Peanuts: gibberellin antagonists and genetically controlled differences in growth habit.

Treatment of peanuts with gibberellin changed the orientation of lateral branches of runners to that of erect ones, and two growth retardants changed those of the erect type to a more horizontal orientation. Little or no difference was found in amounts of endogenous gibberellin in the two types of plants, but amount of native gibberellic acid antagonists was higher in runner plants. Furthermore, runner plants contained a particular gibberellic acid inhibitor not found in erect plants. Applications of various auxins, antiauxins, and a cytokinin had no effect on tropistic growth of the side branches.

An early response to gibberellic Acid not requiring protein synthesis.

Cell-free extracts from gibberellic acid-treated barley (Hordeum vulgare L. cv. Himalaya) aleurone layers show phosphorylcholine glyceride transferase activity greater than that from control layers. The increase in activity is not prevented by a mixture of amino acid analogs nor by cordycepin under conditions in which it is demonstrated that the analogs and the cordycepin are entering the cells in effective concentrations. We conclude therefore that the GA(3)-dependent increase in phosphorylcholine glyceride transferase activity (which occurs within the first 4 hours of GA(3) treatment) does not require RNA synthesis or protein synthesis.

Influence of Giving Salicylic Acid for Different Time Periods on Flowering and Growth in the Long-Day Plant Lemna gibba G3.

When the long-day plant Lemna gibba L., strain G3 is grown under continuous light on ammonium-free half-strength Hutner's medium (NH(4) (+)-free 0.5 H medium) growth is excellent, but flowering is severely inhibited and often is zero. Addition of 10 micromolar salicylic acid (SA) to NH(4) (+)-free 0.5 H medium quickly reverses this inhibition and leads to optimal flowering. The SA treatment also leads to a considerable reduction in the growth rate and increase in frond gibbosity. Removal of SA from the medium quickly leads to an increase in the growth rate and a large decrease in flowering. Thus, for maximal effectiveness SA must be present in the medium for the entire experiment, and the effect of SA is clearly not inductive.

Uptake and Metabolism of [C]Salicylic Acid in Lemna gibba G3.

When the long-day plant Lemna gibba L., strain G3 is grown under continuous light on ammonium-free half-strength Hutner's medium (NH(4) (+)-free 0.5 H medium) there is virtually no flowering, but addition of 10 micromolar salicylic acid (SA) to the medium results in substantial flowering. Using this system, the uptake and metabolism of [(14)C]SA in L. gibba G3 has been examined. SA uptake is rapid and linear for at least the first 24 hours. After 30 minutes, nearly 90% of the radioactivity in the plants is present as free SA. Part of this is rapidly converted to one or more bound forms of SA that appear either in the acidic butanol fraction or in the aqueous residue, and after 12 hours an equilibrium is reached between the free and bound forms of SA. When plants receive SA for 6 days and then are switched to control medium, both the free and bound SA remain nearly constant for at least 5 days. However, there is virtually no transfer of SA from mother fronds to daughter fronds, indicating that the SA is apparently sequestered within the cell. Cell fractionation studies show that nearly 95% of the SA remains in the supernatant even after a 2-hour centrifugation at 300,000 g. Thus, it is unlikely that SA is confined within a specific organelle, but rather is probably secreted into the vacuole.

A florigenic effect of sucrose in Fuchsia hybrida is blocked by gibberellin-induced assimilate competition.

The use of gas chromatography-mass spectrometry-selected ion monitoring along with a (13)C internal standard has allowed sensitive measurements of the sucrose (Suc) content of individual shoot apices of Fuchsia hybrida. With intact plants, as the photosynthetic irradiance increased, so did shoot apex Suc content, reaching saturation at about 500 micromol m(-2) s(-1). These same plants flowered at the higher irradiances, remaining vegetative in 10-h short days at an irradiance of 230 micromol m(-2) s(-1). The strong correlation (r = 0.93) in these studies between flowering and shoot apex Suc content indicates a role for Suc as a stimulus to flowering in this species. However, Suc is not the long-day (LD) "florigen" of F. hybrida because 2 to 4 LD given as a 14-h low-irradiance photoperiod extension (10-15 micromol m(-2) s(-1)) induced flowering but without increase in shoot apex Suc content. Flowering induced by either pathway, the LD- or the Suc-mediated one, was inhibited by applying gibberellin (GA) to the shoot tip. Such inhibition of flowering by GA, at least for the LD pathway, was associated with a reduced apex Suc content, enhanced elongation of subapical stem tissue, and a reduced import into the shoot apex of leaf-sourced assimilate. Thus, our findings show how GA inhibits flowering of F. hybrida and confirm the importance of nutrient diversion in regulating flowering.

Effect of water vapor pressure on the thermal decomposition of 2-chloroethylphosphonic Acid.

Decomposition of 2-chloroethylphosphonic acid (Ethephon) was studied in dried films at various water vapor pressures (0.6 to 86.9 millimeters Hg, 3.2 to 93.9% relative humidity) and temperatures (20, 30, 40, and 50 C) at pH 6.3 and 7.0. The rate of decomposition could be determined equally well by [(14)C]Ethephon or ethylene measurements. The rate increases at increasing water vapor pressures at a constant temperature and pH, up to an optimum. The optimum vapor pressure for decomposition approximately doubles for each 10 C increase. The activation energy for the decomposition reaction in water vapor pressures of 3.2 to 12 millimeters Hg is 8.7 and 14.3 kilocalories per mole at pH 6.3 and 7.0, respectively.Decomposition of Ethephon is inhibited above an optimum vapor pressure. The inhibition is stronger at lower temperatures and at pH 6.3 than at pH 7.0. The rate of decomposition and the inhibition observed at a low temperature (20 C) was found to be similar on various surfaces, including olive leaves.Failure to induce olive (Olea europaea L.) fruit abscission under certain environmental conditions can be readily attributed to rapid breakdown of Ethephon at elevated temperatures and low relative humidities.