Restoration of photosystem II photochemistry and carbon assimilation and related changes in chlorophyll and protein contents during the rehydration of desiccated Xerophyta scabrida leaves

Abstract

Recovery of photosynthesis in rehydrating desiccated leaves of the poikilochlorophyllous desiccation-tolerant plant Xerophyta scabrida was investigated. Detached leaves were remoistened under 12 h light/dark cycles for 96 h. Water, chlorophyll (Chl), and protein contents, Chl fluorescence, photosynthesis–CO2 concentration response, and the amount and activity of Rubisco were measured at intervals during the rehydration period. Leaf relative water contents reached 87% in 12 h and full turgor in 96 h. Chl synthesis was slower before than after 24 h, and Chla:Chlb ratios changed from 0.13 to 2.6 in 48 h. The maximum quantum efficiency recovered faster during rehydration than the photosystem II operating efficiency and the efficiency factor, which is known to depend mainly on the use of the electron transport chain products. From 24 h to 96 h of rehydration, net carbon fixation was Rubisco limited, rather than electron transport limited. Total Rubisco activity increased during rehydration more than the Rubisco protein content. Desiccated leaves contained, in a close to functional state, more than half the amount of the Rubisco protein present in rehydrated leaves. The results suggest that in X. scabrida leaves Rubisco adopts a special, protective conformation and recovers its activity during rehydration through modifications in redox status.

Chlorophyll fluorescence imaging of photosynthetic activity and pigment contents of the resurrection plants Ramonda serbica and Ramonda nathaliae during dehydration and rehydration

“…3 and Table 2). Similar results were reported by Augusti et al (2001), Fv/Fm ratio of R. serbica was significantly decreased after RWC was 30-40 % and increased 24 h after rehydration. In addition, Péli et al (2005) showed that Fv/Fm ratio of H. rhodopensis decreased after 7-10 days of dehydration.…”

“…In addition, the RWC of R. nathaliae decreased from 94.5 % to 3.6 % during dehydration (Jovanoviç et al 2011). Kinetics of relative water content during dehydration-rehydration cycle was reported from other authors in R. serbica (Augusti et al 2001;Quartacci et al 2002;Veljovic-Jovanoviç et al 2006;Sgherri et al 2004) and Haberlea rhodopensis (Nagy- Deri et al 2011;Mihailova et al 2011;Djilianov et al 2011;Georgieva et al 2010).…”

“…In addition, Péli et al (2005) showed that Fv/Fm ratio of H. rhodopensis decreased after 7-10 days of dehydration. Restoration of Fv/Fm ratio after 24 h of rewatering was reported at other resurrection plant X. scabrida (Perez et al 2011). In leaves of B. hygrometrica, the Fv/Fm declined from about 0.8 to 0.4 with change in relative water content from 100 % to 1 % (Deng et al 2000), after that the values of Fv/Fm ratio almost restored to that of normal control leaves upon rehydration.…”

“…During rehydration, chlorophyll re-synthesis and their amounts gradually increased and returned to near control levels in fully rehydrated plants of R. serbica (Degl'Innocenti et al 2008;Augusti et al 2001), R. nathaliae (Jovanoviç et al 2011) and H. rhodopesis (Georgieva et al 2010;Péli et al 2012). According to our results and previous investigation from other authors (Drazic et al 1999;Augusti et al 2001;Markovska et al 1994), R. serbica and R. nathaliae plants may be included among homoiochlorophyllous desiccation-tolerant angiosperms because they retain most of their chlorophyll content during desiccation. Table 1 Photosynthetic pigments content (mg g -1 dry weight) of R. serbica and R. nathaliae species during dehydration and rehydration cycle Control plants (C), from plants in different stages of dehydration, after 7 days (D1), 10 days (D2), 14 days (D3) and 15 days (D4), and upon re-watering, after 6 (R1), 12 (R2), 24 (R3) and 48 (R4) hours.…”

“…Mean in each column followed by same letters are not significantly different at the P 0.05 by one-way ANOVA with Duncan's multiple range tests For the photosynthetic pigment contents changes were reported on other resurrection plants species following dehydration and rehydration cycle, Boea hygrometrica (Deng et al 2000), Craterostigma plantagineum (Scott 2000), Sporobulus stapfianus (Quartacci et al 1997), Boea hygroscopica (Navari-Izzo et al 1995), Xerophyta sp. (Sherwin and Farrant 1996;Farrant et al 2003;Perez et al 2011), Reaumuria soongorica (Xu et al 2008), H. rhodopensis (Nagy-Deri et al 2011).…”