Cauliflower Florets Research Articles

Stimulation by Erwinia carotovora of the synthesis of ethylene in cauliflower tissue.

The synthesis of ethylene by cauliflower floret tissue was increased when the tissue was inoculated with the soft-rot bacterium Erwinia carotovora. This effect was clearly associated with the production of pectic enzymes by the micro-organism. These enzymes, acting together with the plant enzymes, stimulated the production of ethylene from methionine. The increased synthetic activity was due to the release and increased activity of a glucose oxidase enzyme apparently attached to plant cell-wall material and liberated by the action of pectic enzymes of the bacterium.

A comparative study of the ability of methionine or linolenic acid to act as precursors of ethylene in plant tissues.

A comparative study has been made of the ability of three plant tissues to incorporate (14)C into ethylene from (14)C-labelled methionine and derivatives and from (14)C-labelled linolenic acid. Incorporation of label occurs readily from methionine and its derivative 4-methylmercapto-2-oxobutyric acid with apple, tomato or cauliflower floret tissue. No incorporation of label occurred, however, from uniformly (14)C-labelled linolenate.

Biosynthesis of ethylene. 4-methylmercapto-2-oxobutyric acid: an intermediate in the formation from methionine.

The enzyme responsible for the conversion of methionine into a precursor of ethylene in cauliflower florets is a transaminase. The formation of 4-methyl-mercapto-2-oxobutyric acid by this enzyme has been shown. The oxo acid stimulates the synthesis of ethylene when added to floret tissue, and tracer experiments have shown that (14)C is incorporated into ethylene from the labelled oxo acid. The evidence is consistent with the view that the oxo acid is an intermediate in the formation of ethylene from methionine.

Kinetically Distinguishable Populations of Phytochrome

Two or more kinetically distinguishable populations of phytochrome molecules were observed in living tissues of oat, pea, maize, and cauliflower, as well as in extracts of oat. At least 3 different populations occurred in cauliflower florets, while 2 were observed in each of the other species. In extracted oat phytochrome, the relative proportions of the 2 forms remained constant during successive stages of purification. The physiological significance of this multiplicity of forms remains unclear.

Biosynthesis of ethylene. Dual nature of cofactor required for the enzymic production of ethylene from methional.

The heat-stable cofactor in cauliflower florets, which has been shown to be necessary for the enzymic production of ethylene from methional, consists of two components. The first is of a phenolic nature and appears to be an ester of p-coumaric acid. The second component is acidic in character, but has not as yet been identified.

Biosynthesis of ethylene. Enzymes involved in its formation from methional.

1. Two enzymes were shown to be necessary for the production of ethylene from methional; they were separated from extracts of cauliflower florets by fractionation on Sephadex and other methods. 2. The first enzyme, generating hydrogen peroxide, appears to be similar to the fungal glucose oxidase, for like the latter it is highly specific for its substrate d-glucose. 3. The second enzyme, in the presence of cofactors and peroxide generated by the first enzyme, cleaves methional to ethylene. 4. It was also found that hydrogen peroxide in these reactions may be replaced by hydroperoxide generated from linolenic acid by lipoxidase enzymes. 5. Dihydroxyphenols were shown to have a marked inhibitory effect on these reactions and to account for the initial phase of low activity that is always observed in aqueous extracts prepared from the floret tissue.

Intracellular Distribution of p-Nitrophenyl-Phosphatase in Plants

Less than 10% of the acid p-nitrophenylphosphatase activity of plant extracts was sedimentable under a variety of conditions including zonal centrifugation. The sedimentable fraction did not show the latency properties characteristic of animal lysosomes. We conclude that, at least operationally, plant acid phosphatase is a soluble enzyme and that it is not suitable as a lysosomal marker. The plant tissues employed were pea cotyledons, cauliflower florets, turnip storage organs, onion embryos, and leaves of red oak and soybean.

Biosynthesis of ethylene. Formation of ethylene from methional by a cell-free enzyme system from cauliflower florets.

1. The formation of ethylene from cauliflower florets is stimulated by the addition of either methionine or its hydroxy analogue. 2. Formation of ethylene from these compounds may also be demonstrated in cell-free extracts, but the most rapid formation is achieved by the addition of methional. 3. Fractionation of such extracts has shown that both particulate and non-particulate fractions are necessary for the formation of ethylene from methionine or its hydroxy analogues, but only the non-particulate fraction is necessary for its formation from methional. 4. A study of this system has shown that the conversion of methional into ethylene requires the presence of two enzyme systems, the first generating peroxide and the second catalysing the conversion of methional into ethylene in the presence of peroxide. 5. The presence of a heat-stable factor in cauliflower extracts that is necessary for the full activity of the enzyme converting methional into ethylene has also been shown. 6. The nature of this factor is at the present unknown; it is not a metal nor is it identifiable with many of the known coenzymes.

Conversion of L-galactono-gamma-lactone into L-ascorbic acid by plants.

IT has been inferred from feeding-experiments that cress seedlings1, and also pea and mung bean mitochondria2, are capable of converting L-galactono-γ-lactone into L-ascorbic acid. Similar results were obtained with mitochondria from cabbage leaves and cauliflower florets, and a relatively specific L-galactono-γ-lactone dehydrogenase was isolated from the latter3. The results (Table 1) confirm that this system may not be uncommon in the higher plants ; Sphagnum, Spirogyra and Psalliota‡ gave inconclusive results. The figures in Table 1 are either the mean of duplicate estimations, or are taken from single, extended experiments which show how the concentration of ascorbic acid in the tissue varies during the period of feeding. Fig. 1 shows the results of one such extended experiment with parsley, in which the concentration of ascorbic acid in the laminae fed with the lactone rose, during a period of 190 hr., from 1,582 to 12,010 mgm./100 gm. dry-weight, that is, to approximately 12 per cent of the dry weight. During the same period, the value for the controls in de-ionized water fell gradually to 1,120 mgm./100 gm. dry weight, and at this time the experimental laminae possessed more than ten times the concentration of ascorbic acid in the controls.

Reflectance Color Measurements and Judges' Scores for Frozen Cauliflower and Spinach

SUMMARYColor data on stored spinach and cauliflower were correlated with judges’scores to determine best sampling procedures for measurements with the Hunter Color and Color‐Difference Meter. Spinach stems, rather than leaves or mixtures, changed the most and most uniformly, correlated best with scores, and produced the smallest experimental errors. Cauliflower floret surface, instead of stems or mixture, gave smallest significant differences by judges. Good results on the instrument were obtained for both floret surface and a rapidly prepared slurry from a thin surface layer. Best of six color indices of deterioration were Hunter “a” and hue angle