Two clones of Hevea brasiliensis (RRII 105 and PB 235) were grown for one year in two distinct agroclimatic locations (warmer and colder, W and C) in peninsular India. We simultaneously measured gas exchange and chlorophyll (Chl) fluorescence on fully mature intact leaves at different photosynthetic photon flux densities (PPFDs) and ambient CO2 concentrations (Ca) and at constant ambient O2 concentration (21 %). Net photosynthetic rate (PN), apparent quantum yield for CO2 assimilation (Φc), in vivo carboxylation efficiency (CE), and photosystem 2 quantum yield (ΦPS2) were low in plants grown in C climate and these reductions were more predominant in RRII 105 than in PB 235 which was also reflected in their growth. We estimated in these clones the partitioning of photosynthetic electrons between CO2 reduction (JA) and processes other than CO2 reduction (J*) at low and high PPFDs and Ca. At high Ca (700 µmol mol-1) most of the photosynthetic electrons were used for CO2 assimilation and negligible amount went for other processes when PPFD was low (200-300 µmol m-2 s-1) both in the C and W climates. But at high PPFD (900-1 100 µmol m-2 s-1), J* was appreciably high even at a high Ca. Hence at normal ambient Ca and high irradiance, electrons can be generated in the photosynthetic apparatus far in excess of what can be safely utilised for photosynthetic CO2 reduction. However, at high Ca there was increased diversion of electrons to photosynthetic CO2 reduction which resulted in improved photosynthetic parameters even in plants grown in C climate. and B. Alam, D. B. Nair, J. Jacob.
Tobacco (Nicotiana tabacum L.) has been transformed to accumulate different compatible solutes (proline, fructans, or glycine betaine) in order to improve its tolerance to abiotic stress. Photosynthetic activity of wild Type (wt) and transformed tobacco plants before and after freezing stress was studied by measuring chlorophyll (Chl) fluorescence. The JIP test of Chl fluorescence induction was used to analyze in details the functional activity of photosystem 2. No significant differences were found among wild Type and transgenic plants after 12 h of freezing. Both plant Types maintained the same values of the measured parameters [FV/FM, PI(CSM), ABS/RC, TR0/RC, ET/RC] after recovery of stress. The studied Chl fluorescence parameters decreased only for the wild Type plants, stressed for 24 h at -2 °C. The strong inhibition of photosynthetic reactions in the wt plant after 24 h of freezing could not be restored. The evaluated parameters of transgenic plants did not change significantly after 24 h at -2 °C and successfully survived freezing stress. and D. Parvanova ... [et al.].
The ultrastructure and dimensions of chloroplasts in leaf mesophyll cells were quantitatively examined in three parental inbred lines of maize (Zea mays L.) and their four hybrids subjected to two types of four-week low-temperature (LT) treatment: the abrupt onset of chilling temperatures ("severe chilling", SC) and the gradual, more moderate one ("moderate chilling", MC). The relationship between the response of individual genotypes to one or the other type of chilling was analyzed as well as the possibility to predict the behaviour of chloroplasts in hybrids from that of their parents. Although selected parameters of chloroplast ultrastructure (e.g. volume densities of granal and intergranal thylakoids, plastoglobuli, and peripheral reticulum) and dimensions changed due to the exposure of maize plants to LT, no general pattern of such changes was found for this species due to the observed intraspecific variability. The response of some genotype to SC could not be predicted from its behaviour under MC (and vice versa) and no clear rules could be applied for the inheritance of chloroplast response to chilling in the general sense. Thus, great caution should be always taken when interpreting the results of studies aimed at the dissection of chloroplast ultrastructure as affected by LT, particularly in case such studies are made with one genotype or under one type of chilling only. and D. Holá ... [et al.].
The study examines chronicles from the second half of the 18th century written by the České Budějovice master baker Lukas Bernard Schneider. In addition to the Schneider Chronicle recounting the history of the town between 1253 and 1768, attention is paid to its copies. The external dnd internal attributes of the manuscripts have been analysed and the filiation and comparison of Schneider´s Chronicles with other chronicles produced by České Budějovice burghers during the early modern age have been carried out.