular and cellular processes involved in their expression. We discuss the implications of these studies, which provide new knowledge from the molecular to the agrosystem level.     

Andromonoecy and fruit set in three genera of the Proteaceae

It has been suggested by some authors that the low fruit to flower ratio in some Proteaceae is due to andromonoecy, while others, looking particularly at Banksia , have not been able to find evidence for male flowers in the inflorescences. Stirlingia latifolia, Xylomelum occidentals and X. angustifolium are clearly andromonoecous, while no evidence for this condition could be found in Brabejum stellatifoliutn. Production of fertile fruit is related to andromonoecy in Xylomelum and S. latifolia but not in Brabejum. It is unlikely that all-encompassing solutions will be found to what initially seem to be widespread traits in the family, especially in regard to pollination biology, as the genera in the family occupy widely different environments and have very diverse ecological ranges.