THE EFFECT OF DESICCATION ON SUBSEQUENT ASSIMILATION AND RESPIRATION OF THE BRYOPHYTES ANOMODON VITICULOSUS AND PORELLA PLATYPHYLLA

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Summary

Anomodon viticulosus (Hedw.) Hook. & Tayl. and Porella platyphylla (L.) Lindb. show evidence of a consistent pattern in the course of net assimilation following moistening after various periods of desiccation. In the early stages of desiccation (up to 22 days at 50% RH in Anomodon viticulosus; up to 60 days in Porella platyphylla), recovery is rapid and apparently complete within c. 3–4 hours. After longer periods of desiccation the net assimilation rate is initially negative, but becomes positive after lengths of time increasing progressively to several days. This is partly a consequence of delayed (and probably incomplete) recovery of photosynthesis, and partly of an enhanced initial rate of respiration. After prolonged desiccation (more than 70 days) respiration in Anomodon viticulosus builds up to very high values over a period of about 24 hours following moistening and then falls to more normal levels, but subsequent recovery is problematical.

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