Leaf Structure in Relation to Solute Transport and Phloem Loading

这项研究的两个主要目的是确定(1)叶片的光合作用细胞(叶肉细胞)中产生的糖进入叶脉的食物传导细胞(筛管构件)的途径，以及(2)在成熟(源)和未成熟(库)的叶片中糖分别活跃地分泌或加载和卸载的位置。结合光学和电子显微镜进行详细的结构研究，并辅之以实验研究，包括通过显微放射自显影定位14C标记的糖在叶片内的位置；旨在确定各种类型细胞的溶质(主要是糖)浓度的质裂研究；以及使用荧光染料来确定物质是通过细胞壁中的细胞质连接在细胞之间移动(共体移动)，还是通过细胞壁连续体(质外体移动)或两者的组合移动。这些研究的结果将对作物生产力具有长期的实际意义，对于对病毒、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将具有重要价值。大麦、玉米和大豆是重要的经济作物，有待研究。

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.