bluuebunny/crossref_metadata_2025 huggingface dataset:
Mild phosphorus stress in barley and a related low‐phosphorus‐adapted barleygrass: Phosphorus fractions and phosphate absorption in relation to growth
Authors: Chapin F. Stuart , Bieleski Rod L.
Published: April 2006

Barleygrass (Hordeum leporinum) from Australian low‐P (phosphorus) soils and commercial barley (H. vulgare) with high fertilizer requirements were grown in solution culture at 3 levels of P supply. The high‐P‐adapted barley produced more biomass at all levels of P supply and was more responsive to added P in terms of rate of tillering, rate of leaf production, final leaf size, and therefore total shoot weight compared to barleygrass. In both species root: shoot ratio decreased in response to improved tissue P status, even at P levels where total biomass did not respond to P supply. Removal of endosperm reserves of barley reduced total biomass to a greater extent than it altered phosphate absorption rate, thus increasing tissue P status and making plants less responsive to added P. Similarly, barleygrass had a slower growth rate but a comparable P absorption rate to that of barley. Thus barleygrass also accumulated tissue P and was unresponsive to added P. All phosphorus chemical fractions increased in response to improved tissue P status, but to differing extents (inorganic‐P > nucleic acid‐P > lipid‐P > ester‐P), suggesting that all P fractions (particularly inorganic P) serve, in part, a storage function. Both barleygrass and barley without endosperm had higher concentrations of all P fractions (particularly inorganic P) than did unaltered barley, but this was due entirely to their higher P status (due to slow growth) rather than to any major difference in P metabolism between species. We conclude that slow growth is more important than interspecific differences in P metabolism, P absorption, or efficiency of P utilization in explaining the success of barleygrass and other low‐P‐adapted species on infertile soils.
Increased activity of ornithine decarboxylase in tomato ovaries induced by auxin
Authors: Mizrahi Yosef , Heimer Yair M.
Published: April 2006

Auxin, which mimics natural pollination in tomato flowers, induces fruit setting as well as a 3‐fold increase in ornithine decarboxylase activity. In pollinated ovaries ornithine decarboxylase activity increased 4.7 fold. The possible connection between pollination, auxin treatment, fruit set, cell division and ornithine decarboxylase activity are discussed.
Population variation and diurnal changes in the content of indole‐3‐acetic acid of pine seedlings (Pinus sylvestris L.) grown in a controlled environment
Authors: Sandberg Göran , Odén Per‐Christer , Dunberg Arne
Published: April 2006

Pine seedlings (Pinus sylvestris L.) were grown in a growth chamber under simulated summer conditions to an age of eight weeks after the beginning of seed germination. Single seedlings were analyzed for fresh weight, shoot and root lengths, and content of indole‐3‐acetic acid (IAA). The first three variables were normally distributed with standard deviations of 29%, 17% and 18%, respectively. The IAA content had a standard deviation of 39%, and this variable was not normally distributed. If this finding is of general significance, population variation must be considered when experiments involving IAA analyses are planned, and statistical methods based on a normally distributed population cannot be used to evaluate the result of such analyses unless samples of at least 20–30 individuals are analyzed. There were no correlations between the content of IAA and any of the three other variables. The content of IAA showed pronounced diurnal changes, rising from 15 ng g−1 (fresh weight) in the morning to 42 ng g−1 in the late evening. The initial rate of change was about 10% h−1. Obviously, short‐term fluctuations must be checked if long‐term changes in IAA content are to be studied. IAA could also be released from the acidic buffer fraction by means of alkaline hydrolysis. This “bound alkali‐hydrolysable” IAA did not show short‐term fluctuations.
Ethylene effects on growing and gravireacting maize root segments
Authors: Bucher Dominique , Pilet Paul‐Emile
Published: April 2006

The effects of ethylene pretreatments (500 nl/l for 1 h) and treatments (100 nl/1 to 1000 nl/l for 6 h) on elongation and gravireaction of apical maize root segments were tested in light and in the dark. Ethylene was found to affect weakly root elongation and gravireaction, but to induce strong curvatures for root growing vertically.
A relationship between potassium and proline accumulation in salt‐stressed Sorghum bicolor
Authors: Weimberg Ralph , Lerner H. R. , Poljakoff‐Mayber A.
Published: April 2006

The amount of total monovalent cations in leaves of Sorghum bicolor, L. Moench, RS 610, which were exposed to salinity stress, was a function of both the osmotic potential and the concentration of K+ of growth media. The plants have a Na+ exclusion mechanism that keeps the level of Na+ in leaves low. Thus, most of the osmotic adjustment in leaves was due to K+. Proline did not start to accumulate in leaves until the concentration of total monovalent cations in leaves reached a threshold of approximately 200 μmol/g fresh weight. Above this threshold, the contents of prolioe and monovalent cations in leaves increased with increasing salinity of the medium. The ratio of proline to monovalent cation was 5% of that amount of monovalent cation in excess of the threshold concentration. Therefore, if the cations are located in the vacuoles and proline accumulates in the cytoplasm, then the amount of accumulated proline is sufficient to act as a balancing osmoticum across the tonoplast. Very little proline accumulated in roots because this tissue contained much less total monovalent cations than leaves from the same salt‐stressed plants. The same threshold of 200 μmol/g fresh weight of total monovalent cations was required in roots as in leaves to initiate proline accumulation.
Effects of supplemental UV‐B radiation on primary photosynthetic carboxylating enzymes and soluble proteins in leaves of C3 and C4 crop plants
Authors: Vu C. V. , Allen L. H. , Garrard L. A.
Published: April 2006

Effects of increased UV‐B radiation on activities of primary photosynthetic carboxylating enzymes and on contents of soluble proteins were studied in soybean (Glycine max [L.] Merr. cv. Bragg), pea (Pisum sativum L. cv. Little Marvel), tomato (Lycopersicon esculentum L. cv. Rutgers), and sweet corn (Zea mays L. cv. Golden Cross Bantam). The purpose was to evaluate the responses of agronomic crops to increases in solar UV‐B radiation. Plants were grown and exposed under greenhouse conditions for 6 h daily to supplemental UV‐B radiation which was provided by Westinghouse FS‐40 fluorescent sun lamps filtered with 0.127‐mm film of cellulose acetate (UV‐B treated) or Mylar S (Mylar control). Three UV‐B levels were tested: 1.09 (treatment T1), 1.36 (treatment T2), and 1.83 (treatment T3) UV‐Bseu where 1 UV‐Bseu equals 16.0 mW‐m2 weighted by EXP‐[(λ‐265)/21]2. These UV‐B levels corresponded to 6%,21%, and 36%, respectively, of decrease in stratospheric ozone content, based on the interpolations of UV‐B irradiances at a solar elevation angle of 60°.

Leaves of plants of soybean, pea, and tomato exposed to UV‐B radiation were generally low in RuBP carboxylase activity. On a fresh weight basis, all three UV‐B radiation levels significantly reduced the enzyme activity in soybean and pea, whereas tomato plants showed significant reduction in RuBP carboxylase activity only when exposed to 1.83 and 1.36 UV‐Bseu. An apparent decrease in soluble proteins was observed in leaf extracts of soybean and pea plants exposed to 1.36 and 1.83 UV‐Bseu whereas higher amounts of proteins were detected in leaves of tomato plants grown under UV‐B radiation.

Leaves of sweet corn plants grown under Mylar control were low in PEP carboxylase activity and proteins as compared with those of control plants receiving no supplemental UV and UV‐B treatment. Activities of PEP carboxylase in crode extracts from leaves of sweet corn were significantly suppressed under 1.36 and 1.83 UV‐Bseu as compared with the no UV control. Some stimulation of PEP carboxylase activity was observed in corn plants exposed to 1.09 UV‐Bseu.
The effects of inhibitors of cell wall synthesis on tobacco protoplast development
Authors: Galbraith David W. , Shields Barbara A.
Published: April 2006

The effect of 2,6‐dichlorobenzonitrile (DB) and coumarin on tobacco protoplast development has been studied using a combination of flow microfluorimetry and quantitative fluorescence microscopy. The results indicated that, over the initial period of culture, DB largely inhibited cellulose production at the cell surface, but did not inhibit DNA synthesis or protein accumulation by the protoplasts. Continuous culture of protoplasts in DB resulted in the accumulation of an increased capacity for cellulose synthesis as expressed following the removal of inhibitor. The possible sites of the specific inhibitory action of DB are discussed.
Involvement of epidermal cells in stomata movement: The effect of ABA
Authors: Itai Chanan , Roth‐Bejerano Nurit , Zvilich Menachem
Published: April 2006

ABA affected K+ and solute transport between guard cells and epidermal cells as indicated by K+ staining and plasmolysis. ABA enhanced K+ (86Rb) uptake into epidermal cells. To find out whether the ABA enhanced accumulation of K+ (86Rb) in epidermal cells is active, uptake in the presence of exogenous ATP was studied. These studies hinted that K+ (86Rb) uptake by epidermal cells is a passive process, while its release is an active one. This was verified by applying iodoacetate, which interferes with energy supply. The epidermal cells thus seem to play a role in stomatal movement.
The effects of decapitation on the distribution of cytokinins and growth of Phaseolus vulgaris plants
Authors: Van Staden J. , Carmi A.
Published: April 2006

The growth of the primary leaves of Phaseolus vulgaris L. was enhanced greatly by decapitation of the rest of the shoot. This increased growth was manifested by an increase in leaf area, leaf weight, and in a higher synthesis of chlorophyll and soluble proteins. Within the roots and stems decapitation resulted in a detectable increase in the endogenous cytokinins within 2 days after the surgical treatment. In the primary leaves increased cytokinin levels were only detected after 16 days. At this time most of the recorded activity co‐chromatographed with the cytokinin glucosides. When plants which were decapitated were left under normal growing conditions for 16 days and then transferred to continuous darkness for 8 days the senescence of the primary leaves of the decapitated plants, in which the cytokinins had increased, was delayed significantly when compared with that of the primary leaves of the intact plants. the significance of these findings is discussed.
Some physiological effects of podolactone‐type inhibitors
Authors: Sasse Jenneth M. , Wardrop Jennifer J. , Rowan Kingsley S. , Aspinall Donald , Coombe Bryan G. , Paleg Leslie G. , Buta J. George
Published: April 2006

Podolactone‐type inhibitors, including harringtonolide and lycoricidinol, affect several bioassays at 1 to 10 μM. Although these compounds were less active than abscisic acid in inhibiting growth of coleoptiles of wheat embryos, podolactone A significantly decreased the number of mature spikelets of Lolium temulentum at a lower concentration than abscisic acid. Lycoricidinol was more active than podolactone E, the most active of the podolactones, in three bioassays. Inhibition of growth induced by gibberellic acid or zeatin with podolactone‐type compounds was not competitive. Harringtonolide was a strong inhibitor of growth at higher concentrations but did not affect auxin transport, while podolactone E and lycoricidinol inhibited it. Lycoricidinol, podolactone E and harringtonolide did not retard senescence of leaf‐discs. The promotive effects of gibberellic acid in the barley endosperm bioassay were counteracted by podolactone A.
The effect of potassium on growth of Carex species from swamp habitats varying from oligotrophic to eutrophic and comparison of physiological reactions of Carex species to P stress and K stress
Authors: Veerkamp Mirjam T. , Kuiper Pieter J. C.
Published: April 2006

In a growth experiment at potassium levels varying between 0.001 mM and 3.0 mM potassium, relative growth rate (RGR) and other growth parameters were determined in Carex species: C. rostrata Stokes, C. limosa L., C. lasiocarpa Ehrh., C. diandra Schrank and C. acutiformis Ehrh., listed in order of increasing nutrient availability of their habitats. Carex species of nutrient poor sites did grow faster at low potassium concentration than species from nutrient rich habitats. The RGR of C. limosa was not affected by the K concentration, even at the lowest potassium concentration (0.001) mM) used. At high potassium availability Carex species from nutrient‐rich sites responded with greatly increased RGR, whereas the Carex from nutrient‐poor sites absorbed potassium in excess of immediate growth requirements: luxury consumption. A comparison is made of the physiology of the Carex species as affected by stress and abundance of phosphate and potassium.
Activity of some glycolytic and pentose phosphate pathway enzymes during the development of adventitious roots
Authors: Haissig Bruce E.
Published: April 2006

Activities of phosphofructokinase (PFK, EC 2.7.1.11), glyceraldehyde 3‐phosphate (NAD) dehydrogenase [G‐3‐PD(NAD), EC 1.2.1.12], glucose 6‐phosphate dehydrogenase (G‐6‐PD, EC 1.1.1.49), and 6‐phosphogluconate dehydrogenase (6‐PGD, EC 1.1.1.44) were determined in bean cuttings (Phaseolus vulgaris L. cv. Top Crop) over 4 days, encompassing adventitious root primordium initiation and development. Effects of applied auxin and “endogenous root‐forming stimulus”(ERS) on enzyme activities, concentrations of reducing sugars, and primordium development were also determined during the first 4 days of propagation. Effects of auxin were determined through use of applied indole‐3‐acetic acid (IAA) or 2,3,5‐triiodobenzoic acid. Effects of ERS were evaluated by means of decapitation of cuttings. Increased basipetal transport and increased metabolism of reducing sugars occurred in leafy cuttings in response to applied IAA and to ERS. Primordium development and activities of the four enzymes increased in leafy cuttings under conditions that simultaneously increased basipetal transport and metabolism of reducing sugars. Three types of enzyme activity response were found: (i) activity increased over time by ERS and by applied IAA [G‐3‐PD(NAD)], (ii) activity increased over time by ERS but not by applied IAA (PFK, G‐6‐PD), (iii) activity increased over time but not by ERS or applied IAA (6‐PGD). Increases in G‐3‐PD(NAD), G‐6‐PD, and PFK activity in leafy cuttings were positively related to primordium development. 6‐PGD activity increased in leafy cuttings during primordium development and may have supported it. However, equal increases occurred in decapitated cuttings, in which the long‐term development of primordia was supressed. Results for G‐3‐PD(NAD) that were obtained in an experiment with jack pine (Pinus banksiana Lamb.) seedling cuttings were similar to results for the same enzyme in bean cuttings. G‐3‐PD(NAD) activity in naphthaleneacetic acid‐treated jack pine cuttings increased with time, in comparison with untreated cuttings, before root emergence.
Freeze‐preservation of rice cells: A physiological study of freeze‐thawed cells
Authors: Cella Rino , Colombo Roberta , Galli Maria Grazia , Nielsen Erik , Rollo Franco , Sala Francesco
Published: April 2006

Rice (Oryza sativaL.) cells returning to in vitro culture after preservation at superlow temperature in liquid nitrogen are characterized by a number of physiological alterations. These include: reduction in respiration and glucose uptake, loss of intracellular potassium, decrease in the cellular level of key metabolites (ATP, glucose‐6‐phosphate and pyruvate) and fragility of protoplasts following the action of cell wall‐degrading enzymes.

Nevertheless, cell growth resumes after a short lag phase (2–4 days) with an actual 70–100% cell survival, thus indicating that the observed damage is not lethal and can be repaired in a short time.
Photosynthetic energy supply for NO3− assimilation in Scenedesmus
Authors: Larsson Marie , Ingemarsson Björn , Larsson Carl‐Magnus
Published: April 2006

NO3−‐dependent O2 in synchronous Scenedesmus obtusiusculus Chod. in the absence of CO2 is stoichiometric with NH4+ excretion, indicating a close coupling of NO3− reduction to non‐cyclic electron flow. Also in the presence of CO2, NO3− stimulates O2 evolution as manifested by an increase in the O2/CO2 ratio from 0.96 to 1.11. This quotient was increased to 1.36 by addition of NO2−, without competitive interaction with CO2 fixation, indicating that the capacity for non‐cyclic electron transport at saturating light is non‐limiting for simultaneous reduction of NO3− and CO2 at high rates. During incubation with NO3−+ CO2, no NH4+ is released to the outer medium, whereas during incubation with NO2−+ CO2, excess NH4+ is formed and excreted. NO3− uptake is stimulated by CO2, and this stimulation is also significant when the cellular energy metabolism is restricted by moderate concentrations of carbonyl cyanide‐p‐trifluoromethoxyphenylhydrazone, whereas NO3− uptake in the absence of CO2 is severely inhibited by the uncoupler. Also under energy‐restricted conditions NO3− uptake is not competitive with CO2 fixation. Antimycin A is inhibitory for NO3− uptake in the absence of CO2, and there is no enhancement of NO3− uptake by CO2 in the presence of antimycin A.

It is assumed that the energy demand for NO3− uptake is met by energy fixed as triosephosphates in the Calvin cycle. Antimycin A possibly affects the transfer of reduced triose phosphates from the chloroplast to the cytoplasm. Active carbon metabolism also seems to exert a control effect on NO3− assimilation, inducing complete incorporation of all NO3− taken up into amino acids. This control effect is not functional when NO2− is the nitrogen source. Active carbon metabolism thus seems to be essential both for provision of energy for NO3− uptake and for regulation of the process.
Water relations ofLithopsplants embedded into the soil and exposed to free air
Authors: Eller Benno M. , Ruess Beatrice
Published: April 2006

Transpiration and water uptake byLithops leslieiN.E.Br. andL. karasmontana(Dint. et Schwant.) N.E.Br. were measured by means of a potometer in a plant growth chamber under controlled environmental conditions in order to determine whether the embedding of the leaf cones into the soil prevents excessive water loss or not. Plants without embedding increased the transpirational water loss by the cone mantle with decreasing relative humidity of the surrounding air; the diurnal water loss by transpiration was not balanced by the water uptake during the same time. The balance between transpiration and water uptake was maintained during the whole day and was independent of the relative humidity of the free air if the plants were embedded in the soil.
Purification and properties of agmatine amidinohydrolase of Evernia prunastri
Authors: Vicente C. , Legaz María Estrella
Published: April 2006

An agmatine amidinohydrolase (EC 3.5.3.11) has been purified from Evernia prunastri (L.) Ach. thallus incubated on 40 mM L‐arginine at 26°C in the dark. The enzyme was purified 485‐fold with an overall yield of 55%. It shows a pH optimum of 6.9, a temperature optimum at 35–40°C and a molecular mass (weight) of about 320 000. The Evernia hydrolase is significantly activated by L‐arginine, L‐ornithine and putrescine for agmatine concentrations lower than 14 mM and inhibited for agmatine concentrations producing inhibition by an excess of substrate. Urea was always a powerful inhibitor of the enzyme. The Km for agmatine was estimated to be 6.4 mM.
Uptake of neutral and acidic amino acids by Lemna gibba correlated with the H+‐electrochemical gradient at the plasmalemma
Authors: Jung K.‐D. , Lüttge U. , Fischer E.
Published: April 2006

Uptake rates of L‐alanine, L‐serine and L‐aspartate and trans‐membrane electrical potentials (Δψ) were determined for a pH range in the external medium between 3.5 and 9.0. The proton electrochemical gradients () were calculated from Δψ, pH of the medium, and an assumed cytoplasmic pH of 7.5. At external amino‐acid concentrations of 0.1 mol m−3, where carrier‐mediated uptake dominates total uptake, a linear correlation between uptake rates and is obtained, which extrapolates to zero uptake at zero . This corroborates the contention that neutral and acidic amino acids are taken up by Lemna gibba L. by H+‐cotransport.
Changes occurring during aging and senescence in a submerged aquatic angiosperm (Potamogeton pectinatus)
Authors: Jana Sasadhar , Choudhuri Monojit A.
Published: April 2006

Changes occurring during aging and senescence of leaves of a submerged aquatic angiosperm (Potamogeton pectinatus L.) were studied. Total chlorophyll and chlorophylls a and b were maximal in mature, and minimal in old leaves. The chlorophyll a to b ratio was highest in mature leaves. During senescence, the chlorophyll content and the ratio of chlorophyll a to b decreased. The content of DNA, RNA, protein and dry weight, and the activity of alkaline pyrophosphatase decreased while free amino acids, the activity of protease, RNase and acid pyrophosphatase, and the ratio of acid to alkaline pyrophosphatase activity increased during aging and senescence. Kinetin (0.23 mM) deferred leaf senescence by delaying the loss of chlorophyll, protein, nucleic acids and dry weight, and reducing the rise in free amino acids, the activity of protease, RNase and acid pyrophosphatase and the ratio of acid to alkaline pyrophosphatase activity; while both 0.69 mM ethrel and 0.075 mM ABA hastened senescence. Kinetin pretreatment for an optimum period (12 h) followed by ethrel or ABA treatment partially erased the senescence‐promoting effect of the latter. But treatments in a reverse order markedly reduced the delaying effect of kinetin on senescence.
Some characteristics of a fast movement of auxin in intact tomato seedlings (Lycopersicon esculentum)
Authors: Maldiney R. , Sossountzov L. , Miginiac E.
Published: April 2006

Using exogenous 14C‐IAA, a fast movement of auxin was demonstrated in intact tomato plants (Lycopersicon esculentum Mill, cv. Craigella) cultured in vitro. This movement is insensitive to or weakly enhanced by cold temperature (0°C) and not influenced by gravity. In short time experiments (10 min) the main part of the radioactivity which travels through the plant is IAA; in long time ones (6 h) the metabolism is much higher and leads mainly to the formation of IAAsp. The integrity of the plant is necessary for the possibility to observe such a fast movement. Isolated hypocotyl segments show only the classical polar and slow movement of auxin. Microautoradiographic techniques show that the fast movement takes place inside the plant. In the epicotyl, the vascular bundles, mainly phloem cells, are labelled; in contrast, the radioactivity detected in the hypocotyl is low, and the tracers can be visualized only inside the epidermal cells.
Potassium transport in wheat seedlings grown with different potassium supplies.
Authors: Oláh Zoltán , Bérczi Alajos , Erdei László
Published: April 2006

The K+(86Rb) uptake into the roots and the translocation to the shoots of 11‐day‐old intact wheat seedlings (Triticum aestivum L. cv. Martonvásári 8) were investigated using plants grown with different K+ supplies. The effects of environmental conditions (darkness, humidity) and of metabolic and transport inhibitors (oligomycin, disalicylidene‐propanediamine, 2,4‐dinitriphenol, diethylstilbestrol, colchicine) were also studied. Plants with K content of about 0.2 mmol/g dry weight in the root and 0.5 mmol/g dry weight in the shoot (low K status) showed high K+ uptake into the roots and high translocation rates to the shoots. Both transport processes were very low in plants with K content of more than 1.5 and 2.2 mmol/g dry weight in the root and shoot, respectively (high K status).

Darkness and a relative humidity of the air of 100% did not influence K+ uptake by roots, but did inhibit upward translocation and water transport. Inhibition of photosynthesis and treatments with diethylstilbestrol (10−5 mol/dm3), as well as with colchicine resulted in inhibition of translocation in plants of low K status, but these inhibitors had little effect on K+ uptake by the roots. Oligomycin, 2,4‐dinitrophenol and diethylstilbestrol (10−4 mol/dm3), however, inhibited K+ uptake by the roots. In general, K+ transport processes were almost unchanged in plants of high K status. It is concluded that only plants of low K status operating with active K+ transport mechanisms are responsive to environmental factors. In high K+ plants the transport processes are passive and are uncoupled from the metabolic energy flow.
Accumulation of free proline and glycine betaine in Aster tripolium subjected to a saline shock: A kinetic study related to light period
Authors: Goas G. , Goas M. , Larher F.
Published: April 2006

On transferring three‐week‐old plants of Aster tripolium L. growing in a half strength Hoagland's medium to the same medium containing 333 mM NaCl a very quick uptake of salt and, after a lag phase of 3 to 5 h, an increase in free proline level was observed. During the time course of imino acid storage, the accumulation rates were higher in the light than in the dark, thereby suggesting some kind of photocontrol on solute metabolism. At zero time, high levels of glycine betaine were present in young plants grown without salt. However, after the application of saline shock, the betaine level also increased significantly. The highest rate of betaine accumulation was detected during the third day of treatment when the rate of proline storage decreased. Glycine betaine storage could also be linked to light dependent processes; whatever its importance in response to salt shock was, the levels observed were lower than those of plants directly grown on 333 mM NaCl for three weeks. When saline stressed plants were transferred to a medium without NaCl, the proline level quickly decreaed while that of glycine betaine remained stable.
Movement and distribution of 14C‐indole‐3‐acetic acid in branches and rooted cuttings of Douglas‐fir
Authors: Starbuck C. J. , Roberts A. N.
Published: April 2006

The transport of 14C‐indole‐3‐acetic acid in branch terminals and stems of rooted cuttings of Pseudotsuga menziesii (Mirb.) Franco was studied to determine if the plagiotropic growth of cuttings might result from an accumulation of basipetally transported auxin in the morphologically upper side of cuttings stems. Twenty‐four h after application of 10 μl of 14C‐IAA solution to the cut surface of decapitated, rooted cuttings, nearly twice as much activity was detected in extracts of tissue from the morphologically upper than from the lower halves of the stems. A similar distribution of activity was observed in horizontal branch terminals and in branch terminals which had been tied vertically for 2 weeks. The magnitude of the difference in activity between the 2 sides of the stem was greater in the horizontal than in the vertical branches.

There was no significant difference in transport through the upper and lower sides of excised stem segments from cuttings or branch terminals. In segments from rooted cutting stems, however, significantly more radioactivity from 14C‐IAA donor blocks was detected in the lower than in the upper halves of segments.
Gibberellic acid‐stimulated and auxin‐stimulated cell growth in relation to RNA synthesis, protein synthesis and development in the wheat coleoptile
Authors: Rose R. J. , Crossman J. B.
Published: April 2006

Young excised coleoptiles from dark grown wheat have their cell growth promoted by gibberellic acid (GA3), while sections from older coleoptiles have their cell growth promoted by auxin. The GA3 response has a much longer lag period than that of auxin. Neither GA3 nor auxin has any effect on 14C‐leucine and 14C‐uridine incorporation and uptake after 1 h, indicating that the lag in growth stimulation following GA3 application is not associated with changes in protein or RNA synthesis. Following a 6 h incubation there are small increases in 14C‐leucine and 14C‐uridine incorporation in response to both GA3 and auxin, and in the case of auxin this is associated with increased uptake. Studies on protein and RNA turnover using pulse‐chase experiments have shown that both GA3 and auxin have no effect on protein and RNA stability. There are, however, developmental changes in RNA and protein synthesis that should be considered in any explanation of the mechanism of action of these hormones on cell growth. Young GA3‐sensitive tissue has high rates of RNA synthesis and low protein and RNA turnover, while auxin‐sensitive tissue has low rates of RNA synthesis, slightly higher rates of RNA turnover and much higher rates of protein turnover. The evidence overall favours more effective utilisation by GA3 and auxin of a basal control level of RNA and protein synthesis and turnover in coleoptile tissue.
Spectral forms of protochlorophyllide in prolamellar bodies and prothylakoids fractionated from wheat etioplasts
Authors: Ryberg Margareta , Sundqvist Christer
Published: April 2006

The relation between the different protochlorophyllide (PChlide) forms in isolated etioplast inner membranes was dependent on the concentration of sucrose and NADPH in the isolation media. Etioplasts were prepared from wheat (Triticum aestivumL. cv. Starke II, Weibull) by differential centrifugation. The etioplasts were freed of envelope and stroma and the etioplast inner membranes were exposed to a concentration series of sucrose. Fluorescence emission spectra revealed a positive correlation between the emission ratio 657/633 nm and the sucrose concentration in which the membranes were suspended. Addition of NADPH prevented the degradation of 657 nm emission caused by low sucrose concentrations. PChlide already altered to PChide628–632could not re‐form PChlide650–657after the addition of NADPH in darkness. Prolamellar bodies and prothylakoids were separated in a bottom‐loaded sucrose density gradient in the presence of NADPH. The dominating PChlide‐protein complex in the prolamellar bodies was PClide650–657. Only minor amounts of PChlide628–632were found in these membranes. The prothylakoids had a higher content of PChlide628–632, relative to PChlide650–657, than the prolamellar bodies, as judged from absorption and fluorescence spectra. After phototransformation the fluorescence emission at 633 nm increased relative to the emission from phototransformed PChlide indicating an efficient energy transfer between PChlide628–632and PChlide650–657before irradiation.
Lectin involvement in root‐hair tip adhesion as related to the Rhizobium‐clover symbiosis
Authors: Dazzo Frank B. , Truchet Georges L. , Kijne Jan W.
Published: April 2006

Contact of adjacent root hairs of seedlings of white clover (Trifolium repens L. cv. Ladino and Louisiana Nolin) led to cell‐cell adhesion of root hair tips. The involvement of the root lectin, trifoliin A, in this phenomen was examined in slide cultures of axenically grown seedlings. Trifoliin A was detected by indirect immunofluorescence on root hair tips, which had adhered to one another. Seedlings grown under conditions which specifically reduce the levels of this lectin on the root surface (e.g., in the presence of 15 mM NO3– or 5 mM 2‐deoxy‐d‐glucose) had significantly fewer adhesions of root hair tips. In addition, flushing the slide cultures with 20 mM 2‐deoxy‐d‐glucose resulted in an immediate 4‐fold reduction in frequency of tip adhesions. These results are consistent with the lectin cross‐bridging model, which predicts that cell‐cell adhesions would occur when trifoliin A on root hair tips contacts complementary glycosylated receptors on neighboring root hairs.
Soluble auxin‐binding proteins in pea epicotyls
Authors: Jacobsen Hans‐Jörg
Published: April 2006

Auxin‐binding proteins, have been identified in the soluble cytoplasrnic protein fraction of etiolated pea epicotyls, Pisum sativum L., cv. “Dippes Gelbe Victoria”. The binding is specific for the auxins NAA, IAA and 2,4‐D with a KD in the range of 0.1–0.4 μM. Moreover, the binding is competitive, sensitive to digestion by proteinase and shows linearity with the protein content of the assay mixture. The binding proteins appear to be very labile, since repeated freezing and thawing destroys specific binding. No clear pH‐optimum could be detected in the physiological pH‐range 5.5–8.0, but the binding was doubled at pH 8.0 compared to pH 5.5–7.0.
Is uronic acid oxidase involved in the hormonal regulation of abscission in explants of citrus leaves and fruits?
Authors: Huberman Moshe , Goren Raphael
Published: April 2006

The role of uronic acid oxidase in abscission was studied in explants of citrus (Citrus sinensis L. Osbeck; var. Shamouti) leaves and fruits. In leaf explants, activity of uronic acid oxidase prior to onset of abscission and the rate of abscission were markedly accelerated by ethylene and delayed by 2,4‐dichlorophenoxyacetie acid. Similar results were obtained for uronic acid oxidase activity in the exocellular fraction of young fruit explants. In mature fruit explants, treated with ethylene, an immediate increase in activity was evidenty in the non‐active shoot/peduncle abscission zone, whereas in the calyx abscission zone the rise in activity occurred after a prolonged exposure to ethylene, when most of the fruits had already abscised. Whenever ethylene enhanced uronic acid oxidase activity, 2,4‐dichlorophenoxyacetic acid delayed it. A gradient of decreasing activity or uronic acid oxidase was recorded from both sides of the abscission zone in leaves and fruits toward the separation line, where activity was the lowest as compared with the activity found in adjacent tissues. It is suggested that uronic acid oxidase is involved in senescence and cell wall degradation. However, it is yet questionable whether this enzyme is directly related to the control mechanism of abscission.
Light acclimation in leaves of the juvenile and adult life phases of ivy (Hedera helix)
Authors: Hoflacher Hans , Bauer Helmut
Published: April 2006

Hoflacher, H. and Bauer, H. 1982. Light acclimation in leaves of the juvenile and adult life phases of ivy (Hedera helix). – Physiol. Plant. 56: 177–182.

Light acclimation was investigated during the juvenile and adult life phases of the whole‐plant‐development in Hedera helix L. For this purpose, cuttings of the juvenile and adult parts of one single parent plant were grown under low‐light (PAR 30–50 μmol photons m−2 s−1) and high‐light (PAR 300–500 μmol m−2 s−1) conditions: CO2 exchange, chloroplast functions, and specific anatomy of fully developed leaves differentiated under these conditions were determined.

In juvenile plants the leaves formed under low and high light had light‐saturated rates of net photosynthesis of 6.5 and 11.1 mg CO2 (dm leaf area)−2 h−1, respectively. In adult plants the rates were 9.4 and 22.2 mg dm−2 h−1, indicating a more pronounced capacity for acclimation to strong light in the adult life phase. Higher photosynthetic capacities were accompanied by higher conductances for the CO2 transfer through the stomata, leading to almost the same CO2 concentration in the intercellular spaces. Thus, stomatal conductances were not primarily responsible for the different photo‐synthetic capacities. The higher rates in adult and high‐light grown leaves were mainly the result of formation of thicker leaves with more chloroplasts per unit leaf area. Expressed per chloroplast, the photosynthetic capacity, the Hill reaction, and the activity of ribulose bisphosphate carboxylase were almost identical in plants grown in low‐light and high‐light.

Measurements of photosynthetic capacity and thickness of leaves of Hedera sampled from field habitats with contrasting light regimes confirm the results of growth chamber studies. It is, therefore, concluded that both life phases of Hedera are capable of acclimating to strong light, but that during the juvenile phase this capacity is not fully developed.
Control of development of amylolytic and proteolytic activities in cotyledons of germinating black gram seeds
Authors: Morohashi Yukio
Published: April 2006

The development of amylolytic and proteolytic (azocaseolytic and autodigestive) activities was severely retarded in detached cotyledons compared to attached cotyledons in germinating black gram seeds (Vigna mungo L.). The possibility of repression of hydrolase development by the end products of the enzyme activity was examined. Decrease in end product contents did not always bring about a rise in hydrolase activities, nor was inhibition of hydrolase formation always correlated with an increase in end product contents. The results suggest that feedback‐like repression is unlikely to be the mechanism by which hydrolase activity is regulated in black gram cotyledons.
The effect of monochromatic radiation in the range 350 to 750 nm on the carotenogenesis in Verticillium agaricinum
Authors: Guy Valadon L. R. , Osman Mohamed , Mummery Rosemary S. , Jerebzoff‐Quintin Simone , Jerebzoff S.
Published: April 2006

An action spectrum for carotenogenesis in V. agaricinum has maxima at 395, 433, 660 and 737 nm. In a previous study it had been shown that a light‐minus‐dark difference spectrum of a crude extract from V. agaricinum had maxima at 390 and 420 nm, and furthermore a red, far‐red interaction suggesting phytochrome involvement has been proposed. All these data suggest that there may be at least two photoreceptor systems operating in the photoinduction process here; one for the near‐ultraviolet (UV‐A)‐mediated carotenogenesis, presumably a novel pigment, and the other for the red, far‐red region, most likely phytochrome.
Light‐dependent inhibition of photosynthetic electron transport by zinc
Authors: Baker Neil R. , Fernyhough Paul , Meek Ian T.
Published: April 2006

The effects of zinc concentrations up to 400 μM were examined on three photosynthetic electron transport reactions of thylakoids isolated from Pisum sativum L. cv. Meteor. Zinc (400 μM) had no effect on photosystem I mediated electron transport from reduced N,N,N′,N′‐tetramethyl‐p‐phenylenediamine to methyl viologen, but inhibited uncoupled electron flow from water to methyl viologen by ca 50% and to 2,6‐dichlorophenol‐indophenol (DCPIP) by ca 30% at saturating light levels. Zinc inhibition of DCPIP photoreduction was independent of the light intensity to which thylakoids were exposed. Decreasing the photon flux density below 400 μmol m−2 s−1 produced a logarithmic reduction in the zinc‐induced inhibition of methyl viologen photoceduction; a stimulation of this reaction was observed below 80 μmol photons m−2 s−1. Increasing light intensity decreased the amount of zinc tightly bound to the thylakoid membranes, but increased the weakly associated zinc which could be removed by washing the membranes with buffer containing Mg2. The results suggest that zinc acts on the photosynthetic electron transport system at two sites. Site 1 is on the oxidizing side of photosystem 2 and the inhibition by zinc is independent of the light intensity. Site 2 is between photosystems 1 and 2 and the electron flow can be positively or negatively affected by zinc depending on the light intensity.
Inhibition of flower bud abscission and ethylene evolution by light and silver thiosulphate in Lilium
Authors: van Meeteren U. , de Proft M.
Published: April 2006

The ethylene evolution from 3 cm‐long flower buds of Lilium X ‘Enchantment’ increased when the plants were placed in darkness. Also shortening the daily light period led to an increase in ethylene evolution from the buds. Dark‐enhanced ethylene evolution could only be evoked in flower buds between 2 and 3.5 cm long. Flower bud abscission induced by dakrness could be prevented by injecting silver thiosulphate into the flower buds, or by using plants grown from bulbs previously immersed in a silver thiosulphate solution. It is suggested that light‐controlled flower bud abscission in Lilium X ‘Enchantment’ is mediated by ethylene, and that an increase in ethylene evolution in darkness is a consequence of the influence of light on ethylene action rather than a direct influence on ethylene biosynthesis.
Aphidicolin and ethidium bromide as tools to verify dependence of early post‐germinative growth on nuclear and organellar DNA synthesis
Authors: Galli Maria Grazia
Published: April 2006

Embryos of Haplopappus gracilis (Nutt.) Gray were sown in aphidicolin (inhibitor of nuclear DNA synthesis) used alone or in combination with ethidium bromide (inhibitor of organellar DNA synthesis). In both cases germination and the early processes of post‐germinative growth, including enlargement and greening of cotyledons, some elongation of radicle, and formation of root hairs, occurred at the same rate as in the controls. Comparable results were obtained using fluorodeoxyuridine. The effect of aphidicolin is, unlike fluorodeoxyuridine, completely reversible and the side effect on protein and RNA synthesis are negligible. Total non‐dependence on nuclear and organellar DNA synthesis during early post‐germinative growth may not be a generalized situation in all seeds, as was shown by some observations on lettuce and watermelon.
Effects of interrupted K+ supply on growth and uptake of K+, Ca2+, Mg2+ and Na+ in spring wheat
Authors: Jensén Paul
Published: April 2006

Effects of interrupted K+ supply on different parameters of growth and mineral cation nutrition were evaluated for spring wheat (Triticum aestivum L. cv. Svenno). K+ (2.0 mM) was supplied to the plants during different periods in an otherwise complete nutrient solution. Shoot growth was reduced before root growth after interruption in K+ supply. Root structure was greatly affected by the length of the period in K+ ‐free nutrient solution. Root length was minimal, and root branching was maximal within a narrow range of K+ status of the roots. This range corresponded to cultivation for the last 1 to 3 days, of 11 in total, in K+ ‐free nutrient solution, or to continuous cultivation in solution containing 0.5 to 2 mM K+. In comparison, both higher and lower internal/external K+ concentrations had inhibitory effects on root branching. However, the differing root morphology probably had no significant influence on the magnitude of Ca2+, Mg2+ and Na+ uptake. Uptake of Ca2+ and especially Mg2+ significantly increased after K+ interruption, while Na+ uptake was constant in the roots and slowly increased in the shoots. The two divalent cations could replace K+ in the cells and maintain electroneutrality down to a certain minimal range of K+ concentrations. This range was significantly higher in the shoot [110 to 140 μmol (g fresh weight)−1] than in the root [20 to 30 μmol (g fresh weight)−1]. It is suggested that the critical K+ values are a measure of the minimal amount of K+ that must be present for physiological activity in the cells. At the critical levels, K+ (86Rb) influx and Ca2+ and Mg2+ concentrations were maximal. Below the critical K+ values, growth was reduced, and Ca2+ and Mg2+ could no longer substitute for K+ for electrostatic balance. In a short‐term experiment, the ability of Ca2+ to compete with K+ in maintaining electroneutrality in the cells was studied in wheat seedlings with different K+ status. The results indicate that K+, which was taken up actively and fastest at the external K+ concentration used (2.0 mM), partly determines the size of Ca2+ influx.
Light‐induced changes in the lipid composition and ultrastructure of plastids from potato tubers
Authors: Sandelius Anna Stina , Liljenberg Conny
Published: April 2006

Sandelius, A. S. and Liljenberg, C. 1982. Light‐induced changes in the lipid composition and ultrastructure of plastids from potato tubers. – Physiol. Plant. 56: 266–272.

Amyloplasts and starch containing plastids from green tissue – amylochloroplasts – from potato tubers (Solanum tuberosum L., var. King Edward) were separated from other cell organelles by sedimentation in a discontinuous sucrose gradient. Their lipid composition was analysed with emphasis on galactolipids and phospholipids and the fatty acid compositions of these lipids. Irradiation of the tubers caused increased ratios of monogalactosyl diacylglycerol to digalactosyl diacylglycerol and of total galactolipids to total phospholipids in the plastid membranes. Furthermore, the degree of unsaturation of the fatty acids increased in all lipid classes analysed, this effect being most prominent in the galactolipids. The ultrastructural studies made on tuber tissue revealed that irradiation caused a change in starch grain size distribution concomitant with formation of membrane structures resembling grana within the envelope. In many cases prolamellar bodies and plastoglobuli were present.
Effect of CO2, CO2 and Diamox on photosynthesis and photorespiration in Chlamydomonas reinhardtii (green alga) and Anacystis nidulans (Cyanobacterium, blue‐green alga)
Authors: Nilsen S. , Johnsen Ø.
Published: April 2006

Photorespiration by Chlamydomonas reinhardtii and Anacystis nidulans was measured as the oxygen inhibition of CO2 uptake and the CO2 compensation points. Net photosynthesis was oxygen dependent in Chlamydomonas grown in 5% CO2, but CO2 insensitive in cultures bubbled with air. Anacystis, even when cultured in 5% CO2, exhibited an CO2 insensitive net photosynthesis. The CO2 compensation point of Chlamydomonas grown in cultures bubbled with air and Anacystis grown in 5% CO2 enriched air, were reached shortly after the measurement was begun and the values were very low, less than 10 μl CO2 1−1; while Chlamydomonas grown in 5% CO2 enriched air for 4 days showed a high, but temporary CO2 compensation point (60 μl CO2 1−1). After a two hour adaptation in low CO2, a stable, low CO2 compensation point was reached. It seems that photorespiration can only be detected by the methods used in this study when the algae are cultured in high CO2, but a mechanism exists which blocks photorespiration when the green algae are adapted to low CO2 concentrations.

When Chlamydomonas was treated with Diamox, an inhibitor of carbonic anhydrase, after cultivation in low CO2 (air), the cells behaved as if they had been grown in high CO2. They showed an oxygen sensitive net photosynthesis and a high CO2 compensation point. This indicates that carbonic anhydrase plays an important role in the regulation of a measurable photorespiration in Chlamydomonas. The results are discussed in relation to previous observations of photorespiration measured by enzyme assay, metabolic products and gas exchange properties.
Do memory processes occur also in plants?
Authors: Thellier M. , Desbiez M. O. , Champagnat P. , Kergosien Y.
Published: April 2006

Plantlets of Bidens pilosus L. “remembered” a symmetry‐breaking signal (the puncturing of one of the cotyledons), but expressed it only after being made permissive (by removing the apex). The mean value of the memorization index was 0.52. There was a labile short‐term and a well‐fixed long‐term memory. The memorization process was dependent on the number of stimuli, and on the mineral status of the plant.