Little is known about the microscopical symptoms of roots from apple trees suffering from replant disease. Roots were sampled from healthy trees and from such diseased trees in four orchards from May until October. Roots were stained for the detection of mycorrhizal infection and other roots were fixed, dehydrated, embedded in paraffin, sectioned, and stained in safranin and fast green in order to elucidate morphological details. Healthy tree roots possessed considerably higher frequencies of mycorrhizal infection than diseased trees during the entire growing season. Arbuscules and hyphae were very common, vesicles were sometimes present, and possible chlamydospores of Glomus radiatum (Thaxter) Gerd. & Trappe were found in several samples. Whereas roots from healthy trees were structurally intact, roots from declined trees had extensive sloughing away of the epidermal and cortical layers and the cortical cells possessed significant amounts of densely stained material. Nematodes and possible hyphae of Rhizoctonia, Phytophthora, and Pythium were found in roots of declined trees. Althugh the stele of these roots appeared unaltered, hyphae were sometimes observed in the vascular elements.
High concentrations of aluminum in low pH soils are toxic to sugarbeet (Beta vulgaris L.). In a test to determine the effect of increased concentrations on seedling development, 4, 8, and 12 ppm Al nutrient culture caused significant reduction of root and hypocotyl growth. The primary root curved and the root cap broke away. Lateral roots emerged as small outgrowths on the primary root axis and developed abnormally. Anatomical examination of primary and lateral roots revealed extraneous material in the apical meristem, root cap, and cortical region. Apical regions of the primary and lateral roots did not exhibit their typical organization and cells divided in an irregular pattern. Aluminum can be an important factor in the suppression of sugarbeet growth in acid soils.
A study was made of the ontogeny of the achene of Polygonum pensylvanicum L. from fertilization to maturity. The proembryo is classified as the Polygonum Variation, Asterad Type. Cotyledons are initiated three days after anthesis, and by the fifth day procambium is present in the embryo axis. At approximately seven days after anthesis, the embryo begins to curve and occupy a marginal position in the ovary. By ten days the first foliage leaf primordium is initiated at the stem apex of the embryo. At maturity the embryo consists of two cotyledons, a plumule composed of the stem apex and one leaf primordium, and a hypocotyl with a well‐developed radicle. Endosperm nuclei begin to divide before the first division of the zygote. Cell wall formation begins in the endosperm at the micropylar end of the embryo sac and proceeds toward the chalazal region. By the fifth day the endosperm is completely cellular, except for a basal projection; and a peripheral meristem has been established. At approximately ten days the peripheral meristem ceases periclinal cell division and becomes the aleurone. At the time of fertilization the ovary wall has its full complement of cell layers. The walls of the outermost cells elongate and become convoluted. Subsequent thickening and lignification of these cell walls produce the hard epicarp of the mature achene.
Early attempts to cultivate the sugarbeets (Beta vulgaris L.) in Maine were not successful due to large amounts of soluble Al in acid soils. The objectives of this study were to determine if a differential tolerance to Al exists among sugarbeet cultivars grown world‐wide, and whether such tolerance could be detected in early stages of seedling growth by examination of morphological and anatomical structures. All cultivars were grown in culture solutions of 0 and 4 ppm of Al at pH 4.8. Four parts per million was used because this concentration in culture solution was toxic to cultivar IS 922, a cultivar previously grown on a commercial basis in Maine. After 10 days growth, some cultivars exhibited more tolerance than others. This study concentrated on eight cultivars of the 116 originally tested. Cultivar IS 922 was used as the control; two cultivars were chosen for low tolerance, and five for their high tolerance to Al toxicity. At 0 ppm of Al, all cultivars showed normal anatomical and morphological development. At 4 ppm of Al, the two most susceptible cultivars accumulated large amounts of aluminum phosphate. The meristematic zones of primary and lateral roots of these plants lost their normal pattern of organization and further growth appeared inhibited. Variability existed within each of the five cultivars chosen for their apparent tolerance, some plants accumulated aluminum phosphate and others did not. This study indicated that differential tolerance to Al exists among sugarbeet cultivars, and among individual plants within the same cultivar. Tolerance can be determined at early developmental stages.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.