A study of photosynthesis and leakage of solutes in relation to the desiccation effects in bryophytes

Abstract

Photosynthesis and the phenomenon of leakage have been studied in bryophytes Porella platyphylla (L.) Lindb., Plagiochila asplenioides (L.) Dum., Plagiothecium undulatum (Hedw.) B. & S., and Scapania undulata (L.) Dum. which were collected from habitats subjected to a wide range of moisture stresses. The percentage decrease in photosynthesis has been used as a measure of desiccation injury and the desiccation resistance has been denoted as number of days in which a particular injury level occurred. In all the species the rate of leakage reached the highest value in the first 2 min of re wetting, and the slowed down. Such reduction of leakage with time is believed to be due to the reassemblage of membrane structure, which results in a return of normal semipermeability, or to the rapid decrease of solutes in dead or injured tissues that occurs after rewetting. The solutes in the leachate are found to be reabsorbed by the viable cells. The leakage from viable tissues is likely to be due to the shock resulting from sudden immersion of desiccated shoots into water, while in injured or dead cells it is due to the disruption of membranes. The physiological and ecological implications of the leakage phenomenon are also briefly discussed.