Effects of sterilization with calcium hypochlorite and of low oxygen pressures

Abstract

The greater part of the work deals with the effects produced by reduction of the oxygen pressure in the atmosphere surrounding seeds kept in germinative conditions. This was studied with the view to the establishment of correlations between the value of the minimum oxygen pressure necessary for germination and 1) the nature of the food reserve or 2) the extent of aeration of the soil of the usual habitat. After the trial of several forms of apparatus the 'continuous-current. method was adapted to the needs of this problem. Atmospheres with reduced oxygen pressures were obtained by introducing oxygen, produced electrolytically, into a stram of nitrogen supplied from a cylinder. The seeds used in the investigations combined some of the following characteristics:- 1) Presence of absence of endosperm. 2) Carbohydrate or oil as food-reserve. 3) Soil of habitat usually stiff and poorly-aerated or light and well aerated. The results indicate that high minimum oxygen values may be expected for seeds storing oils and usually growing in well- aerated soils whilst low minima are connected with the storage of carbohydrates and the usual occurrence in badly aerated soils. Whilst working on the above it was found necessary to sterilize the seeds. The method recommended by Wilson (A.J.B.1915) was used; but bleaching powder is a strong oxidizing agent and its action upon seed reserves might affect the rate of germination of seeds sterilized in this way. Accordingly a section of the paper embodies attempts made to solve this problem and to determine whether a solution of the specified strength is capable of any action upon the oils stored in seeds. The results indicate a slight stimulatory effect upon the rate of germination of seeds storing oils after sterilization for short periods of time and that such a solution does net react with some classes of oils found stored, in seeds.