Change in the amino-acid content during male gametophyte formation of Datura metel in Situ

Summary Determination of the free and bound aminoacids during microsporogenesis of Datura metel showed that the principal amino-acids were proline, glutamic acid, aspartic acid, threonine-serine and alanine. Of these, only proline showed a consistent increment during pollen development. In contrast, aspartic acid and lysine decreased in the later stages of microsporogenesis. The amounts of other amino-acids did not show any consistent pattern. Four amino-acids, namely proline, glutamic acid and threonine-serine constituted nearly 85% of the free amino-acid pool in the developed anther (stage IV). Proline accumulation, relative to the total free amino-acid pool in mature anthers, was correlated with the water-content. The results were discussed in view of possible relationships between metabolic activity and free and bound amino-acid concentrations.Abbreviations ABA -Aminobutyric acid - mol/g micromoles of each amino-acid per gram of dry material     

Changes in the Free Amino Compounds in Young Tomato Plants in Light and Darkness with particular Reference to {gamma}-Aminobutyric Acid

Tomato plants were grown to the five-leaf stage under uniformconditions in a growth room with a daily light period of 15h. Plants were sampled at intervals through 24 h periods andthe free ninhydrin-positive compounds determined in roots, bleedingsap, stems and shoots (mainly leaves), using ion-exchange columnchromatography and a lithium-buffer separation system. The compoundspresent and their range of concentrations are given for twooccasions: after illumination for 8 hand after 5 h of darkness. Data for -aminobutyric acid (GAB), glutamic acid, glutamine,alanine, aspartic acid and ammonia are summarized graphicallyfor all occasions and for all parts of the plant; asparaginefor sap only. The data were examined for correlations betweenthese substances for both light and dark conditions. Relative amounts of free acids were: root glutamine> glutamicand GAB > aspartic > alanine; bleeding sap glutamine >asparagine > GAB > aspartic> alanine; stem glutamine> glutamic > GAB and aspartic > alanine; shoot (leaf)GAB and glutamine > aspartic > alanine and glutamic. Patternsof change were as follows: in the root GAB and glutamic weresimilar and unlike glutamine; alanine did not change;sap ammonia,GAB and alanine were parallel, glutamine was similar to theseonly in light; in the stem glutamine and glutamic tended toaccumulate in parallel in light, but GAB did not; in the shoot(leaf) GAB and glutamine were similar except that the formeraccumulated more rapidly in the initial light period; glutamicacid and alanine were similar to each other but distinct fromGAB and glutamine. The relatively large amounts of GAB in tomato plants and themagnitude of the changes occurring in light and darkness seemindicative of its importance as a temporary storage productfor protein amino acids, but the factors controlling accumulationand utilization in different parts of the plant are unknown.     

Effects of a dwarfing compound,CCC, on the production and export of gibberellin-like substances by root systems

Summary (2-Chloroethyl)trimethylammonium chloride (Cycocel or CCC), an inhibitor of gibberellin biosynthesis, when repeatedly supplied to the root systems of balsam (Impatiens glandulifera Royle) plants reduces growth in height and the level of gibberellin-like substances in the bleeding sap that exudes from the stumps of detopped plants. Within twelve hours after a single application of the inhibitor to decapitated field peas (Pisum arvense), there are quantitative and qualitative changes in the gibberellins of the sap compared with those in sap collected over the same period of time from untreated plants. These changes are interpreted in terms of the possible blockage by CCC of normal gibberellin production and diversion of precursors into synthesis of abnormal gibberellins.     

Carbon isotope composition of N2-fixing and N-fertilized legumes along an elevational gradient

Dinitrogen-fixing legumes are frequently assumed to be less water-use efficient than plants utilizing soil mineral N, because of the high respiratory requirements for driving N₂ fixation. However, since respiration is assumed not to discriminate against ¹³C, any differences in water-use efficiency exclusively due to respiration should not be apparent in carbon isotope discrimination () values. Our objective was to determine if the source of N (N₂ fixation versus soil N) had any effect on of field-grown grain legumes grown at different elevations. Four legume species, Glycine max, Phaseolus lunatus, P. vulgaris, and Vigna unguiculata, were grown on five field sites spanning a 633 m elevational gradient on the island of Maui, Hawaii. The legumes were either inoculated with a mixture of three effective strains of rhizobia or fertilized weekly with urea at 100 kg N ha^-1 in an attempt to completely suppress symbiotic N₂-fixing activity. In 14 of 20 analyses of stover and 12 of 15 analyses of seed values were significantly higher (p=0.10) in the inoculated plants than the N-fertilized plants. Nitrogen concentrations were generally higher in the fertilized treatments than the inoculated treatments. The different values obtained depending on N-source may have implications in using as an indicator of water-use efficiency or yield potential of legumes.     

Daily fluctuations in water potential and associated ionic changes in Atriplex canescens

Summary Water potential () measurements of Atriplex canescens at the base of the Red Desert near Tipton in Wyoming, revealed a range between-15.5 to-45.1 bars. Minimum values coincided with the lowest air and soil temperatures, maximum with the greatest atmospheric evaporative demand. Change in exceeded 12 bars h^-1 during periods of rapidly moving storm systems. Changes in appeared to be independent of plant size, age, sex, and the spatial location of plants. Chemical analyses revealed that xylem sap was up to three times more concentrated at high than at low . It was observed that the flow rate of sap was greater at lower than at higher and that the increase in water movement accounted for the dilution of the baseline concentration of sap solutes. Together, Ca, Mg, K and Na contributed 58% of the mean osmolality of the xylem sap; the dominant ions, however, were K and Cl. We suggest that the ability of the species to respond rapidly to changing atmospheric conditions affords it a distinct advantage in a harsh environment.     

Identification and quantitation by GC-MS of zeatin and zeatin riboside in xylem sap from rootstock and scion of grafted apple trees

Zeatin and zeatin riboside were identified by full-scan gas chromatography-mass spectrometry (GC-MS) in xylem sap of clonal apple rootstocks (M.27, M.9 and MM.106). These rootstocks exhibit a wide range of control over tree size when grafted to a common scion. The concentrations of zeatin and zeatin riboside were measured by GC-MS selected ion monitoring (SIM) in shoot xylem sap and root pressure exudate obtained from these rootstocks and from trees of Fiesta scion grafted onto the rootstocks. Zeatin was the predominant cytokinin in xylem sap from the dwarfing rootstocks, M.27 and M.9, while zeatin riboside was the predominant cytokinin in xylem sap from the more invigorating rootstock MM.106. Cytokinin concentrations (ng ml^–1) in root pressure exudate and shoot xylem sap, (i.e. from above the graft union in composite trees), increased with increasing vigour of the rootstock, irrespective of whether the plants were non-grafted rootstocks, or were composite plants of Fiesta scion grafted onto the rootstocks. Cytokinin content (ng shoot^–1) of shoot sap differed with rootstock; the more invigorating (MM.106) had greater amounts of cytokinins than the more dwarfing (M.9 and M.27) rootstocks. These results are discussed in relation to possible influences of roots on the growth of shoots via cytokinin supplies in the xylem sap.     

Proteins of Brown Seaweeds as Inhibitors of Endo-1→3-β-D-glucanases of Marine Invertebrates

It has been found that aqueous–ethanol extracts of brown seaweeds contain substances inhibiting endo-13--D-glucanases, the digestive enzymes of marine mollusks. The inhibitors were detected in 14 of 21 brown seaweeds investigated. An irreversible protein inhibitor possessing high specificity toward endo-13--D-glucanases of marine mollusks was isolated from the brown seaweed Laminaria cichorioides. As determined by gel filtration, the molecular mass of the inhibitor is 46 kD. The value of [I]₅₀ (10^–8 M) for the inhibitor is comparable with the corresponding value for natural inhibitors of amylases from terrestrial plants. The results of chemical modification indicated that tryptophan, glutamic acid, aspartic acid, histidine, and probably tyrosine residues are important for the interaction of the inhibitor with the enzyme.(subject: to Zvyagintseva)     

Free Amino-acids in the Endosperm of the Developing Coconut (Cocos nucifera)

The free amino-acids in the sap flowing from the incised inflorescenceof the coconut palm (Cocos nucifera) and in the liquid and solidendosperm of the coconut at various stages of development (4–12months from the time of opening of the spathe) have been studiedby paper and ion-exchange chromatography. The chief amino-acids in the sap were in decreasing order ofmagnitude: glutamic acid, aspartic acid, glutamine, serine,and asparagine. Smaller amounts of threonine, alanine, -aminobutyricacid, proline, valine, arginine, and tryptophan were found,along with traces of tyrosine, ß-alanine, lysine,histidine, leucine, isoleucine, and methionine. The chief amino-acids in the liquid endosperm of the nut until6 months of age were alanine, glutamic acid, serine, valine,and proline with smaller amounts of asparagine, aspartic acid,glycine, threonine, leucine, isoleucine, and glutamine. Thealanine, glutamic acid, proline, and -aminobutyric acid contentsof the liquid endosperm increased greatly as the solid endospermwas laid down, ultimately forming about 75 per cent. of thetotal free amino-acids. Nineteen amino-acids were detected atthe 8–10-month stage. -Aminobutyric acid appears in the liquid endosperm soon afterthe solid endosperm commences to form, and increases strikinglythereafter. It was also found in the free amino-acids of thesolid endosperm at all stages of development. This amino-acidwas not found in the acid hydrolysate of coconut globulin. The free amino-acids in the solid endosperm were found to reflectqualitatively the free amino-acid composition of the correspondingliquid endosperm. In addition, ß-alanine, -aminobutyricacid, phenylalanine, and tryptophan were present in small amounts.Alanine, serine, glutamic acid, and -aminobutyric acid, increasedwith age of the nut while the others increased up to 6 monthsand then decreased, only traces being found at maturity exceptin the case of aspartic acid, proline, and threonine. Twenty-oneamino-acids were detected in the free amino-acids of the solidendosperm. The source of the free amino-acids in the liquid endosperm andthe possible use of these amino-acids for protein synthesisin the coconut are briefly discussed.     

Cytochemical evidence for the leakage of acid phosphatase through ultrastructurally intact lysosomal membranes

Synopsis Fixation under improper conditions ofin vitro cultivated cells results in an extensive diffusion of the lysosomal enzyme acid phosphatase because of the influence of a low effective osmotic pressure. In the present investigation, advantage was taken of this predictable diffusion in order to establish whether or not leakage of acid phosphatase could take place through ultrastructurally intact lysosomal membranes.In order to reveal small holes in the lysosomal membranes, secondary lysosomes were labelled with thorium dioxide particles, which were presumed to appear free in the cell sap if ruptures in the membranes larger than about Ioo Å were created.The experiments revealed that following the fixation ofin vitro cultivated human glia cells under improper conditions, mitochondria and ground cytoplasm show considerable swelling artifacts, while secondary lysosomes appear to be essentially unaffected. The lysosomes, nevertheless, apparently lost most of their content of acid phosphatase, as judged from enzyme cytochemical studies. These findings indicate that leakage of acid phosphatase from ultrastructurally intact lysosomes is possible.     

Apoptosis and nutrition: Involvement of amino acid transport system in repression of hybridoma cell death

Mouse hybridoma cells cultured on the verge of starvation-induced apoptosis, i.e. in a medium diluted with saline, proved to serve as a sensitive screening system for apoptosis-suppressing activity of nutrient medium components. Conventional amino acid mixtures were found to suppress the starvation-induced apoptosis, whereas a vitamin mixture was ineffective. (Frank F (1995) Biotechnol. Bioeng. 45: 86–90). Recent experiments showed that suppression of apoptosis, and concurrent resumption of growth, could be achieved by addition of single substances at millimolar concentrations. The set of active substances included certain coded L-amino acids (glycine, alanine, serine, threonine, proline, asparagine, glutamine, histidine), non-coded amino acids (-alanine, taurine, 4-aminobutyric acid), and a non-metabolizable analogue (2-aminoisobutyric acid). This finding shows that some amino acids do not act solely as nutrients, but also as specific signal molecules. The specificity of the effect points to the involvement of adaptively regulated amino acid transport systems A and N in maintaining the balance between triggering and suppression of starvation-induced apoptosis.     

Glutamine and alpha-ketoglutarate uptake and metabolism by nerve terminal enriched material from mouse cerebellum

In order to provide evidence relevant to the hypothesis that nonsynaptically derived -ketoglutarate serves as a metabolic precursor of the neurotransmitter pools of glutamate and GABA the uptake and metabolism of -ketoglutarate by nerve terminal enriched material was studied and compared to corresponding data for glutamine. Both -ketoglutarate and glutamine were transported across the cell membrane by high affinity and low affinity carriers. Under conditions prevailing in vivo -ketoglutarate probably is transported primarily by its high affinity carrier, whereas gluatmine should be transported primarily by one or more low affinity carriers. Based upon reciprocal uptake inhibition experiments glutamine appeared to be transported by the alanine preferring system, and to a lesser extent by the basic amino acid and large neutral amino acid carriers. A comparison of the rate of uptake by different cellular preparations enriched in either nerve terminals or cell bodies indicated that -ketoglutarate is transported selectively by nerve terminals. Both substrates were rapidly converted to glutamate; however, glutamine was more readily metabolized to GABA. The results of our study are consistent with the concept that both glutamine and -ketoglutarate derived from extra-neuronal sources are taken up by nerve terminals and utilized to replenish the neurotransmitter pools of glutamate and GABA.     

Nucleotide sequence of the 3′-terminal region of chilli vein-banding mottle potyvirus isolated from pepper in Thailand

The sequence of the 2227 nucleotides of the 3-terminus of chilli vein-banding mottle virus-Chiangmai isolate (CVbMV-CM1) genome was determined. This sequence encodes a putative 287 amino acid coat protein. Downstream of coat protein coding region is a 288 nucleotide untranslated sequence terminated by a polyadenylate tract. The amino acid sequence of coat protein contained aspartic acid–alanine–glycine tripeptide, which may correlate with the high frequency of aphid transmissibility. The cleavage site between large nuclear inclusion protein (NIB) and coat protein was glutamine/serine. Comparison of 3 non-coding region nucleotide and coat protein amino acid sequences of CVbMV-CM1 with those of other 18 potyviruses showed 44–56% and 54–65% homology respectively, suggesting CVbMV should be regarded as new potyvirus.     

Two cDNAs encode two nearly identical Cu/Zn superoxide dismutase proteins in maize

Summary SOD-4, a cytosolic form of superoxide dismutase in maize, originally was defined as a single band of activity by zymogram analysis. The protein was purified to homogeneity as shown by a single band on native or denaturing polyacrylamide gels and a single spot on two dimensional gels. The N-terminal amino acid sequence for the first 20 residues was determined for the purified SOD-4 protein. All residues were clearly determined except for residue twelve, where both glutamic and aspartic acids were found. A maize gt11 cDNA library was constructed from scutellar poly(A)⁺RNA. Two cDNAs were isolated, restriction mapped, and their DNA sequences determined. The amino acid sequence deduced from both cDNAs matched perfectly the N-terminal sequence of the purified protein except for the residue at position 12. Significantly, at the twelfth codon, one cDNA was found to code for glutamic acid and the other cDNA had a codon for aspartic acid. Both cDNAs contained similar but not identical 5 and 3 untranslated sequences. Both cDNAs contained polyadenylation signals and tails. cDNA isolations, RNA, and genomic DNA blots confirm the existence and expression of two genes that produce indistinguishable SOD-4 proteins.     

Studies with antitranspirants on tea (Camellia sinensis L.)

The antitranspirant effect of a number of substances on tea was studied and the effects of the most effective substance investigated in detail. The film type of antitranspirants reduced transpiration only at a considerably higher concentration than the stomatal type of antitranspirants. Of the stomatal type of antitranspirants phenyl mercuric acetate (PMA) was the most effective substance. Under actively transpiring conditions a 250 ppm solution of PMA reduced transpiration by about 30 per cent. The effect of PMA was localised and there was no translocation to untreated parts of the leaf blade. A spray of PMA reduced transpiration with gradually diminishing intensity for about 20 days, reduced vegetative growth of young plants grown both under non-water stress and water stressed conditions and reduced the yield of crop of mature plants during a drought. re]19760806     

Characterization of amino-acid transport in Ricinus communis roots using isolated membrane vesicles

The mechanism and specificity of amino-acid transport at the plasma membrane of Ricinus communis L. roots was investigated using membrane vesicles isolated by phase partitioning. The transport of glutamine, isoleucine, glutamic acid and aspartic acid was driven by both a pH gradient and a membrane potential (internally alkaline and negative), created artificially across the plasma membrane. This is consistent with transport via a proton symport. In contrast, the transport of the basic amino acids, lysine and arginine, was driven by a negative internal membrane potential but not by a pH gradient, suggesting that these amino acids may be taken up via a voltage-driven uniport. The energized uptake of all of the amino acids tested showed a saturable phase, consistent with carrier-mediated transport. In addition, the membrane-potential-driven transport of all the amino acids was greater at pH 5.5 than at pH 7.5, which suggests that there could be a direct pH effect on the carrier. Several amino-acid carriers could be resolved, based on competition studies: a carrier with a high affinity for a range of neutral amino acids (apart from asparagine) but with a low affinity for basic and acidic amino acids; a carrier which has a high affinity for a range of neutral amino acids except isoleucine and valine, but with a low affinity for basic and acidic amino acids; and a carrier which has a higher affinity for basic and some neutral amino acids but has a lower affinity for acidic amino acids. The existence of a separate carrier for acidic amino acids is discussed.Abbreviations PM plasma membrane - TPP⁺ tetraphenylphosphonium ion - pH pH gradient - membrane potential This work was supported by the Agricultural and Food Research Council and The Royal Society. We would like to thank Mrs. Sue Nelson for help with some of the membrane preparations.     

An investigation of the role of solutes in the xylem sap and in the xylem parenchyma as the source of root pressure

Summary Solute osmotic potentials (_x) in the vessels of hydroponically grown maize roots were measured to assess the osmotic-xylem-sap mechanism for generating root pressure (indicated by guttation). Solutes in vessels were measured in situ by X-ray microanalysis of plants frozen intact while guttating. Osmotic potentials outside the roots (_o) were changed by adding polyethylene glycol to the nutrient solution. Guttation rate fell when _o was decreased, but recovered towards the control value during 3–5 days when _o was greater than or equal to –0.3 MPa, but not when _o was equal to –0.4 MPa. In roots stressed to _o = –0.3 MPa, _x, was always more positive than _o, and _x changed only slightly (ca. 0.05 MPa). Thus the adjustment in the roots which increased root pressure cannot be ascribed to _x, contradicting the osmotic-xylem-sap mechanism. An alternative driving force was sought in the osmotic potentials of the vacuoles of the living cells (_v), which were analysed by microanalysis and estimated by plasmolysis. _v showed larger responses to osmotic stress (0.1 MPa). Some plants were pretreated with abundant KNO₃ in the nutrient solution. These plants showed very large adjustments in _v (0.4 MPa) but little change in _x (0.08 MPa). They guttated by 4 h after _o was lowered to –0.4 MPa. It is argued that turgor pressure of the living cells is a likely alternative source of root pressure. Published evidence for high solute concentrations in the xylem sap is critically assessed.Abbreviations _o external water potential - _x osmotic potential of xylem sap - _v osmotic potential of vacuolar sap - EDX energy dispersive X-ray microanalysis - CSEM cryo-scanning electron microscope - LN₂ liquid nitrogen - PEG polyethylene glycol     

Control of photosynthesis in barley leaves with reduced activities of glutamine synthetase or glutamate synthase

Wild-type and mutant plants of barley (Hordeum vulgare L. cv. Maris Mink) lacking activities of chloroplastic glutamine synthetase (GS) and of ferredox-in-dependent glutamate synthase (Fd-GOGAT) were crossed to generate heterozygous plants. Crosses of the F² generation containing GS activities between 47 and 97 of the wild-type and Fd-GOGAT activities down to 63 of the wild-type have been selected to study the control of both enzymes on photorespiratory carbon and nitrogen metabolism. There were no major pleiotropic effects. Decreased GS had a small impact on leaf protein and the total activity of ribulose-1,5-bisphosphate carboxylase-oxygenase (Rubisco). The activation state of Rubisco was unaffected in air, but a decrease in GS influenced the activation state of Rubisco in low CO₂. In illuminated leaves, the amino-acid content decreased with decreasing GS, while the content of ammonium rose, showing that even small reductions in GS limit ammonium re-assimilation and may bring about a loss of nitrogen from the plants, and hence a reduction in protein and Rubisco. Leaf amino-acid contents were restored, and ammonium and nitrate contents decreased, by leaving plants in the dark for 24 h. The ratios of serine to glycine decreased with a decrease in GS when plants were kept at moderate photon flux densities in air, suggesting a possible feedback on glycine decarboxylation. This effect was absent in high light and low CO₂. Under these conditions ammonium contents exhibited an optimum and amino-acid contents a minimum at a GS activity of 65 of the wild-type, suggesting an inhibition of ammonium release in mutants with less than 65 GS. The leaf contents of glutamate, glutamine, aspartate, asparagine, and alanine largely followed changes in the total amino-acid contents determined under different environmental conditions. Decreased Fd-GOGAT resulted in a decrease in leaf protein, chlorophyll, Rubisco and nitrate contents. Chlorophyll a/b ratios and specific leaf fresh weight were lower than in the wild-type. Leaf ammonium contents were similar to the wild-type and total leaf amino-acid contents were only affected in low CO₂ at high photon flux densities, but mutants with decreased Fd-GOGAT accumulated glutamine and contained less glutamate.Abbreviations Chl chlorophyll - FBPase fructose-1,6-bisphosphatase - Fd-GOGAT ferredoxin-dependent glutamine: 2-oxoglutarate aminotransferase - GS glutamine synthetase - PEP phosphoenolpyruvate - PFD photon flux density - Rubisco ribulose-1,5-bisphosphate carboxylase-oxygenase This research was jointly supported by the Agricultural and Food Research Council and the Science and Engineering Research Council, U.K. in the programme on Biochemistry of Metabolic Regulation in Plants (PG50/555).     

Salinity dependence,uptake kinetics,and specificity of amino-acid absorption across the body surface of the oligochaete annelidEnchytraeus albidus

Enchytraeus albidus is able to absorb dissolved¹⁴C-labeled neutral amino acids (glycine, L-alanine, L-valine,-aminoisobutyric acid) and an amino-acid mixture from ambient water across the body surface against considerable concentration gradients. Saturation kinetics and susceptibility of glycine uptake to competitive inhibition by alanine suggest mediated transport. Absorption of neutral amino acids is an active process. Exchange diffusion of preloaded-aminoisobutyric acid against external glycine or-aminoisobutyric acid could not be detected. Results on inhibition of glycine uptake by a variety of low-molecular-weight substances indicate that glycine absorption is highly specific for neutral amino acids and somewhat less for basic amino acids; it is unspecific for non--amino acids, acidic amino acids, carbohydrates, and organic acids. Rates of transintegumentary net influx of glycine are nearly identical to¹⁴C-glycine influx, suggesting that only small amounts of amino acids are released, as compared with the capacity for uptake. Thus,¹⁴C-amino-acid influx data are used for characterization of the uptake system. Glycine uptake is positively correlated to external salinity. In fresh water, absorption is nearly zero; between 10 and 20 S, uptake increases markedly reaching maximum values at 30 S; these remain almost constant at 40 S. Transport constants and maximum uptake rates increase with rising salinities. Since absorption of glycine and L-valine is susceptible to sodium depletion, similar mechanisms presumably underly salinity-dependent uptake of amino acids and sodium-dependent solute transport. Oxygen consumption is not significantly modified by different external salinities. Estimates of nutritional profit gained from absorption of amino acids vary between 4 and 15 % of metabolic rate for glycine absorption and between 10 and 39 % for uptake of an amino-acid mixture, according to external concentrations (10 and 50 µM) and salinities (20 and 30 S).     

Development of alfalfa strains with differential tolerance to aluminum toxicity

Summary Aluminum toxicity limits root growth in acid subsoils that are difficult to lime. An alternative to subsoil liming is the development of plants having greater tolerance to Al. Alfalfa (Medicago sativa L.) is considered an Al-susceptible species. Preliminary studies indicated that alfalfa cultivars differ in Al tolerance, but the extreme plant-to-plant variation within cultivars prevented the establishment of clearcut cultivar differences.Tolerant and susceptible plants were selected from each of six cultivars (DuPuits, Atlantic, Team, Buffalo, Grimm, and Sirsa 9) grown on an Al-toxic Bladen soil at pH 4.1 to 4.3. The tolerant selections were repotted and interpollinated to form one population of polycross seed. Susceptible selections were treated similarly to form a second population. These two populations, tolerant and susceptible, were subjected to an additional cycle of recurrent phenotypic selection for tolerance and susceptibility, respectively, to Al-toxic Bladen soil at pH 4.6.Plants from the population selected for tolerance to the acid Bladen soil were significantly higher in both root and top vigor on Al-toxic Tatum soil than plants from the population selected for susceptibility. The results indicated that Al tolerance is a heritable trait in these alfalfa populations and that recurrent selection can be used effectively to develop strains having differential tolerance to Al-toxic soils. The observation that only 2% of the plants from the tolerant population were in the most tolerant class suggests a good opportunity for more progress in selecting toward Al tolerance.     

Genetic transformation in two potato cultivars with T-DNA from disarmed Agrobacterium

Summary Derivatives of potato (Solanum tuberosum cv.'s Maris Bard and Desiree) transformed with disarmed T-DNA from genetically engineered Agrobacterium tumefaciens strains were isolated. The transformed plants were recovered from shoot-forming tumours induced by infection of wounds with mixedcultures of shoot-inducing A. tumefaciens strains T37 and either Agrobacterium strain LBA1834(pRAL1834), (Hille et al. 1983) or LBA4404(pBIN6; pRAL4404), (Bevan 1984). Two small-scale feasibility experiments gave at least four Maris Bard plants transformed with pRAL1834 T-DNA and two Desiree plants with pBIN6 T-DNA. The transformed Maris Bard plants were morphologically abnormal and highly aneuploid. This was probably an unfortunate side-effect of a tissue culture-step introduced to promote the efficiency of shoot regeneration. The transformed Desiree plants, in contrast, were isolated without promoting additional shoot-growth. They were morphologically normal, contained 47 and the euploid 48 chromosomes per cell respectively and had improved growth on media containing kanamycin.