Pattern of the Cyanide-Potential in Developing Fruits : Implications for Plants Accumulating Cyanogenic Monoglucosides (Phaseolus lunatus) or Cyanogenic Diglucosides in Their Seeds (Linum usitatissimum, Prunus amygdalus).

The absolute cyanide content of developing fruits was determined in Costa Rican wild lima beans (Phaseolus lunatus), oil flax (Linum usitatissimum), and bitter almonds (Prunus amygdalus). The cyanide potential (HCN-p) of the lima bean and the almond fruit began to increase shortly after anthesis and then stopped before fruit maturity. In contrast, the flax inflorescence had a higher HCN-p in absolute terms than the mature flax fruit. At all times of its development the bean fruit contained the monoglucosides linamarin and lotaustralin. The almond and the flax fruits contained, at anthesis, the monoglucosides prunasin, and linamarin and lotaustralin, respectively, while, at maturity, only the corresponding diglucosides amygdalin, and linustatin and neolinustatin, respectively, were present.

Demonstration of phenolic compounds in plant tissues by an osmium-iodide postfixation procedure.

A simple procedure to stain phenols in plant tissues is described. Postfixation with an aqueous solution prepared by mixing 2 cc of 2% osmium tetroxide and 8 cc of 3% potassium iodide yields brilliant visualization of phenol-containing vacuoles in different tissues of plants (e.g., coffee, oak, tobacco and spruce) bearing high concentration of phenolic compounds. Areas bearing phenols become dark gray to black. Chemical experiments demonstrate that osmium-potassium iodide (Os-KI) mixture reacts rapidly with several naturally occurring plant phenols, developing black solutions from which black solids precipitate. Phenols containing omicron-dihydroxy groups react with Os-KI solution more rapidly than other structurally different phenols. Therefore, omicron-dihydroxy units in an aromatic ring seem to function as primary sites of reactivity with the osmium-iodide complexes.

Proteolytic Activities in Alfalfa (Medicago sativa L.) Leaves.

Autodigestion in alfalfa (Medicago sativa L. cv Messe) leaves takes place at a higher rate in the acidic range of pH suggesting that acid proteases are probably involved in protein breakdown. Several lines of evidence show that alfalfa leaves contain various proteolytic activities. A carboxypeptidase active on CBZ-Phe-Met and on other CBZ-dipeptides with a pH optimum of 5.5 has been partially purified by CM-cellulose chromatography. Another acid protease, probably endopeptidase, is active on hemoglobin with an optimum at pH 4.5; perhaps it is not a single protease since it shows another peak of activity at pH 7-7.5. In the neutral-alkaline range of pH there are at least three peptidases active on naphthylamides. One of these, active on Lys-NA, is most active in very young leaves and probably is aSH dependent protease.

Gibberellin-like activity in suspensors of Tropaeolum majus L. and Cytisus laburnum L.

Gibberellins in the embryo-suspensor system have been considered so far only in Phaseolus coccineus. We present in this report the localization of gibberellin-like substances in the suspensors of Tropaeolum majus L. and Cytisus laburnum L. The total gibberellin activity (expressed as gibberellic-acid equivalent in the α-amylase bioassay) in 2000 suspensors (106 mg fresh weight; FW) of C. laburnum and in 600 suspensors (236 mg FW) of T. majus were 50.9 µg g(-1) FW and 8.9 µg g(-1) FW respectively.