bluuebunny/crossref_metadata_2025 huggingface dataset:
Consequences of salt stress on conductance to CO2 diffusion, Rubisco characteristics and anatomy of spinach leaves
Authors: Delfine Sebastiano , Alvino Arturo , Zacchini Massimo , Loreto Francesco
Published: January 2006

Spinach (Spinacia oleracea L.) leaves stressed by
irrigation with water containing 1% (w/v) NaCl for 20 days had low
conductance to CO2 diffusion both at the stomata and in
the mesophyll. Mesophyll anatomy changed in salt-stressed leaves, which could
have accounted for the decreased mesophyll conductance. Ribulose-
1,5-bisphosphate carboxylase/oxygenase in vitro
activity and content were not affected by up to 20 days exposure to salinity
but decreased when leaves were exposed to salt stress for longer than 20 days.
Salt accumulation also caused a drop of Ca and Mg which might have decreased
membrane stability and chlorophyll content, respectively. Measurements of
chlorophyll fluorescence indicated that the 20-day-long salt stress did not
directly affect photochemistry. We conclude that salinity reduces
photosynthesis primarily by reducing the diffusion of
CO2 to the chloroplast, both by stomatal closure and by
changes in mesophyll structure which decreases the conductance to
CO2 diffusion within the leaf. The capacity for carbon
metabolism is eventually reduced but that occurs after substantial decreases
in the conductance to CO2 diffusion.
Effects of High Concentrations of KC1 and NaCl on Responses of Malate Dehydrogenase (Decarboxylating) to Malate and Various Inhibitors
Authors: Greenway H , Sims AP
Published: January 2006

The effects of KC1 on catalytic and allosteric properties of malate dehydrogenase (decarboxylating) were studied. Chloride salts (50 mM and higher) strongly inhibited enzyme activity at low malate concentrations. At high malate (4 mM) , on the other hand, the degree of inhibition induced by chloride was very small. The s0.5 value (i.e. the malate concentration required for half maximum velocity) was about 0.4 mM in the absence of KC1 and increased to 0.75 and 1.5 mM at 50 and 100 mM KC1 respectively. High chloride concentrations also removed a small degree of substrate inhibition, which in the absence of KC1 occurred at 8 mM malate. At low malate concentrations (< 0 . 5 mM) 50 mM KC1 increased the Hill number from 1.3 to 1.9. Thus chloride treatment revealed a strong degree of cooperativity for the enzyme. This potential for homotropic effects was much less realized in MES buffer (potassium salt), presumably because affinity of malate for individual active sites was already very high. These effects of KC1 were readily reversible and the enzyme showed no appreciable change in molecular weight in the presence of 200 mM KCl. At malate concentrations between 1 and 12 mM, inhibitions of malate dehydrogenase (decarboxylating) activity induced by oxaloacetate, D-malate, and phosphoglycerate were reduced by KCl. At low malate concentrations, on the other hand, the inhibitory effect induced by oxaloacetate changed to a strong stimulatory effect in the presence of KCl. The inhibitory effect due to oxaloacetate was greatly diminished in malate dehydrogenase (decarboxylating) which was eluted from a DE52 cellulose column, but the inhibitory effect due to KC1 was retained. Elution from DE52 cellulose also reduced the Hill number to 1 and increased the s0.5 value. The above results suggest that KC1 reduced the affinity of both substrate and some allosteric inhibitors of malate dehydrogenase (decarboxylating).
Alteration of Liposomal Membrane Fluidity by Gibberellic Acid
Authors: Wood A , Paleg LG
Published: January 2006

Lipid bilayers (liposomes) with many characteristics of natural membranes exhibit thermal transitions. The transition point can be determined experimentally from the rates of leakage of glucose through the lipid barrier at various temperatures. In response to treatment with gibberellic acid or diethylstilboestrol, the permeability of the liposome to glucose is increased; in addition, the temperature at which the transition occurs is shown to be inversely proportional to the gibberellic acid concentration. The consequences of increased fluidity in the membrane, brought about by the hormone, are discussed. The hypothesis is advanced that the membrane could be the primary target for hormonal action in plants.
Light-Dependent Metabolism of Carbon Compounds by Mesophyll Chloroplasts from Plants with the C4 Pathway of Photosynthesis
Authors: Kagawa T , Hatch MD
Published: January 2006

This paper describes the capacities of intact mesophyll chloroplasts prepared from Atviplex spongiosa and maize for the light-dependent metabolism of carbon compounds. Illuminated chloroplasts converted pyruvate to phosphoenolpyruvate but the initial rate was maintained only when either 3-phosphoglycerate or methylviologen was added. Light-dependent oxygen evolution was observed when 3-phosphoglycerate or oxaloacetate was added to chloroplasts, and the concomitant production of dihydroxyacetone phosphate or malate was observed. The addition of ADP or NADP or both did not produce increases in these activities. Addition of the photophosphorylation uncoupler methylamine stimulated the rate of oxaloacetate reduction and inhibited the conversion of 3-phosphoglycerate to dihydroxyacetone phosphate. These chloroplasts were not capable of oxygen evolution upon the addition of bicarbonate and did not fix CO2. The data also provided information about minimum rates of influx or efflux of metabolites through the chloroplast outer membrane. These studies confirmed that mesophyll chloroplasts of C4 species are unique in terms of their cap- acities for carbon metabolism. These activities are discussed in relation to the role of mesophyll chloroplasts in C4-pathway photosynthesis.
Promotion of Flower Initiation in Apple Trees by Short Exposure to the Ammonium Ion
Authors: Grasmanis VO , Edwards GR
Published: January 2006

Jonathan apple trees on MM104 rootstock, grown in Perlite in pots with controlled nutrient supply, initiated more flowers in the axillary buds of the main stem in the first year of growth if exposed for part of the time to ammonium ions than if grown on nitrate nitrogen continuously. The duration and timing of ammonium treatment was not critical; exposure for 24 h was as effective as exposure for 8 weeks and treatment as late as February was as effective as earlier treatment. Initiation was increased over most of the stem length by all ammonium treatments.
A Comparison of Potential Photosynthesis, Productivity and Yield of Plant Species with Differing Photosynthetic Metabolism
Authors: Gifford RM
Published: January 2006

Maximum recorded values of various parameters for the rate of photosynthetic CO2, fixation, from the biochemical level through the leaf level to crop growth rate, suggests that for two contrasting photosynthetic groups (C3 and C4 species) the large potential advantage of the C4 mechanism at the biochemical level is progressively attenuated in moving from the microscopic to the macroscopic parameters until, at the level of crop growth rate, there is no apparent difference between best examples of the two groups when grown in their own preferred natural environments.
Chemical Regulation of Plastid Development. I. Inhibition of Chlorophyll Biosynthesis in Detached Pumpkin Cotyledons by CPTA. A Pigment and Ultrastructual Study
Authors: Simpson DJ , Chichester CO , Lee TH
Published: January 2006

The effects of 2-(4-chlorophenylthio)ethyldiethylammonium chloride (CPTA) on chlorophyll accumulation, carotenoid biosynthesis and plastid ultrastructure were examined in expanding excised pumpkin cotyledons. CPTA in the dark caused an increased synthesis of non-photoconvertible protochlorophyll but had no effect on the ultrastructure of the starch-containing plastids. In the light, CPTA was a powerful inhibitor of chlorophyll synthesis in greening cotyledons, especially at high light intensity, and induced the accumulation of lycopene. When applied to the greened cotyledons, CPTA caused the transformation of the chloroplasts to chromoplast-like organelles containing osmiophilic globules and lycopene crystalloids. Two other structurally similar compounds,diethyl[4-{3'-(4"-methylphenyl)-3-oxoprop-2'
-enyl}phenoxyethyl]ammonium chloride (SK&F 13831) and (2-chloroethyl)trimethylammonium chloride (chlormequat), also caused lycopene accumulation and inhibited chlorophyll synthesis. It is possible that CPTA can induce the formation of chromoplasts from proplastids and chloroplasts in tissue that does not normally contain such organelles.
Significance of the C4 Pathway in Triodia irritans (Spinifex), a Grass Adapted to Arid Environments
Authors: Mcwilliam JR , Mison K
Published: January 2006

The existence of the C4 pathway of photosynthesis and also a novel form of Kranz-type leaf anatomy in T. irritans support the case for the inclusion of the genus Triodia in the Eragrosteae. They also provide further evidence for the suggestion that C4 plants are at a selective advantage in hot arid environments.
Substrate Transport into Plant Mitochondria: Swelling Studies
Authors: Wiskich JT
Published: January 2006

The presence of substrate transporters in some plant mitochondria has been demonstrated using the
ammonium salt swelling technique. It is shown that isolated cauliflower and beetroot mitochondria
have at least three anion transporters (phosphate ion, dicarboxylate ion and tricarboxylate ion).
Some substrate specificity and inhibitor studies are also reported. The role of these transporters in
plant mitochondria is discussed.
Extraction and Characterization of Gibberellins from Hordeum vulgare L. Seedlings
Authors: Faull KF , Coombe BG , Paleg LG
Published: January 2006

Two gibberellins, one GA1-like, the other GA3-like, were identified in the extracts of roots and tops of 8-,11- and 15-day-old barley seedlings by paper chromatography, paper electrophoresis, thin-layer chromatography, gas-liquid chromatography and bioassay procedures, followed by combined gas chromatography-mass spectrometry. The amounts of gibberellins in the seedlings ranged from 7 to 11 ng per plant. The concentrations of gibberellins in the seedlings were 32-320 ng/g dry weight and 5-28 ng/g fresh weight; concentrations in the roots were higher than those in the shoots.
Effects of Slowly and Rapidly Permeating Osmotica on Permeability of Excised Roots of Zea mays
Authors: Greenway H
Published: January 2006

Excised roots of Z. mays were treated at a water potential of – 20.8 atm, using slowly and rapidly permeating solutes both as osmotica (800 mM ) and as permeants (10 mM ) . The temperature during all experiments was 2�C. The solutes were mannitol, glycerol, and ethylene glycol. In highly vacuolated root tissues there were at least three phases for the influx and efflux of the permeants. These phases presumably represented the free space, the 'cytoplasm', and the 'vacuoIe'. Treatment with slowly permeating osmotica increased the free space of both highly and slightly vacuolated tissues. In highly vacuolated tissues all osmotica doubled the rate of exchange for the 'cytoplasm', but had very little effect on the rate of exchange for the 'vacuole'. The latter observation suggests that the permeability of the tonoplast changed little during plasmolysis. In contrast to highly vacuolated tissues, exposure of slightly vacuolated tissue to osmotica decreased the rates of exchange of the permeant mannitol. Removal of slowly permeating osmotica dramatically increased the permeability of highly vacuolated tissues. Moreover, permeability to rapidly permeating ethylene glycol increased much less than permeability to slowly permeating mannitol and glycerol. These observations suggest that deplasmolysis changed the structure of cell membranes. Permeability of slightly vacuolated tissues was not greatly increased by removal of osmotica. These different effects on the permeability of highly and slightly vacuolated tissues are consistent with earlier results, which showed that removal of slowly permeating osmotica restored metabolism of slightly vacuolated tissues, while it strongly depressed cellular activity of highly vacuolated tissues.
Culture of Protoplasts From Grape Vine Pericarp Callus
Authors: Skene KGM
Published: January 2006

Protoplasts isolated from callus cultures of the pericarp of Vitis vinifera cv. Sultana regenerated cell walls within 3 days, when cultured in semi-solid media adjusted to 0.4-0.5 osmolal. Up to 12% of the cells divided during the next 7 days. A lower proportion passed through two division cycles.
Phytochrome Action in the Induction of Plowering in Short-day Plants: Effect of Photoperiod Quality
Authors: King RW
Published: January 2006

Seedlings of Phavbitis nil and Chenopodium rubrum flower in response to a single inductive dark
period preceded and followed by continuous fluorescent light. However, when a far-red irradiation
for 1 h or longer was substituted for fluorescent light, the flowering response to an ensuing dark
period could be completely inhibited or enhanced up to threefold depending on when the far-red
exposure commenced.
Evidence of red/far-red photoreversibility established phytochrome as the photoreceptor controlling
these responses. There was no indication of the involvement of photosynthetic pigments.
For P. nil prolonged exposure (1.5-6 h) to far-red radiation during the photoperiod could shorten
(2-3 h) or lengthen (2 h) the duration of darkness required for flowering. The degree of change
depended on whether the far-red radiation was imposed just prior to darkness (shortening) or about
9 h prior to darkness (lengthening). In a similar manner the spectral composition of the photoperiod
influenced the timing during darkness for earliest sensitivity to brief (5 min) red light interruptions.
The shorter the critical dark period, the earlier in darkness the seedlings became sensitive to red
light interruptions of darkness.
It is clear that the form of phytochrome during the photoperiod influences the timing of phytochrome-
linked processes in darkness. Two explanations discussed are a coupling via rhythmic
changes in substrate on which phytochrome acts, and an effect on phytochrome reactions which
alters the timing of Pf, disappearance during a subsequent dark period.
Potentials Developed at a Solution-Cytoplasm Interface in Chara corallina during Rest and Excitation
Authors: Coster HGL , George EP , Rendle V
Published: January 2006

Potentials were measured in cells of C. corcillina between two microelectrodes inserted into the
cytoplasm, one filled with concentrated [2 kmol/m3 (E~M)] KC1 and the other filled with various
dilute solutions of KC1 or NaCl. It was found that when both electrodes are in the cytoplasm a
potential difference between the two electrodes is developed which, at kery low concentrations,
varied about 40 mV per tenfold change in concentlation of the dilute electrode.
During excitation this potential difference transiently disappears.
No significant differences could be detected between the results obtained with KCI- and NaClfilled
electrodes.
A comparison is made between the experimental results and computer solutions for the Donnan
and diffusion potentials expected for electrodes inserted into a fixed negatively charged phase.
It was found that the experimental results for the resting state could be reasonably accounted for
if the cytoplasm is assumed to be a negative Donnan phase with a fixed negative charge concentration
of 0.1-0.2~ in which the chloride ion mobility is reduced to 30% of its free solution value.
The results obtained during action potentials would then suggest that excitation is accompanied
by a loss of the fixed charges in the cytoplasm and a return of the chloride ion mobility to its free
solution value.
Gibberellin-Like Activity of Helminthosporic Acid Analogues
Authors: Coombe BG , Mander LN , Paleg LG , Turner JV
Published: January 2006

The activity of some analogues of helminthosporins was tested in three gibberellin bioassay systems. Three compounds showed considerable activity in the barley endosperm bioassay, five were slightly active and three were inactive. The response curves were frequently steeper than that of gibberellic acid, and sometimes bimodal. Comparisons of the structures of active and inactive compounds indicate that the hydroxymethyl moiety of natural helminthosporins is not necessary for biological activity. The carboxyl group is required for activity and appears to have favoured spatial requirements. Similar structureactivity relationships were suggested for the Tan-ginbozu rice bioassay but those for the Rumex leaf senescence bioassay were different.
Effect of High Sodium Chloride Concentrations in the Growth Medium on the Activity of Glucose-6-Phosphate Dehydrogenase From Pea Roots
Authors: Poljakoff-Mayber A , Greenway H
Published: January 2006

The experiments reported in this paper examined discrepant results, obtained in earlier investigations, concerning the effects of NaCl in the growth medium of vascular plants on the specific activity of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) extracted from the plants.
NaCl at 120 mM or higher concentrations increased the specific activity of the enzyme in extracts from roots of germinating peas. However, this effect of NaCl was only clearly expressed when 0.1M phosphate was the buffer used to extract the enzyme. When organic buffers were used the observed increase in enzyme activity was either much smaller or absent.
Increases in specific activity of glucose-6-phosphate dehydrogenase were only found in extracts from roots that showed severely retarded growth and some brown discoloration. No increase in activity was found either when 120 mM NaCl was added to the growth medium after seedling establishment, or if seeds were germinated in 75 mM NaCl.
These observations account for the discrepancies reported in the literature.
Adaptation of Rice to Anaerobiosis
Authors: John CD , Limpinuntana V , Greenway H
Published: January 2006

Responses of established rice plants to anaerobiosis were examined by flushing nitrogen through culture solutions. Although shoot growth was not affected, anaerobiosis reduced root dry weight and caused shortening and increased branching of roots. Oxygen uptake, CO2 evolution and respiratory quotient of excised apical root tissue were lower for plants adapted to anaerobiosis than for non-adapted plants.
Anaerobic treatment of roots inhibited chloride, dihydrogenphosphate and potassium uptake by both adapted and non-adapted plants, the inhibitions usually being more pronounced in non-adapted plants. Oxygen supply to the roots was prevented by creating an atmosphere of nitrogen around the shoots; this induced inhibitions of ion uptake additional to the inhibitions observed with anaerobic treatment of roots alone.
Ion uptake of adapted plants under anaerobiosis was similar to that of non-adapted plants under continuous aeration. This was shown to be due to a higher capacity for ion uptake by adapted plants, since when adapted plants were returned to aerated solutions ion uptake was higher than for plants with continuous aeration. Thus inhibition of ion uptake, due to both smaller roots and anaerobiosis, was counterbalanced by this increased capacity for ion uptake.
It is concluded that oxygen movement to roots from aerial parts does occur in rice, but is insufficient to sustain the full potential of at least some metabolic processes.
An Exploration of the Carbon Economy of the Tobacco Plant. III. Gas Exchange of Leaves in Relation to Position on the Stem, Ontogeny and Nitrogen Content
Authors: Rawson HM , Hackett C
Published: January 2006

Tobacco plants were grown in sunlit, controlled-environment cabinets, and their growth and gas exchange were followed from shortly after emergence to 90 days from sowing. There were three major findings:
1. Summed over all leaves, dark respiration remained at 6-7% of net photosynthesis for a lengthy period (50-90 days from sowing), but in younger plants the fraction reached as high as 18%.
2. In the 12 leaves monitored from their emergence to full expansion, net photosynthesis (Pn) followed a similar time course, even though the first and last leaves in this group emerged nearly 40 days apart and there was a 100-fold difference in final area (Amax). For a sequence of nine of these leaves, the agreement was so close that their photosynthetic histories could be represented by a single relationship with developmental time. Peak Pn was consistently attained at about 37% Amax, when peak dA/dt occurred, and it was held for only 3-5 days. The subsequent decline reduced Pn to less than one-third of peak Pn at Amax.
3. Data for the nitrogen content (w/w) of the leaves after 37% Amax could be combined in a manner similar to that described for Pn. Pn, nitrogen content and leaf ontogeny were therefore directly related after peak Pn had been attained.
The bearing of these findings on the study of photosynthesis in dicotyledonous species is discussed.
Isolation and Partial Characterization of Alcohol Dehydrogenase From Broad Bean (Vicia faba)
Authors: Leblova S
Published: January 2006

Alcohol dehydrogenase isolated from broad bean was found to have a Km value of 1.0 × 1.0 -2 M, a pH optimum of 8.7 and a molecular weight of
60 000 � 5000. The enzyme lost 55 % of its activity after being heated at 55�C, and was totally inactivated at 70°C. Thermal stability of the enzyme was not enhanced by NAD+ or ethanol.
The substrate specificity of the enzyme is reported. Cysteine and mercaptoethanol activated the enzyme, whilep-chloromercuribenzoate, Cu2+, Hg2+, B4O72- -, Zn2+ and EDTA inhibited it. The influence of ethanol, acetaldehyde and growth substances on alcohol dehydrogenase activity in germinating broad bean seeds and plant tissues was also studied.
Further Experiments on the β-Amylase-Containing Lysosomes of Wheat Aleurone Cells
Authors: Gibson RA , Paleg LG
Published: January 2006

The presence of hydrolytic enzymes in sedimentable fractions (lysosomes) of homogenized gibberellic acid (GAS)-treated wheat aleurone tissue has been further examined. Non-specific binding of free α-amylase (EC 3.2.1.1) to any organelle did not occur when added before homogenization to aleurone tissue either treated with GA3 or untreated, nor when amylose was added to GA3-treated tissue. The distribution of sedimentable α-amylase between different centrifugal fractions could be controlled, however, by varying the concentrations of calcium or chelating agents in the grinding medium. The concentration of GA*3 applied to aleurone tissue altered neither the percentage nor the distribution of α-amylase recovered in the various particulate fractions. Of the α-amylase appearing in the supernatant fraction, a large proportion appears to be located in the cell wall and is inactivated by acid treatment prior to homogenization, confirming previous reports. Tissue treated in this way yields more than 80% of the recoverable enzyme in sedimentable fractions.
Growth of Immature Pea Cotyledons in Culture
Authors: Millerd A , Spencer D , Dudman WF , Stiller M
Published: January 2006

Detached immature pea (Pisum sativum) cotyledons grow for several days in liquid medium and synthesize considerable quantities of chlorophyll, starch, DNA, RNA and protein (including the storage proteins vicilin and legumin). Seeds developing in detached pods also synthesize both major storage proteins.
Inhibition by p-Fluorophenylalanine of Protein Synthesis and of Ion Transport Across the Roots in Barley Seedlings
Authors: Schaefer N , Wildes RA , Pitman MG
Published: January 2006

The transport of ions across the plant root can be inhibited by cytokinins, abscisic acid and cycloheximide. It appears that secretion of ions into the xylem vessels is a different kind of process from active transport into the cortical cells, as it is not affected to the same extent by these compounds.
In the present paper it is shown that p-fluorophenylalanine (FPA) also inhibited transport across the root without reducing uptake to the cells, and hence it is concluded that transport involves a specific protein. From the time needed to produce inhibition with FPA it appears that this protein has a short effective life.
Measurement of distribution of 36Cl between stele and cortex showed that these inhibitors did not stop movement of ions into the stele. It seems then that the site of action of the proteins is within the stele, probably between xylem parenchyma and xylem vessels.
Effects of Anions and Cations on Potassium Absorption by Plants of High Potassium Chloride Content
Authors: Johansen C , Loneragan JF
Published: January 2006

The effect of anion type and increasing calcium and sodium concentration on short-term potassium absorption by barley plants grown in nutrient solutions containing KCl was studied; the aim was to determine if such KCl-pretreated plants have the same potassium-absorption characteristics as KCl-starved roots. At a concentration of 20mM potassium, KCl-pretreated plants absorbed potassium from chloride solutions 1.5 times as fast as from sulphate solutions, and faster from nitrate than from chloride solutions. However, at 0.5 mM potassium, absorption rates from nitrate and chloride solutions were similar, as were rates from sulphate and chloride solutions at concentrations of 0.5 mM potassium or less. These results suggest that KCl-pretreated plants have both an anion- independent and an anion-controlled component of potassium absorption.
In 0.5 mM KCl, high concentrations of calcium and sodium chlorides, but not sulphates, stimulated potassium absorption by KCl-pretreated plants. It is suggested that high rates of chloride absorption may stimulate potassium absorption from concentrations of potassium below 1 mM. In 20 mM KCl, neither chlorides nor sulphates of calcium or sodium had any effect on potassium absorption into KCl-pretreated plants. This result contrasts with published results with KCl-starved roots. The different results are interpreted as an increase in selectivity for potassium over sodium with increasing time of treatment with potassium.
Role of Temperature, Light and Growth Regulators in Germination in Anemone coronaria L
Authors: Bullowa S , Negbi M , Ozeri Y
Published: January 2006

The optimal temperature range for germination of achenes of the De Caen type of cultivated A. coronaria L. was 10-20°C. Continuous irradiation with white light retarded germination, particularly at supraoptimal temperature. The retardation was caused by the far-red component of the light. Blue light was inactive by itself but synergized with far-red. Gibberellic acid (GA3) promoted gerrnin- ation only at supraoptimal temperature (25°C). Abscisic acid (ABA) inhibited germination more at 20 than at 15°C. Rinsing the achenes with water completely removed the inhibition caused by 40 p.p.m. ABA. GA3 at a concentration of 100 p.p.m. partly overcame the inhibition caused by ABA. The growth retardants (2-chloroethyl)trimethylammonium chloride and Amo-1618 [2'-isopropyl-4'- (trimethylammonium chloride)-5'-methylphenyl piperidine-1-carboxylate] inhibited germination more at 20 than at 15°C; Amo-1618 was more inhibitory. GA3 at concentrations of 10-1000 p.p.m. partly overcame the inhibition by 100 p.p.m. Amo-1618, but not that by 1000 p.p.m.
Partial stripping or cutting of the pericarp enhanced germination whereas complete removal inhibited it. During the first 6 days of incubation under the optimal conditions the embryo grows within the endosperm, thus accounting for the minimum lag period of 6 days prior to emergence of the seedling from the pericarp.
Diurnal Changes in Photosynthetic Capacity of Barley Leaves
Authors: Pitman MG , Luttge U , Lauchli A , Ball E
Published: January 2006

Measurements of oxygen uptake and loss in dark and light were made on slices of barley leaves cut at different times during the day. Oxygen consumption in the dark was the same at all times, but there was a decrease in oxygen production in the light at about midday. It is suggested this reduction was due to a change in intrinsic photosynthetic capacity of the leaf.
Rate of Protein Synthesis in Senescing, Detached Wheat Leaves
Authors: Brady CJ , Heng Fong Tung
Published: January 2006

In wheat leaves detached and kept turgid and in the light for 48 h, the content of free valine increased eightfold. The rate of valine metabolism in these leaves was not rapid, and the increase in free valine was 80% of the net loss of valine from leaf protein over 48 h.
When L-[14C]valine was fed to detached leaves, the rate of incorporation into protein increased with time of feeding, although uptake of the L-[14C]valine proceeded linearly. Isotope dilution experiments established that the rate of incorporation of valine was independent of the size of the free valine pool, and that incoming L-[14C]valine was substantially diluted by the free valine of the leaves before incorporation into protein. Based on these findings, estimates were made of turnover of valine in protein in detached wheat leaves. In fully expanded leaves of two ages the turnover rate approached 2.0% per hour when the leaves were first detached, and, after 48 h, had fallen to 0.3 % per hour. Valine fed by the transpiration stream was readily incorporated into proteins made on chloroplast ribosomes.
Induction of Glutamine Synthetase During Nodule Development in Lupin
Authors: Robertson JG , Farnden KJF , Warburton MP , Banks JAM
Published: January 2006

Activity of glutamine synthetase (EC 6.3.1.2) in the soluble protein fraction of nodules from 21-day- old lupin plants was measured. On a fresh tissue weight basis, activity was approximately 500 times higher than in the soluble protein fraction from roots of inoculated plants and 300 times higher than in the bacteroid soluble protein fraction. The activity of glutamine synthetase in the bacteroids was approximately 10 times lower than in cultured rhizobia. Glutamine synthetase activity in the nodule cytoplasm was found to increase during nodule development over a time course which followed the induction of leghaemoglobin and nitrogenase. Glutaminase activity, which could be inhibited by L-5-diazo-4-oxo-norvaline, was detected in extracts of bacteroids and cultured rhizobia. The glutamine synthetases present in cultured rhizobia and in the nodule cytoplasm had different electrophoretic mobilities on polyacrylamide gels.
Distribution of Phytochrome in Subcellular Fractions From Maize Coleoptiles Following Glutaraldehyde Treatment
Authors: Yu R
Published: January 2006

Localization of phytochrome in subcellular fractions of maize cells was determined using glutaraldehyde treatment and biochemical fractionation techniques. Glutaraldehyde treatment enhanced phytochrome pelletability in fractions from red-irradiated but not dark-grown or far red-irradiated maize coleoptiles. The glutaraldehyde-induced pelletability of phytochrome represented a bonded form of phytochrome because it was resistant to washings with concentrated salt and EDTA solutions. A number of the characteristics of glutaraldehyde-induced phytochrome pelletability support the claim that inside the cell, phytochrome becomes associated with its reaction partner(s) upon red irradiation and this association can be stabilized by chemical crosslinkage with glutaraldehyde.
Thermal Adaptation of Pennisetum: Seedling Development
Authors: Pearson CJ
Published: January 2006

Germination, establishment, dry weight accumulation and leaf development of seedlings of two Pennisetum typhoides cultivars and a P. typhoides × P. purpureum biotype were studied at four temperatures from 33/28 to 15/10°C (day/night) under natural irradiances.
Percentage seedling germination was independent of temperature. However, rate of germination and emergence were fastest, the spread in populations of time to germination least, and seedling survival highest, at the temperature at which rates of leaf area expansion and dry weight accumulation were greatest, i.e. 33/28°C. Rates of dry weight accumulation differed between the three pennisetums, the ranking in early growth at temperatures below 33/28°C being the same as that for seed size, and in later growth at all temperatures being in the order interspecific hybrid > intra-specific hybrid > selected strain.
Compartmentation in Vicia faba Leaves. III. Photosynthesis in the Spongy and Palisade Parenchyma
Authors: Outlaw WH , Fisher DB
Published: January 2006

Relative rates of photosynthesis in the palisade and spongy parenchyma were found to be dependent upon the intensity of incident photosynthetically active radiation. The rate of photosynthesis in the spongy parenchyma relative to the rate in the palisade parenchyma increased with increasing light intensity. We attribute this behaviour to shading of the spongy parenchyma by palisade parenchyma.
The kinetics of photosynthetic carbon metabolism were qualitatively similar in the two tissues. Immediately after a 6-s 14CO2 pulse, phosphoglyceric acid plus sugar phosphates represented about 85 % of the 14C in the water-soluble compounds in both the palisade and spongy parenchyma, and were the only compounds in which radioactivity declined. Sucrose was the main end-product of photosynthesis and represented 30% of the water-soluble radioactivity after 104 s in both these tissues. Other compounds (phosphoglycollic acid plus phosphoenolpyruvic acid, malic acid plus glyceric acid, and alanine) represented smaller, similar amounts of radioactivity in each tissue. A higher proportion of activity due to 14C-labelled (glycine plus serine) in the water-soluble fraction of the spongy parenchyma may reflect a difference in the proportion of photosynthate being respired there.
Internal Water Balance of Brigalow (Acacia harpophylla F. Muell.) Under Natural Conditions
Authors: Tunstall BR , Connor DJ
Published: January 2006

On one day each month over a period of 2½ years, diurnal measurements of plant water status, leaf diffusive resistance, carbon uptake, irradiance, ambient temperature and humidity were made in a brigalow community. Diurnal changes in leaf diffusive resistance, osmotic potential, plant water potential, and carbon uptake are shown to follow general patterns and the changes in plant water potential were related to the dawn value of plant water potential. The data suggest the development of negative turgor in brigalow and demonstrate the capacity of the plant to maintain high tissue water contents at low water potentials. Measurements of shoot extension and litter fall showed that litter fall occurred principally following shoot extension.
Internal Control of Stomatal Physiology and Photosynthesis. II. Photosynthetic Responses to Phaseic Acid
Authors: Kriedemann PE , Loveys BR , Downton WJS
Published: January 2006

Phaseic acid appears to act as a specific inhibitor of photosynthesis in vivo. Such inhibition is probably associated with the 'after-effects' of moisture stress and with other forms of non-stomatal influences on photosynthesis that follow manipulative treatments (leaf excision, fruit removal).
This naturally occurring inhibitor was extracted from leaves of Vitis vinifera L. and applied to a variety of material (including vine foliage) under laboratory conditions. Photosynthetic activity of both excised leaves (CO2-H2O exchange; cuvette measurement) and tissue slices (oxygen electrode determinations) was strongly inhibited by buffered solutions at physiological concentrations. Phaseic acid inhibited oxygen evolution by isolated spinach chloroplasts (using ferricyanide as an
electron acceptor) but had no effect on spinach leaf ribulosebisphosphate carboxylase activity. Photosynthetic regulation by phaseic acid might therefore relate to its influence over photosynthetic electron flow and generation of high energy metabolites which foster CO2 fixation.
Germination of Cocklebur Seeds: Interactions Between Gibberellic Acid, Benzyladenine, Thiourea, KNO3 and Gaseous Factors
Authors: Esashi Y , Hata Y , Katoh H
Published: January 2006

The germination response of small, upper seeds of cocklebur (Xanthium pensylvanicum Wallr.) was examined with respect to the germination stimulants oxygen, CO2, ethylene, gibberellic acid, benzyladenine, thiourea and KNO3. Thiourea, benzyladenine, ethylene and oxygen-enriched air (50% O2) stimulated germination, but gibberellic acid was only slightly effective and KNO3 had little effect. In contact with thiourea or CO2, seeds usually germinated by extrusion of the radicle without any change of germination pattern, but while in O2-enriched air the seed coat was predominantly ruptured at the cotyledon end. In about half of the seeds germinated with ethylene, benzyladenine and gibberellic acid, the seed coat split at the cotyledon side. Trapping of endogenously evolved ethylene and CO2 from the ambient atmosphere did not affect the actions of benzyladenine and gibberellic acid, but the action of thiourea was significantly reduced by trapping CO2. Except for thiourea, with which the CO2 production was enhanced, benzyladenine, gibberellic acid and KNO3 did not increase CO2 and ethylene production from the seed in the germination period. The maximum germination percentage was obtained by a combi- nation of CO2, ethylene, gibberellic acid and benzyladenine, but the interaction of gibberellic acid and benzyladenine was not significant. In contrast, the interaction of gibberellic acid and ethylene was very effective, and further addition of CO2 to this combination hastened the germination in air and also facilitated it under the semi-anaerobiosis assumed to exist in a natural underground habitat, although the effect of benzyladenine alone was nearly completely suppressed by semi- anaerobiosis. Thus the particular importance of CO2, ethylene and gibberellic acid in the normal germination regulation of this seed is suggested.
A Reappraisal of the Growth and Development of Peach Fruit
Authors: Chalmers DJ , Ende BVD
Published: January 2006

Both the fresh weight and dry weigh increase of peach fruit [Prunus persica (L.) Batsch. cv. Golden Queen] have a double-sigmoid pattern. However, the lag period of slow fresh weight increase (fresh- weight-stage II) began and finished 1 month earlier than the start and finish respectively of the lag period of dry weight increase (dry-weight-stage II). Similarly, after the fruit had matured the rate of fresh weight increase declined 1 week before the rate of dry weight increase declined.
The stone increased in dry weight rapidly in fresh-weight-stage II and this was accompanied by a compensating decline in the rate of dry weight increase of the flesh. There was no rapid increase in the dry weight of the seed until the rate of dry weight increase of the stone declined at the beginning of dry-weight-stage II. Although the decrease in the growth rate of the stone was accompanied by a marked increase in soluble sugar in the flesh, there was no compensating increase in growth rate of the flesh.
While the second rapid stage of fresh weight increase (fresh-weight-stage III) was not accompanied by other apparent physiological changes, the second rapid stage of dry weight increase began at the same time as ripening commenced. The rate of natural abscission and the rate at which chlorophyll was degraded, both of which are known to indicate the level of ethylene present in the tissue, were high in dry-weight-stage I and dry-weight-stage III and low in dry-weight-stage II. The rate of growth of the fruit and its parts during different stages, the growth of the seed, the rate of abscission and chlorophyll degradation and the level of the major metabolites present in the fruit were all intricately interrelated.
We have discussed the physiological significance of these observations and the way in which they may relate to earlier studies of peach fruit growth.
CO2 Storage in Eucalyptus Oil Glands; a Hypothesis Disproved
Authors: Meyer CP , Canny MJ
Published: January 2006

CO2 is known to be highly soluble in oils. The hypothesis investigated was that the contents of leaf oil glands in Eucalyptus spp, might constitute a significant reservoir for CO2 within the leaf. Solubilities of CO2 in extracted oil from E. socialis leaves were measured and found to be 3-6 times that of CO2 in water. The volume of oil glands constitutes up to 12% of the total leaf volume. It is shown that the possible capacity of this reservoir for CO2 could at most amount to the equivalent of about 35 min of dark respiration, and therefore could not constitute a significant internal reservoir in the dark period. There appears to be a correlation between oil-gland percentage volume and the rainfall where the trees grew. Values are given for the percentage volume of the other tissues of the leaf and for cuticular resistance to CO2 diffusion.
Comparison of Isomers of Fluorophenylalanine as Inhibitors of Ion Transport Across Barley Roots
Authors: Wildes RA , Pitman MG , Schaefer N
Published: January 2006

Earlier reports of inhibition of Cl- transport across the root to the xylem by p-fluorophenylalanine (p-FPA) were used to support the need for continual production of a protein used as a carrier. It is now shown that o-FPA and m-FPA are also effective as inhibitors of transport, ruling out the possibility that p-FPA was acting by inhibition of phenylalanine ammonia-lyase activity and so changing endogenous concentration of phenolic compounds.
Leaf Ultrastructure and δ13C Values of Three Seagrasses from the Great Barrier Reef
Authors: Doohan ME , Newcomb EH
Published: January 2006

Leaf anatomy, ultrastructure and 13C/12C ratios were studied in three species of seagrasses collected on the Great Barrier Reef: Cymodocea rotundata Ehrenb. & Hempr., C. serrulata (R. Br.) Aschers. & Magnus, and Thalassia hemprichii (Ehrenb.) Aschers. Although they belong to two different mono- cotyledonous families, the three species are quite similar in the characteristics studied. Cells of the epidermal layer of the leaves are extremely thick-walled and have abundant cytoplasm with large chloroplasts and numerous mitochondria. The chloroplast-microbody profile ratio is c. 4-5 : 1 and the mitochondrion-microbody ratio 10-15 : 1. The epidermal cells resemble transfer cells in having a pronounced development of ingrowths on the radial walls. The mesophyll cells have thin walls, a large central vacuole and a thin layer of cytoplasm with relatively few organelles. There is no specialization of mesophyll cells around the vascular bundles. The δ13C values for the three sea- grasses range from -6.90, to - 12.40, and thus are characteristic of C4 land plants, although the seagrasses do not conform to the C4 syndrome in leaf anatomy or ultrastructure. It is not possible to place the seagrasses in either the C3, C4 or crassulacean acid metabolism category of land plants, but whether they constitute yet a fourth group with respect to characteristics related to CO2 assimilation is not clear.
δ13C Values in Marine Organisms from the Great Barrier Reef
Authors: Black CC , Bender MM
Published: January 2006

The carbon isotope composition of marine organisms collected on the Great Barrier Reef near Lizard Island, Australia, was determined. Emphasis was placed on photosynthetic organisms including algae, zooxanthellae, angiosperms and symbiotic systems. The photosynthetic organisms had δ13C values ranging from -5.1 to -32.40,. Symbiotic systems and non-photosynthetic organisms had δ13C values within this range. CO2 released by acid treatment from coral, shell and cone carbonates had δ13C values between + 3.9 and - 2.70,. The results with photosynthetic tissue generally are interpreted in comparison to terrestrial plants as showing a major assimilation of CO2 into organic compounds via ribulosebisphosphate carboxylase in the marine ecosystem. However, a few photosynthetic organisms exhibited δ13C values between - 5.10, and - 110, and could be assimilating CO2 via phosphoenolpyruvate carboxylase. A unified scheme is presented for the pathway of carbon assimilation in the reef from the sea water through both autotrophic and heterotrophic metabolism, and finally to calcification.
Nitrogen Fixation by Blue-green Algae of the Lizard Island Area of the Great Barrier Reef
Authors: Burris RH
Published: January 2006

Reduction of acetylene and 15N2 by blue-green algae and other organisms from the Lizard Island area of the Great Barrier Reef was measured. The effects of storage of the algae, the partial pressures of acetylene and oxygen, and light intensity were studied. The average ratio of acetylene to N2 reduced was 1.9. With this factor, it was calculated that 6.8 - 30.6 kg nitrogen was fixed annually per hectare of rock surface in the intertidal zone. Fixation of nitrogen by blue-green algae can contribute a substantial portion of the fixed nitrogen required for maintaining the flora and fauna of the coral reef community.
Release of Glycollate from Tropical Marine Plants
Authors: Fogg GE
Published: January 2006

Release of glycollate under conditions of high illumination and high oxygen concentration from tropical seaweeds representing the groups Chlorophyta, Phaeophyta and Rhodophyta, and from two marine angiosperms, has been demonstrated. The amount released is increased by the presence of alumina as an adsorbent. Quantitative determination is rendered difficult by the simultaneous release of a substance(s), also adsorbed on alumina, which interferes in the colorimetric analysis for glycollate. The concentration of glycollate in surface water in the Coral Sea was determined on two occasions as 0.015 mg I-1.
Light and Dark Respiration and Release of Organic Carbon in Marine Macrophytes of the Great Barrier Reef Region
Authors: Hough RA
Published: January 2006

Respiration and organic carbon release were examined in several submersed marine macroalgae and vascular plants of the Great Barrier Reef region by use of a 14C assay. Loss of 14CO2 and organic 14C from prelabelled plants was followed in the light and dark at low and high dissolved oxygen concentrations. While refixation of respired carbon in the light was substantial in some cases, rates of loss of CO2 in the light were significant and suggested presence of photorespiration, particularly in Cymodocea rotundata and Halophila ovata, in which respiration in the light was enhanced by high dissolved oxygen concentration. Release of dissolved organic carbon was relatively low, and lack of enhancement by high oxygen suggested minimal involvement of glycollate excretion.
Carbonate Dehydratase in Marine Organisms of the Great Barrier Reef
Authors: Graham D , Smillie RM
Published: January 2006

Carbonate dehydratase (EC 4.2.1.1, other name 'carbonic anhydrase') activity was found in 28 of 29 species of marine algae and angiosperms and in a mixed culture of phytoplankton collected in the vicinity of Lizard Island on the Great Barrier Reef of Australia. The species included 13 member- of the Chlorophyta, 4 of the Phaeophyta, 7 of the Rhodophyta, 2 of the Cyanophyta and 3 subs merged marine angiosperms. One of the two blue-green algae showed no detectable enzymic activity. The levels of activity ranged from 100 to 4800 units per milligram chlorophyll and were generally comparable with those of terrestrial angiosperms based on chlorophyll content, but were only a small fraction when compared on the basis of fresh weight.
Culture of the green alga Chlorodesmis fastigiata in 'CO2-free' sea water (1.4 mg CO2 per litre) for 4 h did not lead to an induction of carbonate dehydratase activity.
Some of the species of algae producing calcium carbonate contained the highest activities recorded but others had low activities. A correlation between high carbonate dehydratase activity and calcium carbonate deposition could not be adduced.
Symbiotic zooxanthellae (Gymnodinium microadriaticum) of the hard coral Pocillopora damicornis and the clam Tridacna maxima also contained carbonate dehydratase (940 and 340 units per milligram chlorophyll, respectively). The host tissues contained about five times the activity of their respective zooxanthellae.