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The synthesis and assembly of functioning photosynthetic complexes in chloroplasts developing from etioplasts during the de-etiolation of angiosperm seedlings are imperative for the plant's autotrophic lifestyle. This study compared de-etiolation process under monochromatic red or blue light of equal photon flux density during a 24-hour illumination period of etiolated Arabidopsis seedlings. The aim was to elucidate the impact of these light wavelength on the etioplast-to-chloroplast transformation and the initiation of light-dependent photosynthetic reactions. Both treatments lead to the formation of functional young chloroplasts; however, the etioplast-to-chloroplast transition and the assembly of photosynthetic complexes occurred unevenly, with individual steps tuned by red or blue light. Ultrastructural analysis suggested faster prolamellar bodies disassembly under blue light, while low temperature fluorescence studies indicated a slower transformation of protochlorophyllide to chlorophyllide, and chlorophyll a, under these conditions. Red light further promoted the synthesis of chlorophyll b and LHCII antenna proteins. However, the efficiency of antennae in dissipating excess absorbed energy was higher for seedlings de-etiolated under blue light; the maximum quantum yield of the photosystem II reached 0.81 after 24-hour de-etiolation, equivalent to mature plants. Blue light seemed to enhance the development of well-functioning photosystems (I and II) and antennae. These findings are important for gaining a deeper understanding of photoreceptor regulation of de-etiolation and for utilizing selected light regimes to improve crop yield., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.)

Being poikilohydric, lichens are inherently exposed to alternating desiccation and hydration cycles. They can exhibit extraordinary resistance to extreme temperatures in a dehydrated state but thermal thresholds for hydrated lichens are lower. The ability of the lichen Cetraria aculeata to recovery after high temperature treatment (40°C, 60°C) at different air humidity levels (relative humidity [RH]: <15%, 25%, 50%, 75%, ≅100%) was examined to find a linkage between passive dehydration of the lichen and its physiological resistance to heat stress. The response to heating was determined by measuring parameters related to photosynthesis and respiration after 2- and 24-h recovery. A higher RH level resulted in a slower decline in relative water content (RWC) in hydrated thalli. In turn, the stress resistance of active thalli depended on the ambient humidity and associated RWC reduction. Elevated temperature had a negative impact on bioenergetic processes, but only an unnatural state of permanent full hydration during heat stress resulted in a lethal effect. Hydrated lichen thalli heated at 40°C and 50% relative humidity (RH) tended to be least susceptible to stress-induced damage. Although atypical climatic conditions may lead lichens to lethal thresholds, the actual likelihood of deadly threat to lichens due to heat events per se is debatable., (© 2024 John Wiley & Sons Ltd.)

4-[5-(Naphthalen-1-ylmethyl)-1,3,4-thiadiazol-2-yl]benzene-1,3-diol (NTBD) was extensively studied through stationary UV-vis absorption and fluorescence measurements in various solvents and solvent mixtures and by first-principles quantum chemical calculations. It was observed that while in polar solvents (e.g., methanol) only a single emission band emerged; the analyzed 1,3,4-thiadiazole derivative was capable of producing dual fluorescence signals in low polarity solvents (e.g., n -hexane) and certain solvent mixtures (e.g., methanol/water). As clearly follows from the experimental spectroscopic studies and theoretical modeling, the specific emission characteristic of NTBD is triggered by the effect of enol → keto excited-state intramolecular proton transfer (ESIPT) that in the case of solvent mixture is reinforced by aggregation of thiadiazole molecules. Specifically, the restriction of intramolecular rotation (RIR) due to environmental hindrance suppresses the formation of non-emissive twisted intramolecular charge transfer (TICT) excited keto* states. As a result, this particular thiadiazole derivative is capable of simultaneously producing both ESIPT and aggregation-induced emission (AIE).