Comparative Study on the Changes in Photosynthetic Activity of the Homoiochlorophyllous Desiccation-Tolerant Haberlea Rhodopensis and Desiccation-Sensitive Spinach Leaves During Desiccation and Rehydration

Abstract

The functional peculiarities and responses of the photosynthetic system in the flowering homoiochlorophyllous desiccation-tolerant (HDT) Haberlea rhodopensis and the non-desiccation-tolerant spinach were compared during desiccation and rehydration. Increasing rate of water loss clearly modifies the kinetic parameters of fluorescence induction, thermoluminescence emission, far-red induced P700 oxidation and oxygen evolution in the leaves of both species. The values of these parameters returned nearly to the control level after 24 h rehydration only of the leaves of HDT plant. PS II was converted in a non-functional state in desiccated spinach in accordance with the changes in membrane permeability, malondialdehyde, proline and H(2)O(2) contents. Moreover, our data showed a strong reduction of the total number of PS II centers in Haberlea without any changes in the energetics of the charge recombination. We consider this observation, together with the previously reported unusually high temperature of B-band (S(2)Q(B)-) emission of Haberlea to reflect some specific adaptive characteristics of the photosynthetic system. As far as we know this is the first time when such adaptive characteristics and mechanism of the photosynthetic system of a flowering HDT higher plant is described. These features of Haberlea can explain the fast recovery of its photosynthesis after desiccation, which enable this HDT plant to rapidly take advantage of frequent changes in water availability.

Changes in chloroplast morphology of different parenchyma cells in leaves of Haberlea rhodopensis Friv. during desiccation and following rehydration

“…The photosynthesis was one of the latest physiological processes switched off by plant organization during dehydration, thus the chloroplast should be active and provide the energy the plant needed for protection under stress condition. Our previous investigations showed that similarly to chlorophyll content, the photochemical activity of PSII significantly decreased when leaf water content was reduced more than 70% (Georgieva et al 2005(Georgieva et al , 2007. Moreover, the integrity of thylakoids was preserved and the amount of chlorophyllprotein complexes hardly changed during desiccation (Georgieva et al 2007(Georgieva et al , 2009.…”

Photosynthetic activity of homoiochlorophyllous desiccation tolerant plant Haberlea rhodopensis during dehydration and rehydration

“…In addition a part of these centers was less susceptible to DCMU (Peeva and Maslenkova 2004). These features as well as the strong reduction of the number of active PSII centers performing S 2,3 Q B ¡ charge separation during desiccation without any changes in the energetic of the charge recombination in the rest operating centers were considered to indicate modiWcations of the redox properties of Q B (Georgieva et al 2005) related to desiccation tolerance of Haberlea. It is reasonably to suggest these modiWcations to favor S 2 Q A ¡ charge recombination under desiccation.…”

“…Our previous study was performed on detached leaves subjected to rapid desiccation in the dark (Georgieva et al 2005). The data showed a strong reduction of the total number of PSII centers in Haberlea during desiccation without any changes in the energetic of charge recombination, suggesting the involvement of a protective mechanism related to desiccation tolerance that could be speciWc for this resurrection species.…”

Increased Thermostability of Thylakoid Membranes in Isoprene-Emitting Leaves Probed with Three Biophysical Techniques

“…It has been shown that the peak temperature of B band increases in stress-tolerant photosynthetic organisms; for example in thermophilic cyanobacteria or desiccation-tolerant species (Govindjee et al, 1985;Sass et al, 1996;Maslenkova and Homann, 2000;Peeva and Maslenkova, 2004). It has also been shown that stresses do not affect the energetic levels of the stabilized S 2 Q B 2 charge pairs in stress-tolerant plants (Sass et al, 1996;Georgieva et al, 2005).…”