AUTHOR=John Susan P. , Hasenstein Karl H. 

TITLE=Desiccation Mitigates Heat Stress in the Resurrection Fern, Pleopeltis polypodioides

JOURNAL=Frontiers in Plant Science

VOLUME=Volume 11 - 2020

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.597731

DOI=10.3389/fpls.2020.597731

ISSN=1664-462X

ABSTRACT=Although heat and drought stresses often coincide, the response to heat especially in desiccation tolerant plants is rarely studied. We subjected hydrated Pleopeltis polypodioides fronds to temperatures up to 50 °C and dehydrated fronds up to 65 °C for 24 hrs. The effect of heat stress was evaluated using morphological changes, PS II efficiency and metabolic indicators. Pinnae of dried fronds exposed to more than 40 °C curled tighter and became brittle compared to fronds dried at lower temperatures. Exposure to > 50 °C lead to discolored fronds after rehydration. Hydrated fronds turned partially brown at > 35 °C. Chlorophyll fluorescence and quantum yield (Qy) increased following re-hydration but the recovery process after 40 °C treatment lasted longer than at lower temperatures. Similarly, hydrated fronds showed reduced Qy when exposed to > 40 °C. Dried and hydrated fronds remained metabolically active up to 40 °C. Hydroperoxides and lipid hydroperoxides in dried samples remained high up to 50 °C, but decreased in hydrated fronds at > 40 °C. Catalase and glutathione oxidizing activities remained high up to 40 °C in dehydrated fronds and up to 35 °C in hydrated fronds. Major fatty acids detected in both dehydrated and hydrated fronds included palmitic (C16:0) and stearic (C18:0) acids, oleic (18:1), linoleic (C18:2); and linolenic (C18:3) acids. Linolenic acid was most abundant.  In dried fronds, all fatty acids decreased at > 35 °C. The combined data indicate that the thermotolerance of dry fronds is about 55 °C but is at least 10 °C lower for hydrated fronds.