Cyclic electron flow (CEF) plays an important role in photoprotection for angiosperms under environmental stresses. However, no research has previously focused on the role of CEF in the photoprotection of ferns (Pteridophytes) which are more sensitive to drought and their water transport systems are not as efficient as those of angiospermsunder various environmental stresses.
Dr. Zhang Shibao of Xishuangbanna Tropical Botanical Garden (XTBG) and his colleagues used two tropical fern species (Microsorum punctatum and Paraleptochillus decurrens) to study the electron fluxes through both photosystem I (PSI) and photosystem II (PSII) under water stress and their leaf anatomies. They aimed at investigating the role of CEF in photoprotection under water stress and determining whether CEF stimulation is associated with leaf anatomy.
Microsorum punctatum and Paraleptochillus decurrens grow in limestone or montane forests (500–900 m elevation) in southwestern Yunnan Province, China. The former is a bark epiphyte or lithophyte while the latter grows mainly in soil and rarely on tree trunks. These two ferns have significantly different leaf anatomies that can influence their physiological adaptation to water stress. The researchers hypothesized that, although the two species share similar habitats, their differences in leaf anatomy would affect their responses to drought treatment.
The researchers measured the chlorophyll a fluorescence of photosystem II and P700 of photosystem I in the two tropical ferns at different intervals between the time that drought was introduced and re-watering began. They proposed that CEF would not be stimulated by such treatment because both species originated from tropical forests that are characterized by low levels of light.
Their results revealed that CEF has an important role in conferring photoprotection for both M. punctatum and P. decurrens under drought conditions. However, their differences in CEF stimulation are related to variations in their leaf structures, which directly influence their adaptability to water stress.
The study entitled “Differences in the stimulation of cyclic electron flow in two tropical ferns under water stress are related to leaf anatomy” has been published in Physiologia Plantarum, 147 (3): 283-295, DOI: 10.1111/j.1399-3054.2012.01657.x