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Desiccation‐time limits of photosynthetic recovery in Equisetum hyemale (Equisetaceae) spores
Author(s) -
Lebkuecher Jefferson G.
Publication year - 1997
Publication title -
american journal of botany
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.218
H-Index - 151
eISSN - 1537-2197
pISSN - 0002-9122
DOI - 10.2307/2445815
Subject(s) - photosynthesis , spore , desiccation , biology , photosystem ii , botany , chlorophyll fluorescence , horticulture
The chlorophyllous spores of Equisetum survive desiccation, yet cannot tolerate this quiescent state for more than ≈2 wk. The hypothesis that spore viability of Equisetum hyemale L. is limited by inhibition of photosynthetic recovery was tested using chlorophyll a fluorescence and oxygen‐exchange analyses. Experimental spores were desiccated at 2% relative humidity and 25 ° C for time periods of 24 h, 1 wk, and 2 wk, and then rehydrated at 200 μmol photons·m −−2 ·s −−1 (PAR) and 25°C for up to 24 h. Spores desiccated for 24 h recovered photosynthetic competence very rapidly during rehydration, reaching the O 2 compensation point in 6.3 ± 0.3 (X ± SE) min. Recovery of photosynthetic performance of spores desiccated for 1 wk was slower, as judged by significantly slower increases of (1) photochemical efficiency of photosystem (PS) II, (2) PS II quinone B ‐reducing center concentration, (3) quinone B −−2 concentration, (4) water‐oxidation activity, (5) rate of lightinduced O 2 evolution, and (6) apparent quantum yield of net O 2 exchange. Photosystem‐II and whole‐spore photosynthetic competence of 2‐wk desiccated spores was increasingly impaired, and did not recover during rehydration. Origin fluorescence yield and dark respiration were not affected by desiccation time following rehydration. The results suggest that the extremely short viability of disseminated spores of Equisetum hyemale is due to the inability to recover losses of water oxidation and photosystem II‐core function following 2 wk of desiccation.