Endogenous Auxin and Ethylene in Pellia (Bryophyta)

Abstract

The occurrence of endogenous indole-3-acetic acid and ethylene in bryophyte tissue was tentatively demonstrated using gas chromatography, high performance liquid chromatography, and double-standard isotope dilution techniques. Rapidly elongating stalks (or setae) of Pellia epiphylla (L.) Corda sporophytes contain approximately 2.5 to 2.9 micrograms per gram fresh weight of putative free IAA. Ethylene released by setae increases during growth from 0.027 to 0.035 nanoliter per seta per hour. Application of 5 microliters per liter ethylene inhibits auxinstimulated elongation growth of this tissue, a result which suggests that both endogenously produced compounds act in tandem as natural growth modulators.Morphogenetic processes in bryophytes appear to be regulated by hormones that are quite similar to those found in higher plants (3,14). This conclusion is based largely upon the interpretation of morphologic responses to exogenously applied growth regulators. Very few studies have been directed toward isolation and identification of endogenously produced hormones in these plants. Two well-documented exceptions are the chemical characterization of cytokinin from cultured mosses (2,24), and the identification ofa bibenzyl compound that apparently substitutes for ABA in liverworts (9,17,23). Less convincing experimental evidence exists for the endogenous occurrence of auxin in bryophyte tissues (13,18). Criticism (21) has been directed especially toward the adequacy of ethanolic extraction and paper chromatographic purification techniques used until now for characterization, by bioassay, of the trace amounts detected. Ethylene released by Marchantia thalli, on the other hand, is readily detected with modern gas chromatographic techniques (6). The response of thalli and other liverwort tissues to this hormone, however, remain almost completely unknown.The object of this paper is to present further evidence for the occurrence of endogenous free auxin in bryophytes using a modified Bandurski extraction method (1) and a double-standard isotope dilution assay (4). The seta of Pellia sporophytes was selected as experimental material because of its high sensitivity to exogenously applied auxin (1 1, 20, 22). Seta tissue was also used to measure endogenous ethylene production and to test for growth sensitivity to exogenously applied ethylene. C2M4 Measurements. One to two hundred whole seta segments (excised as described above) were placed in a 5-ml vial sealed with a serum septum. Vacuum was then applied by three 10-cc syringes with plungers held out for 4 min, after which the syringes were released and removed. After 15 min, a l-ml air sample was analyzed for C2H4 by flame ionization chromatography (10).IAA Extraction. Excised setae (20-35 g) were extracted by homogenization in 80% acetone as described by Bandurski and coworkers (1,16

The evolution of the stomatal apparatus: intercellular spaces and sporophyte water relations in bryophytes—two ignored dimensions

“…In liverworts, the most prominent ICSs in both generations are at the base of the phylogeny and have three different functions. In liverwort setae ICSs are most likely a key structural component maintaining and augmenting the hydrostatic skeleton solely determined by the turgidity of its constituent thin-walled cells [102][103][104], whereas the most likely role for the presence of liquid-filled cavities in liverwort (and hornwort) thalli is as a buffer against rapid desiccation. It is noteworthy, however, that these occur in both highly In this context, it is most striking that Dendroceros, the only desiccation-tolerant hornwort genus, has many species with fenestrated thalli rather than mucilage cavities.…”

Hormonal regulation in green plant lineage families

“…It suppresses the ventral row of leaves in P. arctica (Basile and Basile, 1983). The elongation of seta in the sporophyte of the thallose liverwort Pellia epiphylla involves a dual regulation by auxin and ethylene (Thomas et al, 1983). Among mosses, as the Funaria protonemal cultures become old and senescent they produce ethylene.…”

Comparative Indole-3-Acetic Acid Levels in the Slender Pea and Other Pea Phenotypes

“…Tall plants possessing the allele Le, have high levels of GA1 because Le regulates production of a 3-13-hydroxylase which converts GA20 to GAI (7). Dwarf (27). While IAA contents of apices (the presumed site of synthesis) do not vary significantly except in the nana line, the range of stem concentrations may arise from differences in degradation, conjugation, or transport rates out of the region capable of elongation.…”