The Use of Seeds with Low Content of Trace Elements in Studies on Essentially of Micro-nutrients

A recent contribution by MEAGHER et al. (2) has pointed out that there is a relatively large accumulation of molybdenum in normal seeds, and as a consequence, it is necessary to produce a special crop of seeds low in molybdenum in order to demonstrate molybdenum deficiency in the growing plant. Similar observations regarding other trace elements in seeds were made at the Biochemical Institute in Helsinki in the 1930's. It was emphasized, in connection with these observations, that it is important to produce seeds relatively low in trace elements in order to demonstrate the effect of micronutrient deficiency in experimental plants. Since these results are largely unknown they will be reviewed in brief. In 1940 VIRTANEN and v. HAUSEN (3) reported on a series of experiments carried out over several years in order to find out how the organic substances present in the soil affect the growth of the pea during several generations. The uninoculated pea plant was grown in a 1.5-liter Erlenmeyer flask in sterile culture system in the nutrient solution of Hiltner (made up with tap water), with Ca (NO3)2 as the nitrogen source. The volume of the nutrient solution was 1.5 liters with a pH 6.1 to 6.7. The variety of pea was Torsdag (Svalof). Two parallel series were grown. In series A the above-mentioned nutrient solution was used without any additions; in series B 200 gm. of airdried garden soil was added to each flask. During the first experimental period the growth was good in both series. The next period, when seeds from the plants of the first experimental period were used, gave a quite different result. In series A the growth of the pea was poor and no seeds developed, whereas in series B the growth was good. Even during the second experimental period a good growth could be induced in the series A when the nutrient solution was supplemented with the ash obtained from the burning of the garden soil used for series B. The growth remained good throughout six successive experimental periods between 1935-1937; in each case the seeds obtained were used for the following experimental period. The results revealed that the normal seeds produced in agriculture obviously contained mineral substances which made relatively good growth of plants possible in nutrient solutions not containing the necessary trace elements in sufficient quantities to ensure normal growth. Only by growing plants in nutrient solutions deficient of trace elements was it possible to produce seeds which themselves were low in trace elements. Such seeds responded sharply to the lack of trace elements in nutrient solutions.