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The short vase life of Acacia holosericea cut stems needs to be improved before they are marketable as cut foliage for floral arrangement. The effects of citric acid, Cu2+ and sucrose were investigated for their efficacy in postharvest treatments to extend vase life of the cut stems. Five experiments were conducted involved combinations of citric acid either with Cu2+ or sucrose. Vase life, relative fresh weight (RFW), and vase solution uptake were measured as indicators of cut stem quality. The effect of Cu2+ alone was shown to be consistently superior in improving vase life by up to 1.9-fold as compared with deionised water control. Citric acid had a smaller effect than Cu2+ and did not act synergistically with Cu2+. Sucrose on its own or in combination with citric acid did not improve vase life significantly; instead sucrose promoted early wilting or desiccation of the cut foliage.

Acacia holosericea is a novel cut foliage line with a short vase life. Postharvest application of salicylic acid (SA) can extend the vase life of cut flower. SA is a host defence inducer, as is jasmonic acid (JA). SA and JA were compared as vase solution additives for A. holosericea. Three experiments were conducted that also compared these two chemicals with H+ and Cu2+ as known vase life extending additives. Vase solutions containing SA at 0.5, 1.5, and 2.5 mM gave ~1.3- to 1.5-fold vase life extensions as compared with the distilled water (DW; control). Provision of Cu2+ and JA at 0.5 mM in vase solutions also prolonged vase life by ~1.3-fold as compared with DW. The positive effect of SA tended to be greater than that of JA, but was inferior to that of Cu2+ at the same concentration. However, trend differences among these treatments were not statistically significant. Cut A. holosericea foliage stems treated with SA and JA exhibited higher relative fresh weight (RFW) and vase solution uptake r...

The pathogenicity of three isolates of Alternaria alternata from Backhousia myrtifolia leaves was characterised and compared. Isolate BRIP 52222 was virulent compared to isolates BRIP 52223 and BRIP 52221. A comparison of inoculation methods showed that abrasion was more effective at establishing an infection than puncture wounding. Koch's postulates were assessed to confirm the pathogenicity of A. alternata on B. myrtifolia foliage and floral tissues using a conidial suspension of the most virulent isolate. Sporulation was triggered by incubating A. alternata (BRIP 52222) at 28 degrees C for 10 d under alternating 12 h black-light/12 h dark conditions on half-strength potato dextrose agar (PDA). In contrast, incubation of A. alternata under continuous black-light on either half- or full-strength PDA did not yield conidia. Host symptoms caused by inoculation with the pathogen included a brown-black discolouration of both foliage and floral tissues. Microscopic examination of cellular structures suggested that perturbation of oil glands may contribute to the tissue discolouration in B. myrtifolia caused by A. alternata infection. Oil gland structures can be disrupted during an active A. alternata infection, causing the leakage of essential oil followed by discolouration.

SummaryWilting associated with diminishing post-harvest water uptake is a major constraint on longevity for cut stems of many Acacia spp. Cu2+ ions have known biocidal activity and may also act as inhibitors of plant wound reaction enzymes. A series of experiments were conducted using Cu2+ ions as a pulse, or as a vase-solution additive to evaluate their potential to extend the vase-life of cut A. holosericea foliage stems. Provision of Cu2+ ions in the vase-water at 0.5 mM, or as a 5 h pulse at 1.0 mM, resulted in 1.4- to 2.8-fold, and 1.7- to 2.1-fold extensions of vase-life, respectively, compared to de-ionised water controls. The pulse treatment was optimised, and a 5 h pulse with 2.2 mM Cu2+ ions resulted in a 2.6-fold extension of vase-life. Thus, Cu2+-pulsing can effectively delay wilting in cut A. holosericea foliage stems.

SummaryBackhousia myrtifolia is a species native to Australia that shows potential as a cut flower crop. During Spring and Summer, it bears numerous small florets with prominent white sepals and glossy deep-green foliage. B. myrtifolia is harvested either when tight white buds are present in the centre of the star-shaped sepals, or following bud burst, after the petals and stamens have abscised to leave only the sepals.Wilting and brown-to-black discolouration of the flowers and foliage can markedly reduce stem quality. Several forms of discolouration were characterised over the 2004 – 2006 flowering seasons and were collectively termed ‘post-harvest browning syndrome’. Further research based on the symptomatology described herein is required to elucidate the causal agent(s).

Post-harvest application of abscisic acid (ABA) can induce stomatal closure in the leaves of cut flower and foliage crops.This effect may be helpful in reducing water deficit stress. Acacia holoser...

SummaryThe cut stem-end wound reaction is potentially important during the physical blockage of water uptake in cut flowers. Phenylalanine ammonia-lyase (PAL; EC 4.3.1.24) is involved in plant wound reactions, being the key regulatory enzyme of phenylpropanoid metabolism. Two full-length PAL genes (DcPAL2 and DcPAL3) cDNAs were isolated from cut carnation (Dianthus caryophyllus L.) flower stem-ends and found to be transiently expressed following wounding. DcPAL2 was 2,439 bp-long with an open reading frame (ORF) encoding a putative protein of 718 amino acids. DcPAL3 was 2,453 bp-long with an ORF encoding a putative protein of 709 amino acids. An increase in PAL enzyme activity within the basal 2-cm stem-end of cut carnation flowers commenced 12 h after wounding and peaked at 48 h. However, DcPAL2 and DcPAL3 transcript levels increased earlier than PAL activity. DcPAL2 transcript levels increased gradually to a peak 12 h after wounding and remained relatively high thereafter. In contrast, DcPAL3 gene trans...

SummaryMethyl jasmonate (MeJA) and acibenzolar-S-methyl (ASM), two potential elicitors which activate plant defence responses, were tested on inflorescences of Freesia hybrida to suppress petal-specking caused by Botrytis cinerea. Compared to the untreated controls, MeJA applied as a vapour, pulse, or spray to freesia ‘Cote d’Azur’ inflorescences significantly reduced disease severity scores, lesion numbers, and lesion diameters on attached petals, and lesion diameters in a detached petal bioassay. ASM alone, at 143 µM, provided a degree of protection to freesia inflorescences by significantly reducing disease severity scores, lesion numbers, and lesion diameters compared to the untreated controls. However, no additive effect was observed for combined treatments with MeJA and ASM. Polyphenol oxidase (PPO) activities in 0.1 µl l–1 MeJA-treated inflorescences, at 24 h and 36 h post-treatment, were 2.7- and 2.0-fold higher, respectively, compared to the untreated controls. In contrast, phenylalanine ammonia-...

The effects of nitric oxide (NO) treatment on the sensitivity of banana fruit slices to ethylene were investigated. Fruit slices were partial-pressure infiltrated for 3 min in a NO donor Solution of 5 mM sodium nitroprusside (SNP), followed by treatment with 100 mu l l(-1) ethylene for 24 h, then packed into polyethylene bags and stored for 5 d at 24 degrees C. Control slices were treated with distilled water instead of SNP, then treated with ethylene. Changes in fruit firmness, chlorophyll content, respiration rate, the activities of three cell wall modifying enzymes [polygalacturonase (PG), endo-beta-1,4-glucanase (EGase), and beta-galactosidase (beta-Gal)], and total amylase activity were measured. Expression of the expansin (MaExp1) and ethylene receptor (MaERS2) genes were also analysed. The application of NO, prior to ethylene exposure, retarded pulp softening and peel de-greening. Pre-treatment with NO also decreased the respiration rate of banana fruit slices during ripening. Delayed pulp softening by NO was associated with decreased activities of PG, EGase, beta-Gal, and total amylase, as well as reduced expression of the MaExp1 gene. Expression of the MaERS2 gene was also suppressed in NO-treated banana fruit slices. Collectively, these findings suggest that NO pre-treament decreased the sensitivity of banana fruit slices to ethylene, and thereby delayed ripening.

SummaryAbscisic acid (ABA) treatment can confer chilling tolerance upon certain plant tissues that suffer injury at low temperatures. The present study investigated the efficacy of two post-harvest ABA treatments in suppressing low temperature injury (LTI) in cut rose (Rosa hybrida L.) flowers stored at 1°C or 5°C. A shortened vase-life was recorded for roses stored at 5°C compared to untreated roses and those stored at 1°C. Storage at 1°C significantly (P ≤ 0.01) increased electrolyte leakage in ‘Akito’ roses compared to roses stored at 5°C, or to untreated roses. Storage of ‘First Red’ and ‘Akito’ roses at 1°C or 5°C significantly (P ≤ 0.01) increased the malondialdehyde (MDA) contents of petal and leaf tissues. The highest MDA contents were recorded in roses stored at 1°C. ABA at 10 µM as a spray, or at 0.1 M as a pulse treatment, did not affect the MDA contents of either leaves or petals. When averaged over the two storage temperature treatments, the ABA content was highest in roses pulse-treated with...

Drought is an irregular feature of World climate and has adverse effects on ornamental plants growing in urban environments. Grevillea 'Moonlight' and Myoporum elipticum are attractive native Australian species that are commonly used in parks and gardens and are generally regarded as being drought-tolerant. Diurnal and seasonal water relations during a drought cycle of G. 'Moonlight' and M. elipticum, growing together in a non-irrigated garden bed, were monitored during a Summer (wetter)-to-Winter (dryer) transition period using a pressure chamber. G 'Moonlight' generally maintained higher xylem water potentials than M. elipticum. Pre-dawn xylem water potentials in drought-affected M. elipticum dropped to around -2.5 MPa, while G. 'Moonlight' maintained pre-dawn xylem water potentials of around -1.0 MPa. This difference suggests that, because pre-dawn xylem water potentials reflect soil water potentials, G. 'Moonlight' accessed a different or additional source of soil water to M. elipticum. Ibis study demonstrates the utility of the pressure chamber for describing the diurnal and seasonal water relations of ornamentals in a mixed planting in urban horticulture.

The effects of nitric oxide (NO) on lipid peroxidation and anti-oxidant activity in longan fruit were investigated during storage. Fruits were dipped for 5 min in a solution containing 1 mM sodium nitroprusside (SNP), an NO donor. They were then packed into polyethylene bags and stored for 6 d at 28 degrees C. Changes in pericarp browning index, membrane permeability, malondialdehyde (MDA) content, the rate of superoxide production, the activities of lipoxygenase (LOX), superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT), alpha,alpha-diphenyl-beta-picrylhydrazy (DPPH) radical scavenging activity, and reducing power were measured. Treatment with SNP inhibited pericarp browning and suppressed increases in membrane permeability and lipid peroxidation. These effects were associated with lower LOX activity, higher APX and CAT activities, better maintenance of DPPH radical scavenging activity and reducing power, and lower superoxide production rate. However, SOD activity was higher in control (non-SNP-treated) fruit than in SNP-treated fruit over the first 4 d of storage. Overall, these findings suggest that treatment with NO enhanced the anti-oxidant activity in pericarp tissue of longan fruit during storage, and contributed to reduced lipid peroxidation. Reduced lipid damage apparently maintained the compartmentation of enzymes and substrates and, thereby, lessened enzymatic browning.

Peeling and cutting processes wound tissues and enhance deterioration in minimally processed fruits. Controlled atmosphere (CA) or modified atmosphere (MA) conditions can help maintain the quality of minimally processed products. The effects of various combinations Of CO2 and O-2 on the quality of fresh pineapple (cv. Smooth Cayenne) slices held at 4.5 degrees C were investigated. Among a range of CA treatments, 15 kPa CO2 maintained flesh colour, with low alcohol and acetaldehyde concentrations, and also prevented microbial growth. O-2 at 5 kPa also maintained a high visual quality, and gave low alcohol and acetaldehyde concentrations. Likewise, O-2 at 80 kPa maintained a high visual quality and prevented the accumulation of fermentation-related volatiles, but caused high electrolyte leakage. Both 5 kPa and 80 kPa O-2 treatments resulted in a reduced loss of firmness. Nonetheless, the respiration rate was higher in 80 kPa O-2 than in 5 kPa O-2. When the Optimum O-2 and CO2 concentrations were combined and compared to 21 kPa O-2 + 0 kPa CO2 (air control), both 5 kPa and 80 kPa O-2, with 15 kPa CO2, maintained the quality of pineapple slices. However, because low O-2 is more readily attained and maintained in MA, 5 kPa O-2 + 15 kPa CO2 appeared to be the most appropriate atmosphere for storage of minimally processed pineapple fruit.

Compounds that activate host plant defence responses potentially offer socio-environmentally sound alternative methods for disease control. In a series of glasshouse trials over 2 years, pre-harvest sprays with acibenzolar-S-methyl (ASM) and methyl jasmonate (MeJA) were tested for suppression of post-harvest infection of cut Freesia hybrida L. flowers by Botrytis cinerea. For the ASM treatments, variability in reducing the incidence of B. cinerea disease was observed between years freesia varieties, incubation temperatures and ASM concentrations. In the first year, the greatest reductions in lesion numbers on ASM-treated var. 'Cote d'Azur' were recorded using 2.86 mM ASM. For three different post-harvest temperature regimes, the relative reductions in lesion numbers, compared to untreated controls, were 45% at 5 degrees C, 40% at 12 degrees C and 30% at 20 degrees C, respectively. In the second year, lesion numbers were most reduced using 1.43 mM ASM to treat freesia var. 'Dukaat' flowers. Here, the relative reductions were to 44% at 5 degrees C, 26% at 12 degrees C and 51% at 20 degrees C. MeJA treatments were, in general, more consistently effective than ASM treatments in reducing lesion numbers and lesion diameters on cut freesia flowers. MeJA-treated (0.2 mM) freesia flowers (var. 'Dukaat') incubated at 20 degrees C showed relative reductions of 62%, and 45% for lesion number and lesion diameter, respectively. The differing efficacy between ASM and MeJA treatments could be attributed to their differential abilities to induce the salicylic acid (SA)-mediated vs. the jasmonic acid (JA)-mediated host defence pathways, respectively.

Grevillea cv. 'Crimson Yul-lo' has large bright red terminal inflorescences on leafy stems and has recognised commercial potential as a cut flower crop. A major limitation is its relatively short vase-life, often terminated by early wilting of the inflorescence despite apparently turgid leaves. An investigation of the water relations of cut Grevillea 'Crimson Yul-lo' stems revealed that the water potential of inflorescences on intact stems in vases was significantly higher (i.e., less negative) than that of leaves from day-0 to day-3 of vase-life. Thereafter, the water potential of inflorescences declined more rapidly than that of leaves, accompanied by visible wilting of the tepals and styles of individual florets. Removal of leaves from the stems reduced both water uptake and water loss, and delayed the onset of a negative water balance in the inflorescence. Bagging of entire stems, leaves only, or inflorescences only, with micro-perforated plastic film to reduce transpiration, reducing leaf number to reduce leaf area, or supplying abscisic acid to reduce leaf stomatal aperture, all aided relative fresh weight retention by stems and extended vase-life. Four or six leaves on a stem caused greater loss in inflorescence water content than zero or two leaves. Considered collectively, these findings show competition for water between the inflorescence and the leaves in cut Grevillea 'Crimson Yul-lo' stems contributes to the onset of inflorescence wilting and their short vase-life.

Genotype, sulphur (S) nutrition and soil-type effects on spring onion quality were assessed using a 32-conducting polymer sensor E-nose. Relative changes in sensor resistance ratio (% dR/R) varied among eight spring onion genotypes. The % dR/R was reduced by S application in four of the eight genotypes. For the other four genotypes, S application gave no change in % dR/R in three, and increased % dR/R in the other. E-nose classification of headspace volatiles by a two-dimensional principal component analysis (PCA) plot for spring onion genotypes differed for S fertilisation vs. no S fertilisation. Headspace volatiles data set clusters for cv. 'White Lisbon' grown on clay or on sandy loam overlapped when 2.9 [Mahalanobis distance value (D2) = 1.6], or 5.8-(D2 = 0.3) kg S ha-1 was added. In contrast, clear separation (D2 = 7.5) was recorded for headspace volatile clusters for 0 kg S hd-1 on clay vs. sandy loam. Addition of 5.8 kg S ha-1 increased pyruvic acid content (mmole g-1 fresh weight) by 1.7-fold on average across the eight genotypes. However, increased S from 2.9 to 5.8 kg ha-1 did not significantly (P > 0.05) influence % dR/R, % dry matter (DM) or total soluble solids (TSS) contents, but significantly (P < 0.05) increased pyruvic acid content. TSS was significantly (P < 0.05) reduced by S addition, while % DM was unaffected. In conclusion, the 32-conducting polymer E-nose discerned differences in spring onion quality that were attributable to genotype and to variations in growing conditions as shown by the significant (P < 0.05) interaction effects for % dR/R.

The effects of modified atmosphere (MA) conditions on the quality of minimally processed pineapple slices were determined. Commercial pineapple slice packs sealed with 40 pm thick polyester film were kept at 4.5 degrees C for 14 d. The oxygen transmission rate of the film was 23 ml m(-2) day(-1) atm(-1) (at 25 degrees C, 75% RH). In-built atmospheres and the quality of the products were determined. O-2 concentrations within the packs stabilised at 2%, while CO2 concentrations increased to 70% by day 14. The high CO2 level suggested an inappropriate lidding film permeability for the product, and hence affected its quality. Three batches of pineapple slices were packed in the laboratory using lidding films with oxygen transmission rate of 75, 2790 or 5000 ml m(-2) day(-1) atm(-1) (at 23 degrees C, 0% RH). Headspace atmospheres from laboratory-packed pineapple slices suggested an optimum equilibrium modified atmosphere of ca. 2% O-2 and 15% CO2. Respiration data from the laboratory-prepared packs were pooled together and used to develop a correlation model relating respiration rates to O-2 and CO2 concentrations. The model showed a decrease in respiration rate with decreasing O-2 and increasing CO2 concentrations. Respiration rate stabilised at 2% 02 and 10% CO2. The high concentrations of CO2 observed in the commercial packs did not fit the range in the respiration model. The model could aid in selection of MA conditions for minimally processed pineapple fruit.

SummaryExposure to ethylene gas elicits flower abscission from cut stems of Geraldton waxflower (Chamelaucium uncinatum Schauer). Ethylene response rates in plants are mediated by temperature. At 20°C, flower abscission from waxflower ‘Purple Pride’ occurred upon 12 h exposure to 1 µ11–1 ethylene. This ethylene treatment did not cause flower abscission at either 10 or 2°C. Moreover, flowers held at 2°C were insensitive to 48 h exposure to 1, 10 and 100 µ11–1 ethylene. However, increasing the duration of treatment with 1 µ11–1 ethylene at 10 and 2°C to 48 and 144 h, respectively, induced flower abscission. When flowers were held at 20°C in air without exogenous ethylene following continuous exposure to 1 µ11–1 ethylene at 2°C, the duration required to elicit flower abscission was reduced from 144 to 72 h. Collectively, these responses show that maintaining harvested waxflower at low temperature (e.g. 2°C) is an effective means to minimise ethylene-mediated flower abscission.

Abscisic acid (ABA) supplied in the vase solution can induce stomatal closure in the leaves of cut flowers, including roses (Rosa hybrida L.). This effect may be beneficial in reducing water deficit stress. Extracellular pH can affect active ABA concentrations in the apoplast of guard cells, with sap alkalisation enhancing the physiological activity of ABA. Accordingly, it was hypothesized that vase solution pH may affect ABA-mediated stomatal closure of cut roses. Two experiments were conducted to study the interaction of vase solution pH and ABA. In the first, cut 'Baccara' roses were held in vase solutions with +/- 10(-5) M ABA at pH 6, pH 7 and pH 8. In the second experiment, roses were held with +/- 10(-5) M ABA at pH 6 and pH 8 in the presence and absence of 1 mg l(-1) AgNO3 as a bactericide. Supply of ABA increased vase life and reduced vase solution usage of flowers held in low pH 6 solutions, indicating induction of stomatal closure. Conversely, ABA supplied at pH 8 was associated with reduced vase life. This negative result was associated with enhanced development of vase solution microbes at high pH, which overrode any potential pH-mediated ABA efficacy effects.

This case study reports the post-harvest qualities of conventionally versus organically grown banana fruit from nearby plantations in the Dominican Republic. The comparison involved six repeated harvests over the transition from cooler to hotter seasons. Green mature Cavendish 'Grande Naine' banana fruit were shipped to the UK. They were triggered to ripen with ethylene gas and kept under simulated retail conditions. Fruit mass, colour, firmness and flavour parameters were measured every second day over 12 d of shelf life. Sensory comparisons were conducted on four of the six harvest times. Significant differences (P

Effects of genotype, sulphur nutrition (0.0, 2.9, 5.8 kg S ha(-1)) and soil type (clay, sandy loam) on spring onion growth were investigated in glasshouse experiments. Leaf greenness, number of green leaves, leaf length, bulb diameter, total plant fresh weight, percentage dry matter (%DM) and total soluble solids content (TSS) varied significantly (P

Maintenance of quality in fresh-cut produce is an important issue for the rapidly expanding minimal processing sector. Treatment of ethylene generating and/or sensitive fresh-cut produce with the ethyle ne-binding inhibitor 1-methylcyclopropene may assist in quality maintenance over time. Intact (control) and sliced 'Golden Delicious' apple fruit at 20degreesC were treated either with I-methylcyclopropene (1-MCP) for 6 h at 0.1 to 10 mul 1(-1) or 1 mul 1(-1) for periods of I to 6 h. Fruit was then kept at either 20degreesC or 4degreesC. Exposure of intact or fresh-cut apple fruit to 1-MCP resulted in reduced respiration and ethylene production rates and delayed softening and colour changes. The degree of benefit generally increased with increasing 1-MCP treatment concentration and duration. Compared with untreated tissue, quality was better maintained at 4degreesC for apple slices to which 1-MCP was applied either before or after the fruit were processed.