The morphological variability of the bordered pit membranes in gymnosperms

Bauch, J.; Líese, W.; Schultze, R.

doi:10.1007/bf00351575

Cited by 101 publications

(99 citation statements)

References 10 publications

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“…Hence I have scored Gnetum as having a torus. Bauch et al (1972) recognized six types of pit membrane corresponding to differing degrees of development of a torus. However, types 1-4 overlap in their systematic distribution and seem best treated as one state, presence of a torus.…”

Section: Methodsmentioning

confidence: 99%

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Perspective: The Origin of Flowering Plants and Their Reproductive Biology?a Tale of Two Phylogenies

Friedman¹,

Floyd²

2001

Evolution

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. Recently, two areas of plant phylogeny have developed in ways that could not have been anticipated, even a few years ago. Among extant seed plants, new phylogenetic hypotheses suggest that Gnetales, a group of nonflowering seed plants widely hypothesized to be the closest extant relatives of angiosperms, may be less closely related to angiosperms than was believed. In addition, recent phylogenetic analyses of angiosperms have, for the first time, clearly identified the earliest lineages of flowering plants: Amborella, Nymphaeales, and a clade that includes Illiciales/Trimeniaceae/Austrobaileyaceae. Together, the new seed plant and angiosperm phylogenetic hypotheses have major implications for interpretation of homology and character evolution associated with the origin and early history of flowering plants. As an example of the complex and often unpredictable interplay of phylogenetic and comparative biology, we analyze the evolution of double fertilization, a process that forms a diploid embryo and a triploid endosperm, the embryo‐nourishing tissue unique to flowering plants. We demonstrate how the new phylogenetic hypotheses for seed plants and angiosperms can significantly alter previous interpretations of evolutionary homology and firmly entrenched assumptions about what is synapomorphic of flowering plants. In the case of endosperm, a solution to the century‐old question of its potential homology with an embryo or a female gametophyte (the haploid egg‐producing generation within the life cycle of a seed plant) remains complex and elusive. Too little is known of the comparative reproductive biology of extant nonflowering seed plants (Gnetales, conifers, cycads, and Ginkgo) to analyze definitively the potential homology of endosperm with antecedent structures. Remarkably, the new angiosperm phylogenies reveal that a second fertilization event to yield a biparental endosperm, long assumed to be an important synapomorphy of flowering plants, cannot be conclusively resolved as ancestral for flowering plants. Although substantive progress has been made in the analysis of phylogenetic relationships of seed plants and angiosperms, these efforts have not been matched by comparable levels of activity in comparative biology. The consequence of inadequate comparative biological information in an age of phylogenetic biology is a severe limitation on the potential to reconstruct key evolutionary historical events.

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Section: Methodsmentioning

confidence: 99%

“…In addition, Agathis, assigned to type 3, shows a conspicuous torus under SEM (Meylan and Butterfield 1978). Bauch et al (1972) reported type 5 only in Gnetum gnemon, where Carlquist (1994) found no torus, and G. scandens, an Asian species of uncertain identity (S.…”

Section: Methodsmentioning

confidence: 99%

Perspective: The Origin of Flowering Plants and Their Reproductive Biology?a Tale of Two Phylogenies

Friedman¹,

Floyd²

2001

Evolution

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“…The y at aspiration (y a , Fig. 1D) was calculated from a membrane strain at aspiration e a ϭ 0.03, as estimated from the measurement of several published micrographs of circular bordered pits of different sizes (Panshin and de Zeeuw, 1970;Siau, 1971;Bauch et al, 1972;Core et al, 1979;Siau et al, 1984). This calculation assumed a constant radius of curvature of the inner chamber wall of r ya (Fig.…”

Section: Output Variablesmentioning

confidence: 99%

Analysis of circular bordered pit function I. Angiosperm vessels with homogenous pit membranes

Sperry

Hacke

2004

American J of Botany

206

244

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A model predicted pit and vessel conductivity, the air-seed pressure for cavitation, and the implosion pressure causing vessel collapse. Predictions were based on measurements from 27 angiosperm species with circular bordered pits and air-seed pressures of 0.2-11.3 MPa. Vessel implosion pressure exceeded air-seed pressure by a safety factor of 1.8 achieved by the increase in vessel wall thickness per vessel diameter with air-seed pressure. Intervessel pitting reduced the implosion pressure by 20 to 40%. Pit hydraulic conductivity decreased by 30-fold from low (Ͻ1 MPa) to high (Ͼ10 MPa) air-seed pressure primarily because of decreasing pit membrane conductivity. Vessel conductivity (per length and wall area) increased with vessel length as higher lumen conductivity overcame low pit conductivity. At the ''saturating vessel length,'' vessel conductivity maximized at the Hagen-Poiseuille value for the lumen per wall area. Saturated vessel conductivity declined by sixfold with increasing air-seed pressure because of increased wall thickness associated with increased implosion resistance. The saturated vessel length is likely the optimal length because: (a) shorter vessels have lower conductivities, (b) longer vessels do not increase conductivity when functional yet decrease it more when cavitated, (c) observed pit structure most closely optimized vessel conductivity at the saturated length, and (d) saturated lengths were similar to measured lengths.

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“…These structures typically consist of a porous web-like structure of microfibril strands (margo) that surrounds a central thickening (torus). The torus acts as a plug, which seals the pit aperture upon C differences between adjacent conduits, thus avoiding air seeding (Strasburger, 1891;Liese, 1965;Bauch et al, 1972;Cochard et al, 2009). However, conifers also exhibit species-specific C thresholds, at which this valve mechanism fails and air seeding occurs.…”

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confidence: 99%

Xylem Sap Surface Tension May Be Crucial for Hydraulic Safety

et al. 2017

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The surface tension (g) of xylem sap plays a key role in stabilizing air-water interfaces at the pits between water-and gas-filled conduits to avoid air seeding at low water potentials. We studied seasonal changes in xylem sap g in Picea abies and Pinus mugo growing at the alpine timberline. We analyzed their vulnerability to drought-induced embolism using solutions of different g and estimated the potential effect of seasonal changes in g on hydraulic vulnerability. In both species, xylem sap g showed distinct seasonal courses between about 50 and 68 mN m 21 . Solutions with low g caused higher vulnerability to drought-induced xylem embolism. The water potential at 50% loss of hydraulic conductivity in P. abies and P. . This indicates up to about 1 MPa seasonal variation in 50% loss of hydraulic conductivity. The results revealed pronounced effects of changes in xylem sap g on the hydraulic safety of trees in situ. These effects also are relevant in vulnerability analyses, where the use of standard solutions with high g overestimates hydraulic safety. Thus, g should be considered carefully in hydraulic studies.

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The morphological variability of the bordered pit membranes in gymnosperms

Cited by 101 publications

References 10 publications

Perspective: The Origin of Flowering Plants and Their Reproductive Biology?a Tale of Two Phylogenies

Perspective: The Origin of Flowering Plants and Their Reproductive Biology?a Tale of Two Phylogenies

Analysis of circular bordered pit function I. Angiosperm vessels with homogenous pit membranes

Xylem Sap Surface Tension May Be Crucial for Hydraulic Safety

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