COMPARATIVE MEASURES OF DESICCATION-TOLERANCE IN THE TORTULA-RURALIS COMPLEX .1. VARIATION IN DAMAGE CONTROL AND REPAIR

A mechanism for desiccation-tolerance in bryophytes based on carbon balance, damage limitation, and cellular repair is proposed. These criteria are incorporated into an experimental framework to measure desiccation-tolerance comparatively. In this report we utilize measures of damage control and damage repair to determine relative differences in tolerance between populations of three tolerant moss species: Tortula caninervis, T. ruralis, and T. norvegica. The measurement of damage control by electrolyte leakage alone was demonstrated not to be useful in determining levels of tolerance by traditional criteria in these closely related and highly tolerant species. Measurement of protein synthetic differences between hydrated and desiccated-rehydrated treatments was used to distinguish between the capabilities of the three moss species to repair cellular damage and to formulate a measure of tolerance. The overall ranking of the three species in descending order of tolerance is calculated to be: Tortula caninervis, T. ruralis, and T. norvegica. However, individual populations of each of these species exhibit variation in tolerance levels that span this broader classification. These rankings correlate well with the perceived ranking of water stress in the species' natural habitat.