RESUMO
The phenomenon of activation of cell proliferation in the quiescent center of excised maize roots is described. The root tips were grown on wet filter paper in Petri dishes. This phenomenon was observed in 8 to 14 maize cultivars and was absent in excised Arabidopsis root tips. The distribution of mitoses in meristems greatly varied in roots of individual seedlings from the same seed lot and seedlings of different cultivars. Meristem opening was observed after the removal of small root tips not longer than 3 mm and intact seminal roots. Sucrose (2%) and 10(-6)-10(-8) M indole-3-acetic acid did not prevent meristem opening. These findings indicate that the state of quiescent center is maintained by a system of intercellular and interorgan relations, which are to be clarified.
Assuntos
Divisão Celular/fisiologia , Raízes de Plantas/citologia , Raízes de Plantas/metabolismo , Zea mays/citologia , Zea mays/metabolismo , Arabidopsis/citologia , Arabidopsis/metabolismoRESUMO
It is shown that when small rats are early (beginning with the 18th day of life) given semisynthetic diets the reactions of the pancreatic and intestinal enzyme systems become nonspecific, and they are expressed in a rise of both proteolytic and carbohydrase activities, regardless of the content of proteins or carbohydrates in the diet. This reaction is of stress nature, and the hypothalamo-hypophysial-medullar system participates in its realization. During further maintenance of the small rats on special diets (30 days) it is recorded that the enzyme spectrum corresponds to the diet composition: when the protein diet is used proteolytic enzyme activity prevails, while in case of carbohydrate diets enzyme activities of pancreatic and enteral carbohydrases predominate. A conclusion has been made that under conditions of early semisynthetic feeding the adaptation of the digestive system to the food content is first realized through the mechanisms of hormonal regulation, and then--the substrate one.
