Cell walls of lichens in sub-order Peltigerineae have much higher activities and a greater diversity of cell wall redox enzymes compared with other lichens. Possible roles of tyrosinases include melanization, removal of toxic phenols or quinones, and production of herbivore deterrents.

Chlorophyll fluorescence was used to study the effect of a hardening treatment on aspects of desiccation tolerance in the moss Atrichum androgynum. Mosses were hardened by reducing the relative water content of apical stem segments to 0.5 for 3 days, followed by storing the material fully hydrated for 1 day. Desiccation tolerance was assessed by storing plants over silica gel for 16 h, and then monitoring the recovery of photosystem II during rehydration. Hardening decreased the efficiency of photosystem II before desiccation, particularly at saturating light intensities. During rehydration, photosystem II activity recovered faster in hardened plants. Hardening also considerably increased non-photochemical quenching during the first few hours of rehydration. Previous data had shown that photophosphorylation, but not carbon fixation, is starting at this time, suggesting that the moss needs strong protection from excess light. Increased nonphotochemical quenching was the result of greater thylacoidal-based or fast-relaxing quenching (qE), rather than reaction centre-based or slow-relaxing quenching (qI). Slow-relaxing quenching was similar in hardened and non-hardened mosses, and was only important during the early stages of rehydration when the need for photoprotection was greatest. In A. androgynum hardening apparently shifts the photosynthetic apparatus from a 'high efficiency' state to a less efficient but 'photoprotected' state.

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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.