Shoot Bark Research Articles

Microwave Supported Extraction and Optimization of Flavonoid Mangiferin from Mangifera indica L. Stem Bark using Orthogonal Array Design

A modest and swift microwave-backed extraction process has been established for the abstraction of a flavonoid mangiferin from the Shoot bark of Mangifera indica L. The content in the extracts was quantified by planar chromatography. An orthogonal array strategy was employed to conclude the effects of variables that affect the efficiency of MAE, namely temperature, irradiation period, the clout of irradiation, and particle size of drug powder. Under optimal conditions, MAE showed expressively higher recovery of mangiferin and markdown in the extraction period as well as solvent intake in comparison to the conventional method.

Anthocyanin Accumulation Provides Protection against High Light Stress While Reducing Photosynthesis in Apple Leaves.

The photoprotective role of anthocyanin remains controversial. In this study, we explored the effects of anthocyanin on photosynthesis and photoprotection using transgenic ‘Galaxy Gala’ apple plants overexpressing MdMYB10 under high light stress. The overexpression of MdMYB10 dramatically enhanced leaf anthocyanin accumulation, allowing more visible light to be absorbed, particularly in the green region. However, through post-transcriptional regulation, anthocyanin accumulation lowered leaf photosynthesis in both photochemical reaction and CO2 fixation capacities. Anthocyanin accumulation also led to a decreased de-epoxidation state of the xanthophyll cycle and antioxidant capacities, but this is most likely a response to the light-shielding effect of anthocyanin, as indicated by a higher chlorophyll concentration and lower chlorophyll a/b ratio. Under laboratory conditions when detached leaves lost carbon fixation capacity due to the limitation of CO2 supply, the photoinhibition of detached transgenic red leaves was less severe under strong white, green, or blue light, but it became more severe in response to strong red light compared with that of the wild type. In field conditions when photosynthesis was performed normally in both green and transgenic red leaves, the degree of photoinhibition was comparable between transgenic red leaves and wild type leaves, but it was less severe in transgenic young shoot bark compared with the wild type. Taken together, these data show that anthocyanin protects plants from high light stress by absorbing excessive visible light despite reducing photosynthesis.

CRISPR/Cas9-Mediated Mutagenesis of MdCNGC2 in Apple Callus and VIGS-Mediated Silencing of MdCNGC2 in Fruits Improve Resistance to Botryosphaeria dothidea

Cyclic nucleotide-gated ion channels (CNGCs) have been reported to be involved in multiple plant physiological processes. Their involvement in plant immunity has been studied in several herbal plant species. It remains unclear whether CNGCs in woody plants play a similar role in plant immunity. In the present study, we identified an apple CNGC (designated as MdCNGC2), which is the homolog of Arabidopsis CNGC2. Analysis of tissue distribution revealed that MdCNGC2 was expressed in all tested tissues. Abundant transcripts of MdCNGC2 were observed in leaves and shoot bark. Low expression was observed in fruits and roots. MdCNGC2 expression was induced in apple callus and shoot bark by Botryosphaeria dothidea. The induction of MdCNGC2 was significantly higher in susceptible cultivars “Fuji,” “Ralls Janet,” and “Gala” compared to the resistant cultivar “Jiguan,” suggesting that MdCNGC2 may be a negative regulator of resistance to B. dothidea. MdCNGC2 mutagenesis mediated by gene editing based on the CRISPR/Cas9 system led to constitutive accumulation of SA in apple callus. A culture filtrate of B. dothidea (BCF) induced the expression of several defense-related genes including MdPR1, MdPR2, MdPR4, MdPR5, MdPR8, and MdPR10a. Moreover, the induction of these genes was significantly higher in mdcngc2 mutant (MUT) callus than in wild type (WT) callus. Further analysis showed that the spread of B. dothidea was significantly lower on MUT callus than on WT callus. Knockdown of the MdCNGC2 gene reduced lesions caused by B. dothidea in apple fruits. These results collectively indicate that MdCNGC2 is a negative regulator of resistance to B. dothidea in apple callus.

Identifying species and hybrids in the genus juglans by biochemical profiling of bark

The biochemical profiling of flavonoids in the bark of winter shoots was conducted with the purpose of ecological management of implicit environmental threats of invasions of the species of the genus Juglans and their hybrids under naturalization. Six species of Juglans, introduced into forests and parks of Kyiv, were studied, namely, J. ailantifolia Carriere, J. cinerea L., J. mandshurica Maxim., J. nigra L., J. regia L., and J. subcordiformis Dode, cultivar J. regia var. maxima DC. ′Dessert′ and four probable hybrids (♀J. subcordiformis × ♂J. ailantifolia; ♀J. nigra × ♂J. mandshurica; ♀J. cinerea × ♂J. regia and ♀J. regia × ♂J. mandshurica). Due to the targeted introduction of different duration, the invasive species are at the beginning stage of forming their populations, sometimes amounting to naturalization. The species-wise specificity of introduced representatives of different ages (from one-year-old seedlings to generative trees), belonging to the genus Juglans, was determined. J. regia and J. nigra are the richest in the content of secondary metabolites; J. cinerea and J. mandshurica have a medium level, and J. ailantifolia and J. subcordiformis-a low level. On the contrary, the representatives of J. ailantifolia and J. subcordiformis are the most diverse in the content of secondary metabolites. Hybrid forms are notable for the decreased content of flavonoids, which may have a considerable impact on their individual resistance and ecological flexibility. The latter circumstance should be considered in the ecological management of walnut plantings in Kyiv. The results of biochemical profiling of secondary metabolites from winter shoot bark demonstrated that six investigated species belonged to four sections: Juglans, Cardiocaryon, Rhysocaryon, and Trachycaryon. The hybrids were usually grouped by the sections, represented by the paternal component in the hybrid pair. However, recent results of complete genome sequencing were used by the scientists to prove a relevant evolutionary role of the phenomenon of hybridization in the genus Juglans between the species, separated in the modern areas between the American and Eurasian continents, in particular, the ones, introduced into the Kyiv plantings. The revealed genomic mosaicism forms a new impression about phylogenetic relations within the genus. The possibility of using the biochemical profiling of winter shoot bark for some utilitarian needs (including the determination of the content of useful biologically active substances and detecting the advantages of hybrids by their performance features) is discussed

Paclobutrazol elevates auxin and abscisic acid, reduces gibberellins and zeatin and modulates their transporter genes in Marubakaido apple (Malus prunifolia Borkh. var. ringo Asami) rootstocks

To examine the dwarfing mechanism in apples, one-year-old Marubakaido (Malus prunifolia Borkh.) (invigorating) apple rootstock stools were foliar-sprayed with 860 mg L−1 of paclobutrazol (PBZ) as a single application or without. M.9 apple rootstock (dwarf) was used as a positive control. The phytohormones were estimated in the shoot bark and sub-apical shoot and gene expression in the apices of terminal shoots. Evident responses to PBZ were observed a fortnight after treatment, as the shoot and internode lengths were suppressed significantly. Endogenous indole-3-acetic acid increased in the PBZ treatment, and the polar auxin transporter genes MdPIN1 and MdLAX1 and the biosynthesis gene MdYUCCA10a were upregulated along with the MdARF2 gene. Additionally, PBZ increased the abscisic acid (ABA) concentration and the biosynthesis-related gene MdNCED1 but repressed the degradation gene MdCYP707A1. The ABA transporter gene MdAITb-like was upregulated by PBZ. The concentrations of the gibberellins (GAs) GA1 and GA4 decreased in the PBZ-treated rootstocks. The GA transporter gene MdNFP3.1-like and the signaling gene MdGID1b-like were strongly downregulated by PBZ, whereas the catabolic gene MdGA2OX2 was upregulated. PBZ treatment significantly reduced trans-zeatin (tZ) levels and downregulated the cytokinin biosynthesis gene MdIPT6 but upregulated the MdCKX7 degradation gene. Additionally, PBZ upregulated the cytokinin-related transporter genes MdPUP7-like and MdPUP9-like. Collectively, our results show that the physiological and molecular effect of PBZ was observed within two weeks, and this was indicated by the modulation of phytohormonal levels as well as transporter and other gene expression in Marubakaido apple rootstocks.

Morphological, physiological and molecular analysis of Line × Tester in Populus deltoides Bartr

In the present investigation, male and female clones/strains/species of Populus deltoides procured from State Forest Department, Haldwani and Shyampur, Haridwar Forest Division and maintained in the germplasm block of Naganji nursery from which 11 male and 13 female clones were included in the reproductive study and the selected plant material of 4 females (G-48, S 1, S 7 C 8 and L-62/84) and 4 males (S 7 C 11, L-17/92, L-124/86 and S 7 C 1) clones were crossed using Line × Tester (4 × 4) mating design. Control crossing was done and seedlings were raised in the nursery at stage-1 and were evaluated for morphological characters. In stage-2 clonal cuttings of selected individuals were raised in RBD and were evaluated for morphological, physiological and wood characters. The gene action study revealed that dominance variance was observed more than the additive variance for all the parameters studied. The proportional contribution of lines was higher than individual contribution of testers or line × tester interaction except for plant height, collar diameter, internodal length, leaf area, maximum width of leaf, angle between the mid rib and 2 nd lower lateral mid rib, shoot bark thickness, root bark thickness, fresh shoot weight, dry shoot weight, dry root weight, dry root shoot ratio, root length, total fresh weight, total dry weight, stomatal conductance and fibre length. Among 18 SSR markers, fifteen markers showed monomorphic allelic pattern, the remaining three markers (PMGC-2060, PMGC-2020 and PMGC-451) showed polymorphic pattern. A close appraisal of the SSR banding pattern obtained after the amplification of genomic DNA of both the parents and their hybrids revealed that, all the hybrids were similar to their parents.

Correlation among Some Biochemical Compounds in Fruit, Leaf, and Shoot Bark of Pomegranate Trees for Breeding Programs

ABSTRACT This study was designed to compare biochemical characteristics in fruit, leaf and shoot bark among some Iranian pomegranate genotypes to determine for any probable correlation between different parts. Twenty genotypes were used in this experiment and biochemical characteristics such as vitamin C, anthocyanin, total phenolic content (TPC), titratable acidity (TA) and total soluble carbohydrate (TSC) were evaluated in leaf, arils, fruit peel, and shoot bark separately. Results of correlation analysis showed that there was significant correlation among anthocyanin, vitamin C, and TPC of arils with anthocyanin (r = 0.93), vitamin C (r = 0.90), and TPC (r = 0.95) of the leaf, respectively. Also, a positive correlation was observed between TA, vitamin C, anthocyanin, and TPC of arils with TSC of the shoot bark. Based on obtained results from this study, biochemical traits of the leaf such as anthocyanin, vitamin C and TPC can be used as a biochemical marker to determine superior genotypes in juvenile phase of plants.

Lenticel infection in Fraxinus excelsior shoots in the context of ash dieback

Common ash (Faxinus excelsior L.) in Europe is declining on a continental scale due to the action of Hymenoscyphus fraxineus, an invasive forest pathogen that causes ash dieback disease leading to the collapse and eventual death of ash trees through shoot infection in the crown and through stem collar infection. This study confirms for the first time lenticels as entry points for pathogens to enter shoot bark. Results show the impact of lenticel infection at a very early stage of invasion by H. fraxineus in a F. excelsior provenance trial and its correlation values with other factors such as shoot dieback, canker-like lesions and bud burst. No significant provenance effects were observed for incidence of shoot dieback, lenticel necrosis or canker-like lesions on shoots, but provenance effects were significant for bud burst phenology. The strongest correlation was observed between lenticel necrosis and canker-like lesions on the lenticels of shoots. Boheremia spp. were most frequently isolated from necrotic ash lenticels and confirmed by ITS sequencing, but also species of Diaporthe, Epicoccum, Aspergillus, Neonectria, Didymella and Hymenoscyphus fraxineus. Finally, lenticel density was similar in sets of ash genotypes that were characterized as having a high and low susceptibility to ash dieback.

The relation of endogenous abscisic acid and indole acetic acid on vigor of some selected dwarf mahaleb (Prunus mahaleb L.) genotypes

Vigor reduction of sweet cherry varieties by dwarfing rootstock is well known, but the mechanism by which a rootstock induces dwarfing is not well understood. Plant hormones have been associated with dwarfing mechanism. This study was conducted, with the main purpose of determining the correlation between of endogenous abscisic acid (ABA) and indole acetic acid (IAA) and vigor of 10 selected dwarf mahaleb (Prunus mahaleb L.) genotypes. Endogenous IAA and ABA levels of selected dwarf genotypes were evaluated, which indicated significant differences for most traits. The IAA level in the shoot bark was the highest in H24 and lowest in M96 genotypes, while ABA level in the shoot bark was highest in M96 and lowest in H14. The mean ABA content decreased as the invigoration capacity of the genotype increased. ABA generally is regarded as an inhibitor of elongation. In our experiment, the endogenous ABA content was negatively correlated with shoot growth. ABA: IAA ratio in shoot bark decreased with increasing genotype vigor. ABA: IAA ratio of the dwarfing genotype M96 was about 1.118. Correlation coefficient showed a significant correlation between crown width, trunk diameter, crown volume, total IAA, total ABA, IAA: ABA and tree vigor. The concentration of ABA in shoot bark showed a good relationship with vigor, thus the content of this phytohormone in shoot bark could be a useful marker of dwarfing character in mahaleb genotype selections. Key words: Mahaleb, Dwarf rootstock, indole acetic acid (IAA), abscisic acid (ABA).

Identification of a xyloglucan-specific endo-(1-4)-beta-d-glucanase inhibitor protein from apple (Malus × domestica Borkh.) as a potential defense gene against Botryosphaeria dothidea

Botryosphaeria dothidea is the causal agent of apple ring rot which is a highly destructive apple disease in China. Here, a putative xyloglucan-specific endo-(1-4)-beta-d-glucanase inhibitor protein from Malus×domestica (designated as MdXEGIP1) was found to be involved in defense against B. dothidea infection. MdXEGIP1 shares high amino acid sequence identity with other apple XEGIPs, but exhibited significantly different responses to B. dothidea infection. Quantitative real-time PCR revealed that MdXEGIP1 expression was significantly induced in shoot bark of apple plant by B. dothidea and showed different expression pattern in resistant and susceptible apple cultivars. In resistant cultivar, MdXEGIP1 expression was elevated with larger amplitude than that in susceptible cultivar after B. dothidea infection. MdXEGIP1 expression was also significantly enhanced by treatment with exogenous methyl jasmonate and salicylic acid in apple plantlets. Further investigation revealed that recombinant MdXEGIP1 has significant inhibitor activity to XEGs from family 12 and 74 of glycoside hydrolase. More importantly, recombinant MdXEGIP1 inhibited crude enzyme solution of XEG from B. dothidea, suggesting that MdXEGIP1 might protect apple plant from B. dothidea infection by inhibiting XEG activity. Taken together, the results indicated that MdXEGIP1 is a potential defense gene against B. dothidea in apple.

Present status of Citrus tristeza virus infecting Citrus spp. in Darjeeling hills and its detection in different plant parts

Darjeeling hills of West Bengal (India) are well known for the production of mandarin orange (Citrus reticulata). The spread of Citrus tristeza virus (CTV) in this area has threatened the cultivation of citrus. Therefore, a study of the incidence and distribution of CTV in Darjeeling hills was undertaken and a geographical map was prepared. In DAS-ELISA, a high titre of CTV was recorded in the tender shoot bark, leaf petiole and mid-rib of seven Citrus spp. Three citrus species, viz., pomelo, trifoliate and kumquat, were found to be free of CTV infection when tested in double antibody sandwich-enzyme linked immunosorbent assay (DAS-ELISA) and reverse transcription polymerase chain reaction (RT-PCR).

Fruit Load and Root Development in Field-Grown Loquat Trees (Eriobotrya japonica Lindl)

Photosynthate translocation to the root in loquat trees decreases as fruit develops. Thus, during the most active period of fruit development, that is, from 50 % of its final size to the beginning of fruit color change, which correspond to BBCH growth scale stages 705 and 801, both translocating and reducing carbohydrate concentrations diminish greatly. Concomitantly, the results from our experiment show an increased abscisic acid (ABA) concentration and a decrease in the respiration rate detected by an accumulation of glucose-6-phosphate, which paralleled a reduced indole-3-acetic acid (IAA) concentration in roots. As a consequence, root development was strongly and significantly reduced. Because loquat fruit develops in winter and nonshoot growth takes place at this time, our results show that root development in loquat trees is controlled by the fruit, mediated by competition for carbohydrates and modulated by hormones. The experiment was conducted using field-grown loquat during two consecutive years and by comparing fruiting and defruited trees. Fruits were detached from the trees in the early fruit developmental stage (10 % of final size, 701 BBCH growth scale), and carbohydrate concentrations in leaves, shoot bark, and roots, as well as nitrogen fractions (N–NO3−, N–NH4+, and N–proteinaceous) and hormone (IAA, zeatin, and ABA) concentrations in roots, were analyzed throughout the period of fruit development. Root development was evaluated by counting the emerging lateral root primordia during the fruit developmental stages BBCH growth scale 701–809 (fruit color fully developed).

Light penetration, growth, and fruit productivity in ‘Fuji’ apple trees trained to four growing systems

The study was conducted to document the range in soil nutrients, trunk and shoot growth, leaf characteristics and nutrient content, flower bud characteristics, yield, fruit quality, disease occurrence, light penetration, and shoot bark color in a 15-year-old ‘Fuji’ apple ( Malus × domestica Borkh.) orchard on M.26 rootstocks trained to four growing systems. SS trees naturally growing had greater width and volume than the LT lightly heading, MLT heavily heading, and S trees thinning and bending. LT trees had more upward terminal shoots at old branches, large numbers of lateral shoots, and longer total shoot length. Leaf [N], [P], and [K] were the lowest for the MLT trees. SS and S trees had greater flower bud density and fruit yield, but LT trees had poor fruit color and less soluble solids and firmness. Percent light penetration into the canopy was the highest with the S system but not different from MLT or SS. The lowest was for the LT system, however, it was not statistically different from MLT or SS.

Lichens on branches of Siberian fir (Abies sibirica Ledeb.) as indicators of atmospheric pollution in forests

The abundance distribution of different ecological groups of lichens depending on bark pH has been studied on 1- to 24-year shoots of Siberian fir in the mountains of southern Siberia. Along with acidophytic lichens commonly found on the Siberian fir (Usnea sp., Bryoria sp., etc.), its young shoots are also colonized by nitrophytic species (Physcia tenella, Melanelia exasperatula, etc.), which is evidence for the increasing pH of shoot bark. The proportion of thalli of nitrophytic lichen species shows a significant positive correlation with the pH of the upper (dusted) bark layer and is greater in the Eastern Sayan (at bark pH averaging 5.4) than in the Western Sayan (pH 4.7). The trends revealed in this study may be used for indication of pollution and ecological monitoring of forest ecosystems.

Start of reproduction and allozyme heterozygosity in Pinus sibirica under different techniques of artificial forest stand establishment

Siberian stone pine (Pinus sibirica Du Tour) is one of the main forest-forming tree species in boreal forests of Eurasia. Large edible seeds of this species have an important resource value because of their high nutritious properties. Development of approaches to establishment of early cone producing Siberian stone pine stands including utilization of corresponding genetic background is one of the priorities of forest resource management. The goal of our study was to evaluate the effect of stand density on the differentiation of trees by the age of first reproduction and the relationship of allozyme heterozygosity and morphological traits variability in Siberian stone pine. Morphological and allozyme variability in artificial Pinus sibirica stands with high and low density was investigated. In the high-density stand the distance between trees was 0.7 and 3 meters (4080 trees per ha) while in the lowdensity stand it was 8 and 8 meters (144 trees per ha). Age of formation of first male and female cones was evaluated by retrospective method based on analysis of tracks of cones on a shoot bark. Tree height, diameter and number of male, female and vegetative shoots in a crown of model trees were measured. Genotypes of the trees were determined by 29 isozyme loci coding for 16 enzymes (ADH, FDH, FEST, GDH, GOT, IDH, LAP, MDH, MNR, PEPCA, 6-PGD, PGI, PGM, SDH, SKDH, SOD). In the low-density stand, the portion of generative trees was higher and differentiation of trees by age of reproduction starting was lower in spite of the smaller age of trees as compared to the high-density stand. In both samples, the age of formation of first generative organs was related negatively with stem height, stem diameter and number of female shoots. In the high-density stand, positive relation of age of first reproduction with total number of shoots and number of male shoots was found. In both samples nonreproductive trees were less heterozygous at isozyme loci as compared to trees starting cone production. Allozyme heterozygosity correlated positively with the age of first cone production in the high-density stand only. We conclude that the degree of competition between trees due to different stand density determined age and timing of first reproduction and development of tree crowns. The relationship of allozyme heterozygosity and the age of first reproduction was expressed more in the high-density stand of Siberian stone pine.

Occurrence and development of Colletotrichum acutatum on symptomless blueberry bushes

The anthracnose fungus Colletotrichum acutatum was detected in symptomless blueberry bushes (Vaccinium spp.) in a Japanese blueberry field. Naturally diseased bushes and their apparently healthy neighbours were selected, and C. acutatum was isolated from the symptomless tissues of each bush from February 2000 to January 2002. Analysis of the diseased bushes during the dormant period revealed that the fungus was able to survive on symptomless tissues, such as shoot bark and bud scales. Furthermore, C. acutatum was consistently isolated from symptomless leaves and shoots of several surrounding symptomless bushes. Arbitrarily primed PCR (ap-PCR) analyses of the fungal isolates obtained from the diseased and symptomless bushes revealed that most C. acutatum isolates were genotypically identical, regardless of their origins. Inoculation tests using leaves of various blueberry cultivars suggested that the presence or absence of symptoms on each bush can not always be explained by differences in cultivar susceptibility, and other factors may be associated with the appearance of symptoms.

Girdling affects carbohydrate-related gene expression in leaves, bark and roots of alternate-bearing citrus trees.

Effects of girdling on carbohydrate status and carbohydrate-related gene expression in citrus trees were investigated. Alternate-bearing 'Murcott' (a Citrus reticulata hybrid of unknown origin) trees were girdled during autumn (25 Sep. 2001) and examined 10 weeks later. Girdling brought about carbohydrate (soluble sugar and starch) accumulation in leaves and shoot bark above the girdle, in trees during their fruitless, 'off' year. Trees during their heavy fruit load, 'on' year did not accumulate carbohydrates above the girdle due to the high demand for carbohydrates by the developing fruit. Girdling caused a strong decline in soluble sugar and starch concentrations in organs below the girdle (roots), in both 'on' and 'off' trees. Expression of STPH-L and STPH-H (two isoforms of starch phosphorylase), Agps (ADP-glucose pyrophosphorylase, small subunit), AATP (plastidic ADP/ATP transporter), PGM-C (phosphoglucomutase) and CitSuS1 (sucrose synthase), all of which are associated with starch accumulation, was studied. It was found that gene expression is related to starch accumulation in all 'off' tree organs. RNA levels of all the genes examined were high in leaves and bark that accumulated high concentrations of starch, and low in roots with declining starch concentrations. It may be hypothesized that changes in specific sugars signal the up- and down-regulation of genes involved in starch synthesis.

Assimilate transport in grapevines -effect of phloem disruption

Assimilate translocation in mature grapevines (cv. Gewürztraminer and cv. Harslevelü) under field conditions was investigated during the growth season by quantifying individual sugars and organic acids in mature leaves, shoot bark and berries, as affected by girdling the shoot just above the bunches. Tissue was sampled at berry set, pea size, veraison and ripeness stages of the vine. Invertase activity was determined in the shoot bark at ripeness. In the leaves, malic acid concentrations reached lowest levels at pea size, but increased thereafter. Tartaric acid decreased after peaking at pea size stage. Tartaric acid concentrations increased with girdling. Despite the increase in leaf age, sucrose concentrations remained virtually stable during the season, emphasising the importance of mature leaves for nourishing bunches. Girdling resulted in a build-up of sucrose in the leaves. In the bark, malic and tartaric acid stayed more or less the same during the growth period, but increased above the girdle. As a result of phloem disruption, sucrose also increased. The increase in glucose and tartaric acid is believed to result from catabolic cleavage of sucrose by invertase. Invertase activity was evident in the bark (of mature Harslevelü vines) at ripeness, which may indicate involvement in osmotic adjustments and gradients in the bark/phloem structure. In the berries, malic and tartaric acids reached peak concentrations at pea size. The volume increase during the ripening period, and in the case of malic acid also respiratory loss, resulted in a decrease in organic acid concentration. Malic acid continued to decrease after the initial decline, whereas tartaric acid stayed virtually stable. Girdling had no marked effect on organic acid accumulation in the berries. Sucrose concentrations were low during the first part of the season, but increased thereafter. Sucrose concentrations during ripening increased with girdling, which may represent a concentration effect and/or import from the rest of the vine. Sucrose concentrations (in mature Harslevelü vines) were indeed lower below than above the girdle. Comparison of sucrose concentrations in the leaves, bark and berries showed the existence of a decreasing concentration gradient, in line with the source:sink transport concept. An equally prominent decrease in sucrose:glucose ratio in the berries from the start of the ripening period indicates that vacuolar integrity (compartmentation) was affected in the ripening berry, most probably allowing hydrolysis of sucrose by invertase and decreasing osmotic potential within the berry. The results provide further evidence for the hypothesis of an osmotic gradient driven transport to the berry.

Sulpholipid reflects plant resistance to stress-factor action

The results of studying the behaviour of sulphoquinovosyldiacylglycerol (SQDG) during environmental-factor action are discussed. Low-temperature action caused SQDG accumulation in 1-year-old shoot bark of resistant apple varieties, and was especially striking in the Siberia apple, a variety of extreme hardiness. Another unfavourable factor, high temperature, induced SQDG accumulation in leaves and chloroplasts of drought-resistant plants while in sensitive plants a decrease in its content took place. Water deficit caused the same effect. SQDG increase was also observed in field experiments with artificial irrigation in the drought region of Ukraine, at the stages of stooling and milk ripeness. Besides, SQDG accumulation was observed in wheat plants infected by Puccinia graminis and kidney bean plants infected by tobacco mosaic and potato x viruses. But lead supplied at various concentrations caused an SQDG decrease in wheat seedling leaves and roots. The reasons for these phenomena seemed to be mainly the stabilization of the photosynthetic processes, particularly ATP synthesis and light-harvesting complex II functioning, but signal function also cannot be excluded.

Polimorfismo enzimático nos tecidos de pereira

O trabalho foi realizado com o objetivo de avaliar o polimorfismo enzimático em diferentes tecidos de oito cultivares de pereira Pyrus communis L. Os genótipos utilizados fazem parte da coleção de plantas disponíveis na Universidade de Estudos de Bolonha. Para as análises isoenzimáticas foram utilizadas gemas floríferas dormentes no inverno, casca de ramos de um ano obtida de plantas em pleno desenvolvimento, folhas obtidas no início da primavera e folhas de plantas mantidas in vitro. A corrida eletroforética foi realizada em gel de poliacrilamida a gradiente com (5% a 12,5%). Os resultados obtidos com os genótipos utilizados indicaram que o sistema enzimático beta-glucosidase (E.C.3.2.1.21) apresentou atividade apenas nas folhas das plantas in vitro, com uma banda na mesma posição para todas as cultivares, ao passo que os sistemas para as enzimas esterase (E.C.3.1.1.2) e peroxidase (E.C.1.11.1.7) apresentaram elevado polimorfismo. Nas gemas dormentes analisadas, o sistema peroxidase permitiu diferenciar todos os genótipos. As formas isoenzimáticas da esterase permitiram separar todos os genótipos independentemente dos tecidos utilizados.