U. Luttge et al., PHOTOSYNTHESIS OF TERRESTRIAL CYANOBACTERIA UNDER LIGHT AND DESICCATION STRESS AS EXPRESSED BY CHLOROPHYLL FLUORESCENCE AND GAS-EXCHANGE, Journal of Experimental Botany, 46(284), 1995, pp. 309-319
Terrestrial mats of cyanobacteria with other associated microscopical
cryptogams were obtained from various sites in the tropics, i.e. rocks
of mountains and rock-outcrops and bare soil surfaces, a valley in th
e Austrian Alps and a glasshouse. Species diversity of each sample was
analysed qualitatively, The samples came from very different light cl
imates, Responses to light and desiccation stress were studied using t
he saturation pulse method for recording chlorophyll fluorescence vari
ables as well as by measuring net CO2 and O-2 exchange in order to con
firm results by independent methods. Under light stress, shade and hig
h-light, samples showed a reduction of gas exchange and of the fluores
cence variables photochemical fluorescence quenching coefficient (qp),
potential quantum yield of photosystem II (F-v/F-m) and effective qua
ntum yield (Delta F/F'(m)) and recovery to different degrees, Short-te
rm desiccation led to suppression of variable fluorescence yield and i
nhibition of gas exchange, but recovery occurred rapidly within 1 h af
ter rewetting, It is concluded that together with the well-known abili
ty for assimilation of atmospheric dinitrogen, desiccation tolerance o
f terrestrial cyanobacteria mats is the major reason for their success
as pioneers on bare substrata, In addition, the capacity to produce s
un and shade forms adapted to a very wide range of light intensities a
ppears to be important.