Methods for the quantitation of abscisic acid and its precursors from plant tissues

Methods are given for the quantitation of the plant stress hormone, abscisic acid (ABA), and its two metabolic precursors, ketone and enolate, that are applicable to all species tested so far. The plant extract is homogenized at neutral pH, hexane-soluble neutrals are extracted and discarded, and then the free ABA and other organic acids are extracted as ion pairs. The remaining aqueous phase is acidified, allowed to stand, neutralized, and extracted to give the ABA ex ketone fraction and then the aqueous phase is treated with base and again extracted to give the ABA ex enolate fraction. Each of these three fractions, free ABA, ABA ex ketone, and ABA ex enolate, along with a deuteriated internal standard, [side-chain-(2)H(4)]ABA, is then derivatized with pentafluorobenzyl bromide and purified on an automated sample preparation system. The resulting pentafluorobenzyl abscisate samples are then quantified using electron capture negative ionization mass spectrometry with methane as the reagent gas. Using these procedures free ABA, and ABA from its precursors, can be quantified at the level of 100 fg on column. If a large volume injector is used so that the total sample is injected it should be possible to quantify ABA and its precursors in the parts per billion range on a few milligrams of plant tissue.     

The importance of linoleic acid and linolenic acid as precursors of hexanal and trans-2-hexenal in black tea

During tea fermentation, linoleic acid in the neutral fat fraction,and linolenic acid in both the neutral fat and phospholipidfractions from leaves decreased. The addition of linoleic orlinolenic acid to leaf macerates during fermentation resultedin an increase in hexanal or trans-2-hexenal in the volatilefraction. Tracer experiments showed the direct conversion oflinoleic-U-¹⁴C and linolenic-U-¹⁴C acids to labeled hexanaland trans-2-hexenal, respectively, which were identified as2,4-DNPH derivatives. Further conversion of hexanal and trans-2-hexenal into hexanoicand trans-2-hexenoic acids during tea fermentation was suggestedby the increases in these compounds after the addition of hexanaland trans-2-hexenal to leaf macerates. (Received December 21, 1971; )     

Cyanide metabolism in relation to ethylene production in plant tissues

HCN is the putative product of C-1 and amino moieties of 1-aminocyclopropane-1-carboxylic acid (ACC) during its conversion to ethylene. In apple (Malus sylvestrus Mill.) slices or auxin-treated mungbean (Vigna radiata L.) hypocotyls, which produced ethylene at high rates, the steady state concentration of HCN was found to be no higher than 0.2 micromolar, which was too low to inhibit respiration (reported Ki for HCN to inhibit respiration was 10-20 micromolar). However, these tissues became cyanogenic when treated with ACC, the precursor of ethylene, and with 2-aminoxyacetic acid, which inhibits β-cyanoalanine synthase, the main enzyme to detoxify HCN; the HCN levels in these tissues went up to 1.7 and 8.1 micromolar, respectively. Although ethylene production by avocado (Persea gratissima) and apple fruits increased several hundred-fold during ripening, β-cyanoalanine synthase activity increased only one- to two-fold. These findings support the notion that HCN is a co-product of ethylene biosynthesis and that the plant tissues possess ample capacity to detoxify HCN formed during ethylene biosynthesis so that the concentration of HCN in plant tissues is kept at a low level.     

Relationship between the presence of linolenic acid and the ability to form respiration-deficient mutants in yeast

The relationship between the presence of linolenic acid and the ability to form respirationdeficient mutants induced by acriflavin has been established. The metabolic coefficients and the composition of fatty acids in samples metabolizing lactose are presented.     

Salicylic acid inhibition of ethylene production by apple discs and other plant tissues

Ethylene production by apple discs is effectively inhibited by salicylic acid. Inhibition is pH dependent, being greatest from pH 3.5–4.5 and minimal at pH 6.5 and above. With 100 M salicylic acid maximal inhibition, approximately 90%, is achieved in 3 h with an apparent K_i of 40 M. At somewhat higher concentrations salicylic acid also inhibits the conversion of 1-aminocyclo-propane-1-carboxylic acid to ethylene by pear discs and mung bean hypocotyls. Salicylic acid interferes with action of the putative ethylene-forming enzyme and in this respect is somewhat more effective than cobalt ion. The inhibitory effects of salicylic acid and cobalt ion are not additive. Implications for the limits and locus of salicylic acid inhibition are discussed.     

A comparative study of the effects of abscisic acid and new terpenoid abscisic acid analogues on plant physiological processes

The effects of new terpenoid abscisic acid analogues in comparison to abscisic acid (ABA) on some physiological and biochemical processes of various plant species have been investigated. The analogues exhibited ABA-like effects by inhibiting cell elongation and germination, and by promoting abscission, as well as the accumulation of proline and induction of stomatal closure coupled by a reduction in transpiration. In response to low temperature, the analogue-treated plants showed improved resistance to cold accompanied by a decrease in electrolyte leakage.     

A comparative study of the effects of abscisic acid and new terpenoid abscisic acid analogues on plant physiological processes

The effects of new terpenoid abscisic acid analogues in comparison to abscisic acid (ABA) on some physiological and biochemical processes of various plant species have been investigated. The analogues exhibited ABA-like effects by inhibiting cell elongation and germination, and by promoting abscission, as well as the accumulation of proline and induction of stomatal closure coupled by a reduction in transpiration. In response to low temperature, the analogue-treated plants showed improved resistance to cold accompanied by a decrease in electrolyte leakage.     

A comparative study of ethylene oxidation inVicia faba andMycobacterium paraffinicum

Vicia faba L. ‘Herz Freya’ (fababean) cotyledons andMycobacterium paraffinicum Bardane strain (MPB) cells were studied to describe and compare physiological and biochemical factors regulating ethylene oxidation. Both organisms demonstrated a linear rate of ethylene uptake as a function of concentration from 1 ppm to 1,000 ppm. CO₂ did not influence ethylene oxidation by either organism. Zero degree temperatures and CO inhibited ethylene oxidation by fababeans but not by MPB. An N₂ gas phase blocked ethylene consumption by fababeans. In contrast, MPB continued to consume ethylene at a reduced rate under anaerobic conditions. Hydrocarbon oxidation was limited to alkenes. Alkanes were not oxidized by either organism. Both organisms were sensitive to diethyldithiocarbamic acid, o-phenanthroline, carbonyl cyanidem-chlorophenyl hydrazone, and CS₂. The possibility that CS₂ acted as a suicide substrate is discussed. Evidence is presented that hydrocarbon gas oxidation by fababeans is not a part of, or reflection of, the way ethylene acts as a hormone.     

Selective enhancement of alternative path capacity in plant storage organs in response to ethylene plus oxygen: a comparative study

The respiration rise in bulky storage organs induced by ethylene plus pure O₂ is accompanied by an increase in the CN-resistant respiration, or alternative path. Whereas a lesser respiratory stimulation in response to ethylene is demonstrable in air and increased by peeling, ethylene-induced alternative path development depends on the synergistic effect of pure O₂, with or without peeling. The effect of ethylene plus O₂ is evident, whether untreated parent organs yield CN-sensitive or CN-resistant fresh slices. Alternative path capacity and maximal cytochrome oxidase-mediated electron transport have been separately estimated. Ethylene plus O₂ selectively enhances the alternative path. It is proposed that the gross rise in respiration evoked by ethylene is implemented by a system with an O₂ requirement much higher than that of cytochrome oxidase, while the ethylene-induced development of the alternative path depends on a system of still higher O₂ requirement.     

A comparative study of the ability of organic nitrogenous compounds to serve as sole sources of nitrogen for the growth of plants

Summary The ability of over 160 organic nitrogen compounds to serve as sole sources of nitrogen for the growth in sterile culture ofNeurospora crassa, Chlorella vulgaris andSpirodela oligorrhiza has been tested. With some forms of organic nitrogen all three organisms grew as well as with the more usual inorganic forms. Neurospora had the ability to use a wider range of compounds than the other organisms. Some compounds, including a few native to the organism inhibited Spirodela.     

A comparative study of recombinant and native frutalin binding to human prostate tissues

Background  

Numerous studies indicate that cancer cells present an aberrant glycosylation pattern that can be detected by lectin histochemistry. Lectins have shown the ability to recognise these modifications in several carcinomas, namely in the prostate carcinoma, one of the most lethal diseases in man. Thus, the aim of this work was to investigate if the α-D-galactose-binding plant lectin frutalin is able to detect such changes in the referred carcinoma. Frutalin was obtained from different sources namely, its natural source (plant origin) and a recombinant source (Pichia expression system). Finally, the results obtained with the two lectins were compared and their potential use as prostate tumour biomarkers was discussed.     

A comparative study of covalently-bound fatty acids in keratinized tissues.

1. Covalently-bound fatty acids were characterized in keratinous tissues obtained from a wide range of animals. 2. 18-Methyleicosanoic acid was a major component in all the mammalian fur samples examined except monotreme fur. In monotreme fur 26-carbon fatty acids predominated. 3. Fatty acids from feather keratin and reptile skin had different profiles to the alpha-keratins of mammalian fur. 4. The major forms of covalently-bound fatty acids are very similar in species that diverged up to 125 million years ago.