Effects of N(6)-benzyladenine on the rate of turnover of [(3)H]GA 20 by shoots of dwarf Pisum sativum.

Application of the cytokinin, N(6)-benzyladenine, to light-grown shoots of dwarf "Meteor" pea seedlings (Pisum sativum L.) markedly increased the rate of turnover of GA20, a native pea gibberellin. It is suggested that endogenous cytokinins may affect gibberellin metabolism in plants by controlling rates of gibberellin turnover.

Effects of benzyladenine on the growth of waterlogged tomato plants.

Treatment of waterlogged tomato plants with benzyladenine relieved most of the symptoms of flooding injury. The effects of benzyladenine included maintenance of chlorophyll levels, reduced epinastic curvature of petioles, absence of adventitious roots, and stem growth greater than that of waterlogged control plants.

Effects of abscisic acid on the levels of endogenous gibberellin-like substances in Solanum andigena.

Treatment of young, fully expanded leaves of Solanum andigena with synthetic abscisic acid resulted in marked increases in gibberellin-like substances. Abscisic acid treatment caused increases in the gibberellin content of leaves excised from both short day and long day grown plants.

Gibberellins and geotropism in Zea mays coleoptiles.

Diffusible gibberellins were obtainable in agar from excised 4 mm tips of etiolated coleoptiles of Zea mays. Placing the tips in a horizontal position increased the total yield of gibberellins by approximately five times. With horizontal tips, the ratio of gibberellin activity recovered from lower and upper halves, expressed as a percentage of total yield, was 80.76:19.24 (lower:upper).

The Catabolism of (+/-)-Abscisic Acid by Excised Leaves of Hordeum vulgare L. cv Dyan and Its Modification by Chemical and Environmental Factors.

Excised light-grown leaves and etiolated leaves of Hordeum vulgare L. cv Dyan catabolized applied (+/-)-[2-(14)C]abscisic acid ([+/-]-[2-(14)C]ABA) to phaseic acid (PA), dihydrophaseic acid (DPA), and 2'-hydroxymethyl ABA (2'-HMABA). Identification of these catabolites was made by microchemical methods and by combined capillary gas chromatographymass spectrometry (GC-MS) following high dose feeds of nonlabeled substrate to leaves. Circular dichroism analysis revealed that 2'-HMABA was derived from the (-) enantiomer of ABA. By selecting tissue samples in which endogenous catabolites were undetectable by gas chromatography, it was possible to identify unequivocally ABA catabolites by GC-MS without the need to employ deuteriated substrate to distinguish the (+/-)-ABA catabolites from the same endogenous compounds. Refeeding studies were used to confirm the catabolic route. The methyl ester of (+/-)-[2(14)C]-ABA was hydrolyzed efficiently by light-grown leaves of H. vulgare. Leaf age played a significant role in (+/-)-ABA catabolism, with younger leaves being less able than their older counterparts to catabolize this compound. The catabolism of (+/-)-ABA was inhibited markedly in water-stressed Hordeum leaves which was characterized by a decreased incorporation of label into 2'-HMABA, DPA, and conjugates. The specific, mixed function oxidase inhibitor, ancymidol, did not inhibit, dramatically, (+/-)-ABA catabolism in light-grown leaves of Hordeum whereas the 80s ribosome, translational inhibitor, cycloheximide, inhibited this process markedly. The 70s ribosome translational inhibitors, lincomycin and chloramphenicol, were less effective than cycloheximide in inhibiting (+/-)-ABA catabolism, implying that cytoplasmic protein synthesis is necessary for the catabolism of (+/-)-ABA in Hordeum leaves whereas chloroplast protein synthesis plays only a minor role. This further suggests that the enzymes involved in (+/-)-ABA catabolism in this plant are cytoplasmically synthesized and are ;turned-over' rapidly, although the enzyme responsible for glycosylating (+/-)-ABA itself appeared to be stable.

Complete Release of Axillary Buds from Apical Dominance in Intact, Light-Grown Seedlings of Pisum sativum L. following a Single Application of Cytokinin.

Single applications of either 6-benzyladenine or zeatin to inhibited axillary buds of intact, light-grown seedlings of Pisum sativum L. cv Black-eyed Susan, resulted in the formation of rapidly elongating, leafy shoots. Similar treatment with kinetin or isopentenyladenine caused only limited but outgrowth which stopped 6 days after application.

Metabolism of Tritiated Gibberellin A(9) by Shoots of Dark-grown Dwarf Pea, cv. Meteor.

Tritium-labeled gibberellin A(9) ((3)H-GA(9)) was metabolized by etiolated shoots of dwarf pea (Pisum sativum cv. Meteor) to GA(20), GA(10), 2,3-dihydro-GA(31), and a number of highly polar, acidic GA-like substances. Identifications were made by gasliquid radiochromatography and combined gas chromatography-mass spectrometry. Kinetic studies showed that GA(30) and 2,3-dihydro-GA(31) were produced within 5 hours following (3)H-GA(9) application to pea shoots. The polar GA-like substances were produced between 5 and 10 hours after (3)H-GA(9) application. Levels of GA(10) increased with time, and since no GA(10) was produced during the purification procedures, GA(10) was, in all probability, produced from (3)H-GA(9) within the plant tissue. The radioactive interconversion products produced by pea from (3)H-GA(9) have chromatographic properties similar to biologically active GA-like substances present in etiolated shoots of dwarf pea. Large scale applications of (3)H-GA(9) with very low specific activity to etiolated pea shoots showed that the radioactivity of the interconversion products was correlated exactly with biological activity as assayed by dwarf rice (Oryza sativa cv. Tan-ginbozu).

Effects of Light, Abscisic Acid, and N-Benzyladenine on the Metabolism of [H]Gibberellin A(4) in Seeds and Seedlings of Lettuce, cv. Grand Rapids.

Gibberellin A(4) (GA(4)) can substitute for light in the germination of Grand Rapids lettuce seeds. Seeds imbibed in [(3)H]GA(4) do not convert this to other GAs prior to, or immediately following, visible germination: thus GA(4) alone can promote radicle expansion. Abscisic acid inhibited [(3)H]GA(4)-induced germination, but did not significantly affect [(3)H]GA(4) uptake or metabolism during germination. (6)N-benzyladenine overcame the inhibitory effect of abscisic acid and increased [(3)H]GA(4) uptake, although radicle emergence was delayed somewhat.During hypocotyl extension there was a large conversion of [(3)H]GA(4) to [(3)H]GA(1) in light or darkness, the major conversion site being the growing root. Hypocotyls of dark-grown seedlings contained more [(3)H]GA(1) than those of light-grown seedlings. The apparent inability of exogenous GA(1) to promote greater hypocotyl extension than GA(4) is related to its poorer uptake. Abacisic acid markedly inhibited hypocotyl expansion, root growth, and the conversion of [(3)H]GA(4) to [(3)H]GA(1).

Activity of the aldehyde and alcohol of gibberellins A12 and A 14, two derivatives of gibberellin A 15 and four decomposition products of gibberellin A 3 in 13 plant bioassays.

The biological activities of the aldehyde and alcohol of gibberellins (GAs) A12 and A14, 3α-OH-GA15, 3ß-OH-GA15 wrong lactone (i.e. GA37 wrong lactone) and the four major decomposition products of GA3 (isogibberellic, allogibberic, epiallogibberic and Δ9(11)-dehydroallogibberic acids) were tested over a wide range of concentrations on 13 plant bioassays in order to ascertain certain of the structural requirements for biological activity. Generally modification of the basic GA-molecule decreased its activity in all assays except for derivatives of GA12 and GA14 (suggesting conversion of these derivatives to more polar, active GAs). Modification of the 3-OH from the usual 3ß to 3α configuration markedly reduced activity. Neither the presence of an inverted lactone ring (i.e. 3ß-OH-GA15 wrong lactone) nor changes to the lactone ring of GA3 (4→10) to form iso-GA3 (4→2) appreciably reduce activity. Further decomposition of GA3 to allogibberic and Δ9(11)-dehydroallogibberic acid reduced activity only slightly, but epimerization of allogibberic acid at C-9 essentially eliminated biological activity.

Characterization of abscisic acid in chloroplasts of Pisum sativum L. cv. Alaska by combined gas-chromatography-mass spectrometry.

Abscisic acid was characterized from extracts of isolated pea chloroplasts by combined gas-chromatography-mass spectrometry. By single ion monitoring of the base peak (m/e 190) in the mass spectrum, 8.6 µg ABA were detected in chloroplasts isolated from 1 kg fresh weight of pea shoots.

Red-light-enhanced conversion of tritiated gibberellin A9 into other gibberellin-like substances in homogenates of etiolated barley leaves.

Irradiation of homogenates of etiolated barley leaves with red light resulted in an increase in the levels of gibberellin (GA)-like substances as compared to dark controls. When homogenates were fed with [(3)H]-GA9 there was as incorporation of the radioactivity into a number of other GA's: this process occurred to a greater extent in red light than in darkness, and could be inhibited by boiling the extract prior to addition of the [(3)H]-GA9.