The epiphytic fern Platycerium bifurcatum grows in different habitats characterized by drought and high irradiance stress. The plant shows diurnal malate oscillations, indicative for CAM expression only in cover leaves, but not in sporotrophophyll. In P. bifurcatum cover leaves exposed to high irradiance and desiccation, the decrease in both CO 2 assimilation (P N ) and stomatal conductance (g s ) was accompanied with occurrence of diurnal malate oscillations. Exogenously applied abscisic acid (ABA) induced the decrease in P N and g s , but no clear change in malate oscillations. The measurements of the maximum quantum efficiency of photosystem 2 (F v /F m ) under high irradiance showed distinct photoinhibition, but no clear changes in F v /F m due to desiccation and ABA-treatment were found.
Diurnal fluctuations in the contents of malate in gametophores of Polytrichum commune Hedw. and Polytrichum piliferum Hedw. were small. In gametophores of Mnium undulatum Hedw. and leaves of Hieracium pilosella L. significant differences were found in the accumulation of malate between day and night. However, no significant diurnal differences were found in the contents of citrate. High irradiance, desiccation, and submergence by water resulted in increases in daily fluctuations of malate, particularly in the gametophores of P. piliferum and leaves of H. pilosella. Accumulation of malate during night may show the adaptation of the studied species to unfavourable conditions caused by stresses. The change in activity of NADP-malic enzyme may characterize a response to stress factors.Additional key words: Hieracium; Mnium; NAD-and NADP-malic enzymes; Polytrichum; phosphoenolpyruvate carboxylase; pyruvate orthophosphate dikinase.
1 De part ment of Plant Phys i ol ogy, In sti tute of Bi ol ogy, Ped a gog i cal Acad emy, 30-054 Kraków, Podbrzezie 3, Po land 2 In sti tute of Plant Phys i ol ogy, Pol ish Acad emy of Sci ences, 30-239 Kraków, ul. Niezapominajek 21, Po land * cor re spond ing au thor Key words: catalase, chlo ro phyll a flu o res cence, hypoxia, Mnium undulatum, ox i da tive stress, photo syn the sis, superoxide dismutase
Ab stractThe ef fects of hypoxia caused by com plete sub merg ing of Mnium undulatum gametophores in wa ter, on their photosynthetic ac tiv ity and the ac tiv ity of two antioxidative en zymes: superoxide dismutase (SOD) and catalase (CAT) were in ves tigated. The net pho to syn the sis was strongly in hib ited throughout the ex per i ment, and the strong drop in the max i mum quantum yield of the PSII (F v / F m ) was also ob served. Three classes of SOD: MnSOD, FeSOD, Cu/ZnSOD and three isoforms of Cu/ZnSOD were iden ti fied. A sig nif i cant de crease in ac tiv ity of MnSOD, FeSOD and one Cu/ZnSOD isoform was ob served af ter 24 and 48 h of hypoxia. FeSOD ac tiv ity de creased already af ter 1 h of sub merg ing in wa ter and its ac tiv ity re mained at the low level dur ing whole pe riod of the ex per i ment. CAT ac tiv ity was also strongly in hib ited in re sponse to hypoxia stress. The ob tained re sults sug gest re la tion ships be tween photosynthetic ac tiv ity and antioxidative sys tem in M. undulatum gameto phores un der ox y gen de fi ciency stress.List of ab bre vi a tions: BSA -bo vine se rum al bumin; CAT -catalase; DTT -dithiothreitol; EDTAethylenediamine tetraacetic acid; EGTA -ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetracet ic acid; F m -max i mum chlo ro phyll a flu o res cence yield; F o -min i mum chlo ro phyll a flu o res cence yield; F v -the dif fer ence be tween F m and F o ; F v / F m -max i mum quan tum yield of PSII; NBTnitroblue tetrazolium salt; PAGE -polyacrylamide gel elec tro pho re sis; PAR -photosynthetically active ra di a tion; P n -net pho to syn the sis in ten sity; PSII -photosystem II; ROS -re ac tive ox y gen species; SOD -superoxide dismu tase; Tricine -N-[tris-(hydroxymethyl)me thyl] gly cine; Tris -tris(hydroxymethyl)aminomethane,
The aim of the present work was to look at the background levels of plutonium in air and rain samples. Two sets of Petryanov type filters through which ca. 0.5 Mm 3 each of air had passed and two large samples of collected rain (170 L and 182 L) were analysed for the content of plutonium alpha-emitters. In the article the radiochemical procedure applied to these samples is described. Obtained Pu activities in air were 0.5 _+ 0.1 nBqm" 3 and 0.7 -+ 0.1 nBqm 3 for 238pu and 3.1 + 0.2 nBqm 3 and 8.3 _+ 0.6 nBqm 3 for 239+240pu. Activities of rain samples were 7.5 + 0.7 mBqm 3 and 14.3 _+ 0.8 mBqm 3 for 239+240pu and 0.4 + 0.1 mBqm "3 and 2.1 + 0.2 mBqm 3 for 238pu, respectively, for the two samples. The most interesting finding is the largely different 23Spu to 239+240pu activity ratios (from 0.03 +_ 0.01 to 0.18 + 0.01) measured in the samples. This result needs confirmation, but as now it suggests different origins of plutonium isotopes in incoming to KrakSw air.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.