Silicon and Plant Growth

Abstract

INTRODUCTION More than a hundred years ago, Julius Sachs (53), one of the early pio­ neers of plant nutrition studies, asked in his article, Ergebnisse einiger neuerer Untersuchungen liber die in Pflanzen enthaltene Kieselsaure, the following questions: . . . whether silicic acid is an indispensable substance for those plants that contain silica, whether it takes part in the nutritional processes, and what is the relationship that exists between the uptake of sil­ icic acid and the life of the plant? These questions are still relevant today. A hundred years ago, however, the methods of plant physiology and bio­ chemistry were not well enough advanced to find a definitive answer to the questions that Sachs asked. He concluded on the basis of nutrition experi­ ments on Z ea mays and morphological observations made by Mohl (44) that . .. silicic acid is insignificant for the nutritional process of the maize plant. During the intervening years, many plant nutrition studies involving the use of water cultures have been made, and evidence both pro and con relative to Sachs' questions has accumulated. Today, the tendency of au­ thors of textbooks on plant physiology is to dismiss silicon as being of little importance in plant nutrition. For example, Epstein (12) in his chapter on mineral metabolism devotes only a single paragraph to silicon in higher plants, concluding, There seem to have been no physiological studies, like those with diatoms, that would throw light on the metabolic and biochemical .events resulting in these silica depositions in higher plants. On the other hand, if one surveys the published research appearing during the past 10 years, it is obvious that investigations seeking a possible role for silicon in plant nutrition are still continuing quite vigorously. Some rather new ap­ proaches have been tried and new data have been forthcoming which are certainly of interest, worth reviewing at this time, and which offer enough encouragement to make further investigations well worthwhile.