Conducting tissues and phyletic relationships of bryophytes

Abstract

Internal specialized conducting tissues, if present, are restricted to the gametophytic generation in liverworts while they may occur in both generations in mosses. Conducting tissues are unknown in the anthocerotes. Water-conducting cells (WCCs) with walls perforated by plasmodesma-derived pores occur in the Calobryales and Pallaviciniaceae (Metzgeriales) among liverworts and in Takakia among mosses. Imperforate WCCs (hydroids) are present in bryoid mosses. A polarized cytoplasmic organization and a distinctive axial system of microtubules is present in the highly specialized food-conducting cells of polytrichaceous mosses (leptoids) and in less specialized parenchyma cells of the leafy stem and seta in other mosses including Sphagnum. A similar organization, suggested to re£ect specialization in long-distance symplasmic transport of nutrients, also occurs in other parts of the plant in mosses, including rhizoids and caulonemata, and may be observed in thallus parenchyma cells of liverworts. Perforate WCCs in the Calobryales, Metzgeriales and Takakia, and hydroids in bryoid mosses, probably evolved independently. Because of fundamental di¡erences in developmental design, homology of any of these cells with tracheids is highly unlikely. Likewise, putative food-conducting of bryophytes present highly distinctive characteristics and cannot be considered homologous with the sieve cells of tracheophytes.

Dehydration protection provided by a maternal cuticle improves offspring fitness in the moss Funaria hygrometrica

“…As the sporophyte tissues are exposed from beneath the covering of the calyptra they develop a multilayered cuticle (Budke et al, 2012) that most likely limits direct water uptake from the surrounding environment. Thus the maternally supplied, internally transported water (Ligrone et al, 2000) must be essential for maintaining sporophyte hydration. Without the calyptra and its cuticle covering the apical tissues, which have yet to develop their own multilayered cuticle (Budke et al, 2012), this critical supply of water would be rapidly lost through transpiration.…”

Amino acid uptake among wide-ranging moss species may contribute to their strong position in higher-latitude ecosystems

“…The low amino acid uptake of Polytrichum commune in the lab, and the virtual absence of uptake by this moss in our field experiment, is of particular interest, since this is the only endohydric species among the 11 studied here. Since P. commune has internal conducting tissues which may also transport inorganic nutrients from the soil relatively efficiently (Ligrone et al 2000), it may rely mostly on inorganic N sources in the soil rather than on amino acids. However, injecting amino acids broadly at the boundary of brown and green parts means that potential uptake through rhizoids could have been partly missed in our experiment.…”

Biogeography of Sri Lankan bryophytes: the present status

“…They also, require external water for their swimming sperms to bring about fertilization. However, despite these primitive characteristics, bryophytes show a variety of adaptations to thrive in extreme environmental conditions: there are many desiccation-tolerant species and some with efficient though simple systems to conduct water and food (Vitt, 1981;Ligrone et al, 2000). Due to their small size and efficient dispersal and survival mechanisms, bryophytes frequently have much wider distributions than higher plants.…”