CORTICAL AIR SPACES IN THE ROOTS OF ZEA MAYS L.

Abstract

S ACHS (I882) placed on record what seems to be first critical study of structures with which this investigation is concerned. He divided large air-filled lacunae found in many plants into two groups. One he held to be due to the splitting of partition wall (between cells) and growth of its now separated lamellae, while other arose from the cessation of growth of inner masses of tissue and their drying and splitting, while surrounding tissues continue to grow. De Bary (I884) applied adjectives schizogenetic and lysigenetic to two types, latter of which forms basis of present paper. References to air spaces and their probable value for aeration of tissues in water plants are scattered through literature, but comparatively few attempts have been made to extend our knowledge of their development beyond what is contained in Sachs's statement. Interest has not been entirely lacking, however, and a search of literature disclosed eight papers touching on this phase of subject. Norris (I9I 3) carried out a number of experiments, growing Zea Mays in various soils and water cultures. He found that air spaces were invariably present in water cultures, but were reduced in roots growing in porous soils, and from this concluded that the development of air spaces appears to depend largely upon quantity of air available in medium surrounding root. Hunter (I9I5), after investigating condition in Vicia Faba, suggested that boring action of lateral roots may be responsible for some of extensive system of air spaces found. Folsom (I9I8) reported that in roots of Ranunculus sceleratus amount of aerenchyma varied directly with water supply except in case of totally submerged plants. In R. abortivus roots it varied inversely with water supply except when plants grew under pronouncedly xerophytic conditions. Miss Snow (I920), working with Scirpus validus, was unable to influence production of air spaces consistently by variations in atmospheric pressure. Miss Dunn (I92I), working on Marquis wheat and White Dent corn grown in solution cultures, found cortical lacunae invariably appearing in roots. They were not observed in sand or soil cultures of wheat, either in summer or winter, but none of cultures was continued for more than thirteen days. In Indian corn, she invariably obtained cortical lacunae, and noted that time of appearance seemed to vary with rate of growth of roots. Stover (I928) published a research on roots of Zizania aquatica. He