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1. Photosynthetic electron transport at low temperatures in the green algal foliose lichens Lasallia pustulata and Umbilicaria hirsuta affected by manipulated levels of ribitol

Creator:
Hájek, J., Váczi, P., and Barták, M.
Format:
bez média and svazek
Type:
model:article and TEXT
Subject:
chlorophyll fluorescence imaging, freezing tolerance, photosystem II, and polyols
Language:
Multiple languages
Description:
In lichens, ribitol is known as a carbon storage compound, an osmotic agens involved effectively in cell compartments protection during dehydration of lichen thalli and as a cryoprotective compound. In our study, we investigated the effect of ribitol on photochemical processes of photosynthesis in foliose lichens [Lasallia pustulata (L.) Mérat., Umbilicaria hirsuta (Sw. ex Westr.) Hoffm.] at low temperature. The effects of three concentrations of ribitol, added externally to thalli segments on several chlorophyll (Chl) fluorescence parameters, were evaluated. The 72 h exposition to 8, 16, and 26 mM ribitol led to a concentration-dependent increase in FV/FM, decrease in non-photochemical quenching (NPQ) but no change in quantum yield of photosystem II photochemistry (ΦPSII) values at -5 °C). At higher temperature (0, +5 °C), no effect of ribitol addition on the photosynthetic parameters was apparent. and J. Hájek, P. Váczi, M. Barták.
Rights:
http://creativecommons.org/licenses/by-nc-sa/4.0/ and policy:public

2. Seasonal activity-profiles of enzymes involved in cryoprotectant biosynthesis in Pyrrhocoris apterus (Heteroptera: Pyrrhocoridae)

Creator:
Tollarová, Michaela
Type:
article, model:article, and TEXT
Subject:
Diapause, overwintering, metabolism, enzymes, polyols, Heteroptera, and Pyrrhocoris apterus
Language:
English
Description:
The activities of three enzymes involved in polyol biosynthesis (aldose reductase, AR; ketose reductase, KR; and polyol dehydrogenase, PDH) were studied in adult females of the linden bug, Pyrrhocoris apterus, collected from the field during 2005/2006. While the activities of three enzymes were low in reproductive females, activities greater by one or two orders were seen in reproductively arrested females. AR and KR showed similar seasonal trends in activity. Activities were low during diapause initation and later increased and stabilized during autumnal diapause development. Further increases of AR and KR activities were seen during low temperature quiescence and finally the activities sharply decreased during vernal resumption of direct development. The activity of PDH was relatively high (but fluctuating) during diapause, then decreased in quiescent insects and almost disapeared in reproductively active females. Insects collected in February were subjected to laboratory de-acclimation (exposure to high temperatures) followed by re-acclimation (exposure to low temperatures) which resulted in loss of activity in all three enzymes and no regain. High activities of AR, KR and PDH in reproductively arrested females thus conform well with their previously observed high capacity to synthesize and accumulate polyol cryoprotectants.
Rights:
http://creativecommons.org/publicdomain/mark/1.0/ and policy:public