期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：1975
卷号：72
期号：3
页码：1107-1111
DOI：10.1073/pnas.72.3.1107
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：Gibberellic acid (10 {micro}M) causes lettuce hypocotyl cells to elongate by 400-500% more than water controls in 72 hr. Kinetic data indicate that whereas in water controls cell elongation occurs between 24 and 48 hr, in gibberellic-acid-treated material it starts at 8 hr and continues to 72 hr. Dry weight of the cell wall shows a corresponding increase with cell elongation. Two-hour pulse labeling with [14C]glucose, however, indicates a peak in the incorporation of label in the wall fraction at 8 hr, when growth has only just begun, and a progressive decline later, when elongation is occurring at maximum rate. The peak coincides with extensive dictyosomal activity, proliferation of endoplasmic reticulum and polyribosomes, and connections between the endoplasmic reticulum and plasmalemma in both water- and gibberellic-acid-treated hypocotyls. At later times, the cells contain only a thin layer of cytoplasm and no special cytological features are observed. These observations indicate that, although cell growth in lettuce hypocotyls is accompanied by wall synthesis, nevertheless the cells undergo their most rapid polysaccharide and protein synthesis prior to extension growth. They also explain the earlier reported "enhanced sensitivity" of lettuce hypocotyls to gibberellic acid application at 8 hr after the beginning of the experiment.
