C 3 Photosynthesis in the Gametophyte of the Epiphytic CAM Fern Pyrrosia longifolia (Polypodiaceae)

Abstract

Sporophytes of some epiphytic species in the fern genus Pyrrosia exhibit Crassulacean acid metabolism (CAM), generally considered to be a derived physiological response to xeric habitats. Because these species alternate between independent sporophytic and gametophytic generations yet only the sporophyte has been characterized physiologically, experiments were conducted to determine the photosynthetic pathways present in mature sporophytes, immature sporophytes, and gametophytes of Pyrrosia longifolia. Diurnal C0 2 exchange and malic acid fluctuations demonstrated that although the mature sporophytes exhibited CAM, only C 3 photosynthesis occurred in the gametophytes and young sporophytes. Consideration of the above results and those from previous studies, as well as the life cycle of ferns, indicates that the induction of CAM probably occurs at a certain developmental stage of the sporophyte and/or following exposure to stress. Elucidation of the precise mechanisms underlying this C^-CAM transition awaits further research.

trnL-F is a powerful marker for DNA identification of field vittarioid gametophytes (Pteridaceae)

“…In another case, although the gametophyte Wade1694 was identified as A. parvulum, it could be another case of an independent gametophyte of an unknown Antrophyum species due to the extent of its sequence variation. In congruence with previous studies, these observations imply that gametophytes have a greater tolerance for environmental stresses such as desiccation and low temperatures than do their counterpart sporophytes (Martin et al, 1995;Watkins et al, 2007;Farrar et al, 2008;Watkins and Cardelu ´s, 2012).…”

Contribution of fern gametophytes to the growth of produced sporophytes on the basis of carbon gain

“…Friend (1975) reported that the maximal photosynthetic rate of Cibotium glaucum at 25°C was 0.16 µmol CO 2 g -1 s -1 . Hagar and Freeberg (1980) and Martin et al (1995) reported that the rate of Todea barbara at 22°C was 0.03 µmol CO 2 g -1 s -1 and 0.057 µmol CO 2 g -1 s -1 for Pyrossia longifolia (these units are converted), respectively. The respiration rate was also reported by Hagar and Freeberg (1980) and Martin et al (1995).…”

“…Many studies have been carried out on the photosynthesis of mature fern sporophytes (Böhning & Burnside 1956;Maeda 1969;Friend 1975;Prange et al 1983Prange et al , 1984Nobel et al 1984;Bauer et al 1991); however, few studies have been performed on that of gametophytes and young sporophytes. Although, photosynthesis and respiration of gametophytes have been measured by Friend (1975), Hagar and Freeberg (1980) and Martin et al (1995), they carried out the measurements on only a certain stage of growth; therefore, changes in activities with increasing growth cannot be determined from their data. For example, Hagar and Freeberg (1980) measured photosynthesis of young sporophytes with six to eight leaves, and Martin et al (1995) compared the activity of young and mature sporophytes.…”

“…Although, photosynthesis and respiration of gametophytes have been measured by Friend (1975), Hagar and Freeberg (1980) and Martin et al (1995), they carried out the measurements on only a certain stage of growth; therefore, changes in activities with increasing growth cannot be determined from their data. For example, Hagar and Freeberg (1980) measured photosynthesis of young sporophytes with six to eight leaves, and Martin et al (1995) compared the activity of young and mature sporophytes.…”

The ecology and physiology of fern gametophytes: A methodological synthesis

“…f.) C. V. Morton have evolved the Crassulacean acid metabolism (CAM) photosynthetic pathway, a highly water‐efficient strategy to capturing and fixing carbon often seen in sporophytes of desert plant species (Cushman, 2001 ; Kluge and Ting, 2012 ). In 1995, Martin et al used an IRGA (in conjunction with other tools) to characterize the photosynthetic pathway of Pyrrosia longifolia gametophytes, and demonstrated that this species of fern transitions from C 3 photosynthesis in the gametophyte stage to CAM in the sporophyte stage (Martin et al, 1995 ). Many epiphytic fern species have been shown to exhibit CAM photosynthesis (Martin et al, 2005 ), yet the adaptive value of this transition in these species has not been well demonstrated and is ripe for experimentation.…”