Water relations and growth of shrubs before and after fire in a semi-arid woodland

Summary Plant water relations and shoot growth rate of shrubs resprouting after fire or unburnt were measured in a semi-arid poplar box (Eucalyptus populnea) shrub woodland of eastern Australia. In vegetation unburnt for about 60 years, the dawn xylem water potential (_x) of the dominant shrub species was about-1.0 MPa when the soil was wet and-8.0 MPa when the soil was very dry. At any one time, the dominant shrub species,Eremophila mitchellii, E. sturtii, Geijera parviflora andCassia nemophila, were similar in _x butAcacia aneura andDodonaea viscosa were consistently higher in _x than this group when the soil was moist and lower when the soil was dry. The dominant tree species,Eucalyptus populnea andE. intertexta, appeared to have access to additional water beneath the hardpan which is located 60–80 cm below the surface. When shrubs were under extreme water stress (_x of-8 MPa), the trees had a _x of-3 to-3.6 MPa. Following a fire, both _x and leaf stomatal conductance (g _s) of resprouting shrubs were higher for about 5 years than comparable-aged unburnt vegetation, with relative differences in _x increasing with drought stress. Elongation rate of resprouts was positively linked to prefire shrub height in 3 of 4 species. However, shrubs resprouting after high intensity fires had substantially higher rates of shoot elongation than after low intensity fires which were in turn higher than for foliar expansion of unburnt shrubs. It is concluded that the growth rate of resprouting shrubs is primarily determined by physiological/ morphological factors associated with plant size but is also assisted by greater availability of water and possibly nutrients for a period after fire.     

The mitochondrial membrane potential (deltapsi(m)) in apoptosis; an update

Mitochondrial dysfunction has been shown to participate in the induction of apoptosis and has even been suggested to be central to the apoptotic pathway. Indeed, opening of the mitochondrial permeability transition pore has been demonstrated to induce depolarization of the transmembrane potential (_m), release of apoptogenic factors and loss of oxidative phosphorylation. In some apoptotic systems, loss of _m may be an early event in the apoptotic process. However, there are emerging data suggesting that, depending on the model of apoptosis, the loss of _m may not be an early requirement for apoptosis, but on the contrary may be a consequence of the apoptotic-signaling pathway. Furthermore, to add to these conflicting data, loss of _m has been demonstrated to not be required for cytochrome c release, whereas release of apoptosis inducing factor AIF is dependent upon disruption of _m early in the apoptotic pathway. Together, the existing literature suggests that depending on the cell system under investigation and the apoptotic stimuli used, dissipation of _m may or may not be an early event in the apoptotic pathway. Discrepancies in this area of apoptosis research may be attributed to the fluorochromes used to detect _m. Differential degrees of sensitivity of these fluorochromes exist, and there are also important factors that contribute to their ability to accurately discriminate changes in _m.     

Autumn stomatal closure in six conifer species of the Central Rocky Mountains

Summary Environmental and water relations parameters during fall were monitored for six conifer tree species common to the central Rocky Mountains growing naturally at the same location (Pinus contorta, Pinus ponderosa, Pinus flexilus, Pseudotsuga menziesii, Abies lasiocarpa, Picea engelmannii). Subsequent to what appeared to be the beginning of seasonal stomatal closure, leaf conductance to water vapor declined sharply following the onset of freezing air temperatures at night. A coincident rapid decline in morning xylem pressure potentials (_p) also occurred which resulted in values that were considerably below afternoon _p. Continuing decreases in maximum leaf conductance during the day were highly correlated with corresponding decreases in minimum nocturnal air temperatures of the preceding night. By mid-December, morning _p returned to values very near afternoon _p and were only slightly lower than before the onset of subfreezing nights. A preliminary model is proposed which interprets the qualitative interaction between air and soil temperatures, soil and plant water potentials, and leaf conductance during seasonal stomatal closure in fall.     

Leaf water potential,component potentials and relative water content in a xeric grass,Agropyron dasystachyum (Hook.) Scribn.

Summary Leaf water potential ( _l ), osmotic potential ( _s ), pressure potential ( _p , turgor pressure), relative water content (R) and their interrelationships were determined for a xeric grass (Agropyron dasystachyum) found in the grasslands of Canada. Thermocouple psychrometers were used to measure _l and _s ; _p was obtained by subtraction. _l dropped from near 0 bars to about-28 bars as R went from 90% to 75%. R greater than 90% was not observed, perhaps because of a systematic error in determination of turgid water content. R remained relatively high in A. dasystachyum, even at low _l . The slope of the _l -R relationship was similar to other species which are generally considered to be drought tolerant. _p as high as 14 bars was observed. Most of the decrease in _l was accounted for by a decline in _p . The ability of A. dasystachyum to adjust to fluctuating water stress over the growing season is probably as much related to changes in tissue structure and turgor relationships as to simple changes in osmotic potential.     

Shifts in carbon isotope ratios of two C3 halophytes under natural and artificial conditions

Summary The total carbon ¹³C values of two C₃ halophytes,Salicornia europaea L. ssp.rubra (Nels.) Breitung andPuccinellia muttalliana (Schultes) Hitch., native to inland saline areas of Alberta, Canada, were determined for plants grown under controlled conditions of supplied NaCl in the nutrient solution, and for plants found growing in the field. Field specimens were collected along line transects which ran from areas of high salinity to areas of low salinity across the pattern of species zonation. The ¹³C value of the two species seemed to reflect the water potential of the soil ( _w ^soil ) as measured arbitrarily at a depth of 10 cm, becoming less negative as the _w ^soil decreased. Over a linear distance of 5.55 m,S. europaea spp.rubra showed a shift of +5.3 as the _w ^soil went from-25x10² kPa to a minimum of-73x10² kPa. ForP. nuttalliana, the ¹³C values differed by 3.4 over a distance of 7.45 m where the maximum difference in _w ^soil was 12.7x10² kPa. However, ¹³C values ofP. nuttalliana only roughly reflected the spatial trends in _w ^soil at the time of collection. In the growth chamber, the ¹³C value ofS. europaea ssp.rubra changed by a maximum of +8.0 when the solute potential of the nutrient solution ( _w ^soil ) was dropped from-0.25x10² kPa to-64.25x10² kPa; while the ¹³C value ofP. nuttalliana changed by a maximum of +10.8 when the _w ^soil was dropped from-0.25x10² kPa to-40.25x10² kPa. Linear regression analyses indicated that the ¹³C values of both species were strongly correlated (P<0.2%) with _w ^soil . The observed shifts in ¹²C may represent changes in the mode of photosynthetic CO₂ fixation. However, a number of other explanations, some of which are discussed in the text, are also possible. A proper ecophysiological interpretation of such shifts in ¹³C values of C₃ plants awaits a better understanding of the isotope fractionation mechanisms involved.     

Potential-sensitive response mechanism of diS-C3-(5) in biological membranes

Summary The potential-sensitive response mechanism of 3,3-dipropylthiodicarbocyanine iodide (diS-C₃-(5)) was examined based on our previous model of diS-C₃-(5) interaction with brush border membrane vesicles (BBMV) in the absence of a membrane potential. The model contained binding (6 msec), reorientation (30 msec), dimerization (<10 nsec), and translocation (1 sec) reaction steps (Cabrini & Verkman, 1986.J. Membrane Biol. 90:163–175). Transmembrane potentials () were induced in BBMV by K⁺ gradients and valinomycin. Steady-state diS-C₃-(5) fluorescence (excitation 622 nm, emission 670 nm) increased linearly with . The reorientation and translocation reaction steps were resolved by the stopped-flow technique as a biexponential decrease in fluorescence following mixture of diS-C₃-(5) with BBMV at varying . The fractional amplitude of the faster exponential increased from 0.36 to 0.73 with increasing (–17 to 87 mV); the time constant for the faster exponential (30–35 msec) was independent of . There were single exponential kinetics (0.5–1.5 sec) for diS-C₃-(5) fluorescence response to a rapid (<2 msec) change in in the absence of a diS-C₃-(5) concentration gradient. These results, and similar findings in placental brush border vesicles, red cell vesicles, and phosphatidylcholine vesicles, support a translocation mechanism for diS-C₃-(5) response, where induced membrane potentials drive diS-C₃-(5) redistribution between sites at the inner and outer membrane leaflets, with secondary effects on diS-C₃-(5) dimerization and solution/membrane partitioning. Fluorescence lifetime and dynamic depolarization measurements showed no significant change in diS-C₃-(5) rotational characteristics or in the polarity of the diS-C₃-(5) environment with changes in . Based on the experimental results, a mathematical model is developed to explain the quantitative changes in diS-C₃-(5) fluorescence which accompany changes in at arbitrary dye/lipid ratios.     

Organization of Methanobacterium thermoautotrophicum bacteriophage psi M1 DNA

Summary M1 is a virulent bacteriophage of Methanobacterium thermoautotrophicum strain Marburg. Restriction enzyme analysis of the linear, 30.4 kb phage DNA led to a circular map of the 27.1 kb M1 genome. M1 is thus circularly permuted and exhibits terminal redundancy of approximately 3 kb. Packaging of M1 DNA from a concatemeric precursor initiates at the pac site which was identified at coordinate 4.6 kb on the circular genome map. It proceeds clockwise for at least five packaging rounds. Headful packaging was also shown for M2, a phage variant with a 0.7 kb deletion at coordinate 23.25 on the map.     

Temperature and moisture effects on C and N mineralization from surface applied clover residue

A better understanding of the effect of temperature (T) and moisture on soil microbial activity should improve our ability to predict N mineralization from soil organic matter and crop residues. The objective of this study was to evaluate the effects of water potential () and T on C and N mineralization from unamended Cecil loamy sand soil (clayey, kaolinitic, thermic Typic Kanhapludult) and from crimson clover (Trifolium incarnatum L.) residues applied on the soil surface. Cecil soil was packed into acrylic plastic cylinders, adjusted to -5.0, -1.5, -0.03, or -0.003 MPa, treated with clover residues on the surface or left unamended, and incubated at 10, 20, 28, or 35°C for 21 d. Headspace gas samples for CO2 and N2O determinations were taken periodically and NH3 evolved was trapped. Inorganic N in soil and residue extracts was analyzed after 21 d. When increased from -5.0 to -0.003 MPa, total CO2 evolved from unamended soil increased linearly with ln(-), whereas total CO2 evolved from clover residue increased exponentially with . In both cases the effect of was enhanced as T increased. Two-dimensional (T, ) equations were developed to describe these effects. Apparent net mineralized N from the clover residue increased with until it reached a maximum between -0.5 and -0.03 Mpa.     

Ecophysiological analysis of woody species in contrasting temperate communities during wet and dry years

This study employed an intensive sampling regime in which leaf gas exchange and tissue-water relations were measured simultaneously on the same leaf at midday on 19 tree species from three distinct forest communities during wet (1990) and dry (1991) growing seasons. The study sites were located on a xeric barrens, a misic valley floor, and a wet-mesic floodplain in central Pennsylvania, United States. The xeric, mesic, and wetmesic sties had drought-related decreases in gravimetric soil moisture of 53, 34 and 27%, respectively. During the wet year, xeric and mesic communities had high seasonal mean photosynthetic rates (A) and stomatal conductance of water vapor (g _wv) and low midday leaf water potential (), whereas the wet-mesic community had low A and g _wv and high midday . The mesic and wet-mesic communities had dry year decreases in predawn , g _wv and A with the greatest drought effect occurring in the mesic community. Regression analysis indicated that species from each site that exhibited high wet-year A and g _wv tended to have low midday . This trend was reversed only in the mesic community in the drought year. Despite differences in midday , all three communities had similar midday leaf turgor pressure (_p) in the wet year attributable to lower osmotic potential at zero turgor ( ⁰ ) with increasing site droughtiness. Lower wet year ⁰ in the xeric community was due to low symplast volume rather than high solute content. Species with the lowest ⁰ in the wet year often did not have the lowest ¹⁰⁰ possibly related to differences in tissue elasticity. Moreover, increased elasticity during drought may have masked osmotic adjustment in ¹⁰⁰ but not in ⁰ , via dilution of solutes at full hydration in some species. Despite the sampling regime used, there were no relationships between gas exchange and osmotic and elastic parameters that were consistently significant among communities or years. This result questions the universal, direct effect of osmotic and elastic adjustments in the maintenance of photosynthesis during drought. By including a large number of species, this study provided new insight to the ecophysiology of contrasting forest communities, and the community-wide impact of drought on contrasting sites.     

Preparations of Ψ-peptide bond and peptide-aldehyde inhibitors of atrial granule serine proteinase, a candidate processing enzyme of pro-atrial natriuretic factor

Pseudo-peptide bond inhibitors (-bond inhibitors) and peptide-aldehyde inhibitors of atrial granule serine proteinase, the candidate processing enzyme of pro-atrial natrieuretic factor, are prepared in high yield and purity by novel synthetic routes. The -bond compounds retain essential residues for enzyme binding, but place the enzyme inhibition site in the midst of the peptide sequence. Thus, Bz-APR--LR and Bz-APR--SLRR can be considered readthrough inhibitors of atrial granule serine proteinase. The most potent -peptide, Bz-APR--SLRR (IC₅₀=250 M), is about fivefold less potent than the best peptide-aldehyde inhibitor (EACA-APR-CHO), and both the -bond and peptide-aldehyde compounds are competitive, reversible inhibitors of the enzyme. The -bond peptides containing two C-terminal Arg residues are three-to tenfold more potent than the analogous compounds containing only one C-terminal Arg residue, confirming the importance of both Arg residues in the enzyme processing recognition site. As expected, because of their moderate potencies, the -peptides are not useful affinity ligands for purification of atrial granule serine proteinase, but both peptide aldehydes are effective affinity ligands [Damodaran and Harris (1995),J. Protein Chem., this issue].Abbreviations AGSP atrial granule serine proteinase - ANF atrial natriuretic factor - Bz benzoyl - DIEA diisopropylethylamine - DIPCDI diisopropylcarbodiimide - DMF dimethylformamide - DMSO dimethylsulfoxide - EACA 6(e)-aminocaproic acid - EtOAc ethyl acetate - HEPES N-2-hydroxyethylpiperazine-N-propanesulfonic acid - HOBt N-hydroxybenzotriazole - HPLC high-performance liquid chrornatography - NMR nuclear magnetic resonance - PEG polyethylene glycol-3350 - PyBOP benzotriazole-1-yl-oxy-trispyrrolidino-phosphonium-hexafluorophospate - TEA triethylamine - TFA trifluoroacetic acid - THF tetrahydrofuran - TLC thin-layer chromatography - UV ultraviolet - pseudo-peptide bond -CH₂-NH-. Single-letter abbreviations are used to denote amino acids     

Protocol-dependence of equivalent circuit parameters of toad urinary bladder

Summary Determinations of current-voltage relationships are widely employed in the characterization of epithelial sodium transport. In order to determine the protocol dependence of transport parameters in the toad urinary bladder, studies were carried out in the presence and absence of amiloride, an inhibitor of active sodium transport. With symmetric positive and negative perturbations of the transepithelial electrical potential difference (0±100 mV) for 30 sec, the amiloride-sensitive current-voltage (i ^a -) relationship was near linear over the range –75+100 mV, indicating constancy of the conductance ^a and the apparent electromotive force E _Na, lumped parameters of the standard electrical equivalent circuit model of the active transport system. With a reverse protocol (±1000 mV) or 15 min perturbations thei ^a - relationships were highly nonlinear. Nonlinearity reflected voltage dependence of parameters: perturbations that increased active transport decreased E _Na and increased ^a, as evaluated from 10 sec perturbations of ; slowing of active transport produced the converse changes. These effects are usefully analyzed in both quasi-steady states and true steady states by means of a detailed equivalent circuit incorporating the significant ionic currents across each plasma membrane. Precise understanding of the significance of ^a and E _Na will require characterization of the partial ionic conductances on perturbation of .     

Measurements of electrical potential differences across yeast plasma membranes with microelectrodes are consistent with values from steady-state distribution of tetraphenylphosphonium inPichia humboldtii

Summary Electrical potential differences across the plasma membrane () of the yeastPichia humboldtii were measured with microelectrodes (filled with 0.1m KCl) inserted into cells immobilized in microfunnels. The registered signals were reproducible and stable for several minutes. On attainment of stable reading for the specific membrane resistanceR _sp was determined by applying square-current pulses to the preparation. Both andR _sp were pH dependent and displayed equal but opposite deflection, reaching its maximal value of –88±9 mV (n=13) andR _sp its minimal value of 10 k·cm² (maximal conductance) at pH 6.5. Uncouplers and the polyene antibiotic nystatin depolarized the cells, decreasing to –21±15 mV (n=10) with concomitant decrease ofR _sp. Comparison of values from microelectrode measurements with those calculated from the steady-state distribution of tetraphenylphosphonium ions agreed within 10 mV under all physiological conditions tested, except at pH values above 7.0. During microelectrode insertion transient voltage signals (a few msec long) were detected by means of an oscilloscope. These voltage signals were superimposed on the stable recordings described above. These short voltage signals disappeared in uncoupled cells. The closely related values obtained by two independent methods (direct measurements with microelectrodes and calculation from steady-state distribution of a lipophilic cation) provide evidence that these values reffect the true membrane potential of intact cells.     

The carotenoids of Flavobacterium strain R1560

The main carotenoid of Flavobacterium strain R1560 has been identified as (3R,3R)-zeaxanthin. Also present were small amounts of 15-cis-phytoene, phytofluene, -carotene (7,8,7,8-tetrahydro-, -carotene plus 7,8,11,12-tetrahydro-, -carotene), neurosporene, lycopene, -zeacarotene, -carotene, -carotene, -cryptoxanthin, rubixanthin, 3-hydroxy--zeacarotene and several apo-carotenals. Zeaxanthin production was inhibited by nicotine (10 mM), and lycopene and rubixanthin accumulated. The biosynthesis of zeaxanthin is discussed in terms of pathways and also of half-molecule reaction sequences. The presence of zeaxanthin may be a characteristic of a group of Flavobacterium species, and may thus be useful in the taxonomic classification of these organisms.     

Chloroplast acclimation to low osmotic potential

Photosynthetic potential of isolated chloroplasts was investigated during in situ water deficits. An eight day stress cycle imposed on spinach plants reduced leaf _w by 0.57MPa, and leaf by 0.50MPa, resulting in partial turgor maintenance during the stress cycle. Pressure/volume curves confirmed the occurrence of osmotic adjustment. Leaf depression was associated with an altered response of chloroplasts to low in vitro. Optimum reaction medium for photosynthesis shifted from –1.04 to –1.57MPa, and low was not as inhibitory to photosynthesis of plastids pre-exposed to stress in situ. These data indicate that chloroplasts acclimate to low external in response to leaf water deficits. This response was still evident four days after a stress cycle ended, but was nearly reversed eight days after stress. Repeated stress cycles in situ did not increase the degree of chloroplast acclimation to low in vitro. Fast dehydration of leaves did not induce this apparent chloroplast acclimation.Abbreviations osmotic potential - _w water potential - PEG polyethylene glycol 8000 - MPa megapascals     

Effects of water stress on the gas exchange,the activities of some enzymes of carbon and nitrogen metabolism,and on the pool sizes of some organic acids in maize leaves

Water-stressed maize (Zea mays L.) leaves showed a large decrease in leaf conductance during photosynthesis. Net CO₂ uptake and evaporation declined fast at mild stress (=–0.6 to –1.0 MPa) and slower at more severe stress (=–1.0 to -1.2 MPa), whereas the CO₂ concentration in the intercellular spaces (C_i) did not drop to the CO₂ compensation point. The activities of the enzymes of photosynthetic carbon metabolism tested in this study dropped by approx. 30% at =-1.2 MPa. Glutamine synthetase activity was unaffected by water stress, whereas the activity of nitrate reductase was almost completely inhibited. The decline of enzyme activities in relation to was correlated with a concomitant decrease in the content of total soluble protein of the stressed leaves. The total leaf pools of malate, pyruvate and oxaloacetate decreased almost linearly in relation to , thus obviously contradicting the almost constant C_i. In comparison to the controls (=0.6 MPa) the content of citrate and isocitrate increaed markedly at =-0.9 MPa and decreased again at =-1.2 MPa.Abbreviations PCR photosynthetic carbon reduction cycle - PCO photosynthetic carbon oxidation cycle - PEP phosphoenolypyruvate - RuBP ribulose-1,5-bisphosphate     

Ornithine decarboxylase prevents tumor necrosis factor alpha-induced apoptosis by decreasing intracellular reactive oxygen species

Ornithine decarboxylase (ODC) plays an essential role in various biological functions, including cell proliferation, differentiation and cell death. However, how it prevents the cell apoptotic mechanism is still unclear. Previous studies have demonstrated that decreasing the activity of ODC by difluoromethylornithine (DFMO), an irreversible inhibitor of ODC, causes the accumulation of intracellular reactive oxygen species (ROS) and cell arrest, thus inducing cell death. These findings might indicate how ODC exerts anti-oxidative and anti-apoptotic effects. In our study, tumor necrosis factor alpha (TNF-) induced apoptosis in HL-60 and Jurkat T cells. The kinetic studies revealed that the TNF- -induced apoptotic process included intracellular ROS generation (as early as 1 h after treatment), the activation of caspase 8 (3 h), the cleavage of Bid (3 h) and the disruption of mitochondrial membrane potential ( _m) (6 h). Furthermore, ROS scavengers, such as glutathione (GSH) and catalase, maintained _m and prevented apoptosis upon treatment. Putrescine and overexpression of ODC had similar effects as ROS scavengers in decreasing intracellular ROS and preventing the disruption of _m and apoptosis. Inhibition of ODC by DFMO in HL-60 cells only could increase ROS generation, but did not disrupt _m or induce apoptosis. However, DFMO enhanced the accumulation of ROS, disruption of _m and apoptosis when cells were treated with TNF- . ODC overexpression avoided the decline of Bcl-2, prevented cytochrome c release from mitochondria and inhibited the activation of caspase 8, 9 and 3. Overexpression of Bcl-2 maintained _m and prevented apoptosis, but could not reduce ROS until four hours after TNF- treatment. According to these data, we suggest that TNF- induces apoptosis mainly by a ROS-dependent, mitochondria-mediated pathway. Furthermore, ODC prevents TNF- -induced apoptosis by decreasing intracellular ROS to avoid Bcl-2 decline, maintain _m, prevent cytochrome c release and deactivate the caspase cascade pathway.     

Estimation of Membrane Potential Δψ in Reconstituted Plasma Membrane Vesicles Using a Numerical Model of Oxonol VI Distribution

A model of membrane potential-dependent distribution of oxonol VI to estimate the electrical potential difference across Schizosaccharomyces pombe plasma membrane vesicles (PMV) has been developed. was generated by the H⁺-ATPase reconstituted in the PMV. The model treatment was necessary since the usual calibration of the dye fluorescence changes by diffusion potentials (K⁺ + valinomycin) failed. The model allows for fitting of fluorescence changes at different vesicle and dye concentrations, yielding in ATP-energized PMV of 80 mV. The described model treatment to estimate may be applicable for other reconstituted membrane systems.     

Non-hydraulic signals from maize roots in drying soil: inhibition of leaf elongation but not stomatal conductance

Conditions of soil drying and plant growth that lead to non-hydraulic inhibition of leaf elongation and stomatal conductance in maize (Zea mays L.) were investigated using plants grown with their root systems divided between two containers. The soil in one container was allowed to dry while the other container was kept well-watered. Soil drying resulted in a maximum 35% inhibition of leaf elongation rate which occurred during the light hours, with no measurable decline in leaf water potential (_w). Leaf area was 15% less than in control plants after 18 d of soil drying. The inhibition of elongation was observed only when the soil _w declined to below that of the leaves and, thus, the drying soil no longer contributed to transpiration. However, midday root _w in the dry container (-0.29 MPa) remained much higher than that of the surrounding soil (-1.0 MPa) after 15 d of drying, indicating that the roots in drying soil were rehydrated in the dark.To prove that the inhibition of leaf elongation was not caused by undetectable changes in leaf water status as a result of loss of half the watergathering capacity, one-half of the root system of control plants was excised. This treatment had no effect on leaf elongation or stomatal conductance. The inhibition of leaf elongation was also not explained by reductions in nutrient supply.Soil drying had no effect on stomatal conductance despite variations in the rate or extent of soild drying, light, humidity or nutrition. The results indicate that non-hydraulic inhibition of leaf elongation may act to conserve water as the soil dries before the occurrence of shoot water deficits.Symbol _w water potential Contribution from the Missouri Agricultural Experiment Station, Journal Series No. 10881     

Book reviews

Consider the perturbed harmonic oscillator Ty=-y+x²y+q(x)y in L²(), where the real potential q belongs to the Hilbert space H={q, xq L²()}. The spectrum of T is an increasing sequence of simple eigenvalues _n(q)=1+2n+_n, n 0, such that _n 0 as n. Let _n(x,q) be the corresponding eigenfunctions. Define the norming constants _n(q)=lim_xlog |_n (x,q)/_n (-x,q)|. We show that for some real Hilbert space and some subspace Furthermore, the mapping :q(q)=({_n(q)}₀, {_n(q)}₀) is a real analytic isomorphism between H and is the set of all strictly increasing sequences s={s_n}₀ such that The proof is based on nonlinear functional analysis combined with sharp asymptotics of spectral data in the high energy limit for complex potentials. We use ideas from the analysis of the inverse problem for the operator -ypy, p L²(0,1), with Dirichlet boundary conditions on the unit interval. There is no literature about the spaces We obtain their basic properties, using their representation as spaces of analytic functions in the disk.     

Water relation parameters of the CAM plant Kalanchoë daigremontiana in relation to diurnal malate oscillations

Summary In the CAM plant Kalanchoë daigremontiana, kept in an environmental rhythm of 12 h L: 12 h D in a growth chamber at 60% relative humidity and well watered in the root medium, decreasing water potentials and osmotic potentials of the leaves are correlated with malate accumulation in the dark. In the light increasing water and osmotic potentials ( _W and _S ) are associated with decreasing malate levels. Transpiratory H₂O loss is high in dark and low in light.In continuous light, the CAM rhythm rapidly disappears in the form of a highly damped endogenous oscillation. Malate levels, and water and osmotic potentials of the leaves remain correlated as described above. However, transpiration is very high as malate levels decrease and water and osmotic potentials increase.It can concluded, that water relation parameters like total water potential ( _W ) and osmotic potential ( _S ) change in close correlation with changes of malic acid levels. As an important osmotically active solute in CAM plants, malic acid appears to affect water relations independently of and in addition to transpiration. The question remains open, whether turgor ( _P ) is involved in CAM regulation in intact plants in a similar way as it determines malate fluxes in leaf slices.Abbreviations CAM Crassulacean Acid Metabolism - L Light - D Dark