Primary tissues may affect estimates of cavitation resistance in ferns

Abstract

Different methods of measuring cavitation resistance in fern petioles lead to variable results, particularly with respect to the P 50 metric. We hypothesised that the fern dictyostele structure affects air entry into the xylem, and therefore impacts the shape of the vulnerability curve.Our study examined this variation by comparing vulnerability curves constructed on petioles collected from evergreen and deciduous ferns in the field, with curves generated using the standard centrifuge, air-injection and bench-top dehydration methods. Additional experiments complemented the vulnerability curves to better understand how anatomy shapes estimates of cavitation resistance.Centrifugation and radial air injection generated acceptable vulnerability curves for the deciduous species, but overestimated drought resistance in the two evergreen ferns. In these hardy plants, axial air injection and bench-top dehydration produced results that most closely aligned with observations in nature. Additional experiments revealed that the dictyostele anatomy impedes air entry into the xylem during spinning and radial air injection.Each method produced acceptable vulnerability curves, depending on the species being tested. Therefore, we stress the importance of validating the curves with in situ measures of water potential and, if possible, hydraulic data to generate realistic results with any of the methods currently available.

From cells to stems: the effects of primary vascular construction on drought‐induced embolism in fern rhizomes

“…To our knowledge, no study has documented the relationship between stelar architecture and vulnerability to drought‐induced embolism in the stems of any vascular plant lineage. However, work on this level of vascular construction in fern leaves indicates that increased dissection confers increased drought resistance (Brodersen et al ., 2012; Pitterman et al ., 2021). It has also been shown that the leaves of certain fern species with dissected vascular architectures are highly drought resistant (i.e.…”

“…At the cellular level, it has been demonstrated that larger conduits and thinner pit membranes are both correlated with higher vulnerability to drought-induced embolism in the petiole (Pittermann et al, 2011;Brodersen et al, 2014). At the architectural level, two studies have suggested that increased architectural dissection (greater separation of the vasculature into discrete 'bundles') in the leaf may increase drought resistance (Brodersen et al, 2012;Pitterman et al, 2021), an analogous trend to increasing embolism resistance with increased vessel dissection in woody plants (Loepfe et al, 2007). At the histological level, nothing is known about the effects of xylem tissue organization on embolism resistance in ferns.…”

“…Within ferns, an herbaceous clade relying entirely on primary xylem, hydraulic work has focused almost exclusively on the leaf, probably due to the difficulty of working with rhizomes (Brodribb & Holbrook, 2004; Brodribb et al ., 2005; Lo Gullo et al ., 2010; Watkins et al ., 2010; Pittermann et al ., 2015; Pitterman et al ., 2021). At the cellular level, it has been demonstrated that larger conduits and thinner pit membranes are both correlated with higher vulnerability to drought‐induced embolism in the petiole (Pittermann et al ., 2011; Brodersen et al ., 2014).…”

“…In fact, only a modest number of studies have documented vulnerability to drought-induced embolism in stems of New Phytologist herbaceous seed plants (Stiller & Sperry, 2002;Kocacinar & Sage, 2003;Li et al, 2009;Maherali et al, 2009;Rosenthal et al, 2010;Nolf et al, 2014Nolf et al, , 2016Lens et al, 2016;Skelton et al, 2017;Volaire et al, 2018), and even fewer have tried to elucidate structure-function relationships (Holste et al, 2006;Dória et al, 2018Dória et al, , 2019Alemán-Sancheschúlz et al, 2020;Thonglim et al, 2020). Within ferns, an herbaceous clade relying entirely on primary xylem, hydraulic work has focused almost exclusively on the leaf, probably due to the difficulty of working with rhizomes (Brodribb & Holbrook, 2004;Brodribb et al, 2005;Lo Gullo et al, 2010;Watkins et al, 2010;Pittermann et al, 2015;Pitterman et al, 2021). At the cellular level, it has been demonstrated that larger conduits and thinner pit membranes are both correlated with higher vulnerability to drought-induced embolism in the petiole (Pittermann et al, 2011;Brodersen et al, 2014).…”

A reduced role for water transport during the Cenozoic evolution of epiphytic Eupolypod ferns

“…Fern rhizomes function as holdfasts and can be difficult to work with because they are often mucilaginous and contorted. Hence, our efforts focused on the petioles, as in earlier studies, because the petioles support the pinnae, an arrangement analogous to twigs supporting leaves (Watkins et al ., 2010; Holmlund et al ., 2016; Pittermann et al ., 2021). Of the 39 species sampled, hydraulic measures were performed on a subset of 14 species (five epiphytic, three hemiepiphytic, and six terrestrial species), bfecause stipes of the remaining taxa released mucilage upon cutting, and/or copious starch granules, both of which were associated with unusually low flow rates of water when connected to the hydraulic apparatus.…”