The effects of enhanced ultraviolet-B (UV-B, 0.4 W m -2 ) irradiance and nickel (Ni, 0.01, 0.10 and 1.00 mM; Ni 0.01 , Ni 0.10 , Ni 1.00 , respectively) treatment, singly and in combination, on growth, photosynthetic electron transport activity, the contents of reactive oxygen species (ROS), antioxidants, lipid peroxidation, and membrane leakage in soybean seedlings were evaluated. Ni 0.10 and Ni 1.00 and UV-B declined the growth and chlorophyll content, which were further reduced following combined exposure. Contrary to this, Ni 0.01 stimulated growth, however, the effect together with UV-B was inhibitory. Carotenoids showed varied response to both the stresses. Simultaneous exposure of UV-B and Ni as well as UV-B alone reduced the activities of photosystems 1 and 2 (PS1 and PS2) and whole chain activity significantly, while Ni individually, besides strongly inhibiting PS2 and whole chain activity, stimulated the PS1 activity. Both the stresses, alone and together, enhanced the contents of superoxide radical ( − ⋅ 2 O ), hydrogen peroxide (H 2 O 2 ), malondialdehyde (MDA), electrolyte leakage, and proline content, while ascorbate content declined over control. Individual treatments increased the activities of catalase (CAT), peroxidase, and superoxide dismutase (SOD), but Ni 1.00 declined SOD activity significantly. Combined exposure exhibited similar response, however, CAT activity declined even more than in control. Compared to individual effects of UV-B and Ni, the simultaneous exposure resulted in strong inhibition of photosynthetic electron transport and excessive accumulation of ROS, thereby causing severe damage to soybean seedlings.

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UV-B (0.4 W m -2 ) irradiation and cadmium (2 and 8 µM) treatments separately inhibited the survival, growth, pigment content, and photosynthetic electron transport in Plectonema boryanum. Phycocyanin was the main target to UV-B and Cd and it was followed by chlorophyll a and carotenoids. UV-B and Cd caused strong inhibition on activities of photosystem 2 (PS2) and the whole electron transport chain, whereas photosystem 1 (PS1) was the least affected. UV-B and Cd treatment accelerated respiration, lipid peroxidation, and the activities of superoxide dismutase and catalase. However, enhancement in catalase activity was considerably less (5 -50 %) as compared to SOD activity. As compared to individual treatment, the effect of their combination (UV-B + Cd) was more detrimental to the above parameters. A synergistic interaction of UV-B and Cd is probably due to increased cadmium uptake as a result of increased membrane permeability caused by lipid peroxidation in P. boryanum after UV-B exposure.Additional key words: carotenoids, catalase, chlorophyll, lipid peroxidation, oxidative stress, photosynthetic electron transport activity, photosystem 1 and 2, superoxide dismutase.

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Generation of photon pairs from quantum dots with near-unity entanglement fidelity has been a long-standing scientific challenge. It is generally thought that the nuclear spins limit the entanglement fidelity through spin flip dephasing processes. However, this assumption lacks experimental support. Here, we show two-photon entanglement with negligible dephasing from an indium rich single quantum dot comprising a nuclear spin of 9/2 when excited quasi-resonantly. This finding is based on a significantly close match between our entanglement measurements and our model that assumes no dephasing and takes into account the detection system's timing jitter and dark counts. We suggest that neglecting the detection system is responsible for the degradation of the measured entanglement fidelity in the past and not the nuclear spins. Therefore, the key to unity entanglement from quantum dots comprises a resonant excitation scheme and a detection system with ultralow timing jitter and dark counts.