The carbon dioxide concentrating system in C4 photosynthesis allows high net photosynthetic rates (PN) at low internal carbon dioxide concentrations (Ci), permitting higher PN relative to stomatal conductance (gs) than in C3 plants. This relation would be reflected in the ratio of Ci to external ambient (Ca) carbon dioxide concentration, which is often given as 0.3 or 0.4 for C4 plants. For a Ca of 360 µmol mol-1 that would mean a Ci about 110-140 µmol mol-1. Our field observations made near midday on three weedy C4 species, Amaranthus retroflexus, Echinochloa crus-galli, and Setaria faberi, and the C4 crop Sorghum bicolor indicated mean values of Ci of 183-212 µ mol mol-1 at Ca = 360 µmol mol-1. Measurements in two other C4 crop species grown with three levels of N fertilizer indicated that while midday values of Ci at high photon flux were higher at limiting N, even at high nitrogen Ci averaged 212 and 196 µmol mol-1 for Amaranthus hypochondriacus and Zea mays, respectively. In these two crops midday Ci decreased with increasing leaf to air water vapor pressure difference. Averaged over all measurement days, the mean Ci across all C4 species was 198 µmol mol-1, for a Ci/Ca ratio of 0.55. Prior measurements on four herbaceous C3 species using the same instrument indicated an average Ci/Ca ratio of 0.69. Hence midday Ci values in C4 species under field conditions may often be considerably higher and more similar to those of C3 species than expected from measurements made on plants in controlled environments. Reducing gs in C4 crops at low water vapor pressure differences could potentially improve their water use efficiency without decreasing PN.
High temperature is a common constraint during anthesis and grain-filling stages of wheat leading to huge losses in yield. In order to understand the mechanism of heat tolerance during monocarpic senescence, the present study was carried out under field conditions by allowing two well characterized Triticum aestivum L. cultivars differing in heat tolerance, Hindi62 (heat-tolerant) and PBW343 (heat-susceptible), to suffer maximum heat stress under late sown conditions. Senescence was characterized by measuring photosynthesis related processes and endoproteolytic activity during non-stress environment (NSE) as well as heat-stress environment (HSE). There was a faster rate of senescence under HSE in both the genotypes. Hindi62, having pale yellow flag leaf with larger area, maintained cooler canopy under high temperatures than PBW343. The tolerance for high temperature in Hindi62 was clearly evident in terms of slower green-leaf area degradation, higher stomatal conductance, higher stability in maximum PSII efficiency, Rubisco activity and Rubisco content than PBW343. Both the genotypes exhibited lower endopeptidase activity under HSE as compared to NSE and this difference was more apparent in Hindi62. Serine proteases are the predominant proteases responsible for protein degradation under NSE as well as HSE. Flag leaf of both the genotypes exhibited high-molecular-mass endoproteases (78 kDa and 67 kDa) isoforms up to full grain maturity which were inhibited by specific serine protease inhibitor in both the environments. In conclusion, the heat-tolerant Hindi62 exhibited a slower rate of senescence than the heat-susceptible PBW343 during HSE, which may contribute towards heat stability. and S. Chauhan ... [et al.].
Implicit causality (IC) verbs influence the pronoun ambiguity resolution by directing the speakers’ (readers’ or listeners’) attention to the referent that is likely to be the cause of the event or state. Although IC bias is considered universal, there are cross-linguistic differences in its direction and strength. Previous studies have attempted to build large datasets of IC verbs, but very few Slavic languages have been investigated. In this experimental study, we examined the direction and strength of IC bias in Croatian, an understudied Slavic language in this regard, and compared it with IC bias observed in English. After selecting 137 verbs and classifying them according to thematic roles (agent-patient, agent-evocator, stimulus-experiencer, experiencer-stimulus), 86 participants were asked to complete sentence fragments containing these verbs. The study was conducted under the semantic structure account. Our results show that most Croatian verbs followed the predicted direction, which is consistent with findings suggesting that the direction of IC bias is relatively generalizable across languages. We also detected cross-linguistic variability in the strength of IC bias, especially in stimulus-experiencer verbs. This is consistent with studies showing that the strength of IC bias can vary across languages. Implications for theoretical and methodological approaches are discussed. and Implicitnouzročni glagoli utječu na razdvosmislenje upućivanja zamjenicom usmjeravajući govornikovu (čitateljevu ili slušateljevu) pozornost na referent koji je vjerojatniji uzrok događaja ili stanja. Iako se implicitnouzročna pristranost smatra univerzalnom, pronađene su međujezične razlike u smjeru i jačini glagolske pristranosti. U prijašnjim se istraživanjima težilo stvaranju velikih baza implicitnouzročnih glagola, no ta je jezična pojava nedovoljno istražena u slavenskim jezicima. Cilj ovoga eksperimentalnoga istraživanja bio je ispitati smjer i jačinu pristranosti implicitnouzročnih glagola u hrvatskome, koji je slavenski jezik i u kojem je ta pojava slabo istražena, te dobivene podatke usporediti s podatcima u engleskom jeziku. Izabrano je 137 glagola koji su razvrstani prema semantičkim ulogama (agens – pacijens, agens – pobuđivač, poticajnik – doživljavač, doživljavač – poticajnik). Ukupno je 86 sudionika dovršavalo rečenice s tim glagolima. Istraživanje je provedeno u okviru pristupa značenjske strukture. Rezultati pokazuju da većina hrvatskih glagola pokazuje predviđeni smjer pristranosti, što je u skladu s istraživanjima koja upućuju na to da je smjer implicitnouzročne pristranosti sličan u različitim jezicima. S druge strane, pronađene su međujezične razlike u snazi glagolske pristranosti, ponajprije u kategoriji poticajnik – doživljavač. Taj je rezultat u skladu s istraživanjima koja pokazuju da se jačina implicitnouzročne pristranosti može razlikovati među jezicima. U radu se raspravlja o teorijskim i metodološkim implikacijama.
The thermoluminescence signals from leaflets of the same pea plant varied gradually according to their developmental stage. The AG emission, due to a back flow of electrons towards photosystem 2 (PS2) along a cyclic/chlororespiratory pathway, was stronger in mature leaves than in the growing ones. These age-related variations could be explained by a higher capacity of cyclic electron flow in mature leaves.
In the following essay-manifesto, Contradictions editor Joseph Grim Feinberg lays out his view of the journal as a platform for confronting the central contradictions of post-communism, working through the problems of Central and Eastern Europe in global context, and seeking the continued contemporary relevance of the history of emancipatory and critical thought. Contradictions, he writes, should enable philosophy and its neighboring fields to engage with this region, at this moment, while telling world history something that no other time or place has told it before.
During the last decades several studies in cognitive psychology have shown that many of our actions do not depend on the reasons that we adduce afterwards, when we have to account for them. Our decisions seem to be often influenced by normatively or explanatorily irrelevant features of the environment of which we are not aware, and the reasons we offer for those decisions are a posteriori rationalisations. But exactly what reasons has the psychological research uncovered? In philosophy, a distinction has been commonly made between normative and motivating reasons: normative reasons make an action right, whereas motivating reasons explain our behaviour. Recently, Maria Alvarez has argued that, apart from normative (or justifying) reasons, we should further distinguish between motivating and explanatory reasons. We have, then, three kinds of reasons, and it is not clear which of them have been revealed as the real reasons for our actions by the psychological research. The answer we give to this question will have important implications both for the validity of our classifications of reasons and for our understanding of human action.