A 32-Gb ReRAM test chip has been developed in a 24-nm process, with a diode as the selection device and metal oxide as the switching element. The memory array is constructed with cross-point architecture to allow multiple memory layers stacked above the supporting circuitry and minimize the circuit area overhead. Die efficiency is further improved by sharing wordlines and bitlines between adjacent blocks. As the number of sense amplifiers under the memory array is limited, a pipelined array control scheme is adopted to compensate the performance impact while utilizing the fast switching time of ReRAM cells. With the chip current consumption being dominated by the array leakage and sensitive to array bias and operating conditions, a charge pump stage control scheme is introduced to dynamically adapt to the operating conditions for optimal power consumption. Smart Read during sensing and leakage current compensation scheme during programming are applied to the large-block architecture and achieve a chip density that is several orders of magnitude higher than prior ReRAM developments.

A 3.3 V, 512 Mb PROM uses a transistorless memory cell containing an antifuse and diode. A bit area of 1.4F/sup 2/ including all overhead is achieved by stacking cells 8 high above the 0.25 /spl mu/m CMOS substrate. Read bandwidth is 1 MB/s and write bandwidth is 0.5 MB/s. A 72 b Hamming code provides fault tolerance.

A 512-Mb one-time-programmable memory is described, which uses a transistorless two-terminal memory cell containing an antifuse and a diode. Cells are fabricated in polycrystalline silicon, stacked vertically in eight layers above a 0.25-mum CMOS substrate. One-time programming is performed by applying a high voltage across the cell terminals, which ruptures the antifuse and permanently encodes a logic 0. Unruptured antifuses encode a logic 1. Cells are arranged in 8-Mb tiles, 1 K rows by 1 K columns by 8 bits high. The die contains 72 such tiles: 64 tiles for data and eight tiles for error-correcting code bits. Wordline and bitline decoders, bias circuits, and sense amplifiers are built in the CMOS substrate directly beneath the memory tiles, improving die efficiency. The device supports a generic standard HAND flash interface and operates from a single 3.3-V supply.

Spore germination in Dryopteris filix-mas occurs via a cascade of cellular responses, and chlorophyll formation, mitosis or rhizoid elongation are commonly used as parameters to determine spore germination. Detailed investigations of these parameters led to the hypothesis that they are regulated by different, independent phytochrome-mediated responses. This concept could be confirmed, as is described in this paper which demonstrates that perception of Light via phytochrome occurs within two different phases separated in time. Presence of the far-red absorbing phytochrome form, P-fr, for 36 h, induces chlorophyll formation and the first unequal cell division, by which a rhizoid initial and a protonemal initial are formed (first phytochrome-mediated response). However, rhizoid elongation requires a second period of P-fr presence (second phytochrome-mediated response). There is a clear temporal distinction between the first and the second phytochrome-mediated response with respect to the coupling of P-fr to the transduction chain; P-fr is unable to induce rhizoid growth until 60 h after the start of the first red irradiation. The effectivity of P-fr for inducing the second response shows an optimum at ca 96 h after the beginning of the presence of P-fr; thereafter, it declines slowly. The fluence-response relationship and the presence of red/far-red reversibility demonstrate that rhizoid elongation is a low-fluence response mediated by phytochrome and is independent of the first phytochrome response.

Photoinhibition of photosynthesis was investigated in the marine macroalga Ulva laetevirens by measuring chlorophyll fluorescence (PAM) and oxygen evolution. After exposure to unfiltered solar radiation the ratio of the variable fluorescence to the maximal fluorescence F-v/F-m (F-v = F-m-F-O) as well as the oxygen production declined rapidly with increasing duration of the exposure. Fluence rate-response curves for the oxygen production showed a decrease in the slope with exposure time and a shift of the compensation point to higher fluence rates as well as a decrease in the photosynthetic oxygen production. Solar radiation deprived of most of the W-B (long pass above 320 nm) induced a similar degree of photoinhibition of the ratio F-v/F-m as unfiltered solar radiation, whereas the oxygen production was less affected. The photoinhibitory effect of solar radiation was diminished when the solar radiation was filtered by a filter which passes wavelengths above 400 nm. Even though UV-B accounts for a very small fraction of solar radiation, it has a considerable effect on photosynthesis. In addition, UV-A and visible radiation contribute to photoinhibition in Ulva.

It is demonstrated that in vivo irradiation with artificial UV-B for several hours significantly reduces the amount of large DNA extractable from immobilized Euglena in comparison with non-irradiated controls. This UV-B effect can be eliminated by a drastic reduction of the divalent ion concentration in the extracellular medium, i.e. the substitution of the culture medium by Tris-buffered agarose. Moreover, in vitro degradation of large DNA is demonstrated for crude protein extracts isolated from non-irradiated or UV-B-irradiated Euglena. The nuclease activity is shown for both crude protein extracts and purified nucleases; in both cases, two protein bands possessing nuclease activity are obtained with apparent molecular masses of 26 and 40 kDa and their activity is inhibited by specific nuclease inhibitors, i.e. aurintricarboxylic acid and ATP, applied at a concentration as low as 10−8 M. Moreover, in vitro, nuclease activity clearly depends on the pH, with an optimum around pH 4.5, and on the ion composition of the extracellular medium. A strong stimulating effect is shown for Ca2+ with an optimum around 10−4 M; this effect is potentiated by Zn2+ and Mn2+, but strongly counteracted by Mg2+ and the calmodulin inhibitors trifluoperazine and N- (6-aminohexyl)-5-chloro-1-naphthalenesulphonamide (W5). These results favour the concept which explains the lethal UV-B effect on Euglena as arising from a change in the general metabolic state of the cell and activation of a DNA-degrading system, i.e. activation of metal-dependent nucleases (U.K. Tirlapur, D.-P. Häder and R. Scheuerlein, UV-B mediated damage in the photosynthetic flagellate, Euglena gracilis, studied by image analysis, Beitr. Biol. Pflanzen, 67 (1992) 305–317).

Biologia plantarum, an international journal for experimental botany founded in 1959 by Professor Bohumil Němec. Covers all branches of experimental botany ranging from molecular biology and biotechnology to whole-plant and stand functioning.

The effects of solar and artificial ultraviolet radiation on the motility and graviorientation of three strains of the dinoflagellate Prorocentrum were studied. P. micans isolated from the Baltic Sea shows a pronounced negative gravitaxis which switches to a positive one even after short exposure times to either solar or artificial UV irradiation. In constrast P. minimum strains isolated from the Kattegat and the Atlantic coast off Portugal showed only a weak upward orientation. In all three strains the linear swimming velocity decreases after short exposure times and, in addition, the percentage of motile cells in the populations drastically decreases. Removing the ultraviolet component of solar radiation with a cut-off filter prolongs the tolerated exposure times.

Biologia plantarum, an international journal for experimental botany founded in 1959 by Professor Bohumil Němec. Covers all branches of experimental botany ranging from molecular biology and biotechnology to whole-plant and stand functioning.

Induction of germination in spores of Dryopteris paleacea and in turions of Spirodela polyrhiza is phytochrome mediated. The presence of Ca2+ in the culture medium is required in both cases during a defined period after red light (R). To understand the role of Ca2+ in the phytochrome-mediated response Ca-45-uptake into cells (R-irradiated or non-irradiated) was investigated. Ca-45-uptake into turions occurred under all conditions tested, but was not significantly altered by R. Moreover, the release of Ca-45 from turions into a Ca2+-free medium was not affected by R. Corresponding results were found in case of the single-celled spores. Furthermore, the Ca2+-antagonists La3+ and Co2+ reduced the Ca-45-uptake into spores strongly. The results indicate that uptake as well as release of Ca2+ depend on the Ca2+-gradient established on both sides of the plasmalemma. It is concluded that calcium uptake or release is not an essential step within the phytochrome-induced chain of events, rather calcium has to be considered as a prerequisite (permissive factor) in both, spores of D. paleacea (Pteridophyta) and turions of S. polyrhiza (Angiospermae).

The effects of solar and artificial ultraviolet radiation on pigment composition and photosynthetic oxygen production were studied in three strains of the dinoflagellate Prorocentrum. Extended exposure to UV radiation caused bleaching of the photosynthetic pigments; the carotenoids were less resistant than chlorophyll c2 but more than chlorophyll a. In addition, there was a bathochromic shift in the chlorophyll a absorption after extended UV irradiation. Photosynthesis was impaired by solar radiation in all three strains, however Prorocentrum micans isolated from the Atlantic off Portugal was much more resistant than the Prorocentrum strains isolated from Kattegat or from the Baltic Sea. In contrast, respiration was hardly affected by exposure to solar radiation and even increased in two of the strains.

The effects of solar and artificial ultraviolet radiation on the motility and orientation of the dinoflagellate Y-100 were studied. The cells show a weak photokinesis but a pronounced phototaxis which is consistently positive between 1 and 100 klx ( = 4 mW m−2 to 400 mW m−2); the precision of orientation increases with the fluence rate. Unfiltered solar radiation as well as artificial ultraviolet radiation reduce the percentage of motile cells increasingly with exposure time but the velocity of the still motile cells is less affected. Unirradiated control cells show a negative gravitaxis. After short exposure to solar or artificial ultraviolet radiation the precision of gravitaxis decreases and after prolonged exposure the cells start to actively move downward in the water column (positive gravitaxis). Phototaxis is also strongly impaired by ultraviolet radiation.

Spore germination in Anemia phyllitidis can be induced by red light (R) via the phytochrome system and by gibberellic acid (GA3) in the dark. An enhancing effect of NO3‐ions on the Pfr‐mediated germination could be demonstrated. This NO3‐effect was found to be pronounced during the preinduction phase and could be described by biphasic kinetics depending on the formation of Pfr by the R‐irradiation. Besides NO3, other electron accepting substances also increased germination significantly. In contrast to Pfr‐mediated germination, no enhancing effect by NO3 could be obtained for the GA3‐induced germination response. The application of an inhibitor of gibberellic acid synthesis, AMO1618, as well as the analysis of combined R and GA3 treatment, support the hypothesis that for germination of Anemia phyllitidis spores no synergism between the factors exists. Thus, it is proposed that the gibberellic acid receptor starts a signal‐transduction pathway resulting in germination which is in part independent of the Pfr‐mediated signal‐transduction chain. The NO3‐effect is specific for the Pfr‐mediated signal‐transduction chain.

The alkaloid staurosporine, currently known as the most potent inhibitor of protein kinase C, PKC, was tested for its ability to inhibit phytochrome-mediated spore germination in Dryopteris fllix-mas L., evaluated by the induction of chlorophyll synthesis. Approximately half-maximal inhibition was obtained at a concentration of 10-5 M. This effect of staurosporine was phase-specific and was found during the same period in which the presence of extracellular calcium is necessary for realization of the light signal. Furthermore, the ability of staurosporine to prevent progression of a germinated spore into early gametophyte development, evaluated by the accumulation of chlorophyll, was examined. Again, staurosporine (10-5 M) significantly diminished chlorophyll accumulation, determined quantitatively in vivo by single-cell measurements, in a non-phase specific way. The fact that the phase-specific inhibitory effect of staurosporine in preventing germination was coincident with the phase-specific requirement of Ca2+ suggests that both Ca2+ and staurosporine affect the same step in the signal-transduction chain. A phosphorylation event catalysed by PKC or any Ca2+-dependent protein kinase is proposed as the target of staurosporine and Ca2+.

Germination ofDryopteris spores is mediated by the physiologically active, far-red-absorbing form of phytochrome, Pfr, and external Ca2+ is necessary for the transduction of the light signal. Because knowledge about the cytoplasmic calcium ion concentration, [Ca2+]i, is of great importance for understanding the role of calcium during signal transduction, this value was measured using fura-2 in fern spores undergoing the normal developmental progression into germination. Fura-2 was loaded into the spores by electroporation, which does not disrupt the normal process of germination. The intensity of the fluorescence emission of the loaded fura-2 was analysed by a microspectrophotometric assay of single spores, and successful loading could be obtained by the application of ten electrical pulses (field strength 7.5 kV · cm−1, half-life (time constant) 230 μs). Fura-2 was alternately excited by light of wavelengths 355 and 385 nm through an inverted fluorescence microscope, and the emitted fura-2 fluorescence was collected by a silicon-intensified video camera. The cytoplasmic calcium ion concentration was calculated from the ratio of the camera output obtained for both wavelengths and displayed by a pseudo-color technique. Spores responded to changes of the extracellular Ca2+ concentration, and this observation is considered as evidence that fura-2 is loaded into the cytoplasm. The substitution of a low external [Ca2+] (1 mM ethyleneglycol-bis(2-aminoethyl-ether) N,N,N′,N′-tetraacetic acid (EGTA)) by 1 mM CaCl2 caused a fast increase of [Ca2+]i from approx. 50 nM to above 500 nM. In contrast, the subsequent substitution of CaCl2 by EGTA decreased [Ca2+]i again below 100 nM within 0.5 h. Furthermore, the application of ionomycin could initiate a change in [Ca2+]i according to the Ca2+ gradient established between the extracellular medium and cytoplasm. In spores sown on a Ca2+-free medium, [Ca2+]i, analysed in a buffer containing EGTA, was found to be around 50 nM during the first days of cultivation, independent of the irradiation protocol. However, if spores were grown in darkness on a Ca2+-containing medium and analysed in EGTA, [Ca2+]i was significantly higher (≧ 500 nM). In red-light-irradiated spores, [Ca2+]i was found to decrease with increasing time after irradiation, and was determined to be less than 100 nM when analysis was done 44 h after germination was initiated by the light treatment.

Abstract— For phytochrome‐mediated fern‐spore germination in Dryopteris paleacea Sw., initiated by a saturating red light (R) irradiation 20 h after imbibition, an almost absolute requirement for extracellular Ca2+ is found. To investigate the kinetics of this Ca2+ requirement spores were sown on a Ca2+‐free medium (Ca2+ < 10−8M) and Ca2+ was raised to 1 mM at defined periods after R. Alternatively, spores were sown on a Ca2+‐containing medium (1 mM) and transferred to a Ca2+‐free medium. A clearly defined period for the Ca2+ requirement is found between 30 and 50 h after R, while Ca2+ had to be present in the medium for at least 9 h to obtain half‐maximal germination. However, since the kinetics of deprivation and delayed addition of Ca2+ do not provide significantly different results, only a relative short presentation time for extracellular Ca2+ has to be expected at the level of a single cell. Ca2+ sensitivity is determined by the timing of the R irradiation, i.e. the timing of Pfr formation, which has been concluded from the observation that the variation of the imbibition time does not affect the kinetics of Ca2+ requirement and that the temporal application of polyethylene glycol (PEG), which is assumed to interrupt Pfr action, shifts the Ca2+ requirement to delayed intervals. These observations, as well as the fact that the requirement of Ca2+ has been observed for a limited period are interpreted as indirect evidence that Ca2+ action plays the role of a specific link in the phytochrome‐mediated signal‐transduction chain. The “Ca2+ kinetics” are compared with the kinetics of escape from reversibility by far‐red (FR) light and with kinetics of basic cell physiological processes occurring during germination. “Escape kinetics”, indicating “coupling” of Pfr to subsequent dark reactions, are observed at significant earlier intervals, and a gap of about 15 h is found for both the action of Pfr and of Ca2+. Thus, the direct interaction of Pfr with external Ca2+ as a first transduction step can be excluded experimentally. The kinetics of chlorophyll formation are found to be only slightly delayed, whereas the kinetics of mitosis are shifted by approximately 30 h. Almost the same slope is obtained for all kinetics investigated so far and one reaction spans a period of approximately 35 h. Obviously, variability found in the spore population is due to the coupling of Pfr whereas subsequent reactions proceed with almost identical velocity.

Abstract. Chloroplasts redistribute and/or reorientate in the cell as a response to the light direction, resulting in patterns typical for light of low or high fluence rate, respectively. Usually, the main photoreceptor pigment is a blue‐UV‐absorbing pigment (‘cryptochrome’), but in a few exceptional cases, the reversible red/far‐red system phytochrome is involved. Detection of light direction is based on light refraction and/or on dichroic orientation of photoreceptor molecules. Membrane effects, intracellular calcium redistribution and calcium‐calmodulin interaction are discussed as likely steps in signal transduction. In the response mechanism the actin‐myosin system is involved. However, several details of perception, transduction and response are still unsolved and open for discussion. Particularly interesting are the cases of multiple photoreceptor systems, i.e. those where separate transduction chains are started which coact or interact with each other. This raises the question as to the evolution of multiple photoreceptor systems under the assumption that light‐oriented chloroplast movements serve to optimize photosynthesis.

Abstract— Induction of germination in spores of Dryopteris filix‐mas L. shows an absolute requirement for light with phytochrome as photoreceptor. The effectiveness of a red light (R) irradiation is affected by the ionic composition of the culture medium (Haupt, Planta164,63–68, 1985). In this paper NO3−is identified as the component mediating this effect whereas ammonium or organic nitrogen‐containing compounds, tested so far, are ineffective. Enhancement by NO3− can be observed at concentrations 1 μM and an optimum is found around 1 mM. The kinetics of NO3− action are elucidated by restricting the presence of NO3− to defined periods after sowing, and they are compared with kinetics of Pfr action. As a result, the enhancement of NO3− can be attributed to a specific phase in the signal‐transduction chain: the promotive effect of nitrate is only obtained if the Pfr presence coincides with or slightly preceeds the presence of NO3−. If Pfr can act for 15 or 20 h and is reversed thereafter by far‐red light (FR), NO3− added during this period or immediately after FR is effective and this enhancement vanishes during 6 h following FR. In contrast, NO3− has no effect as long as it is applied only during a period before Pfr is formed. Moreover, a modulation of the effectiveness of the photoconversion Pr to Pfr by NO3− can be excluded. These results are interpreted by the action of NO3− during early steps in the Pfr‐induced signal‐transduction chain. However, an additional effect of NO3− on the “coupling” of Pfr itself to subsequent dark reactions cannot be excluded yet.

Phytochrome-mediated germination of fern spores of Dryopteris paleacea Sw. was initiated by a saturating red-light (R) irradiation after 20 h of imbibition. For its realization external Ca2+ was required, with a threshold at a submicromolar concentration, and an optimum was reached around 10-4 M. At concentrations ≥10-1 M only a reduced response was obtained, based probably on an unspecific osmotic or ionic effect. The germination response was inhibited by La3+, an antagonist of Ca2+. From these results it is concluded that Ca2+ influx from the medium into the spores may be an important event in phytochrome-mediated germination. In the absence of Ca2+ the R-stimulated system remained capable of responding to Ca2+, added as late as 40 h after R. Moreover, Ca2+ was effective even if added after the active form of phytochrome, Pfr, had been abolished by far-red (FR) 24 h after R. Thus, the primary effect of Pfr, that initiates the transduction chain, does not require calcium. “Coupling” of Pfr to subsequent dark reactions has been investigated by R-FR irradiations with various dark intervals. The resulting “escape kinetics” were characterized by a lag phase (6 h) and half-maximal escape from FR reversibility (19 h). These kinetics were not significantly changed by the presence or absence of calcium. Thus, direct interaction of Pfr and calcium is not a step in the transduction chain initiated by the active form of photochrome.

In spores of the fern Dryopteris filix-mas, we have followed loss of Pfr activity shortly after sowing, using a null method: with a (start) pulse of red light a steady state level of Pfr is established 0.5 h after sowing, thus inducing germination. 7.5 – 23.5 h thereafter, the Pfr level still remaining is tested with a second saturating pulse. If this (test) pulse is given with various wavelengths, it increases or decreases the germination response, and these changes are used to determine, by interpolation, the actual Pfr level at the time of the test pulse. Assuming that there is dark destruction or dark reversion underlying this apparent Pfr decay, its kinetics are calculated. For both these assumptions the kinetics are significantly slowed down as the age of the spores increases (i.e. the time of storage, after harvest, at 6 °C). Interestingly, with increasing spore age a single pulse of red light becomes increasingly more effective in the induction of germination. This correlates well with the slower decay, thus enabling a higher Pfr level to act for a longer time. Virtually identical results are obtained for D. paleacea.