Changes in the activities of catalase, peroxidase, and polyphenol oxidase in apple buds during bud break induced by thidiazuron

The breaking of dormancy in apple buds (Malus domestica Borkh cv. York Imperial) by thidiazuron (N-phenyl-N-1,2,3,-thidiazol-5-ylurea) was investigated in relation to catalase, peroxidase, and polyphenol oxidase activities and their isoenzyme patterns. The activity and number of isoenzymic components of catalase increased progressively during bud break, then decreased after buds started to grow. Peroxidase activity was highest during dormancy and declined during bud swell, increased at bud break, and decreased after bud expansion. Several isoperoxidases were observed in gel electrophoresis. Similar patterns were found at different growth stages of apple buds except for one peroxidase isoenzyme, P3, which disappeared 12 days after thidiazuron treatment. There was an inverse relationship between the activities of polyphenol oxidase and peroxidase during the development of apple buds. Apple buds have a very similar polyphenol oxidase isoenzyme pattern throughout bud development. However, the appearance and disappearance of minor isoenzymes were also observed. Phloridzin, rutin, p-coumaric, epicatechin, naringin, chlorogenic acid, and catechol were found in apple buds. Among them, phloridzin, rutin, and p-coumaric were the dominant phenolic compounds. Dormant buds contained a high amount of phenolic substances which decreased after bud break (4 days after thidiazuron treatment) then increased until the start of bud expansion. Phenolic compounds are found to be potent modifiers of catalase, peroxidase, and polyphenol oxidase activity, as both inhibitors and stimulators in apple buds.     

Changes in the activities of catalase,peroxidase, and polyphenol oxidase in apple buds during bud break induced by thidiazuron

The breaking of dormancy in apple buds (Malus domestica Borkh cv. York Imperial) by thidiazuron (N-phenyl-N′-1,2,3,-thidiazol-5-ylurea) was investigated in relation to catalase, peroxidase, and polyphenol oxidase activities and their isoenzyme patterns. The activity and number of isoenzymic components of catalase increased progressively during bud break, then decreased after buds started to grow. Peroxidase activity was highest during dormancy and declined during bud swell, increased at bud break, and decreased after bud expansion. Several isoperoxidases were observed in gel electrophoresis. Similar patterns were found at different growth stages of apple buds except for one peroxidase isoenzyme, P3, which disappeared 12 days after thidiazuron treatment. There was an inverse relationship between the activities of polyphenol oxidase and peroxidase during the development of apple buds. Apple buds have a very similar polyphenol oxidase isoenzyme pattern throughout bud development. However, the appearance and disappearance of minor isoenzymes were also observed. Phloridzin, rutin, p-coumaric, epicatechin, naringin, chlorogenic acid, and catechol were found in apple buds. Among them, phloridzin, rutin, and p-coumaric were the dominant phenolic compounds. Dormant buds contained a high amount of phenolic substances which decreased after bud break (4 days after thidiazuron treatment) then increased until the start of bud expansion. Phenolic compounds are found to be potent modifiers of catalase, peroxidase, and polyphenol oxidase activity, as both inhibitors and stimulators in apple buds.     

Effect of thidiazuron on abscisic acid content in apple bud relative to dormancy

The effect of N -phenyl- N '-1,2,3,-thidiazol-5-ylurea (thidiazuron, Dropp, SN 49537) on abscisic acid (ABA) level in apple ( Malus domestica Borkh. cv. York Imperial) buds associated with bud break and bud development was determined. The data showed that increased ABA content in apple buds was associated with thidiazuron-induced bud break and bud development. ABA stimulated growth of apple buds that had emerged from dormancy by thidiazuron treatment. The ABA in apple buds was confirmed by GC-EIMS and GC-CIMS.     

Rapid in vitro propagation of Aloe barbadensis Mill

Axillary bud development and adventitious bud formation was obtained with decapitated shoot explants of Aloe barbadensis Mill. Maximal bud growth and rooting of shoots was obtained on a modified medium of Murashige and Skoog supplemented with 5 M IBA. More adventitious and axillary buds developed on nutrient media supplemented with IBA than with NAA. Axillary buds but not adventitious buds developed with IAA in the medium. Morphogenesis was inhibited by 2,4-D. Kinetin, benzyladenine and thidiazuron were toxic to the explants and did not stimulate the development of axillary of adventitious buds. The optimal temperature for bud growth and development was 25°C. Axillary bud growth and the formation of adventitious buds was slowed down at 10°C and totally inhibited by 30°C. The optimal sucrose concentration was 3% with the inhibition of bud growth and development by higher sucrose levels.     

环剥对红松(Pinus koraiensis)韧皮部和木质部碳水化合物的影响

树干环剥可以阻碍韧皮部光合产物的运输并进一步影响光合产物的分配。长时期内,环剥能够导致环痕上部可溶性糖和淀粉的积累,但对于短期内如何影响碳水化合物在木质部和韧皮部内的运输模式所知甚少。以38年生红松(Pinus koraiensis Sieb.etZucc.)为研究材料,分别对环剥上部、下部每隔1~2d采样,区分木质部和韧皮部(树皮)进行可溶性糖和淀粉含量及树干糖呼吸消耗速率测定,确定环剥后的日变化和周变化,并对木质部可溶性糖、淀粉含量与韧皮部中相应指标进行相关关系的回归分析。结果发现:(1)环剥后4周内,在环剥痕上、下部间木质部可溶性糖和淀粉含量,韧皮部中淀粉含量均不存在显著差异(p>0.05),而韧皮部内可溶性糖含量,环剥后第2周出现显著差异,从第4周出现环剥上部显著高于下部的碳水化合物积累现象(p<0.05);(2)环剥阻隔了韧皮部可溶性糖的纵向运输,但是并不影响木质部的纵向运输,而且环剥并没有影响木质部和韧皮部之间的糖和淀粉的相关关系;(3)环剥第1周内环剥上部和下部呼吸消耗速率差异不显著,第2周环剥上部显著高于环剥下部,从第3周开始环剥下部呼吸消耗速率显著下降。推断认为,在环剥处理的4周内,环剥上部冠层新形成的碳水化合物很大一部分均被呼吸消耗掉,导致环剥上部较环剥下部可溶性糖稍有增加;红松胸高直径以下部分所储藏的碳水化合物足以保障2周内红松树干呼吸。     

Effects of thidiazuron and N6-benzylaminopurine on shoot regeneration of Phalaenopsis

Adventitious bud formation from the vegetative buds of the flower stalks of Phalaenopsis occurred on Vacin and Went medium with 15% coconut water and 5 to 40 M thidiazuron (TDZ) or 40 M N⁶-benzylaminopurine. The highest efficiency of induction was achieved with 5 or 10 M TDZ. Adventitious buds developed into shoots on VWC medium. TDZ was more effective than BAP in stimulating the axillary buds of intact shoots to develop. Regenerated shoots rooted after about two months of culture on VWC medium with 1% sucrose. Shoot tips excised from the regenerated shoots initiated protocorm-like bodies after two months of culture on VWC medium.Abbreviations VWC medium Vacin and Went medium with 15% (by volume) coconut water - TDZ thidiazuron - BAP N⁶-benzylaminopurine - Plbs protocorm-like bodies     

In vitro Shoot Bud Differentiation from Leaf Segments of Achras sapota

Direct shoot bud differentiation was achieved in leaf segments of Achras sapota cv. Cricket Ball inoculated on Schenk and Hildebrandt's medium supplemented with 5.0 M thidiazuron and 8.88 M benzylaminopurine. Leaves from middle part of the shoots and segments obtained from middle portion of leaf showed highest potential to regenerate shoot buds. Histological examination of developing shoot buds showed their de novo regeneration with clear vascular connection with the mother tissues.     

Effect of phytoregulators and physiological characteristics of the explants on micropropagation of Maytenus ilicifolia

Micropropagated shoots of Maytenus ilicifolia Mart. were obtained from axillary buds cultured in Murashige & Skoog medium supplemented with 13.3 M 6-benzyladenine (BA). Addition of 1.1 M 1-indole-3-acetic acid (IAA) to the medium increased shoot elongation. The number of shoots formed was influenced by BA concentration, degree of juvenility of the explant, and by bud explant position on the stem. Cultures of buds taken from stem parts located close to the shoot tip yielded more callus than shoots, whereas axillary buds at distant positions from the apical bud yielded more shoots.Abbreviations BA 6-benzyladenine - IAA indole-3-acetic-acid     

Bud development in corydalis (Corydalis bracteata) requires low temperature: a study of developmental and carbohydrate changes

Background and Aims

Spring geophytes require a period of low temperature for proper flower development but the mechanism that underlies the relationship between cold treatment and flowering remains unknown. The present study aims to compare the developmental anatomy and carbohydrate content of the tuberous geophyte Corydalis bracteata growing under natural winter conditions from 10 to −10 °C (field-grown) and under a mild temperature regime of 18 °C (indoor-grown plants).

Methods

Samples were studied under light and electron microscopy. A histochemical test (periodic acid – Schiff''s) was employed to identify starch in sectioned material. Sugars were analysed by capillary gas chromatography. Apoplastic wash fluid was prepared.

Key Results

Under natural conditions, shoots were elongated, and buds gained in dry mass and developed normally. For indoor-grown plants, these parameters were lower in value and, from December, a progressive necrosis of flower buds was observed. The tuber consisted of the new developing one, which was connected to the bud, and the old tuber with its starch reserve. Due to the absence of plasmodesmata between new and old tuber cells, sugar transport cannot be through the symplast. Thus, a potential apoplastic route is proposed from old tuber phloem parenchyma cells to the adjacent new tuber cells. Sugar content in buds during the autumn months (September–November) was lower for indoor-grown plants than control plants, whereas the sugar content in tubers during the same period was similar for plants from both temperature treatments. However, the amount of apoplastic sugars in tubers of field-grown plants was almost 15-fold higher than in indoor-grown tubers.

Conclusions

The results suggest that low temperature activates the apoplastic route of sugar transport in C. bracteata tubers and a consequent carbohydrate delivery to the bud. In the absence of cold treatment, the carbohydrate reserve is locked in old tuber cells so the nutrient supply to the buds is suppressed, possibly leading to bud abortion.     

Changes in membrane polar lipids associated with bud break in apple induced by nitroguanidines

The predominant lipids in membranes obtained from apple buds were galacto- and phospholipids. The major galactolipid components in apple bud were monogalactosyl diglyceride (MGDG) and digalactosyl diglyceride (DGDG). Phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were the major phospholipids in the apple buds. -Linolenic acid (C 18:3) was the major fatty acid in MGDG, DGDG, and PC. Phosphatidylglycerol (PG) is the only lipid to contain significant amounts of palmitic acid (C 16:0) in the dormant buds. An increase in the galacto- and phospholipids and the ratio of the unsaturated fatty acids to the corresponding saturated fatty acids of the buds occurred as a result of induction by 1-(3,5-dichlorophenyl)-3-nitroguanidine or 1-(-ethylbenzyl)-3-nitroguanidine during bud break. The identities of fatty acids in apple buds were confirmed by gas chromatography-mass spectrometry.     

Changes of fatty acids and sterols in apple buds during bud break induced by a plant bioregulator, thidiazuron

The effects of N-phenyl-N'-l,2,3,-thidiazol-5-ylurea (thidiazuron; Dropp; SN 49537) on fatty acids of membrane lipids and sterol content in apple ( Malus domestica Borkh cv. Golden Delicious) buds associated with bud break and bud development were determined. The predominant fatty acids in the membrane lipids of apple buds were palmitic acid (C16:0), linoleic acid (C18:2) and linolenic acid (C18:3). β -Sitosterol and sitosteryl ester were the predominant sterols. An accumulation of unsaturated polar membrane fatty acids started after thidiazuron treatment. A decrease in the percentage of the sitosterol was accompanied by an increase in campesterol and stigmasterol at the beginning of rapid growth. An increase in the ratio of campesterol and stigmasterol to sitosterol and a decrease in the ratio of free sterols to membrane lipids upon breaking of dormancy also occurred in apple buds induced by thidiazuron.     

长白山阔叶红松林3个主要树种的非结构性碳储存特征

非结构性碳水化合物(NSC,包括可溶性糖和淀粉)作为树木生命代谢的关键物质之一,在树木器官中的储存特征受到了广泛关注,但NSC在器官内部具有不同功能的组织间(韧皮部与木质部)的分配和权衡还不清楚.本研究以长白山阔叶红松林的3个优势树种——红松、水曲柳和紫椴为研究对象,对比分析NSC在根、树干韧皮与木质部中的浓度和分配特征.结果表明: 树木韧皮部和木质部间的NSC浓度差异显著,总体分配趋势为韧皮部以可溶性糖为主,而木质部以淀粉为主.树干外侧(以年轮划分,0～20年)、中段(20～40年)和内侧(>40年)的NSC浓度在不同树种间差异显著,而根中的差异不显著.红松和水曲柳树干韧皮部可溶性总糖浓度显著高于紫椴,在木质部中差异不显著.本研究结果表明,树体内部NSC在韧皮部和木质部上的分配存在明显分异,这与树种的演替阶段及组织的功能进化有关.研究结果对于深入理解温带树木的碳储存特征和分配机理具有参考意义.     

Factors influencing shoot regeneration from cotyledonary explants ofCucumis melo

Cotyledonary explants of 4-day-oldCucumis melo cv. Hale's Best Jumbo in vitro seedlings showed maximum initiation of shoot buds when cultured onto a revised Murashige & Skoog medium supplemented with 5 M indole-3-acetic acid and 5 M benzylaminopurine and cultured at 25–29°C under low light intensity (5–30 mol m^-2 s^-1). Subculture of the shoot buds onto the same medium without auxin and supplemented with 3 M benzylaminopurine caused the development of shoots from 30% of the buds. The presence of abscisic acid significantly increased the number of explants producing shoot buds. Bud initiation was affected by genotype, seedling age, light intensity, and temperature. Addition of gibberellic acid, thidiazuron or silver nitrate to regeneration medium did not improve either bud initiation or shoot regeneration.     

A cybernetic model of growth correlation in young apple trees

Growth correlations among lateral shoots of one-year-old apple treesMalus Mill., were described. The existence of a mechanism was postulated through which small original differences between buds or young shoots are quickly augmented, thus leading to differentiation of long shoots and short shoots. Existing hypotheses do not seem sufficient for explaining correlative phenomena of this type; a cybernetic approach was therefore applied. Studying growth correlations in terms of cybernetic revealed that previous hypotheses concerning correlations do not contradict each other as often thought, but depict different links in a more general chain of events. A cybernetic model points out the importance of root influences in interaction among shoots. It also shows that synergism between auxin, gibberellin and cytokinin in xylem and phloem differentiation and in starch metabolism is very important for understanding correlations in apple trees.     

In vitro regeneration of silktree (Albizzia julibrissin) from excised roots

Root segments (1 cm long) were excised from 15–20 day old seedlings of silktree (Albizzia julibrissin) grown on B5 medium. About 50% of the control (no growth regulators added) root explants formed shoot buds within 15 days after placement on the culture medium. After 30 days, there were about 4 shoots per control explant. Addition of low levels of various auxins (0.5 M) did not influence the formation of shoot buds from the explants. Higher concentrations (5M), however, decreased shoot regeneration. Kinetin and 2iP did not influence shoot regeneration at the concentrations tested (1 & 10 M). Addition of benzyladenine, Zeatin, or thidiazuron to the culture medium increased both the percentage of explants that formed shoots and the number of shoots per explant. Thidiazuron was highly effective in stimulating shoot formation at low concentrations (<1 M). At 0.05 M thidiazuron, 95% of the explants produced shoots and about 10 shoots were formed per explant. Compared to TDZ, higher concentrations (10 M) of benzyladenine and Zeatin were required to enhance shoot formation. Upon excision and transfer to B5 medium, regenerated shoots developed into normal rooted plantlets.Abbreviations BA Benzyladenine - IAA Indoleacetic acid - IBA Indolebutyric acid - NAA Naphthaleneacetic acid - TDZ Thidiazuron - 2ip Isopentenyladenine     

Variation in gene transcription and protein for key enzymes of carbohydrate metabolism in poplar xylem with respect to growth phase

We compared gene expression levels for enzymes of carbohydrate metabolism in the twig xylem of two Populus species with the seasonal levels of starch and soluble sugars (sucrose, glucose, and fructose) and relative levels of the enzymes. Plants of Populus deltoides Bartr. ex Marsh and P. balsamifera L., 3–4 years old, were grown outside in Lubbock, TX, USA in 43 L pots. The xylem in the middle portion of the twigs was sampled during the dormant period (November–February), at bud break (for P. balsamifera), and during the growth flush (April–July). The gene expression for ADP-glucose pyrophosphorylase (AGPase), sucrose synthase (SuSy), and sucrose-phosphate synthase (SPS) generally coincided with the levels of the carbohydrates in whose metabolism these enzymes are involved. Gene expression for AGPase and its protein levels were high when the xylem starch content was high (growing period). However, P. balsamifera maintained high AGPase levels in dormant and growing twigs, unlike P. deltoides whose dormant twigs had low AGPase and low gene expression. Compared to growing twigs, gene expression for SuSy and SPS and their protein levels were higher in dormant twigs when soluble sugar content was higher. No down-regulation of these genes appears to occur when pools of the associated carbohydrates are high. Contrary to our expectation, the gene expression for β-amylase was highest in growing twigs when starch content was high. High β-amylase gene expression in growing twigs may be involved in maintaining a sufficient level of soluble sugars for growth through possibly controlling the extent of starch accumulation.     

Long-term effects of thidiazuron are intermediate between benzyladenine,kinetin or isopentenyladenine in Miscanthus sinensis

The thidiazolylurea derivative thidiazuron has been reported to be considerably more effective than benzyladenine in promotion of in vitro shoot formation in a number of dicotyledonous species. In the present study, axillary shoots of Miscanthus sinensis (Thunb.) Anderss. Giganteus that had been subcultured four times on modified Murashige & Skoog medium with 20M benzyladenine were transferred to media with benzyladenine, kinetin, isopentenyladenine or thidiazuron at concentrations of 0.01, 0.1, 1, 10, 30 or 100M and grown over four subcultures. Shoot and root formation stabilized after the first subculture and results from the three subsequent subcultures are presented. The common effects of cytokinins, i.e., promotion of axillary bud growth, inhibition of root formation, reduced stem growth and delay of senescence, were observed for all four cytokinins. In a descending order regarding shoot formation, the four cytokinins at the optimum concentration could be ranked as follows: benzyladenine, thidiazuron, kinetin and isopentenyladenine. Benzyladenine and thidiazuron had optimum effects at the same concentration with regard to axillary shoot formation but thidiazuron induced a significantly lower number of shoots than benzyladenine. The number of roots, shoot size and percentage of chlorotic shoots were also the same for benzyladenine and thidiazuron. When transferring shoots from benzyladenine or thidiazuron medium to rooting medium, shoots previously grown on thidiazuron became taller and formed fewer roots than shoots previously grown on benzyladenine.Abbreviations BA benzyladenine - 2iP isopentenyladenine - KIN 6-(furfurylamino)-purine (kinetin) - MS Murashige & Skoog medium - NAA naphthaleneacetic acid - THI N-phenyl-N(1,2,3-thidiazol-5-yl)-urea (thidiazuron)     

Changes in ascorbate, glutathione, and related enzyme activities during thidiazuron-induced bud break of apple

The changes of ascorbic acid, dehydroascorbic acid, and glutathione content and related enzyme activities were studied in apple buds during dormancy and thidiazuron-induced bud break. An increase in ascorbic acid, reduced form of glutathione (GSH), total glutathione, total non-protein thiol (NPSH) and non-glutathione thiol (RSH) occurred as a result of induction by thidiazuron during bud break, whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased during the same period. Thidiazuron also enhanced the ratio of GSH/GSSG, and activities of ascorbate free radical reductase (AFR; EC 1.6.5.4), ascorbate peroxidase (EC 1.11.1.11). dehydroascorbate reductase (DHAR; EC 1.8.5.1) and glutathione reductase (GR; EC 1.6.4.2). The ascorbic acid content and the activities of AFR, ascorbate peroxidase, and DHAR peaked when buds were in the side green or green tip stage just prior to the start of rapid expansion, and declined thereafter. The GSH, NPSH, RSH, ratio of GSH/GSSG, and activities of GR increased steadily during bud development.     

Changes in the lanthanum distribution following decapitation of the sporophytes of an aquatic fern,Marsilea drummondii A. Br.

Summary The active terminal bud and the quiescent lateral buds and corresponding nodes inserted at different levels on the main rhizome ofMarsilea drummondii were examined with the EM afterin vivo feeding with lanthanum nitrate. These tracer experiments demonstrate that all the buds are fed by their phloem cells. In the lateral bud axis the labelling of the sieve elements apoplast indicates that a solute transfer took place in the node between xylem and phloem via xylem transfer cells. La³⁺ deposits are completely absent from the apical dome of inhibited buds indicating that the walls of the quiescent meristematic cells are not permeated by the tracer. The removal of the terminal bud has two effects. It rapidly (in 2 hours) allows the lanthanum to penetrate the lateral bud tip walls at a stage when no fine structural changes are discernable and to bind to the outer surface of the plasmalemma as it does in the active terminal bud. This study including inhibited buds and buds released from apical dominance support the view that changes in the state of the cell surface (cell wall and plasma membrane) may be a prerequisite for the resumption growth activity.This study was supported in part by a grant from the Centre National de la Recherche Scientifique to L.Sossountzov (AI 031275).     

陇东红富士果树养分回流对土壤表层管理的响应

地处陇东黄土高原的庆阳市苹果园普遍缺乏有效的土壤表层管理措施,以盛果期的"红富士"果树为对象,研究不同土壤表层管理方式在养分回流期对苹果树体贮藏养分的动态变化。研究结果表明:优化覆膜(T2)与优化覆草(T3)一年生枝条叶片的叶绿素含量均显著高于常规处理(T1)。T2和T3处理的一年生春梢、秋稍和封顶枝中的碳素贮藏物质(可溶性糖、淀粉)和氮素贮藏物质(总游离氨基酸、可溶性蛋白质)的含量均显著高于T1,T3比T2处理对碳素贮藏物质含量的提升效果更为明显。此外,相同枝条类型不同组织中的贮存养分含量不同,可溶性糖和可溶性蛋白质的含量表现为表皮积聚,韧皮部木质部,淀粉与总游离氨基酸含量表现为主轴积聚,木质部韧皮部。不同枝条类型中贮藏物质的含量整体表现为秋梢封顶枝春梢,秋梢在提升养分贮藏水平中起到了重要作用。