Physiological and anatomical changes associated with ripening in the inner and outer mesocarp of cold stored ‘Songold’ plums and concomitant development of internal disorders

Plums (Prunus salicina cv. Songold) were cold stored for 10 d at -0.5°C followed by 18 d at 7.2°C and 7 d at 10°C. On the day of harvest and after 15,30 and 35 d of storage, the physiology, anatomy and development of internal disorders in inner and outer mesocarp tissue were assessed. Soluble solids, juice pH, internal conductivity, viscosity of soluble pectin and membrane leakage were significantly higher in the inner tissue, while titratable malic acid levels were lower, indicating that fruit was riper on the inside than the outside. Changes as indicated by the same variates showed that the rate of ripening in inner tissue was more rapid than in the outer mesocarp tissue over storage time. Gel breakdown in inner tissue was associated with high viscosities of water soluble pectin, permeable membranes, and as a result, binding of cell fluids which led to low levels of extractable juice. In outer tissue where extractable juice levels were higher, overripeness developed. At the ultrastructural level, it was evident that cell walls of inner tissue were thicker and had a better developed middle lamella than outer tissue. Inner mesocarp tissue was composed of larger cells than outer tissue.     

Influence of 1-methylcyclopropene on pectic enzyme activities,gene expression,and cell wall modification in papaya (Carica papaya cv. ‘Sunrise’) fruit

SUMMARY

‘Sunrise’ papaya fruit harvested at two stages of maturity [colour break (< 10% yellow peel colour) and 25% yellow peel colour] were treated with 100 nl l^–1 1-methylcyclopropene (1-MCP) to determine its effects on ripening, on the activities and levels of gene expression of polygalacturonase (PG), pectin methyl esterase (PME), and βgalactosidase ( βGal), and on the degradation of cell wall components. 1-MCP delayed ripening and the onset of the climacteric, although the peak in the respiration rate was almost the same as that in untreated control fruit. Colour-break fruit treated with 1-MCP exhibited a continuous increase in ethylene production, but at a lower rate than in control fruit. Consequently, 1-MCP-treated fruit ripened with a concomitant reduction in firmness, which was accompanied by an increase in PG and βGal enzyme activities and gene expression. On the other hand, fruit treated with 1-MCP at the 25% yellow stage exhibited lower levels of ethylene production and developed pulp with a rubbery texture at the ripe stage which was attributed to reduced PG, βGal, and PME enzyme activities and gene expression. This was consistent with the higher level of cell wall polysaccharides measured in 1-MCP-treated fruit. The above results indicated that ‘Sunrise’ papaya fruit can be treated with 1-MCP at the colour break stage since they have a greater capacity to recover from the effects of 1-MCP than fruit treated at the 25% yellow stage.     

Biochemical and physiological changes during chlorophyll degradation in lime (Citrus aurantifolia Swingle cv. ‘Paan’)

Summary

Lime (Citrus aurantifolia Swingle cv. ‘Paan’) native to South East Asia, has a distinct flavour and quality characteristics. Maintenance of the green colour in the peel of lime is a desirable quality attribute during storage. Post-harvest chlorophyll degradation in lime was studied in fruit stored at room temperature (30°C) at a relative humidity (RH) of 70 – 85%. Within 7 d of storage, the total chlorophyll content decreased to 53.9% of its initial level. The highest chlorophyllase activity (1.68 units mg^–1 protein) was observed after 4 d of storage and declined thereafter. Peroxidase activity differed from chlorophyllase activity and increased significantly to 6.25 units mg^–1 protein after 9 d of storage, (i.e., at the late maturity stage). Respiration rate and 1-aminocyclopropene-1-carboxylic acid (ACC) oxidase activity did not significantly affect the chlorophyll degradation process in lime.The total nitrogen content of lime peel was inversely correlated with its chlorophyll content. A higher soluble protein content was observed in yellow peel than in mature green peel. A colour index chart was developed for maturity stages 1–4 in lime based on peel colour changes from mature green to full-yellow, and its correlation with chlorophyll content and fruit quality attributes.     

Acclimatization of Codiaeum variegatum L. ‘Aucubaefolia’ to changes in photon flux density. II. Net photosynthesis,dark respiration and chlorophyll content

Summary

Net photosynthesis, dark respiration and chlorophyll content were studied in plants of Codiaeum when transferred” from a glasshouse to photon flux densities 6, 18, or 66 μE m^?2s^?1 in growth rooms. The diurnal patterns of daily net photosynthesis and dark respiration were recorded during the first 12 days and 3, 7, 11 and 19 weeks after the transfer. Only plants transferred to 66 μE m^?2s^?1 reached a positive total net photosynthesis per day within the first 12 days. This was achieved only between the 12th day and 3 weeks when transferred to 6 μE m^?2s^?1. The rate of net photosynthesis increased until the 11th week and then declined, while dark respiration decreased until the 11th week and then increased. The diurnal patterns of net photosynthesis and dark respiration changed significantly with time of acclimatization. The rate of change in daily net photosynthesis and dark respiration was highest in the plants transferred to the lowest photon flux density. Changes in chlorophyll content of the leaves were similar to those in net photosynthesis.     

Pollen-tube growth behaviour in ‘Chanee’ and ‘Monthong’ durians (Durio zibethinus L.) after selfing and reciprocal crossing

Summary

Two durian cultivars, ‘Monthong’ and ‘Chanee’, were investigated with respect to post-pollination processes in the pistil and the percentages of fruit set after self-pollination or reciprocal crossing. Pollen grains from each cultivar germinated normally on both stigmas and grew downwards healthily. The percentage of penetrated ovules exceeded 40% in all treatments. However, fruit set after self-pollination in ‘Chanee’ was extremely low. The percentage of fruit set in ‘Chanee’ 35 d after self-pollination (DAP) was 0% in 2002 and 2003, while that of ‘Monthong’ was 6.9% in 2002, and 23.6% in 2003. The percentage of fruit-set after cross-pollination was significantly higher. On the basis of pollen-tube growth behaviour and the non-synchronisation of fruit drop between self-pollination and the two cross combinations, it may be that ‘Monthong’ and ‘Chanee’ durians possess post-zygotic barriers to selfing, especially in ‘Chanee.’     

Short-term effects of changes in soil management and nitrogen fertilizer application on ‘Bramley’s Seedling’ apple trees.

Soil managment in a ‘Bramley’s Seedling’ orchard, established in a system of herbicide treated tree rows and mown grass alleys, was changed to provide three treatments: complete grass cover, overall herbicide and a continuation of the existing system. Differential rates of N fertilizer (nil, 62.5 kg ha-1) were applied to each soil management regime. In comparison with herbicide strips, complete grass was intensely competitive, particularly with nil application of N fertilizer, reducing tree growth and yield and greatly decreasing leaf N. Leaves from trees in complete grass (nil N) plots contained higher concentrations of P, K and B but lower ones of Ca, Mn and Cu. Compared with the change from herbicide strip to complete grass management, effects of changing to overall herbicide were smaller. There were slight increases in leaf N concentration but no increases in tree growth or fruit yield. Leaf Mn concentration was increased in overall herbicide. Although application of N fertilizer to grass plots increased leaf N concentration by 0.4% and the three-year girth increment, yield was less than that of trees in herbicide strips. Nitrogen fertilizer applied to herbicide strips or overall herbicide plots slightly increased leaf N content but there was no effect on yield or girth increase. Applying N fertilizer to complete grass plots reduced the concentration of P, K and B in leaves but increased leaf Ca, Mn and Cu.     

Seasonal changes in cellular compartmentation and membrane permeability to sugars in relation to early or high temperature-induced watercore in ‘Orin’ apples

Summary

The intensity of watercore in ‘Orin’ apples (Malus domestica Borkh.) from the outer canopy increased from early-July to mid-August, followed by a decrease through late-October, while no watercore was detected in inner canopy fruit during the same period. Seasonal changes in sorbitol content in each cellular compartment paralleled the development of watercore. Significantly higher sorbitol, fructose and glucose contents in the vacuoles of cells in outer canopy fruit than in inner canopy fruit suggest that active metabolism and uptake of sorbitol might occur in watercored apples in mid-August. The permeability of sorbitol across the tonoplast was significantly higher in outer than in inner canopy fruit after mid-August, whereas no difference was observed between bearing position for the other sugars or for the plasma membrane. These data suggest that elevated sorbitol levels in the intercellular spaces might result from active apoplastic unloading and not from an inhibition of metabolism and/or an increase in leakage from cells.     

Regeneration from in-vitro leaves of ‘Conference’ and other pear cultivars (Pyrus communis L.)

Summary

Regeneration of shoots from in-vitro grown leaf tissues of the pear cv. Conference was achieved at rates of up to 40%. The highest regeneration percentage was achieved using a phytohormone combination of benzylamino purine (5 mg 1^?1) and 1-naphthalene acetic acid (1.0 mg 1^?1) on a basal medium of Murashige and Skoog, to which had been added 200 mg I^?1 of the antibiotic cefotaxime. The percentage regeneration was reduced when a higher concentration of cefotaxime (400 mg 1^?1) was used. Cefotaxime had little beneficial effect on regeneration at a lower concentration of 1-naphthalene acetic acid (0.5 mg l^?1). Regenerated shoots were easily micropropagated, rooted and transplanted to soil. To date, the plants have a true-to-type phenotypic appearance. Regeneration was also achieved with other cultivars—‘Abbé Fetel’, ‘Doyenne d’Hiver’, ‘Doyenne du Comice’ and ‘Passé Crassane’—but percentage regeneration was lower and, apart from ‘Passé Crassane’, the regenerated shoots were weak and could not be subcultured.     

Somatic embryogenesis and plant recovery from callus of ‘Nabali’ Olive (Olea europea L.)

Regeneration via somatic embryogenesis from callus was studied in ‘Nabali’ olive (Olea europea L.). Among different explant sources (leaf blades, leaf petioles, hypocotyls of germinated seeds and roots of germinated seeds), roots gave the highest (46%) callus induction. Somatic embryogenesis was induced from root callus on embryogenesis induction medium (EIM) containing 5.0 μM 2,4-D, 0.5 μM kinetin and 5.0 μM NAA in darkness. Embryo regeneration was studied by transferring the callus from EIM to embryogenesis expression medium (EEM) containing different concentrations (0.0, 5.0, 10.0 and 15.0 μM) of 2-isopentenyladenine (2iP), BA, thiadiazuron (TDZ), zeatin or kinetin. Among the tested concentrations, 2iP at 10.0 μM outperformed the other growth regulators. 2,4-D at 5.0 μM in the EIM was satisfactory for embryogenesis induction. Sucrose at 0.2 M evoked higher embryogenesis than any other concentration of fructose and glucose in EIM, while sorbitol and mannitol at 0.1, 0.2 or 0.3 M reduced embryogenesis significantly and inhibited it totally at 0.4 M. Somatic embryos were rooted by transferring them to hormone-free medium (HFM). About 85% of embryos converted to rooted plantlets, 5% showed secondary embryogenesis and 10% were not developed and died. Rooted plantlets gave 95% survival when acclimatized ex vitro. Acclimatized plantlets developed into whole plants in the greenhouse and they were phenotypically similar.     

Effect of green tea extract powder on the vase-life of fresh-cut rose (Rosa hybrida L.) ‘Carola’ stems

To develop an innocuous, easy-to-use, and inexpensive preservative for the cut flower industry, green tea extract (GTE) powder was applied in the fresh-cut rose stem preservation process to exploit its high anti-oxidative and anti-microbial properties. The effects of 2.0 g l^?1 GTE powder in the vase solution on the vase-life and flowering profile of cut rose (Rosa hybrida ‘Carola’) stems were investigated. The effectiveness of GTE powder was also compared with other preservatives such as 2% (w/v) sucrose, 200 mg l^?1 8-hydroxyquinoline citrate plus 2% (w/v) sucrose, or 0.2 mM silver thiosulphate in the vase solution, with distilled water as a control. The results showed that, compared to the control, the 2.0 g l^?1 GTE powder treatment extended the vase-life and reduced the loss in fresh weight in cut rose stems in the vase solution. GTE at 2.0 g l^?1 provided the highest anti-bacterial activity (4.2 log₁₀ CFU ml^?1 on day-6) and prevented the decline in anthocyanin concentrations compared to that seen in the control stems, suggesting that GTE powder could be used as a preservative to extend the vase-life of fresh-cut rose flowers.     

Analysis of differentially expressed proteins in the pollen of Malus spectabilis (crabapples) and Malus domestica (‘Gala’ apples) and their role in pollination

Our objective was to study the differentially expressed proteins (DEP) in various Malus spectabilis (crabapple) varieties (M. ‘Snowdrift’, M. ‘Hongling’ and M. ‘Hongjin’) in relation to Malus domestica (‘Gala’) and their role in pollination. Our method used a two-dimensional electrophoresis (2-DE) to analyse the differential proteins in the pollen of several crabapples. The 2-DE apples combined with the tandem mass spectrometry (MS-MS) and protein database retrieval helped us to identify the nature and function of DEPs in ‘Gala’ apples and crabapples. We identified 1195 proteins through 2-DE. Among these, six DEPs, namely chloroplast ferritin, Actin, Beta-fructofuranosidase, vacuolarH+-ATPase catalytic subunit, Full = Phosphoglucomutase, and Cytochrome b were identified by MS-MS. This study identified six DEPs among the pollen from the ‘Snowdrift’ crabapple, ‘Hongling’ crabapple, ‘Hongjin’ crabapple, and ‘Gala’ apples. The DEPs included metabolism related proteins, stress/regulatory proteins, and proteins involved in signal transduction.     

Studies on the hawthorn (Crataegus azarolus L.): III. A potential rootstock for ‘Golden Delicious9 apple and ‘Williams’ pear

Seedlings of the hawthorn Crataegus azarolus L. were budded with ‘Williams’ pear and ‘Golden Delicious’ apple and followed for compatibility, growth control, precocity and suckering. Four years of observations indicated that the hawthorn is compatible with ‘Williams’ and ‘Golden Delicious’, conferring growth control and precocity; and producing suckers profusely. On the other hand, bud break in ‘Williams’ started 10 d earlier and gave longer shoots than ‘Golden Delicious’. Delayed symptoms of incompatibility and long-term reciprocal influences require further study.     

Identification and expression analysis of 11 MADS-box genes in peach (Prunus persica var. nectarina ‘Luxing’)

MADS-box genes play a central role in the development of flowers in plants. In this study, 11 PpMADSs were isolated from ‘Luxing’ peach, and the expression levels were detected in different tissues and fruit development. Eleven PpMADSs, designated as PpMADS13, 14, 18, 23, 24, 25, 32, 33, 34, 35, and 39 were isolated. Phylogenetic analysis revealed that PpMADS13, 14, and 18 belonged to SVP, AGL15, and MIKC* group respectively; PpMADS23, 24, 25, and 39 were in the Mα group; PpMADS32, 33, 34, and 35 belonged to the Mγ group. Predictions from subcellular localization showed that 10 PpMADS were located in the nucleus. RT-PCR revealed that PpMADS13 was expressed in stems, leaves, and during fruit development (70d); PpMADS14 was expressed in sepals, stamens, petals, and during flower development; PpMADS18 was expressed in roots, stems, leaves, sepals, ovaries, stamens, petals, and during flower and fruit development; all MADS-box genes (expect for PpMADS33) in the Mα and Mγ group were expressed in roots, stems, leaves, sepals, ovaries, stamens, petals, and during flower development; few genes were expressed during fruit development. These results indicated that PpMADS may play a crucial regulatory role in vegetative growth and development processes of flowers and fruits in peaches.     

Agronomic,cytogenetic and molecular studies on hermaphroditism and self-compatibility in the Greek kiwifruit (Actinidia deliciosa) cultivar ‘Tsechelidis’

The development of hermaphrodite cultivars of kiwifruit (Actinidia deliciosa) to overcome dioecism is a priority for all breeding programmes, worldwide. If successful, the number of pollinators in the orchard could be reduced, allowing more space for reproductive vines. Hermaphroditism and the expression of self-compatibility were studied in A. deliciosa, using the new kiwifruit cultivar, ‘Tsechelidis’, as a model. This plant material was chosen for investigation as its female flowers produced viable pollen. The aim of the present study was to investigate the expression and nature of self-compatibility in ‘Tsechelidis’ and to evaluate its potential for breeding purposes. The expression of self-compatibility in ‘Tsechelidis’, between years, was investigated by controlled self-pollination of female flowers in the field and by microscopic studies on pollen viability in the laboratory. The commercial cultivar ‘Hayward’ and the pollinator ‘Matua’ were used as controls. Controlled self-pollination in the field confirmed that ‘Tsechelidis’ exhibited a degree of hermaphroditism and self-compatibility. Its flowers produced viable pollen and could set fruit of an acceptable size and quality after self-pollination, compared to open-pollinated fruit. The average fruit set percentage for ‘Tsechelidis’ was 34%, and ranked from 20% to 60% per vine, while the corresponding rate for ‘Hayward’ was only 4%. Microscopic studies on ‘Tsechelidis’ pollen revealed variations in pollen viability between different vines, which were even greater between different flowers on the same vine, ranging, in some cases, from 0% (absolutely sterile) to 70% (significantly fertile) per flower. Female control ‘Hayward’ vines were found to be practically sterile (0%), while male control ‘Matua’ vines were almost 100% fertile. The nature of self-compatibility in ‘Tsechelidis’ was investigated further by molecular analysis using the sex-linked sequence characterised amplified region (SCAR) markers, SmX, SmY, and SmY1, and by single nucleotide polymorphism (SNP) analysis. Hermaphroditism in ‘Tsechelidis’ was related to sex expression, as observed by SNP analysis, but complete genome mapping would be required to fully understand the mechanisms involved and to exploit this new genetic material for breeding purposes.     

Water relations and microbial proliferation in vase solutions of Narcissus tazetta L. cv. ‘Shahla-e-Shiraz’ as affected by biocide compounds

Summary

Disruption of cut flower water relations due to the growth and proliferation of microorganisms in the vase solution is one of the most important factors causing reduced vase-life and deterioration in cut flowers. These experiments were conducted to study the effects of some biocides in controlling microbial proliferation in vase solutions and on water relations in cut Narcissus tazetta L. cv. ‘Shahla-e-Shiraz’, a native bulbous cut flower of Iran. The stems of ‘Shahla-e-Shiraz’ Narcissus cut flowers were exposed to 17 treatments: aluminium sulphate (at 100, 200 or 300 mg l^–1), citric acid (at 150, 300 or 450 mg l^–1), 8-hydroxyquinoline citrate (at 200, 300 or 400 mg l^–1), sodium hypochlorite (at 400, 600 or 800 mg l^–1), calcium hypochlorite (at 400, 600 or 800 mg l^–1), sterilised distilled water, or tap water (control). Generally, the least effective compounds in controlling microbial proliferation were low concentrations of aluminium sulphate or citric acid. 8-Hydroxyquinoline citrate treatments were most effective, and the vase solution did not contain any microbes until day-6. Vase solution contaminants were yeasts, Bacillus ssp., Staphylococcus ssp., Actinomycetes and Aspergillus ssp. Yeasts and bacilli were the most common microorganisms. Severe symptoms of phytotoxicity such as bud abortion and yellowing in aluminium sulphate-treated flowers, stem proximal-end browning and shrinking in 8-hydroxyquinoline citrate-treated flowers, and bleaching of soaked parts in sodium hypochlorite treatments, were seen. Most solution was taken up in 150 mg l^–1 citric acid, while the reduction in fresh weight was least in 200 mg l^–1 8-hydroxyquinoline citrate. The correlation between microbial counts and growth rate with solution uptake was slightly negative, but their correlation with fresh weight loss was slightly positive.     

In vitro colchicine-induced polyploid plantlet production and regeneration from leaf explants of the diploid pear (Pyrus communis L.) cultivar, ‘Fertility’

Summary

Polyploid plantlets, including triploid, tetraploid, and mixoploid, were induced from the European pear (Pyrus communis L.) cultivar ‘Fertility’ by in vitro colchicine treatment of leaf explants. The leaf explants were incubated in 0.4% (w/v) colchicine for 24, 48, or 72 h, then transferred to adventitious shoot-induction medium. Regenerated shoots were pre-selected according to their morphological characteristics when compared to control shoots from untreated shoot proliferation cultures. Shoots with putative polyploid morphological characteristics were maintained and proliferated. The ploidy levels of all putative polyploid individuals were analysed by flow cytometry and identified by chromosome counts of shoot tip tissue squashes. Polyploid shoots were rooted, and the resulting plantlets were transferred to the field. Polyploid plantlets had a higher specific leaf mass and larger stomata than those of diploid plantlets.     

The ‘habitat backbone’ as strategy to conserve pioneer species in dynamic port habitats: lessons from the natterjack toad (Bufo calamita) in the Port of Antwerp (Belgium)

Biodiversity conservation in economic areas like ports has recently become more important in the European Union due to a stricter interpretation of nature protection laws. In this study we develop a planning and design strategy—the ‘habitat backbone’—with which to support the long-term survival of pioneer species that occur in ports and have low dispersal abilities. For those species, long-term survival in port areas is uncertain because supply of their habitats (on vacant lots) is capricious and depends on land use dynamics. By gaining knowledge about spatial and temporal characteristics of these dynamics we were able to develop a solution to conserve such species. Our solution is based on the creation of permanent habitat—defined as a ‘backbone’—on (semi-) public land with an overall carrying capacity sufficient to support persistent populations. This best ensures long-term survival, and the backbone may also act as refugium. Satellite populations that emerge on adjacent vacant lots will thereby add to the persistence of the overall metapopulation. Management of permanent habitat is focused on retaining early-successional stages of vegetation. Implementing this strategy in the case of the natterjack toad in the Port of Antwerp taught us that realization of a habitat backbone is possible only if landowners, local governments and environmental NGOs cooperate. In the case at hand, such cooperation resulted in a plan that should ensure a coherent and persistent habitat network in which a chorus of some 1,400 natterjack toads could be accommodated—more than the number of toads currently observed. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Fruit Characteristics and Detachment Parameters of Sour Cherry (Prunus cerasus L. cv. ‘Kütahya’) as Affected by Various Maturity Stages

The variability in fruit maturity and quality has difficulties in determining the optimal harvesting maturity. Therefore, maturity stage in harvest is crucial for both fruit quality and minimizing the fruit detachment force. This study investigates the fruit characteristics and detachment parameters of sour cherry (cv. ‘Kütahya’) in terms of different maturity stages. Sour cherries were grouped into five different maturity stages by observation according to their color and dimensions. The fruit mass and dimension increased as a function of maturity stage; however, the fruit mass remained almost same after the 4th stage. The highest values of total soluble solids and titrable acid contents of sour cherry were gained in the last stage of maturity. The value of chroma of fruit outer color was higher 50?% than that of fruit inner color in the 1st maturity stage. However, it was almost same in the 5th stage of maturity. Increasing fruit maturity caused a decrease in the values of fruit detachment force ranging from 4.25 to 1.78 N, giving the coefficient of determination of 0.947. Similarly, the ratio of fruit detachment force to fruit mass, detachment stress, and specific energy decreased as the fruit maturity increased. The harvest of sour cherry is done only once in the optimum time to decrease the harvest cost. Minimizing the variability in fruit maturity throughout the tree is essential for gaining the maximum profit and lower fruit detachment force in this convenient time. Results of this study indicated that 3rd?5th maturity stages were critical for harvest. In order to attain the maximum poundage per tree and color for the market the most of the fruits should be in these stages. Therefore, appropriate management strategies that could homogenize the maturity throughout the tree should be applied.