The Physiology of the Lichen Peltigera aphthosa, with Special Reference to the Blue-green Phycobiont (Nostoc sp.)
33
Citation
20
Reference
10
Related Paper
Citation Trend
Abstract:
Abstract Variations in the morphology and physiology were noted when parts of the Peltigera aphthosa Willd. thallus differing in age were examined. The many small cephalodia on the growing apex of the lichen showed a lower heterocyst frequency (14%) than those on the rest of the thallus (21–22%), which was reflected in the nitrogenase activity. In contrast, highest levels of photosynthesis ( 14 CO 2 uptake and O 2 evolution) were noted at the growing apex. while respiration rates were fairly stable over the thallus. The water‐holding capacity was greatest in the midparts. Cephalodial biomass represented an average of 2.6% of total thallus biomass. while the number and size of these structures varied considerably. A minor part of the total carbon fixation ( 14 CO 2 ) and net oxygen evolution (O 2 electrode) was performed by the blue‐green phycobiont ( Nostoc ) in light. A rapid excretion of ammonia from isolated cephalodia was noticed, which together with a comparatively constant C:N ratio throughout the thallus indicated a rapid transport of metabolites facilitated by close physical contact (electron microscopy).Keywords:
Thallus
Nostoc
Thallus
Cite
Citations (25)
S ummary The content of the blue‐green alga phycobiont, Nostoc sp. in the lichen Peltigera canina has been estimated using various techniques and represents on average 2.7% of the total thallus nitrogen. Expressed in terms of cell numbers, this represents approximately 3 × 10 6 cells cm 2 , mature thallus. The nitrogenase activity, expressed as nil ethylene evolved/minute/mg Sostoc protein, varies considerably with the thallus sample, but a mean value of 10 , considerably greater than that in free‐living Nostoc , has been found. The nitrogenase activity of the algal cells is particularly sensitive to disturbance of the thallus structure and the implications of these findings are discussed.
Thallus
Nostoc
Cite
Citations (34)
In lichenology the term “thallus” or “body” is less contentious than “individual,” as a lichen thallus is not a single genetic entity. The status of “individual” has sometimes been applied loosely to physically distinct thalli, such as the stalked umbrella-shaped structure of Umbilicaria, or to discrete thalli of any lichen species. A more sophisticated approach, and one which is more meaningful biologically, is to consider a lichen “individual” as any thallus material which is genetically uniform with respect to the dominant, or fungal, symbiont. This, of course, requires genetic information which may not always be available.
Thallus
Cite
Citations (14)
SUMMARY Predictive simulation models of lichen growth and distribution should be sensitive to the pattern of production and growth within thalli, and yet little work has dealt directly with the problem of intrathallus variability in production and thus growth. It has been assumed for many years that lichens show marginal or apical growth as a result of the allocation of local supplies of photosynthate to the proliferating tissues. Only recently have intrathallus gradients in photosynthetic activity been demonstrated in foliose and fruticose species which mirror the observed pattern of growth. This present study aimed to determine whether there was intrathallus variation in production in the form of production gradients in Umbilicaria lichens. Discs of tissue were removed from large thalli of four species of Umbilicaria and sampled for net CO 2 exchange under constant conditions. The results were plotted as maps of physiological activity both on a weight and area basis, but showed an absence of clear intrathallus gradients in activity. This suggests that production is diffuse over the entire surface of the thallus and thus the growth pattern is diffuse. These results are interpreted to mean that not all lichens grow apically and that greater research effort should be directed towards discovering the extent of variation in growth pattern amongst various families of lichens.
Thallus
Cite
Citations (24)
Thallus
Cite
Citations (8)
The growth of two lichens, Parmelia sulcata and P. physodes, has been examined under controlled conditions. It has been shown that continuous light leads to early death of both lichens. Evidence from fine structure work following pretreatment of the lichen thallus with different levels of thallus saturation indicates that fluctuating wet and dry conditions are also vitally necessary for continued thallus growth. This is explicable in terms of the relative mobility of fixed carbon from the algal component at different levels of thallus saturation.
Thallus
Saturation (graph theory)
Cite
Citations (39)
Culture experiments with lichens and lichen symbionts are helpful for giving answers to many open questions in different fields of modern lichenology. Cultures are especially required for investigations where the analysis of naturally grown thalli is inconclusive and more standardized research material is needed. In the first part a short review of the artificial resynthesis of the cyanobacterial Peltigera praetextata along with new results obtained by the culture of isidia are presented. Another series of experiments report a successful resynthesis of the photosymbiodeme Peltigera leucophlebia. Details of the thallus morphogenesis and the formation of cephalodia in culture are shown. The related Peltigera aphthosa was cultured from small thallus fragments. In this case, the alpine P. aphthosa forms solely the cephalodiate thallus. A cyanobacterial morphotype as known from other culture experiments and the related P. britannica is missing in culture. Further culture experiments are conducted with alpine species of the genus Cladonia (e.g., Cl. fimbriata, Cl. furcata). Results show a quick redifferentiation and regeneration of squamules and podetia both by soredia and fragments. The high capacity of thallus regeneration as shown for Cl. furcata seems to be absent in representatives of the Cladina group (e.g., Cl. portentosa, Cl. rangiferina). Key words: lichen culture, resynthesis, tissue culture, Peltigeraceae, cyanobacterial lichens, photosymbiodemes, Peltigera leucophlebia, Peltigera aphthosa, Cladoniaceae, Cl. fimbriata, Cl. furcata.
Thallus
Cite
Citations (46)
The development of characteristic thallus structures in lichen-forming fungi requires the association with suitable photoautotrophic partners. Previous work suggests that fungi have a specific range of compatible photobionts and that selected algal strains are also correlated with the habitat conditions. We selected the rock-inhabiting crust lichen Protoparmeliopsis muralis, which exhibits high flexibility in algal associations. We present a geographically extended and detailed analysis of algal association patterns including thalli which host superficial algal colonies. We sampled 17 localities in Europe, and investigated the photobiont genotypic diversity within and between thalli and compared the diversity of intrathalline photobionts and externally associate algal communities between washed and unwashed thalli by single-strand conformation polymorphism analyses and ITS sequence data. The results show that (1) photobiont population within the lichen thalli is homogeneous; (2) multiple photobiont genotypes occur within single areoles and lobes of individual lichens; and (3) algal communities which superficially colonize the lichen thalli host taxa known as photobionts in unrelated lichens. Photobiont association patterns are extremely flexible in this ecologically versatile crust-forming lichen. We suggest that lichen surfaces represent a potential temporary niche for free-living stages of lichen photobionts, which could facilitate the establishment of further lichens in the proximal area.
Thallus
Cite
Citations (107)
Thallus
Cite
Citations (14)
The Gunnera/Nostoc symbionts evolved H2 through nitrogenase in a predictable manner. However, the relative efficiency of nitrogen fixation in the Gunnera/Nostoc symbionts widely from 0. 26 to 0. 80. Nitrogen fixation activity was carbohydratelimited in normal gtowth conditions and glucose addition (1. 5%) rapidly increased nitrogen fixation activity and respiratory rate with a maximum stimulation of ca. 100% and 160% respectively. The stimulation of nitrogen fixation activity was alSO affected by H2 addition, when the maximum stimulation of ca. 100% occurred in seriously carbohydrate-limited condition.However, respiration rate decreased by about 50% on H2 addition. Net H2evolution was strongly stimulated byglucose addition. In addition. nitrogenfixation activity decreased by about 70% on the addition of NH4Cl.It is postulated that carbohydratesupply and uptake hydrogenase could regulate the activity of nitrogen fixation by supplying a common reductant pool and that the recycling of H2 through nitrogenase, when (CH2O )nsupply was low, could sustain nitrogenase at a reasonably high level and could thus be able to tube advantage of an influx of carbohydrate.
Nostoc
Carbon fixation
Cite
Citations (0)