Studies of the Mechanism of the Physiological Effects of Certain Mineral Salts in Altering the Ratio of Top Growth to Root Growth in Seed Plants

poor'' soil untreated, in others he added stable manure ranging from 5,000 p.p.m. to 50,000 p.p.m.! He drew the conclusion from his work that variation in tops is correlated with the number and length of lateral roots.He found that poor soil inhibits growth of lateral roots and also brings on a premature aging of the cortical cells, both of which conditions inhibit the intake of water.He thus explains the dwarfing of tops in his " poor''-soil plants largely on the basis of an inadequacy of water.Soil cultures are not wholly comparable to water cultures, yet the poverty of certain mineral nutrients in water cultures will bring about a lowered ratio of tops to roots, as Livingston found in his "'poor''-soil experiments, and in such case there is no evidence that a deficiency of water supply is afactor.Ina soil devoid of nutrients, there would be, undoubtedly, retardation of the growth of both tops and roots.Harris (12), working in 1913 at Cornell University, sought to determine to what extent the ratio of tops to roots in certain plants is affected by moisture, plant food, and age.He grew plants in aqueous extracts of soil and in sand in which moisture and fertilizer were controlled.His results indicate that all three factors considered in the experiment influence the ratio of tops to roots in a positive way.His experiments with plants grown in solution and in soil, while in no way conclusive as to the relative parts played by moisture and fertilizer in altering ratios of tops to roots, are very suggestive.A brief table (table 1) of some of his results will bring out very well the conclusions.1 P.p.m. = parts per million.Oct., 10922!TURNER -EFFECTS OF CERTAIN MINERAL SALTS AU].TABLE.I Ratio of Tops to Roots Fertilizer Treatment Moisture in Soil at Maturity (Wheat) INIGIS 2G Sean Soe nn ae sd beara aettexs 30%) 8.1 21 ENKI MEH tis Welt cce.rote She kare one Wt ae E50 2 eo COTM SCSI RAY se oye nV yh oF aE a dd Weil tans 30% 'Sie Wonnpletes as Gad t Pleo PhS is wk 15% Age i Complete with high nitrogen ............ 30% 9.8551 Complete with high nitrogen ........... TS o/e 2.9 21It will be seen from table 1 that fertilizer and moisture appear to increase the ratio of tops to roots, but that the fertilizer factor pee apparently a small rdle in comparison with moisture.More or less recently three workers, Tottingham (31), Brenchley (2), and Stiles (29), employing nutrient solutions, have given considerable attention to the relative behavior of tops and roots of plants growing in solutions.But such attention as was given was only a side issue and not Turner, Thomas Wyatt.1922."Studies of the mechanism of the physiological effects of certain mineral salts in altering the ratio of top growth to root growth in seed plants."