Leaf Structure in Relation to Solute Transport and Phloem Loading

本研究的两个主要目的是确定(1)叶片光合细胞（叶肉细胞）制造的糖到叶脉的食物传导细胞（筛管成员）的途径，以及(2)糖在成熟（源）和未成熟（汇）叶片中分别活跃分泌或装载和卸载的位置。通过光学和电子显微镜进行详细的结构研究，辅以实验研究，包括通过显微放射自显影术定位叶片内14c标记糖；质解研究旨在确定各种细胞类型的溶质（主要是糖）浓度；并使用荧光染料来确定物质是通过细胞壁内的细胞质连接（共塑运动），还是通过细胞壁连续体（胞外运动），或两者的结合在细胞间移动。这些研究的结果将对作物生产力具有长期的实际重要性，对研究病毒、昆虫、支原体和其他寄生虫的关系，以及杀虫剂和生长调节物质在栽培植物中的运动感兴趣的研究人员具有重要价值。大麦、玉米和大豆是经济上重要的植物。

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.