Search Results
Abstract
Aqueous sprays of NH4F applied to ‘Early Improved Elberta’ peach trees significantly increased the % of abnormal fruits. Tissue firmness was increased on the dorsal side but decreased on the suture side. Suture tissues contained more F than dorsal tissues and both had higher F levels as the F spray concn increased. The climacteric of treated fruits was initiated before the untreated fruits at every sampling date where a climacteric occurred. Both malic and citric acids were decreased in the suture tissues of F treated fruits.
Abstract
Growth retardants [ancymidol (0.1-1.0 mg·liter−1), chlormequat (0.5-500 mg·liter−1), and paclobutrazol (0.1-1.0 mg·liter−1)] reduced shoot extension, promoted root initiation, and increased root weight in apple seedlings (Malus domestica Borkh ‘York Imperial’). The induction of root formation and increase in root weight were accompanied by a considerable increase in polyamine levels. Daminozide (0.1-250.0 mg·liter−1) and dikegulac (0.25-500 mg·liter−1) also inhibited apple seedling growth; however, these compounds did not promote rooting. Chemical names used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride); butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); 2,3:4,6-bis-O-(l-methylethylidene)-α-L-xylo-2-hexulofuranosonic acid (dikegulac); β-(4-chlorophenyl)methyl]-α-(l,l-dimethylethyl)-lH-1,2,4-triazole-l-ethanol (paclobutrazol).
Fruit of the cultivated strawberry (Fragaria ×ananassa Duchesne ex Rozier) are a good source of natural antioxidants, which play an important role in protecting human health. Antioxidant levels vary considerably among strawberry genotypes. The cultivated strawberry is a hybrid of two very different wild progenitor species: F. virginiana Mill. and F. chiloensis (L.) Mill. The progenitor species are valued by strawberry breeders as sources of novel traits, but have not been evaluated for antioxidant capacity or levels of antioxidant compounds. The objectives of this study are 1) to evaluate the antioxidant contents and antioxidant activities in representatives of F. virginiana and F. chiloensis in comparison with representatives of the cultivated strawberry species (F. ×ananassa), 2) to determine which strawberry compounds are most closely correlated with antioxidant capacity among these three species, and 3) to identify wild strawberry genotypes with high antioxidant activity and bioactive compounds for use in cultivar development. Fruit of 19 accessions from each of the three species, cultivated strawberry plus the two progenitor species (F. ×ananassa, F. virginiana, and F. chiloensis), were evaluated for levels of antioxidant capacity (oxygen radical absorbance capacity), total phenolics, total anthocyanins, ellagic acid, quercetin 3-glucoside plus quercetin 3-glucuronide, kaempferol 3-glucoside, kaempferol 3-rutinoside, p-coumaryl–glucose, pelargonidin 3-glucoside, pelargonidin 3-glucoside–succinate, cyanidin 3-glucoside, and cyanidin 3-glucoside–succinate. Fruit of the 13 accessions tested from the wild progenitor species F. virginiana had significantly higher antioxidant capacity, total phenolics, and total anthocyanins than did the fruit of three accessions tested from the cultivated strawberry F. ×ananassa, or the three accessions tested from the other wild progenitor species (F. chiloensis), and will be valuable as a source of parent material for developing more nutritious strawberry cultivars. The high correlation with antioxidant capacity, relative efficiency, and lack of genotype-by-year interaction in this study suggests that the measurement of total phenolics may be the better assay to use for the later selection stages in a strawberry cultivar development program. Of the evaluated F. virginiana accessions, NC 95-19-1, JP 95-1-1, CFRA 0982, NC 96-5-3, and RH 30 fruit were highest in antioxidant capacity and should prove useful toward development of strawberry cultivars with high antioxidant capacities.
Abstract
Pollen tube growth in styles of ‘d’Anjou’ pear (Pyrus communis L.) is largely dependent on prevailing temp. At 21°C the process was completed within 24 hr, while at 15.5° and 10° growth was completed by 72 and 120 hr respectively. The initial fruit development 14 days following pollination was greatly influenced by day temp (ranging from 13° to 23.4°) during an thesis.
Micropropagated plantlets of Gerbera jamesonii H. Bolus ex Hook. F. `Terra Mix', Nephrolepis exaltata (L.) Schott `Florida Ruffles', and Syngonium podophyllum Schott `White Butterfly' were inoculated with two vesicular-arbuscular mycorrhizal (VAM) fungi, Glomus intraradices Schenck and Smith and G. vesiculiferum Gerderman and Trappe. They were potted in three peat-based media to determine the effects of mycorrhizal peat substrate on acclimatization and subsequent growth of micropropagated plantlets under greenhouse conditions. Symbiosis was established between the three ornamental species and VAM fungi within 4 to 8 weeks of culture in the greenhouse, but not during acclimatization. Mortality of Gerbera and Nephrolepis mycorrhizal plantlets was reduced at week 8 compared to the noninoculated control. A peat-based substrate low in P and with good aeration improved VAM fungi spread and efficiency. Mycorrhizal substrates had a long-term benefit of increasing leaf and root dry weight of Gerbera and Nephrolepis. Mycorrhizal Gerbera plants flowered significantly faster than non-mycorrhizal plants.
Abstract
The physiology of dormancy in Lilium longiflorum ‘Ace’ was studied by determining the relationships between plant growth and composition and treatments such as bulb scale removal, cold treatment, field soil heating and chemical stimuli. Initiatory activity was continuous in the daughter bulb until its anthesis, but elongation of daughter axis leaves and internodes were normally inhibited until autumn. Inhibition of the daughter axis was high during the spring prior to anthesis of the mother, but progressively decreased following anthesis and disappeared completely by autumn. Balances of inhibitor-promoter growth substances were found in the bulb scales. Daughter scales were found to be the principal source of inhibitors. Treatments conducive to breaking dormancy included 40°F storage, GA3 treatment and field soil heating in early spring. Dormancy-breaking cold treatments were followed by changes in nitrogenous substances characteristic of dormancy removal in other species. The period of dormancy in the daughter portion of the lily bulb is of the correlated type and involves scale inhibition of axis elongation rather than initiatory activity in the apex.
Duration of growth is dependent on morphological events or changes in growth rate. It is the latter that is associated with phasic development. The most productive phase of plant growth is the linear or constant rate phase, primarily because it endures longer than the exponential phase. The purpose of our research was to objectively determine the true tree-height growth pattern, the linear and stationary phases of height growth, and to mathematically derive the maximum slope (maximum growth rate) of the growth curve, its location (inflection point), and the maximum slope of the logarithmic form (maximum relative growth rate) of the growth curve. The data were composed of 333 tree-height records covering 240 years from 200 beechwoods in the U.K. Height-age data were fitted using a splined function (S) and the Chapman-Richards function (CR). The growth curve and critical points on the curve were derived from the CR model. The linear phase began when trees were 9 and lasted 43 years. However, the stationary phase did not begin until age 162. Anecdotal evidence suggests that very little fruiting occurs before age 50. Based on derived critical points and anticipated source-sink dynamics, the reproductive stage should have taken place during the progressive “deceleration phase” when trees were between 31 (location of the maximum slope, also inflection point) and 162 (from quadratic root). The linear phase ended at 52 years, (coinciding with minimum acceleration) and may prove a more accurate estimate than 31. Maximum slope was 1.2 m per year occurring at age 31. Maximum slope of the log curve was 0.14 m·m–1 per year. The advantage of the CR function and the importance of the derived quantities and growth phases will be discussed.
Abstract
Apple trees (Malus domestica Borkh. ‘Spartan’ grafted on MM 106 rootstock) planted in 1976 in an orchard at Beltsville, Md., were treated with paclobutrazol a gibberellin biosynthesis inhibitor, in Spring 1982 and again in 1983. In 1982, paclobutrazol [50 wettable powder (WP)] was applied as a foliage spray on 4, 14, and 25 May 1982, at 333 mgliter−1. On 27 Apr. 1983, trunks of these trees were painted with 75 g·liter−1 of paclobutrazol. Paclobutrazol did not inhibit shoot growth in 1983 but it retarded the shoot growth significantly during 1984. The carbohydrate content of paclobutrazol-treated wood was generally higher at all sampling dates from the winter dormant period through growth resumption in the spring. Negative correlation coefficients were found between starch and soluble carbohydrates in the wood during the winter sampling dates, whereas positive correlation coefficients were evident during the spring growth resumption period. The increase in carbohydrates induced by the treatment was similar in both years, when growth was not inhibited (1983) or inhibited (1984), indicated that paclobutrazol has an effect on carbohydrate metabolism as well as growth. Chemical name used: β-[(4-chlorophenyl)methyl]-α-(l,l-dimethylethyl)-1H-1,2,4-triazole-1 -ethanol (paclobutrazol).
An increase in ascorbic acid, reduced form of glutathione (GSH), total glutathione, total non-protein thiol (NPSH) and non-glutathione thiol (RSH) occurred as a result of induction by thidiazuron during bud break, whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased during the same period. Thidiazuron also enhanced the ratio of GSH/GSSG, and activities of catalase, superoxide dismutase (SOD), ascorbate free radical reductase (AFR), ascorbate peroxidase (POD), dehydroascorbate reductase (DHAR), ascorbate oxidase (AAO), and glutathione reductase (GR). The ascorbic acid content and the activities of catalase, SOD, AFR, POD, AAO, and DHAR peaked when buds were in the side green or green tip stage just prior to the start of rapid expansion, and declined thereafter. The GSH, NPSH, RSH, ratio of GSH/GSSG, and activity of GR increased steadily during bud development.
Abstract
A study of shoot apex size and initiatory activity in August-harvested ‘Ace’ bulbs following 0, 6, and 18 weeks vernalization at 40°F showed negetative correlations between leaf and flower number and length of vernalization treatment, and between apex size and this cold treatment. Growth acceleration as reflected in earlier shoot emergence, internode elongation and rapid leaf unfolding was evident following 6 weeks’ 40°F storage, but prolonged (18 weeks) treatment drastically reduced subsequently initiatory activity and rate of leaf unfolding.