RESPIRATION OF THE RHIZOMES OF NUPHAR ADVENUM AND OTHER WATER PLANTS

NUMEROUS STUDIES have been made on the respiration of land plants and some on water plants, but very few such studies have been made on semi-submerged water plants (Samantarai, 1938). Yet, from the standpoint of the environment, semi-submerged plants offer very interesting material because of the belief that they were once terrestrial and have subsequently invaded the water, and because it is difficult to understand how the rhizomes of plants with terrestrial form are able to endure the condition of low aeration that exists in the mud at the bottom of a pond (Cole, 1932).2 That this ability is not due to particular structural features may be deduced from the fact that rhizomes of very diverse structures are found imbedded in the submerged mud. For example, Furthermore, the ability to endure the nearly anaerobic conditions of the submerged mud is not associated with a particular habit of growth and fruiting, because all of the species of thick spongy rhizomes mentioned above as well as one of the toughest and firmest of rhizomes to be found anywhere, namely, that of Scirpus validus, grow progressively through the mud, branching only occasionally, sending up fruiting culms at irregular intervals, and always dying and becoming decayed at the rear; while the hard young rhizomes of Typha latifolia and Sparganiurn eurycarpum and the corms of Sagittaria latifolia are formed one at the terminal end of each of the slender spongy stolons that radiate from a parent plant which dies at the end of its fruiting season.