Leaf Structure in Relation to Solute Transport and Phloem Loading

点击翻译按钮获取中文摘要

Two broad aims of this research are to determine (1) the pathways followed by sugars manufactured in the photosynthesizing cells (mesophyll cells) of the leaf to the food-conducting cells (sieve-tube members) of the leaf veins, and (2) the sites at which the sugars are actively secreted, or loaded, and unloaded in mature (source) and immature (sink) leaves, respectively. Detailed structural studies, with light and electron microscopes, are complemented by experimental studies, including localization of 14C-labeled sugars within the leaf by microautoradiography; plasmolysis studies designed to determine the solute (primarily sugar) concentrations of the various cell types; and the use of fluorescent dyes to determine whether substances move from cell to cell via cytoplasmic connection in their walls (symplastic movement), via the cell wall continuum (apoplastic movement), or a combination of the two. The results of these studies will be of long-term practical importance in relation to crop productivity and will be of great value to investigators interested in relations of viruses, insects, mycoplasmas, and other parasites, and in the movement of insecticides and growth regulating substances in cultivated plants. Barley, maize, and soybean, species to be studied, are economically important plants.