Lawrence Rappaport

Stimulation of rice coleoptile growth by ethylene.

SummaryThe growth rate of rice coleoptiles is increased by low concentrations of ethylene, especially in oxygen concentrations lower than air; carbon dioxide enhanced this response. C2H4 is produced by rice seedlings, and this production is also enhanced by carbon dioxide. Ethane and propane were produced in trace amounts but were inactive in growth stimulation as were also methane, propylene, and butane.

Sprouting, plant growth, and tuber production as affected by chemical treatment of white potato seed pieces

SummaryA curtailment of the rest period, resulting from treatment with gibberellic acid (GA), of newly dug White Rose, Kennebec, and Russet Burbank potatoes was indicated by a 2-to 3-week acceleration of sprouting. Five- and 90-minute dip treatments were equally effective. Concentrations of 50, 500, or 2000 μg/ml of GA produced comparable stimulation. Differences among varieties in the percentage of sprouting and in sprout elongation were observed following GA treatment. Preliminary results indicated that GA failed to overcome “chemical dormancy” of tubers from plants which had been sprayed three months earlier with 6000 μg/ml of maleic hydrazide.

Gibberellins, inhibitors, and tuber formation in the potato, Solanum tuberosum

Endogenous gibberellins were measured in extracts of ‘Red Pontiac’ potato tubers sampled during tuber ontogeny. Stolons contained high levels of activity and developing tubers low activity, as indicated by elongation in the dwarf pea and maize mutant bioassays. However, dilution of the extracts of young tubers revealed that low gibberellin-like activity may have been due to the presence of an inhibitor. Based on co-chromatography this inhibitor was found not to be abscisic acid nor did abscisic acid induce tuber formation after treatment of the intact plant, treatment of the developing stolons or after addition to potato stolons grown in tissue culture medium.ResumenGiberelinas endógenas fueron medidas en extractos de tubérculos de la papa “Red Pontiac” durante la formación de los tubérculos. Los estolones contenían altos niveles de actividad y los tubérculos en desarrollo mostraban una actividad baja como fué indicado por un bioensayo por la elongación del frijol enano y de un mutante del maiz. Sinembargo, una diluición de los extractos de tubérculos jóvenes indicó que la baja actividad puede haber sido debida a la presencia de un inhibidor. Por la co-cromatografía se encontró que este inhibidor no era el ácido abscísico ni tampoco indujo el ácido abscísico la formación de tubérculos después del tratamiento de plantas intactas, tratamiento de estolones en desarrollo o después de añadirlo a los estolones de papa mantenidos en una cultura de tejidos.

Metabolism of gibberellin A1 in germinating bean seeds

Abstract Tritium labeled gibberellin A 1 ([ 3 H]GA 1 ) was synthesized by selective hydrogenation of GA 3 and a method was developed for its isolation from two other radioactive side-products. Seeds of Phaseolus vulgaris , cv. Kentucky Wonder, were imbibed for 30 hr in an aqueous solution containing [ 3 H]GA 1 . Extraction with methanol and solvent fractionation was followed by a thorough search for radioactive metabolic products. The primary conversion product of [ 3 H]GA 1 , detected by GLC, was [ 3 H]GA 8 -glucoside along with traces of [ 3 H]GA 8 . The absence of radioactive GA 3 and GA 3 -glucoside was indicated by GLC.

The synthesis of [3H]gibberellin A3 and [3H]gibberellin A1 by the palladium-catalyzed actions of carrier-free tritium on gibberellin A3

Abstract Reaction of gibberellin A 3 (GA 3 ) with carrier-free tritium gas and 5% palladium on calcium carbonate as catalyst gave a complex mixture of products, several of which were isolated and identified. Three of the purified products are the radioactive forms of naturally occurring gibberellins: [ 3 H]GA 3 ( 1 ), [ 3 H]GA 1 ( 2 ) and [ 3 H]tetrahydro GA 3 ( 4 ). Another substance was isolated and tentatively identified as [ 3 H]16,17-dihydro GA 3 ( 3 ). GLC was used to determine the specific activities of 1 and 2 . [ 3 H]GA 3 likely arises from palladium catalysed nonspecific exchange of GA 3 alkane hydrogen atoms with tritium. [ 3 H]GA 1 is also exchange labeled but most of its radioactivity is due to tritium addition to the C-1,2 olefinic bond of GA 3 .

Uptake and metabolism of 3H-Gibberellin A1 by barley aleurone layers: Response to abscisic acid

SummaryWhen barley aleurone layers were incubated with 3H-Gibberellin A1 (3H-GA1), the hormone was converted to 3H-GA-X (not identified), 3H-GA8 and two other compounds tentatively identified as 3H-GA1-glucoside, and 3H-GA8-glucoside. Uptake and metabolism of the 3H-GA1 were markedly enhanced by simultaneous treatment with abscisic acid (ABA). Uptake of 3H-GA1 from the medium containing ABA was linear over a 24-h period, whereas in the absence of ABA, uptake of 3H-GA1 leveled off after 5 h. After 24 h, aleurones treated with 3H-GA1 and 3H-GA1 plus ABA, had taken up 9 and 24%, respectively, of the original 3H-GA1 provided. Metabolism of 3H-GA1 proceeded at a linear rate in the presence of ABA. The amount of 3H-GA1-metabolites which had accumulated by the end of a 24-h incubation appeared to be linearly correlated to the logarithm of the ABA concentration. Gibberellins A8 and-A8-glucoside did not reverse GA1-enhanced synthesis of α-amylase.

Characterization of an enzyme from Phaseolus vulgaris seeds which hydroxylates GAi to GA8

Abstract Hydroxylation of gibberellin-[ 3 H] A 1 (GA 1 -[ 3 H]) to GA 8 -[ 3 H] by the 95000 g supernatant fluid from imbibed bean seeds required Fe 2+ or Fe 3+ and O 2 but was insensitive to CO. The hydroxylating enzyme has a sedimentation coefficient of 4·5 S , and was precipitated by (NH 4 ) 2 SO 4 at 35–60% saturation. This hydroxylase was specific for GA 1 and did not hydroxylate either pseudo-GA 1 -[ 3 H] or 16-ketoGA 1 -[ 3 H]. Virtually all hydroxylase activity was localized in the cotyledons.

Stimulation of furanocoumarin accumulation in celery and celeriac tissues by Fusarium oxysporum F. SP. APII

Root and petiole tissues of celery and celeriac accessions were shown to contain linear furanocoumarins (LFCs) when infected with the root fungus Fusarium oxysporum f. sp. apii. LFC levels were low (< 5 ppm in young celery and celeriac roots seven weeks post-inoculation, but levels as high as 50 ppm were detected in severely rotted celery root and crown tissues of mature 5270R plants. Petioles of young plants contained higher amounts than the roots. Analysis of variance showed significant differences among the genotypes for LFC content in the petioles, but there was little correlation with disease resistance. In addition to the linear furanocoumarins, angelicin, an angular furanocoumarin was detected as well. Trimethylpsoralen was not detected in any of our samples. The implications of elevated furanocoumarin content for human health are discussed.

Sprouting, plant growth, and tuber production as affected by chemical treatment of white potato seed pieces. II. Effect of temperature and time of treatment with gibberellic acid

SummaryThe effect of gibberellic acid on sprouting of potato seed pieces is conditioned by the stage of rest period, concentration, temperature, and time after seed treatment. Sprouting response to gibberellin treatment decreases with time after harvest. Gibberellic acid promoted sprouting more at 77° F. than at 41° F. and consistently increased the total percentage of sprouted tubers at 77° F. In field studies, treatment of resting seed with concentrations of 5 ppm or less hastened plant emergence. In a normal growing season gibberellic acid treatment resulted in a larger subsequent crop without deleterious effects on plant growth or tuber characteristics.

Sprouting, plant growth, and tuber production as affected by chemical treatment of white potato seed pieces: IV. Responses of dormant and sprouted seed potatoes to gibberellic acid

SummaryWhole, dormant or sprouted seed potatoes were treated with various concentrations of gibberellic acid, cut, and planted at three locations. Emergence of plants from treated seed was more rapid than from untreated seed. However, vigorously sprouting seed is less affected by GA than dormant seed. Concentrations of GA as high as 5 ppm had no material effect upon total yield of tubers, but concentrations higher than 5 ppm caused marked reduction of yield and changes in tuber shape. A more uniform size of U.S. No. 1 tubers resulted in some instances with GA treatment; specific gravity was not affected by GA treatment. With the possible exception of its use in producing small potatoes for seed, GA is not recommended as a seed treatment for dormant or sprouting potatoes.