Application of acetaldehyde (AA) at 90 to 360 mm to intact grape berries (Vitis vinifera L. cv. Sultanina and Vitis vinifera L. cv. 103) caused an increase in CO2 production rate and a reduction in ethylene evolution rate. The increase in CO2 production rate was accompanied by a decrease in juice acidity without any change in the total soluble solids content. Addition of ACC to berry halves dramatically increased ethylene production, which was inhibited by AA. Ethanol, applied at the same concentrations as AA, neither caused a reduction in ethylene evolution nor inhibited the conversion of ACC to ethylene. Chemical name used: 1-aminocyclopropane-1-carboxylic acid (ACC).
et al., 1976 ; Zimmerman, 1977 ) and, more recently, olive ( De la Rosa et al., 2006 ; Pritsa et al., 2003 ; Rallo et al., 2008 ). In this latter species, early elimination of plants with a long juvenile period is based on plant height measured
1 To whom reprint requests should be addressed; e-mail raul.rosa@juntadeandalucia.es . This research was supported by Projects OLI96-2184, CAO97-001-C12-11 and CAO99-008 of the Spanish Ministry of Agriculture
Haploid (2x) roses derived from modern tetraploid breeding lines would allow for crosses to diploid species at the diploid level. In addition, inheritance studies are easier at the diploid level, using diploids derived from tetraploids possessing economically important traits. Haploidization of 4x roses through anther culture has not been successful due to challenges in callus induction and shoot regeneration. This study investigates rose anther responses to recently reported methods that optimize in vitro adventitious shoot regeneration in rose leaves. Anthers of three cultivars (Akito, Grand Gala, and Orlando) were put in a two-step callus induction (CI) and shoot regeneration procedure with varying CI factors. Experiment one (E1) compared continuous light/dark and silver nitrate (0,30,60 mg·L-1) and experiment two (E2) used the optimal E1 treatment comparing two and four weeks on CI media. Twenty-five anthers per treatment per cultivar were used in E1 and n = 100 for E2. Although no adventitious shoots were generated, callus formed on anther tissue and frequency of formation was variable across treatments. Continuous light resulted in 100% lethality. Darkness and silver nitrate (30 or 60 μm) favored callus generation and significant differences for callus generation were found among cultivars. Darkness and 30 μm silver nitrate were used in E2. Two and four weeks on initiation media were not significantly different for generation of anther-derived callus. Identification of factors which optimize callus formation on rose anthers is a positive step toward reliably generating rose haploids.
Response to alkalinity was evaluated in two hibiscus cultivars, Bimini Breeze and Carolina Breeze, grown in a soilless growing medium and in hydroponic culture. For soilless growing medium, plants were potted in a sphagnum peat–perlite-based substrate and irrigated with solutions containing 0 to 10 mm NaHCO3 for 12 weeks. In hydroponic culture, bare-rooted plants were transferred to a 9-L tray containing a Hoagland's nutrient solution prepared with NaHCO3 at the concentrations previously indicated. In soilless growing medium, shoot dry weight was minimally affected by NaHCO3 concentration for `Bimini Breeze', but `Carolina Breeze' exhibited a significant decrease in shoot mass with increasing NaHCO3 concentration. In hydroponic culture, increasing concentration of NaHCO3 induced a decrease in shoot and root mass in both cultivars, but root mass decrease was more pronounced in `Bimini Breeze'. In soilless growing medium, increasing the concentration of NaHCO3 caused an increase in growing medium pH. The pH increase was less pronounced for `Bimini Breeze' than for `Carolina Breeze', indicating a higher capacity for root zone acidification by `Bimini Breeze'. Newly developed leaves of both cultivars showed increasing chlorosis with increasing NaHCO3 concentration. However, `Bimini Breeze' was more tolerant because, according to regression models, 5.7 mm NaHCO3 would be required to reduce chlorophyll levels by 10%, compared with 2.2 mm for `Carolina Breeze', when grown in soilless medium. Fe reductase activity decreased when `Carolina Breeze' plants were grown in 5 mm NaHCO3. However, in `Bimini Breeze', Fe reductase activity was enhanced. These observations indicate that the increased tolerance of `Bimini Breeze' to increasing alkalinity is the result of enhanced Fe reductase activity and increased acidification of the root zone.
Desiccation of containerized plants at retail outlets due to inadequate watering is a recurring problem. Water stress can decrease plant quality and survivability. Treatments that could reduce plant transpiration without lowering plant quality could be beneficial in maximizing the likelihood that plants would not become water stressed between waterings at retail outlets. Abscisic acid (ABA) is known to be involved in the regulation of stomatal aperatures, the major control mechanism for transpirational water loss. Containerized plants of four cultivars of hibiscus were thoroughly sprayed with S-ABA at concentrations of 0, 125, 250 or 500 mg·L–1. Plants were held under simulated retail conditions and were not watered until visible wilting occurred. Transpiration and pot weights were monitored over time. Transpiration rates and weight loss percentages were negatively correlated with S-ABA concentrations. Effects on transpiration rates lasted for at least 30 hours after treatment. For mean hours to wilt, there was interaction between S-ABA treatments and cultivars. For the most sensitive cultivar (`Double Apricot'), treatment with S-ABA at 500 mg·L–1 almost doubled the time to plant wilt (130 h) compared to the control treatment (72 hours). Hours to wilt was increased 24% for `Double Pink' treated at the highest rate. For `Double Red' and `Single Pink', hours to wilt was not affected by treatments. For some hibiscus, S-ABA treatments prior to placement of plants at retail outlets might decrease the chances that the plants would become severely water stressed.
Growth and flowering of shoots of `Mercedes' rose was investigated as a function of the level and spectral quality of photosynthetic photon flux (PPF). Experiments were performed with single-shoot plants decapitated above the two most basal leaves with five leaflets. The development of the two lateral shoots emerging from the axillary buds of these leaves was studied for 4 to 6 weeks. To discriminate between the effects of irradiance and light quality, plants were grown in growth chambers in which PPF and its spectral composition could be controlled. At a photoperiod of 12 hours, the length, weight, and flowering of the shoots strongly increased with irradiance. The growth and number of flowering shoots were always higher for the uppermost than for the second shoot. At the highest PPF (270 μmol·m-2·s-1), flowering occurred in 89% and 33% of the uppermost and second shoots, respectively. At an irradiance level of 90 μmol·m-2·s-1, these percentages were 6% and 0%. Although length and dry weight of both types of shoots were significantly increased by reducing the amount of blue light at constant PPF, flower development was not affected. In a second experiment, plants grown in white light (12 h/day) received a short treatment with low-intensity red or far-red `light at the end of each photoperiod. An end-of-day treatment with red light resulted in significantly more flowering shoots than far-red. The red far-red reversibility of this flowering response indicates the involvement of the photoreceptor phytochrome.
The effects of carbon dioxide enrichment on growth, photosynthesis, and postharvest characteristics of `Meijikatar' potted roses were determined. Plants were grown in 350, 700, or 1050 μl CO2/liter until they reached 50% flower bud coloration and then were placed into dark storage for 5 days at 4 or 16C. Plants grown in 700 or 1050 μl CO2/liter reached the harvest stage earlier and were taller at harvest than plants produced in 350 μl CO2/liter, but there were no differences in the number of flowers and flower buds per plant among CO2 treatments. Plants grown in early spring were taller and had more flowers and flower buds than plants grown in late winter. Shoot and root growth of plants grown in 700 or 1050 μl CO2/liter were higher than in plants produced in 350 μl CO2/liter, with plants grown in early spring showing greater increases than plants grown in late winter. Immediately after storage, plants grown in 350 μl CO2/liter and stored at 4C had the fewest etiolated shoots, while plants grown in 1050 μl CO2/liter and stored at 16C had the most. Five days after removal from storage, chlorophyll concentration of upper and lower leaves had been reduced by ≈50% from the day of harvest. Carbon dioxide enrichment had no effect on postharvest leaf chlorosis, but plants grown in early spring and stored at 16C had the most leaf chlorosis while plants grown in late winter and stored at 4C had the least leaf chlorosis.