Dormancy Associated with Repression of Genetic Activity.

Dormancy of buds and seeds is a well known and common phenomenon in the plant world. It is of interest because it has not yet become understandable. The dormant tissue has available to it by definition all of the environmental conditions of temperature, water supply, nutrition, etc., required for growth. The dormant tissue is alive, it respires, and in some cases grows very slowly in size (10). Yet a dormant tissue lies idle; it does not groNw normally. There is within the dormant tissue some factor or mechanism wlhiclh restricts growth and cell multiplication. Many physical and chemical factors are known which possess the ability to end dormancy in one or another tissue or organ. These factors include, for example, proper photoperiod, treatment with the appropriate temperature, application of gibberellic acid, application of ethylene chlorohydlrin, application of potassium thiocyanate, or thiourea, and in some cases, the mere passage of time. It is not immediately obvious that these dormancy-breaking factors possess any characteristic in common. Nonetheless, it is probable that there must be some point at which the mechanisms by which the several factors act upon dormancy merge, and play upon one or a few common facets of cell function. If we view the problem of dormancy within the framework of molecular biology, a hypothesis immediately suggests itself, namely, that in the dormant cell the genetic material is completely, or nearly completely, repressed. According to this hypothesis, the genetic material would be unable to express itself in the form of production of the messenger RNA which is essential to enzyme synthesis and hence to growth and metabolism. The present paper constitutes a first approximation analysis of whether the hypothesis of gene repression as the cause of dormancy is a tenable one. The method consists firstly in comparison of the rates of RNA synthesis by dormant and awakening buds, and secondly in comparison of the abilities of the chromatin of such buds to support DNA-depenclent RNA synthesis.