Light environment, growth and morphogenesis in a peach tree canopy

Morphogenic and growth processes were studied in relation to photosynthetically active radiation (PAR), and red, far red and blue spectral bands monitored at three different heights of a peach canopy during the vegetative season. The PAR intercepted by the bottom of the tree was significantly lower than that at the top, and blue fluence rate changed with height and season in a manner similar to PAR. Phytochrome photoequilibria indicated spatial and temporal differences in the three layers of the canopy: significantly lower values were detected at the bottom in correspondence with the maximum leaf area index. In this layer, a stimulation of internode elongation and a decrease of flower density were detected. Higher shoot growth rates and about double number of lateral shoots were found at the top of the canopy, where a greater number of sun leaves was present. Possible explanations in terms of different growth strategies induced by shade, depletion of blue, and low phytochrome levels at the bottom of the canopy are given.     

遮光对桃幼树形态及一些生理指标的影响

对不同遮光条件下,桃（Prunus persica L.）不同品种（‘朝晖’、‘早露蟠桃’和‘南方早红’）1年生幼树的形态和生理反应进行了研究。结果表明,在中度遮光条件下,品种‘朝晖’和‘南方早红’的叶面积增大;在重度遮光条件下,3个供试品种的新梢直径、新梢长度、叶面积、比叶鲜重和比叶干重均减小,且不同品种的变化幅度不同。以干物质增加量为耐弱光能力的判定指标,可以看出品种‘朝晖’较耐弱光,‘南方早红’耐弱光能力差。遮光能引起3个品种可溶性糖含量的下降。叶绿素a／b值的变化可用于判定桃品种的耐弱光能力。     

Partial deglycosylation of an anionic isoperoxidase from peach seeds – effect on enzyme activity, stability and antigenicity

An anionic isoperoxidase (EC 1.11.1.7) purified from peach seeds ( Prunus persica L. Batsch cv. Merry) was partially deglycosylated by glycopeptidase F (EC 3.2.2.18) treatment. A 40% deglycosylation resulted in an activity loss of 50% when assayed with o -dianisidine. 60% with guaiacol and 78% with 2,2'-azino-bis(3-ethyl)benzethiozoline-6-sulfonic acid (ABTS) as substrate. The indole-3-acetic acid oxidase activity loss was close to 55%. The partially deglycosylated isoperoxidase also showed a higher K_m value for H₂O₂ and higher values for Arrhenius activation energy and enthalpy of activation. There was a decrease in enzyme stability at 4°C after deglycosylation. Native and partially deglycosylated isoperoxidase reacted equally well in an enzyme-linked immunosorbent assay (ELISA) with rabbit polyclonal antibodies raised against the native enzyme. The carbohydrate moiety of this peach seed isoperoxidase appears to be important for enzyme activity and stability.     

Purification of an anionic isoperoxidase from peach seeds and its immunological comparison with other anionic isoperoxidases

A soluble anionic isoperoxidase (EC 1,11,1,7) was purified from peach ( Prunus persica L. Batsch cv. Merry) seeds. Purification was achieved by DEAE-Sephacel, Sephacryl S-300 and CM-cellulose chromatography. The purified isoperoxidase de-carboxylated indole-3-acetic acid (S_0.5 0.13 m M , Hill coefficient 1.7). Molecular mass, determined by gel filtration and sodium dodecyl sulfate polyacrylamide gel electrophoresis, was ca 60 kDa. Polyclonal antibodies were raised in rabbit against this isoperoxidase. Using immunoprecipitation this isoenzyme was found to be immunologically different from other soluble anionic isoperoxidases isolated from peach seeds.     

Changes in carbohydrate and enzyme levels during development of leaves of Prunus persica, a sorbitol synthesizing species

Carbohydrate levels and activities of enzymes associated with starch, sucrose and sorbitol metabolism were assayed in leaves of peach [ Prunus persica (L.) Batsch cv. Redhaven] of different ages, in order to examine developmental changes in leaf carbohydrate metabolism. Dry matter, soluble protein, chlorophyll and the activities of key enzymes of the reductive pentose phosphate pathway increased during leaf development. The levels of leaf carbohydrates, especially sorbitol and starch, also increased. Changes of starch levels were related to increases in the activities of enzymes associated to starch metabolism, such as ADPglucose-pyrophosphorylase (E.C. 2.7.7.27) and amylase (E.C. 3.2.1.1. plus E.C. 3.2.1.2). The activities of enzymes involved in sucrose and sorbitol degradation decreased during leaf development, whereas the activities of aldose-6-phosphate reductase (E.C. 1.1.1.200) and cytosolic fructase-1,6-bisphosphatase (E.C. 3.1.3.11) increased. In contrast, the activity of sucrose-phosphate synthase (E.C. 2.4.1.14) did not vary in a significant manner. The results suggest that the ability to synthesize and utilize both sucrose and sorbitol changes as peach leaves mature, and also that there are differences in metabolism of these two transport sugars during leaf development.     

Molecular cloning, identification, and chromosomal localization of two MADS box genes in peach （Prunus persica）

MADS box proteins play an important role in floral development. To find genes involved in the floral transition of Prunus species, cDNAs for two MADS box genes, PpMADS1 and PpMADS10, were cloned using degenerate primers and 5'- and 3'- RACE based on the sequence database of P. persica and P. dulcis. The full length of PpMADS1 eDNA is 1, 071bp containing an open reading frame (ORF) of 717bp and coding for a polypeptide of 238 amino acid residues. The full length of PpMADS10 cDNA is 937bp containing an ORF of 633bp and coding for a polypeptide of 210 amino acid residues. Sequence comparison revealed that PpMADS1 and PpMADS10 were highly homologous to genes AP1 and PI in Arabidopsis, respectively. Phylogenetic analysis indicated that PpMADS1 belongs to the euAP1 clade of class A, and PpMADS10 is a member of GLO/PI clade of class B. RT-PCR analysis showed that PpMADS1 was expressed in sepal, petal, carpel, and fruit, which was slightly different from the expression pattern of AP1; PpMADS10 was expressed in petal and stamen, which shared the same expression pattern as PI. Using selective mapping strategy, PpMADS1 was assigned onto the Bin 1:50 on the G1 linkage group between the markers MCO44 and TSA2, and PpMADS10 onto the Bin 1:73 on the same linkage group between the markers Lap-1 and FGA8. Our results provided the basis for further dissection of the two MADS box gene function.     

硬肉桃果实成熟前后钙含量和钙ATP酶活性的变化及其与果实硬度的关系

以硬肉桃新品种‘双久红’果实为试材,以常规优良品种‘川中岛白桃’为对照,分别研究了成熟前20d和成熟后20d内两品种果实中钙含量和Ca^2＋-ATP酶活性变化以及它们与果肉硬度关系的结果表明：‘双久红’果实的总钙和Ca^2＋含量从成熟前15d开始极显著高于同期‘川中岛白桃’的,两者与果实硬度变化呈极显著相关（P〈0．01）,随着果实的成熟两者均呈下降趋势,Ca^2＋-ATP酶的调控能力也逐渐减弱,但‘双久红’果实中的Ca^2＋-ATP酶活性比‘川中岛白桃’高一些。     

中国武夷山脉地区野生毛桃资源收集与初步评价

为明确中国武夷山脉地区野生毛桃(Prunus persica(L.) Batsch)资源分布现状,对浙江、江西、福建武夷山脉地区野生毛桃资源进行了系统的考察、收集和评价。此次考察共收集野生毛桃资源244份,来自于武夷山脉地区24个采集点。物候期评价发现这些资源多态性丰富。相关性分析显示,叶芽萌动期、花期与采集点海拔、纬度呈极显著正相关。果实评价显示果实性状多态性丰富。通过2年抗涝性评价,初步筛选出53株较抗涝野生毛桃资源后代单株。净光合速率、气孔导度、蒸腾速率与淹水时间相关性分析显示淹水时间与净光合速率、气孔导度、蒸腾速率均呈极显著负相关,而净光合速率、气孔导度、蒸腾速率三者之间呈极显著正相关关系。     

桃树修剪分枝模式的模拟

在不同修剪手法下,对栽培桃树(Prunuspersica(L.)Batsch)不同母枝上的分枝模式进行了比较研究。从分枝模式来看修剪后的母枝基本由3个不同的区域组成,基部是不萌发的潜伏芽形成的未分枝区域;中部是延迟分枝和多次分枝组成的分枝区域(主要的枝条类型有短枝、长枝和多次枝);顶部是被剪除的部分。我们通过隐式半马尔可夫模型来模拟这一分枝模式,主要是定量描述1次枝和多次枝在母枝上的数量及其分布状况。在上述模型中,未分枝区、延迟分枝区和多次分枝区称为瞬时态,被剪除的部分称为吸收态。模拟的结果与观察的结果进行对比后发现,两者具有很好的一致性。这说明隐式半马尔可夫模型是模拟植物分枝过程的一种有效方法,尽管隐式半马尔可夫链模型只是一个描述性的模型,但仍能对其所描述的生物现象进行解释,在预测修剪手法对母枝分枝模式影响方面比传统的方法具有明显的优势。本研究结果是建立三维虚拟桃树树冠分枝结构的基础。     

观赏桃品种需冷量的研究

采用0℃～7.2℃模型的累积低温计算方法,以加权法为萌芽计算标准,通过对29份观赏桃Prunus persica Batsch.(L.)品种资源的需冷量研究,结果表明:我国重瓣桃花品种的需冷量分布范围为400h～1250h,并以900h以上的品种为主.红花垂枝桃、红花重瓣寿星桃、鸳鸯垂枝、红叶桃、洒红桃和菊花桃等名优品种的需冷量分别为926h、930h、1188h、1112h、1214h 和1250h,郑州地区需冷量的满足时间基本在1月底之后.     

Two forms of exopolygalacturonase increase as peach fruits ripen

Abstract. Freestone peach cultivars are distinguished from clingstone cultivars by a more extensive softening of the mesocarp tissue, and by the separation of mesocarp and endocarp during ripening. Cultivars of both types have been reported to develop exopolygalacturonase activity during ripening, but the enzyme has not been characterized in any detail. During development of freestone peaches ( Prunus persica L. var Coronet), two exopolygalacturonase enzymes were detected 42, 65 and 85 d after full bloom and in ripe fruit. During ripening one enzyme (exoPG 1) increased 36-fold and the other (exoPG 2) 90-fold but exoPG 2 accounted for a 73% of the total activity in ripe fruit. ExoPG 1 was purified 24-fold and exoPG 2 540-fold. ExoPG 2 is a slightly acidic glycoprotein. ExoPG 1 and exoPG 2 differ slightly in their pH optima and in their responses to calcium: each produces monogalacturonic acid as a reaction product. Similar enzymes were found in Flavorerest, a semi-freestone peach.     

Exopolygalacturonase protein accumulates late in peach fruit ripening

Two exo-acting polygalacturonase enzymes (exoPG, EC 3.2.1.67) increase in activity as peach ( Prunu persica L. Batsch cvs Coronet and Flavorcrest) fruits ripen. By examining populations of fruit, we show that the increase in activity occurs late in ripening when the fruit are very soft (below 2 kgf). The more abundant form of the enzyme, exoPG 2, was extensively purified and analyzed for its amino acid content and N-terminal amino acid sequence. ExoPG 2 is a polypeptide of M, 66 000 and has a substantial excess of basic over acidic amino acids. Polyclonal antisera to exoPG 2 were raised in mice. The antisera inhibited the enzyme activity and recognized a M_r 66 000 polypeptide in Western blots. Western blot analyses of extracts of fruit ranked for softness revealed a M_r 66 000 polypeptide only in the softest fruit (less than 2.5 kgf). We conclude that the increased in exopolygalacturonase activity that occurs in very soft fruit is due to an increase in the amount of enzyme protein.     

Construction and characterization of a bacterial artificial chromosome library of peach

A peach [Prunus persica (L.) Batch] bacterial artificial chromosome (BAC) library of var. Jingyu was constructed. Jingyu is a traditional variety, that displays many of the important agronomic characters of stone fruits. Since peach leaves are rich in polysaccharides, high-molecular-weight (HMW) DNA was extracted from leaf nuclei using a protocol adapted to peach. The HMW DNA embedded in agarose plugs was partially digested by HindIII. After size-selection by pulsed field gel electrophoresis, the selected DNA fragments were ligated to pBeloBAC11 and transformed into E. coli DH10B cells by electroporation. In total 20,736 recombinant clones were obtained. The BAC library has an average insert size of 95 kb and represents approximately 6.7 peach haploid genome equivalents. The BAC clones were stable in E. coli cell after 100 generations. The lack of hybridization to chloroplast and mitochondrial genes demonstrated that the library is predominantly composed of nuclear DNA. The library was screened with two molecular markers, W4 and P20, that are linked to white flesh and nectarine genes of peach, respectively. Ten positive clones were detected. Their fingerprints will be used to determine clone relationships and assemble contigs. This library should be well-suited for the map-based cloning of peach genes and genome physical mapping. Received: 18 January 2000 / Accepted: 29 May 2000