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- Author or Editor: Hazel Y. Wetzstein x
Herbs have been long known to provide health-promoting benefits and are demonstrated to have antioxidant, anti-inflammatory, antibacterial, analgesic, and antitumor activities. This study evaluated the effects of drying conditions and extraction protocols on the biochemical activity of three culinary and medicinal herbs: rosemary (Rosmarinus officinalis), motherwort (Leonurus cardiaca), and peppermint (Mentha piperita). Leaf tissues were dried by sun, oven-dried at 40 °C, or oven-dried at 70 °C and extracted using 80% methanol or 80% ethanol. Total polyphenol (TPP) using the Folin-Ciocalteu reagent method and antioxidant capacity using the Trolox-equivalent antioxidant capacity (TEAC) assay were determined. Both drying and extraction conditions significantly impacted TPP content and TEAC in the three herb species. Sun-dried or 40 °C oven-dried herbs exhibited significantly higher TPP content and TEAC capacity than fresh samples, suggesting low-temperature drying may be a good postharvest means to store medicinal/culinary herbs. Exposure to 70 °C oven-drying caused significant antioxidant loss. In addition, the current study showed that with fresh tissue, 80% ethanol extraction had significantly higher TPP and TEAC than 80% methanol extraction for all three herbs, yet for dried herbs, the efficacy of ethanol/methanol extraction varied with different drying treatments.
Ozone is a highly oxidizing phytotoxic air pollutant, whose effects are documented to adversely affect crop growth and productivity. In contrast to the large body of published work investigating the effects of atmospheric ozone on outdoor agronomic and forestry crops, relatively few studies have addressed the effects of ozone exposure on greenhouse-grown crops. Outdoor concentrations of ozone can commonly attain concentrations in the 50–150 ppb range, which are known to detrimentally impact plant growth. The objective of this study was to characterize ozone exposure in commercial greenhouses as a prelude to the determination of dose–response effects on specific greenhouse crops and the development of ozone abatement methods, if appropriate. This study documented the levels and diurnal fluctuations in atmospheric ozone concentrations over two annual June–October “ozone seasons.” Measurements were taken every 10 min. for both indoor and outdoor ozone concentration, solar radiation, and temperature. Unexpectedly, indoor ozone concentrations often exhibited elevated levels that were 25% to 35% higher than outdoor concentrations, even in well-ventilated houses. These findings suggest that additional ozone production may occur within the greenhouse environment. Evaluations of causative factors and ozone effects on commercial crop production are warranted.
Zinc deficiency is a widespread nutritional disorder in plants and occurs in both temperate and tropical climates. In spite of its physiological importance, cytological and ultrastructural changes associated with zinc deficiency are lacking, in part because zinc deficiency is difficult to induce. A method was developed to induce zinc deficiency in pecan (Carya illinoinensis (Wangenh.) C. Koch) using hydroponic culture. Zinc deficiency was evaluated in leaves using light and electron microscopy. Zinc deficiency symptoms varied with severity ranging from interveinal mottling, overall chlorosis, necrosis, and marginal curving. Zinc deficient leaves were thinner, and palisade cells were shorter, wider, and had more intercellular spaces than zinc sufficient leaves. Cells in zinc deficient leaves had limited cytoplasmic content and accumulated phenolic compounds in vacuoles. Extensive starch accumulation was observed in chloroplasts. This work represents the first detailed microscopic evaluations of zinc deficiency in leaves, and provides insight on how zinc deficiency affects leaf structure and function.
Tomato (Lycopersicon esculentum Mill.) transplants can be affected by an intermittent physiological problem manifested by loss of apical meristem function and retarded growth rates, referred to herein as apical meristem decline (AMD). Production losses associated with this condition can be substantial. Similar abnormal and arrested development of the shoot apex has been observed in a number of other species, and referred to as blindness, budlessness, toplessness, blindwood, and bud abortion. A developmental study using scanning electron microscopy was conducted in `Agriset' tomato during an occurrence of AMD to evaluate and compare normal and afflicted plants. The AMD condition was associated with cessation of leaf primordia development and lack of flower initiation. The shoot apex of plants with AMD remained vegetative compared to normal plants which at the same age had well-differentiated flower primordia. No evidence of abortion, die back, or necrosis of the shoot apex was observed. The effects of mineral nutrient additions on symptom development varied with year. In year 1, N fertilization reduced the incidence of both AMD and retarded bud growth (i.e., the percentage of normal plants increased from 29% to 97% with N applications). Preplant applications of P, alone or in conjunction with CaCO3 and trace elements, also ameliorated AMD. In year 2, AMD was observed only at very low levels, i.e., 4% or less, and mineral nutrition had no apparent effect on AMD or normal plant number.
Georgia plume (Elliottia racemosa Muhlenb. ex. Elliott) is a rare deciduous shrub or small tree. It has sustained severe loss of habitat and its range is now restricted to a limited number of sites in the state of Georgia. Tissue culture protocols have been developed as a means to propagate and conserve this threatened species using leaf explants induced on medium supplemented with 10 μm thidiazuron (TDZ) and 5 μm indole-3-acetic acid (IAA). Bud-like clusters, elongated embryo-like protrusions, and shoot-like structures were produced from the leaf explants. Morphological and histological evaluations of cultures during induction and development were conducted using light microscopy of sectioned material and scanning electron micrography. Histology of explant tissues indicates that plant regeneration of Georgia plume occurs through a shoot organogenesis pathway that involves the formation of actively dividing meristematic regions originating in subepidermal cell layers that proliferate to form protuberances on the explant surface. Numerous well-formed shoot apical meristems with leaf primordia are produced, as well as fused shoot-like structures. Elongated, embryo-like structures had various degrees of shoot apex development. Evaluations of serial sections found that they lacked a defined root apex, and that basal portions were composed of parenchymatous files of cells with a broad point of attachment to the parent tissue. The lack of bipolarity and a root pole signifies that true somatic embryogenesis does not occur.
Stigma characteristics and morphology can be useful in taxonomic and phylogenetic studies, indicate relationships in stigma function and receptivity, and be valuable in evaluating pollen–stigma interactions. Problematic is that in some taxa, copious stigmatic exudate can obscure the fine structural details of the stigmatic surface. Such is the case for Citrus, which has a wet stigma type on which abundant exudate inundates surface papillae. The components of stigmatic surface compounds are highly heterogeneous and include carbohydrates, proteins, lipids, glycoproteins, and phenolic compounds. This study evaluated the efficacy of several pre-fixation wash treatments on removing surface exudate to visualize the underlying stigmatic surface. Wash treatments included various buffer solutions, surfactants, dilute acids/bases, and solvents. Stigmas prepared using conventional fixation methods in glutaraldehyde had considerable accumulations of reticulate surface deposits with stigmatic cells obscured. Pre-fixation washes containing solvents such as methanol, chloroform, and ethanol left accumulations of incompletely removed exudate and crystalline deposits. Alkaline water washes produced a crust-like deposit on stigma surfaces. Buffer washes left residues of plaque-like deposits with perforated areas. In contrast, excellent removal of stigmatic exudate was obtained with a pre-fixation wash composed of 0.2 M Tris buffer, pH 7.2, containing 0.2% Triton X-100 surfactant and allowed clear imaging of the stigma and surface papillae morphology. A central sinus and radially arranged openings on the stigmatic surface were clearly visible and shown for the first time using scanning electron microscopy (SEM).
Somatic embryogenic cultures of pecan (Carya illinoinensis) were induced on medium with either naphthaleneacetic acid (NAA) or 2,4-dichlorophenoxyacetic acid (2,4-D). Percent embryogenesis, embryo development, and subsequent performance were assessed. Cultures induced on medium with NAA were more zygotic-like, with a higher frequency of embryos that had well-defined shoot apices. In contrast, cultures induced with 2,4-D exhibited more extensive callusing and more fused and/or abnormal embryos. Adjustment of the auxin used during induction may be a means of obtaining higher quality embryos, that have higher rates of conversion into plants.
Pomegranate fruit is valued for its juice-containing arils and is consumed and marketed as whole fresh fruit, extracted arils, juice, syrup (grenadine), wine, teas, seed oil, and other products. Recent consumption has rapidly increased attributable in part to reported health benefits that include efficacy against coronary heart disease, atherosclerosis, cancer, hypertension, and infectious diseases. Within commercial orchards, the size of fruits produced can be quite variable even with trees of the same genotype grown under similar cultivation practices. Although pomegranates have been cultivated since antiquity, fruit attributes, particularly those related to size, are poorly defined. In this study, compositional changes in pomegranate fruits of the Wonderful cultivar, including volume and weight, aril weight and number, pericarp weight, seed weight, and juice/pulp content, were evaluated in fruits of variable sizes. Correlations between fruit characteristics were determined, and factor analysis established fruit and aril indices. Results indicated that because fruit volume, fruit weight, and total aril weight are closely correlated, any of these characteristics can be used as an indicator of fruit size. The number of arils per fruit was highly correlated with fruit size with larger fruit containing greater numbers of arils. This is in contrast to individual average aril weight, which showed no significant relationship to fruit size. Crop production strategies aimed at increasing aril numbers may be a means for obtaining larger fruit in pomegranate.
As a plant nutrient, nitrogen is the element in highest demand in terms of quantity and makes up about 2% to 3% of plant dry matter. In this study, we evaluated the effect of nitrogen source on plant growth and nutrient uptake in pecan (Carya illinoensis). Seedlings were hydroponically grown under three nitrogen nutrient regimes where the ratio of nitrate: ammonium was varied, i.e., 3:1, 1:1, and 1:3. High ammonium nutrition had an inhibiting effect on seedling growth. Plants grown under 1:3 (nitrate: ammonium) exhibited significantly lower biomass, decreased root/shoot ratio, and lower specific leaf weight than other treatments. Total nitrogen uptake on a dry weight basis was highest in the high ammonium treatment. In the equal molar treatment (1:1 nitrate: ammonium), plants exhibited preferential uptake of ammonium-form nitrogen. Ammonium-form nitrogen is generally used in pecan orchard practice. Our data suggest that further studies evaluating the effects of nitrogen source are warranted to determine if similar detrimental effects on pecan growth occur in the field. Such studies would be useful for optimizing current fertilization practices.
In almond [Prunis dulcis (Mill.) D.A. Webb.], fungicide sprays are required to prevent blossom blight, which can infect open flowers. Numerous studies have reported detrimental effects of agrochemical sprays on pollination, fruit set, and yield in tree fruit crops. However, effects of fungicides on pollen germination and growth in almond are little known, particularly those from recently developed active ingredients. In this study we evaluated the effects of commercial formulations of 10 fungicides on pollen germination and tube growth in almond using in vitro assays. Assays conducted at 1/100 recommended field rates (RFR) were effective in delineating differences in almond pollen sensitivity to different fungicides. Captan and azoxystrobin were the most inhibitory, with germination percentages of less than 1% of the no-fungicide control. Germination was not significantly affected by propiconazole and benomyl. Intermediate inhibitory effects on pollen germination were observed with ziram, cyprodinil, maneb, thiophanate-methyl, iprodione, and myclobutanil. In contrast to germination, tube growth was less affected by the presence of fungicide. In pollen that germinated, tube elongation was the same as in controls in five of 10 of the fungicides evaluated. Nonetheless, azoxystrobin and captan reduced tube elongation by ≈90%. Some fungicide treatments also influenced tube morphology. In the absence of field evaluation studies, in vitro germination data may provide insight on how specific chemicals may impact pollination processes and further guide in vivo studies, particularly in the case of new chemical formulations.