Color in apple skin is a composite of varying concentrations of chlorophyll, carotenoids, and anthocyanins/flavanols. Anthocyanin biosynthesis is influenced by a number of factors including rootstock, nitrogen status, wounding, certain plant growth regulators, light, and temperature. This study investigated changes in the optimum temperature for anthocyanin accumulation of `Braeburn', `Delicious', `Fuji', and `Gala' apple tissue disks. Preclimacteric (core ethylene < 1.0 ul·liter-1) apples with little color development were harvested in September, 1992 and immediately brought to the laboratory. Six 15mm disks about 3mm thick were removed from the shaded side of each fruit and transferred to moistened filter paper on temperature-controlled blocks preset at temperatures ranging from 15C to 40C at intervals of 5C and covered with plastic (CO2 permeable) film. The disks were illuminated for up to 48 hours with a high pressure sodium lamp at a distance of about 1m. Following the illumination period individual peel disks were extracted with acidic methanol for anthocyanins. The temperature optimum for maximum anthocyanin biosynthesis for each cultivar will be reported.
Modified Atmosphere Packaging (MAP) in combination with temperature control were investigated for qualify enhancement of sweet cherries (Prunus avium L.). `Bing', `Lambert' and `Rainier' cherries (1 kg/pkg/rep) were wrapped in 1 of 3 different MAP films (5,303; 8,900 and 11,286 cc/sq M/24 hrs of O2 and stored at 0 or 4 C for 3 weeks. Post-storage evaluations included both fruit and stem color, fruit firmness, weight loss, soluble solids, titratable acidity, bruising and pitting valuations, respiration rates and visual assessment. MAP films helped maintain fruit and stem color, and fruit firmness, Whereas weight loss and bruising were reduced. Visual assessment was best with fruit in MAP film packages, There was little change in soluble solids and titratable acidity among fruit in the different MAP films. Control (unwrapped) fruit had considerably higher soluble solids and titratable acidity than wrapped fruit. This difference in soluble solids and titratable acidity between control and MAP fruit was associated with a considerable weight loss in the control fruit. Respiration rates of the fruit varied among the different MAP films and was cuitivar dependent. Fruit stored at 0 C had better quality after 3 weeks of storage than fruit stored at 4 C.
Postharvest temperature and transport duration affect the vase life of cut flowers. necessitating temperature control throughout the marketing chain. However, in practise interruptions of this cold chain often occur, e.g. at the auction, airport or other transfer points. We investigated the effect of an early interruption of the cold chain on water loss, rate of development and vase life of four cut flower species. The experiment had a factorial design: three durations of interruption (8.16 and 40 h), each at five temperatures (8, 12, 16, 20 and 24C), and three containers (replicates) per treatment. A standard marketing chain simulation and vase life evaluation followed each treatment. Controls were 0 h interruption with and without marketing chain simulation. The experiment was carried out twice for each species. Water loss was proportional to vapor pressure deficit, with a sometimes synergistic effect of temperature. A short exposure to 20C accelerated the development of all flower species compared to continuous 8C. The effect of the higher temperature became more apparent later in the marketing chain. Averaged over the interruption temperatures, a one-day delay in the marketing chain resulted in a one day (Aster and Gypsophila) to three days (Dianthus and Chrysanthemum) decrease in vase life. A temperature of 20C for 40 hours reduced the vase life by 30% to 40% compared to continuous 8C.
Eureka lemon (Cirrus limon L. `Eureka') trees were grown in factorial combinations of low (L) or high (H) temperature [day/night temperature regimens of 29.4C/21.1C or 40.5C/32.2C] and ambient (C380) or enriched (C680) atmospheric CO2 concentrations [380 umol mol-1 or 680 umol mol-1, respectively]. After growth under these conditions for 5 months, morning and afternoon leaf carbon assimilation measurements were made with a temperature-controlled cuvette attached to a portable photosynthesis system. Net (P3) and gross (Pg) photosynthesis were measured at 30 umol mol-1 intervals as leaves were exposed to cuvette CO2 drawndowns from 700 to 300 umol mol-1 at 21% and 1% O2, respectively. Photorespiration (Rp) was estimated as the difference between Pg and Pn. Generally, Rp increased as cuvette CO2 decreased. Morning and afternoon Rp of leaves adapted to LC380 conditions were similar. Morning Rp was higher than afternoon Rp for leaves adapted to LC680 conditions. Morning Rp was higher for leaves adapted to HC380 conditions as compared to HC680-adapted leaves. In contrast, afternoon Rp was higher for leaves adapted to HC680 conditions than for H&,-adapted leaves.
Mexican production of vegetables under greenhouse conditions has been increased notably during the last year to about 1500 ha. The main crop in greenhouse production is tomato, but european cucumber is a potential crop due to high yield and quality, with a good price in the marketplace and a short growing season. The objective of this trial was to evaluate eight european cucumber varieties and to choose those with high yield and fruit quality, and disease resistance. The experiment was carried out at the experimental station (INIFAP-CIRNO). Greenhouse conditions were: polyethylene (8.0 mL), without temperature control; natural ventilation; and soil with electrical conductivity of 1.22 dS·m-1 and pH 7.96. Sowing date for seed was 15 Oct. 2004. Plant density was 3.78 plants per m2. The harvest period was 26 Dec. 2004 to 11 Mar. 2005, with an average of 10 cuttings. Varieties with highest yield were `Imanaol', `Bermejo', `Dominica', and `Kalunga', with 18.9, 15.2, 14.8, and 14.3 kg·m2, respectively. Fruit quality was excellent in all varieties; however, `Imanaol' had the highest percentage of size and fruit number. The main insect pest during the year was white fly (Bemissiasp.) and the most important disease was powdery mildew (Erishipecichoracearum).
High temperature stress is a major limitation to commercial production of habanero pepper (Capsicum chinense Jacq.) in tropical and subtropical regions. The ability to sustain physiological activity under stress is an important trait for newer varieties. We evaluated leaf thermotolerance [based on the cell membrane stability (CMS) test] of three habanero pepper varieties to: 1) determine genetic variability in CMS among the genotypes studied; and 2) to assess correlations between CMS, photosynthesis and chlorophyll fluorescence [(CF), an indicator of membrane-dependent photosystem II quantum efficiency, ΦPSII]. The genotypes evaluated were TAM Mild Habanero (TMH, a recently developed mild habanero pepper) and its closely related parents (Yucatan and PI 543184). Net CO2 assimilation rate (An) of intact leaves was measured in the field and leaf samples collected and exposed to heat stress (55 °C for 20 min) in temperature-controlled water baths under dim light conditions. The CF was assessed before and after the heat treatment. The CMS was highest in PI 543184, lowest in TMH and intermediate in Yucatan. All genotypes maintained high An rates in the field (25 ± 6 μmol·m-2·s-1); however, correlations between An and CMS were weak. The Φ values were similar among the genotypes (∼0.8) under nonstress conditions, but differed significantly following stress exposure. PI 543184 had the highest post-stress ΦPSII values (0.506 ± 0.023), followed by Yucatan (0.442 ± 0.023) and TMH (0.190 ± 0.025). Observed differences in CMS and ΦPSII indicate plasticity in the response to heat stress among these genotypes.
Intercontinental trade in floriculture products exceeds US$ 1,250 mln annually. One fourth are tropical commodities. Most of the US$ 200 mln of tropical floriculture products imported into western Europe arrive by airplane and are transhipped before arriving at the country of destination. For cut flowers, it takes four to seven days from arrival at the port of entry to destination at the consumer. Mode of transport and market structure have as result that postharvest requirements for individual products are seldomly met. Potential vase life is reduced by five to ten percent for every day spent in the marketing chain. Because quality loss is often invisible, there is a necessity to have measures of internal quality. The only measure currently being used is a test on bacterial contamination. Internal quality tests based on carbohydrates, chlorophyll fluorescence or near-infrared spectra are being developed. Control on the application of pretreatments against bacteria, ethylene and drought needs to be intensified. Extension efforts continue to emphasize hygene and temperature control.
On 6 Sept. 1996, container-grown vegetatively propagated Phalaenopsis Atien Kaala `TSC22' plants were harvested and individually weighed. The bare-root plants were packed in cartons with shredded newspaper and placed in incubators at 15, 20, 25, or 30°C air temperature. Control plants were undisturbed. After 4, 7, or 14 days, one-third of the plants were removed from each temperature treatment, weighed, planted in pots, and then placed in a greenhouse. Mass loss (primarily water) increased with increasing air temperature and duration in storage. Symptoms of chilling injury (yellow blotches on leaves) were inversely related to 15 and 20°C storage temperatures. Chilling injury became more severe as storage duration increased. Plants had little or no chilling injury at 25 and 30°C, regardless of storage duration. Leaf loss was most severe on plants stored at 15°C for 7 or 14 days or at 30°C for 14 days. Increased storage duration up to 14 days did not affect the time of spiking (appearance of the flowering shoot) for plants stored between 15 and 25°C. Those kept at 30°C, regardless of the duration, spiked 5 to 8 days after the control. The results suggest that vegetative Phalaenopsis plants harvested in late summer should be stored and shipped at 25°C. Under such conditions, plants could lose 20% of the fresh mass between harvesting and planting without adversely affecting subsequent performance.
Heat stress induces leaf senescence and causes changes in protein metabolism. The objective of this study was to investigate effects of exogenous application of a synthetic form of cytokinin, zeatin riboside (ZR), on protein metabolism associated with leaf senescence under heat stress for a cool-season grass species. Creeping bentgrass (Agrostis stolonifera L.) (cv. Penncross) plants were exposed to optimum temperature control (20/15 °C, day/night) and heat stress (35/30 °C) in growth chambers. Before heat stress treatments, foliage was sprayed with 10 μmol ZR or water (untreated) for 3 days and then once per week during 35 days of heat stress. Leaf chlorophyll content, photochemical efficiency (Fv/Fm), and soluble protein content declined, whereas protease activity increased during heat stress. Treatments with ZR helped maintain higher leaf chlorophyll content, Fv/Fm, and soluble protein content under heat stress. Protease activity in ZR-treated plants was lower than that of untreated plants. Zeatin riboside-treated plants had less severe degradation of ribulose-1,5-bisphosphate carboxylase proteins than untreated plants exposed to heat stress. In addition, ZR treatment upregulated the expression of 32- and 57-kDa proteins under heat stress conditions. These results demonstrated that the exogenous application of ZR ameliorated the negative effects of heat stress, as manifested by suppression or delay of leaf senescence. Cytokinins may have helped to alleviate heat stress injury, probably by slowing down the action of protease and by induction or upregulation of heat-shock proteins.
Observations of leaf number accumulation rate (LNAR) and light integrals (DLI) were used to develop a predictive model for time to flower for a novel hybrid of Limonium sinuatum (L.) Mill. × Limonium perezii (Stapf) Hubb. Plants were established in a temperature-controlled greenhouse at seven planting times from fall to late spring. Long days were maintained using daylength extension lighting. Two light regimes, full sun or 50% shade, were also used. DLI was highly correlated with the time to appearance of the first visible flower bud, explaining in excess of 80% of the variation. When combined with plant growth variables describing either LNAR or rates of increase in groundcover index, a second model was able to predict the date of first visible flowers and accounted for more variation than DLI alone. Daily average temperature (DAT) did not significantly contribute to variation in time to first visible flower because temperatures were uniform between successive plantings at 18 to 21.7 °C. However, DAT was significant for the period from visible flower through to flower harvest maturity. Growers of these hybrids for cut flowers can therefore use historical records of DLI to determine planting dates to schedule flowering. Once planting has occurred, by measuring actual DLI, DAT, and leaf number per plant, growers can use the second model to more accurately predict the dates for visible flowers and flower harvest.