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- Author or Editor: James D. Metzger x
The effect of cool temperature treatments on flowering of Osteospermum ecklonis Norl. cv. Nairobi was evaluated. Plants vernalized at temperatures from 4 to 15 °C for 4 to 6 weeks exhibited increased flower numbers, more synchronized flower development among individual plants, and reduced forcing times. Part of the increased flower number observed in the vernalized plants could be attributed to a small increase in branch numbers from 2 to 3. However, a longer period of vernalization slowed flower development, and therefore increased overall production times. Vernalization also reduced stem growth, primarily through a reduction in the number of nodes produced by each branch.
Vermicomposting is a promising method of transforming unwanted and virtually unlimited supplies of organic wastes into usable substrates. In this process, the digestive tracts of certain earthworm species (e.g., Eisenia fetida) are used to stabilize organic wastes. The final product is an odorless peat-like substance, which has good structure, moisture-holding capacity, relatively large amounts of available nutrients, and microbial metabolites that may act as plant growth regulators. For these reasons, vermicompost has the potential to make a valuable contribution to soilless potting media. The objective of this study was to evaluate the transplant quality and field performance of vegetable transplants grown in vermicompost. Tomato (Lycopersicon esculentum Mill.), eggplant (Solanum melongena L.), and pepper (Capsicum annuum L.) transplants were grown in a commercial soilless mix including 0%, 10%, or 20% (v/v) worm-worked cattle manure. Growth of vegetable transplants was positively affected by addition of vermicompost, perhaps by altering the nutritional balance of the medium. Transplant quality was improved in peppers and eggplants while tomato transplant quality was slightly reduced. There were no significant differences in field performance.
Interest in using alternative materials for potting substrate is increasing in response to availability and rising costs of peat and other conventional materials. Vermicompost (VC) is one such material. It is important to understand physical and chemical changes in potting substrate when amended with VC produced from different waste sources, pig (PVC) and beef cattle (BVC) manure in this study. Distribution of particles greater than 2 mm decreased, particles 0.5 to 1 mm increased, and particles less than 0.5 mm remained unchanged as PVC and BVC amendment increased. Dry bulk density and water-holding capacity increased with increasing PVC and BVC amendment. Porosity and air volume were inversely related to VC amendment, decreasing with increasing VC amendment. Saturated substrate extract sampling revealed nitrate nitrogen, phosphorus, calcium, magnesium, zinc, copper, iron content as well as electrical conductivity increased with increasing PVC and BVC amendment.
Seed germinability and storability are important aspects of seed quality determined by the genotype and environment of seed development. Lettuce (Lactuca sativa L.) is produced commercially in most temperate and subtropical areas of the world. The objective of this study was to determine how photoperiod and light quality of the mother plant environment affects lettuce seed quality. Seeds of cv. Tango were produced in growth chambers under one of two treatments: a) short day (SD), consisting of 8 hours of fluorescent light (≈310 μmol·m−2·s−1) plus 16 hours of darkness daily, and b) long day (LD), consisting of 4 hours of incandescent light (≈21 μmol·m−2·s−1), 8 hours of fluorescent light, 4 hours of incandescent light, and 8 hours of darkness daily. The red to far-red ratio was ≈6.8 and 1.0 for the fluorescent and incandescent light, respectively. In both treatments, the temperature was 23 °C. The LD treatment produced significantly heavier seeds; however, germination at optimal conditions (20 °C-light) was similar for both treatments. Germinability (percentage and rates) at suboptimal conditions (30 °C, 20 °C with different external ABA concentrations, negative osmotic potentials, or dark) was higher for seeds produced under the LD treatment. On the other hand, seeds produced under the LD treatment presented better storability (evaluated by the accelerated aging test and standard germination after storage at 30 °C and 74% RH). The critical period for light environment effects was also studied. Seed weight patterns were determined early in seed development, during the first 6 days after flowering. Conversely, light environment effects on seed germinability and storability were determined at the end of seed development, after physiological maturity, which occurred by 11 days after flowering. These results show that lettuce seed germinability and storability may be modified by management of light conditions during seed production and provide useful information for seed producers, seed companies, and seed conservation institutions.
Shoot stretching in plug production reduces quality and makes mechanized transplanting difficult. The objectives of this study were to measure seedling emergence and shoot height of plugs as affected by paclobutrazol application during seed soaking, priming, or coating on seedling emergence and height. Verbena (Verbena ×hybrida Voss. `Quartz White'), pansy (Viola wittrockiana L. `Bingo Yellow Blotch'), and celosia (Celosia cristata L. `New Look') seeds were soaked in water solutions of paclobutrazol and subsequently dried on filter paper at 20 °C for 24 h. Soaking seeds in paclobutrazol solutions before sowing reduced growth and percentage seedling emergence of verbena and pansy but had little effect on those of celosia. Verbena seeds soaked in 50, 200, or 500 mg paclobutrazol/L for 5, 45, or 180 min produced fewer and shorter seedlings than controls. Osmopriming verbena seeds with 10 to 500 mg paclobutrazol/L reduced seedling emergence. Seedling height and emergence percentage of pansy decreased with increasing paclobutrazol concentrations from 2 to 30 mg·L–1 and with soaking time from 1 to 5 min. The elongation of celosia seedlings was reduced by soaking seeds in 10, 50, 200, or 500 mg paclobutrazol/L solutions for 5, 180, or 360 min. However, these reductions were negligible and without any practical application.
Plant architecture is a major consideration during the commercial production of chrysanthemum (Dendranthema grandiflora Tzvelev). We have addressed this problem through a biotechnological approach: genetic engineering of chrysanthemum cv. Iridon plants that ectopically expressed a tobacco phytochrome B1 gene under the control of the CaMV 35S promoter. The transgenic plants were shorter, greener in leaves, and had larger branch angles than wild-type (WT) plants. Transgenic plants also phenocopied WT plants grown under light condition depleted of far-red wavelengths. Furthermore, the reduction of growth by the expressed PHY-B1 transgene did not directly involve gibberellins. The commercial application of this biotechnology could provide an economic alternative to the use of chemical growth regulators, and thus reduce the production cost.
Anthocyanins are plant pigments that are in demand for medicinal and industrial uses. However, anthocyanin production is limited due to the harvest potential of the species currently used as anthocyanin sources. Rough bluegrass (Poa trivialis L.) is a perennial turfgrass known for accumulating anthocyanins, and may have the potential to serve as a source of anthocyanins through artificial light treatments. The objectives of this research were to determine optimal light conditions that favor anthocyanin synthesis in rough bluegrass, and to determine the suitability of rough bluegrass as a source of anthocyanins. When exposed to high-intensity white light, rough bluegrass increased anthocyanin content by 100-fold on average, and anthocyanin contents greater than 0.2% of dry tissue weight were observed in some samples. Blue light, at intensities between 150 and 250 μmol·m−2·s−1, was the only wavelength that increased anthocyanin content. However, when red light was applied with blue light at 30% or 50% of the total light intensity, anthocyanin content was increased compared with blue light alone. Further experiments demonstrated that these results may be potentially due to a combination of photosynthetic and photoreceptor-mediated regulation. Rough bluegrass is an attractive anthocyanin production system, since leaf tissue can be harvested while preserving meristematic tissues that allow new leaves to rapidly grow; thereby allowing multiple harvests in a single growing season and greater anthocyanin yields.
Determination of plant growth regulator accumulation in fruits and vegetables for human consumption is an important safety issue even when it is applied to seeds. Paclobutrazol accumulated preferentially in the seedcoats when soaking cucumber (Cucumis sativus L., cv. Poinsett 76SR) seeds in 1000 or 4000 mg·L–1 paclobutrazol. Cucumber plants grown from seeds soaked in 1000 mg·L–1 paclobutrazol had lower average fruit weights than the control plants. Individual fruit length in cucumber was reduced by 40% when seeds were soaked in 1000 mg·L–1 paclobutrazol solutions for 180 minutes. Soaking tomato (Solanum lycopersicum L., cv. Sun 6108) seeds in 0 to 1000 mg·L–1 paclobutrazol did not reduce average fruit weight or diameter per treatment. Paclobutrazol residue was not detected in cucumber and tomato fruits harvested from plants grown from seeds soaked in 1000 mg·L–1 paclobutrazol for 180 minutes. Soaking seeds in paclobutrazol solutions represents a promising method of applying plant growth regulators to tomato and cucumber without accumulation of paclobutrazol residue in fruits.
Decreased light quantity or quality affects the growth of turfgrass plants. Shade causes thinning of turfgrass stands and loss in surface quality. Plant changes include increased chlorophyll levels, lower soluble sugars, and loss of canopy cover. The objective of this research was to investigate if applications of foliar nitrogen and trinexapac-ethyl [4-(cyclopropyl-α-hydroxy-methylene)-3,5-dioxo-cyclohexane carboxylic acid ethyl ester] (TE) would result in beneficial biochemical changes in creeping bentgrass (Agrostis stolonifera L. cv. Penncross) grown in different shaded environments. Foliar applications of three nitrogen treatments, (NH2)2CO, Ca(NO3)2, or (NH4)2SO4, were made weekly at 0.43 g N/m2. Growth regulator treatments consisted of an untreated control or TE applied biweekly at an a.i. rate of 0.057 kg·ha−1. Plots were established in full sun (FS), neutral shade (NS), and deciduous shade (DS). Chlorophyll content, soluble carbohydrates, flavonoids, clipping yield, and color were measured. Nitrogen treatments caused some variation in levels of soluble carbohydrates in shaded conditions. Chlorophyll (Chl) levels varied between TE treatments, with increased levels of chlorophyll b (Chl b) found in TE-treated plots under FS. Application of TE resulted in higher flavonoid concentrations in leaf tissue in shaded conditions. Repeated applications of (NH2)2CO significantly improved color (P = 0.05). Turfgrass managers maintaining creeping bentgrass in shade may benefit from applications of TE and (NH2)2CO.
Height control is a major consideration during commercial production of chrysanthemum [Dendranthema×grandiflora Kitam. (syn. Chrysanthemum×morifolium Ramat.)]. We have addressed this problem by a biotechnological approach. Plants of `Iridon' chrysanthemum were genetically engineered to ectopically express a tobacco (Nicotiana tabacum L.) phytochrome B1 gene under the control of the CaMV 35S promoter. The transgenic plants were shorter in stature and had larger branch angles than wild type (WT) plants. Reduction in growth caused by the ectopic expression of the tobacco phytochrome B1 gene was similar to that caused using a commercial growth retardant at the recommended rate. Another morphological effect observed in the leaves of the transgenic plants was more intense green color that was related to higher levels of chlorophyll. The transgenic plants appeared very similar to WT plants grown under a filter that selectively attenuated far red wavelengths. Furthermore, when plants were treated either with gibberellin A3 (which promoted growth) or 2-chlorocholine chloride, an inhibitor of gibberellin biosynthesis (which inhibited growth) the difference in the average internode length between the transgenic plants and WT plants was the same in absolute terms. This suggests that reduction of growth by the expressed PHY-B1 transgene did not directly involve gibberellin biosynthesis. The commercial application of this biotechnology could provide an economic alternative to the use of chemical growth regulators, thereby reducing production costs.