Growth

Hale, Mason E.

doi:10.1016/b978-0-12-044950-7.50019-2

Cited by 51 publications

(27 citation statements)

References 18 publications

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“…In general, foliose species grow at 0n5-4 mm yr −" ; fruticose species 1n5-5 mm yr −" and crustose species 0n5-2 mm yr −" (Hale, 1973), but many lichens fall outside these ranges (Nash, 1996). However, these linear measures have a somewhat limited value when attempting to understand lichen growth processes mechanistically.…”

Section: Growth Rates and Environmental Limitationsmentioning

confidence: 99%

Tansley Review No. 117

Palmqvist

2000

New Phytologist

221

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Lichens are nutritionally specialized fungi (the mycobiont component) that derive carbon and in some cases nitrogen from algal or cyanobacterial photobionts. The mycobiont and photobiont live together in an integrated thallus, but they lack specific tissue for the transport of metabolites and resources between them. Carbon is acquired through photosynthesis in the photobiont, which is active when the lichen is wet and exposed to light. Lichen photosynthesis is limited primarily by water, light and nitrogen, but can also be constrained by slow diffusion of CO # within the wet thallus. The assimilated carbon is exported from photobiont to mycobiont, which also predominates in terms of biomass, and apparently regulates the size of the photobiont population. It has therefore generally been assumed that most of the carbon is used for growth and maintenance of the fungal hyphae. However, the extent of photobiont respiration in relation to mycobiont respiration has seldom been quantified ; neither do we know the pool sizes of various carbon sinks within lichens. Owing to this lack of fundamental data we do not know whether, or how, carbohydrate resources are regulated to maintain an optimal balance between energy input and expenditures in these symbiotic organisms. This review summarizes data on growth, carbon gain and carbon expenditures in lichens, with particular emphasis on factors determining the photosynthetic capacity of their photobionts. An attempt is made to introduce an economic analysis of lichen growth processes, a view that has often been adopted in studies of higher plants. Areas in which more data are needed for the construction of a model on ' lichen resource allocation patterns ' are discussed.

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Section: Growth Rates and Environmental Limitationsmentioning

confidence: 99%

Tansley Review No. 117

Palmqvist

2000

New Phytologist

221

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“…In some species, there are alternating light and dark bands at the margin -the lighter bands being interpreted as rapid summer growth and the narrow dark zones much lower growth in winter (Hale, 1973). Each 'zone' is therefore assumed to represent growth in one year and, in some thalli, growth can be traced back three to ten years.…”

Section: Introductionmentioning

confidence: 99%

The use of lichen growth rings in lichenometry: some preliminary findings

Armstrong

Bradwell

2010

Geografiska Annaler: Series A, Physical Geography

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R.A., and Bradwell, T. 2010: The use of lichen growth rings in Lichenometry: some preliminary findings. Geogr. Ann., 92A (x): xx-xx. AbstractCertain species of crustose lichens have concentrically zoned margins which probably represent yearly growth rings. These marginal growth rings offer an alternative method of studying annual growth fluctuations, establishing growth rate-size curves, and determining the age of thalli for certain crustose species. Hence, marginal growth rings represent a potentially valuable, unexploited, tool in lichenometry. In a preliminary study, we measured the widths of the successive marginal rings in 25 thalli of Ochrolechia parella (L.) Massal., growing at a maritime site in north Wales. Mean ring widths of all thalli varied from a minimum of 1.02 mm (the outermost ring) to a maximum of 2.06 mm (the third ring from the margin). There is some suggestion that marginal ring width and thallus size are positively correlated; and hence that growth rates increase in larger thalli in this small population. In a further study on recently exposed bedrock adjacent to Breiðarlon, SE Iceland, we examined the potential for using marginal growth rings to estimate thallus age of a lichen tentatively identified as a Rhizocarpon (possibly R. concentricum (Davies) Beltram.) and thus confirm the timing of surface exposure (c. 50 years). Collectively, these results suggest: 1) the measurement of marginal rings is a possible alternative method of studying the growth of crustose lichens; 2) O. parella may grow differently to other crustose species, exhibiting a rapidly increasing radial growth rate in thalli >40 mm; 3) where lichens with marginal rings grow on recently exposed surfaces (<60 yrs), minimum age estimates can be made using growth rings as an in situ indication of lichen growth rate; 4) it is suggested that this phenomenon could provide a valuable, previously unexploited, in situ lichenometric-dating tool in areas lacking calibration control.

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“…However, lobes in mature thalli do not fuse extensively when they come into contact, unlike the earlier more undifferentiated stages where fusion of different parts are common. Hence, individual lobes maintain their individuality and a considerable degree of autonomy (Hale, 1973;Aplin and Hill, 1979;Armstrong 1991Armstrong , 1993a resulting in substantial variations in radial growth (RG) from lobe to lobe (Phillips, 1969;Lawrey and Hale, 1977;Benedict and Nash, 1990;Armstrong and Smith, 1992).…”

Section: Introductionmentioning

confidence: 99%

Monthly fluctuations in radial growth of individual lobes of the lichenParmelia conspersa (Erhr. ex Ach.) Ach.

Armstrong

2009

Symbiosis

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The radial growth (RG) of 120 lobes from 35 thalli of the foliose lichen Parmelia conspersa (Ehrh. ex Ach.) Ach. was studied monthly over 22 months in south Gwynedd, Wales, UK. Autocorrelation analysis of each lobe identified three patterns of fluctuation: 1) random fluctuations (58% of lobes), 2) a cyclic pattern of growth (23% of lobes), and 3) fluctuating growth interrupted by longer periods of very low or zero growth (19% of lobes). In 80% of thalli, two or three patterns of fluctuation were present within the same thallus. Growth fluctuations were correlated with climatic variables in 31% of lobes, most commonly with either total rainfall or number of rain days per month. Lobes correlated with climate were not associated with a particular type of growth fluctuation. RG of a lobe was positively correlated with the degree of bifurcation of the lobe tip. It is hypothesised that lobes of P. conspersa exhibit a cyclic pattern of growth due in part to lobe division. The effects of climate, periods of zero growth, and microvariations in the environment of a lobe are superimposed on this cyclic pattern resulting in the random growth of many lobes. Random growth fluctuations may contribute to the maintenance of thallus symmetry in P. conspersa.

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Growth

Cited by 51 publications

References 18 publications

Tansley Review No. 117

Tansley Review No. 117

The use of lichen growth rings in lichenometry: some preliminary findings

Monthly fluctuations in radial growth of individual lobes of the lichenParmelia conspersa (Erhr. ex Ach.) Ach.

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