Responsivencess of Intact and Scarified Seeds of Barbarea vulgaris to Gibberellic Acid and Changes in Phytochrome

Either red light or millimolar levels of gibberellic acid promoted germination of seeds of yellow rocket (Barbarea vulgaris R. Br.), and their effects were generally additive. Buffering the substrate pH at 3.0, addition of 20 mM nitrate to the substrate, preliminary incubation at 10 or 30°C, and brief scarification of the seeds increased responsiveness of the seeds to gibberellic acid. Scarification increased several thousandfold the sensitivity of the seeds to gibberellic acid. Pretreatment of the seeds in darkness or far-red light did not lower their responsiveness to gibberellic acid. These results suggest that uptake of gibberellic acid is a limiting factor in the stimulation of germination in intact seeds and that there is only a minimal requirement for active phytochrome to express gibberellic acid action.     

Abscisic Acid and Gibberellic Acid Contents in Ripening Barley Seeds

The ABA and GA3 contents were investigated in barley seeds during maturation and after harvest. The highest amount of ABA was found in milk and wax ripeness – 13 ng and 11 ng per seed respectively. The level decreased during the later stages of maturation and during release of dormancy and was 1 ng per seed 6 weeks after harvest. The content of gibberellic acid decreased in a similar way but in an earlier stage of maturation. The determined amounts of GA₃ were: 0.4, 0.1, 0.03 and about 0.05 ng per seed respectively, in milk, wax and full ripeness and after harvest. The results of quantitative determination, obtained with the GLC method, corresponded to the growth effects in the test of the first leaf of oat.     

Embryo Development in Ripe Seeds of Eranthis hiemalis and its Relation to Gibberellic Acid

The ripe seeds of Eranthis hiemalis (L.) Salisb., the winter aconite, contain undeveloped embryos. At 20–25°C the embryos grow only little, and the seeds do not germinate. Rapid embryo development starts if the seeds, after 3 weeks of “after-ripening” at 20–25°C, are placed at low temperature, 3–4°C; germination then takes place after 2–3 months, Embryo development without germination occurs when the seeds are placed in gibberellic acid solutions at 20–25°C. Embryo development is inhibited at low temperature by the specific inhibitor of gibberellin biosynthesis, 2-chlorethyl cholin chloride, but is restored by the simultaneous addition of gibberellic acid. It is suggested that one early effect of the cold is to bring about a synthesis of gibberellin.     

The Effect of Abscisic Acid on the Uptake and Distribution of Ions in Intact Seedlings of Phaseolus vulgaris cv. Redland Pioneer

Abscisic acid (ABA) was found to increase the accumulation of ³⁶Cl, total Cl, ²²Na and total Na⁺ in roots of intact bean seedlings. After an initial promotion. ABA inhibited longdistance transport of these ions from the root to the shoot. However, it consistently inhibited both uptake and transport of ⁴²K and total K⁺ in intact bean seedlings. A promotion of net ³⁶Cl influx (ψ_oc) and its accumulation in the root (Q*_v) concomitant decrease in transport index (long-distance transport as percentage of total influx) showed that ABA stimulates -³⁶Cl transport at the tonoplast. It inhibited H⁴ extrusion and net ⁸⁶Rb influx which agrees with a cation exchange theory K⁺/Rb⁺ transport.     

Abscisic Acid Accumulation in Developing Seeds of Phaseolus vulgaris L

Free and bound abscisic acid (ABA) in the pod, seed coat, and embryo were determined separately throughout seed development of Phaseolus vulgaris L. cv. `Taylor's Horticultural.' An internal standard method of gas-liquid chromatography was used for ABA quantification. In the embryo, two peaks of free ABA occurred at days 22 (1.18 micrograms per gram or 5.5 micromolar) and 28 (1.74 micrograms per gram or 12 micromolar); and a single peak of bound ABA at day 30. In the seed coat, there was one peak of free ABA at day 22 and only small amounts of bound ABA. Very small amounts of ABA were detected in the pod at any stage of development. In cv. PI 226895, in which seed development is more rapid than in `Taylor's Horticultural,' the embryo ABA peaks occur on days 20 and 26. The timing of the ABA peak in the embryo, and the concentration attained, are consistent with previous reports on the natural pattern of RNA synthesis and with ABA inhibition of RNA synthesis in developing bean fruit.     

Genetic diversity and similarity in the Barbarea vulgaris complex (Brassicaceae)

Two subspecies of Barbarea vulgaris are taxonomically recognized as ssp. vulgaris and ssp. arcuata. In addition, two types of Barbarea vulgaris ssp. arcuata occurs in Denmark. The G‐type is resistant to an herbivorous flea beetle (Phyllotreta nemorum) whereas the P‐type is susceptible. A previous study suggested that the P‐type evolved by a loss of resistance from a resistant progenitor. We analyzed the genetic relatedness among eight Barbarea taxa: B. vulgaris spp. vulgaris, B. vulgaris ssp. arcuata G‐ and P‐types, hybrids between the types, B. verna, B. intermedia, B. stricta, B. orthoceras and B. australis, using AFLP and SSR markers. A clear distinction between the G‐ and P‐types was revealed. Both were distinct from B. vulgaris ssp. vulgaris, the G‐type less so than the P‐type. Barbarea verna and B. intermedia formed unambiguous clusters, whereas the remaining taxa produced less discrete groupings. Possible evolutionary scenarios for flea‐beetle resistance and susceptibility are discussed, including lineage sorting from a polymorphic ancestral population, and de novo loss of resistance in the P‐type of B. vulgaris ssp. arcuata.     

Coupling of Mitochondrial Fatty Acid Uptake to Oxidative Flux in the Intact Heart

The coordination of long chain fatty acid (LCFA) transport across the mitochondrial membrane (V_PAL) with subsequent oxidation rate through β-oxidation and the tricarboxylic acid (TCA) cycle (V_tca) has been difficult to characterize in the intact heart. Kinetic analysis of dynamic ¹³C-NMR distinguished these flux rates in isolated rabbit hearts. Hearts were perfused in a 9.4 T magnet with either 0.5 mM [2,4,6,8,10,12,14,16-¹³C₈] palmitate (n = 4), or 0.5 mM ¹³C-labeled palmitate plus 0.08 mM unlabeled butyrate (n = 4). Butyrate is a short chain fatty acid (SCFA) that bypasses the LCFA transporters of mitochondria. In hearts oxidizing palmitate alone, the ratio of V_TCA to V_PAL was 8:1. This is consistent with one molecule of palmitate yielding eight molecules of acetyl-CoA for the subsequent oxidation through the TCA cycle. Addition of butyrate elevated this ratio; V_TCA/V_PAL = 12:1 due to an SCFA-induced increase in V_TCA of 43% (p < 0.05). However, SCFA oxidation did not significantly reduce palmitate transport into the mitochondria: V_PAL = 1.0 ± 0.2 μmol/min/g dw with palmitate alone versus 0.9 ± 0.1 with palmitate plus butyrate. Thus, the products of β-oxidation are preferentially channeled to the TCA cycle, away from mitochondrial efflux via carnitine acetyltransferase.     

A heritable glucosinolate polymorphism within natural populations of Barbarea vulgaris

In natural populations of Barbarea vulgaris we found two distinctly different glucosinolate profiles. The most common glucosinolate profile is dominated (94%) by the hydroxylated form, (S)-2-hydroxy-2-phenylethyl-glucosinolate (glucobarbarin, BAR-type), whereas in the other type 2-phenylethyl-glucosinolate (gluconasturtiin, NAS-type) was most prominent (82%). NAS-type plants have a 108-fold increase of gluconasturtiin concentration in rosette leaves compared to BAR-type plants. The glucosinolate composition of both chemotypes is consistent throughout all plant organs and after induction with jasmonic acid. Although the glucosinolate profile of the roots has a more diverse composition than other plant organs, it still matches the chemotype. In 12 natural populations that we sampled in Germany, Belgium, France and Switzerland solely BAR-type plants were found. However, eight out of the 15 Dutch populations that were sampled contained 2-22% NAS-type plants. Controlled crosses showed that the chemotype was heritable and determined by a single gene with two alleles. The allele coding for the BAR-type was dominant and the allele for the NAS-type was recessive. The different glucosinolate profiles will yield different hydrolysis products upon damage, and therefore we expect them to differentially affect the multitrophic interactions associated with B. vulgaris in their natural environment.     

The Effects of Gibberellic Acid on Organelle Biogenesis in the Endosperm of Germinating Castor Bean Seeds

Mature seeds of castor bean (Ricinus communis L.) were imbibedin tap water or 0.3 mM GA₃, planted in vermiculite moistenedwith tap water or 0.3 mM GA₃, and incubated at 32 ?C. Duringthe course of germination, GA₃ promoted marked increases inthe activities of the glyoxysomal marker enzyme isocitrate lyaseand certain mitochondrial marker enzymes, but did not affectthe ER marker enzyme choline phosphotransferase. Glyoxysomaland ER protein and phospholipid were not increased in amountby GA₃, whereas mitochondrial protein and phospholipid were.SDS-polyacrylamide gels of the glyoxysomal matrix polypeptidesfrom GA₃-treated beans exhibited two polypeptides additionalto those found to be common to both GA₃-treated and controltissue. Incorporation of CDP-(methyl ¹⁴C)-choline into intactendosperm tissue and the distribution amongst the glyoxysomes,mitochondria, and ER of newly synthesized phosphatidyl-(methyl¹⁴C)-choline was unchanged by GA₃.     

Early Actions of Gibberellic Acid on the Embryo and on the Endosperm of Avena fatua Seeds

Gibberellic acid at 0.1 μm stimulates amylase synthesis in dormant Avena fatua seeds without inducing germination; at 0.5 mm it enhances biosynthesis of proteins and RNA in both the embryo and the endosperm and utilization of the endosperm sugars by the embryo. These events occur in early hours (0-14th hour) and prior to germination, which begins 24 hours after gibberellic acid application. These observations are in agreemeent with the concept that in cereal grains gibberellic acid has two morphological sites of actions: the embryo and the endosperm, and that germination (radicle protrusion) is not caused by gibberellic acid-induced amylase synthesis in the endosperm.     

Stimulation of Endomitotic DNA Synthesis and Cell Elongation by Gibberellic Acid in Epicotyls Grown from Gamma-irradiated Pea Seeds

Large doses of γ-irradiation, given to air-dried pea seeds, inhibit the endomitotic DNA synthesis in pea epicotyls during germination in darkness. The cortex cells of the etiolated epicotyls reach only the 4 C DNA level, whereas cortex cells of unirradiated seeds reach the 8 C DNA level. Epicotyl elongation and cell elongation are also reduced.     

Effects of Exogenous Gibberellic Acid3 on Iron and Manganese Plaque Amounts and Iron and Manganese Uptake in Rice

Gibberellins (GA) regulate various components of plant development. Iron and Mn plaque result from oxiding and hydroxiding Fe and Mn, respectively, on the roots of aquatic plant species such as rice (Oryza sativa L.). In this study, we found that exogenous gibberellic acid₃ (GA₃) spray decreased Fe plaque, but increased Mn plaque, with applications of Kimura B nutrient solution. Similar effects from GA₃, leading to reduced Fe plaque and increased Mn plaque, were also found by scanning electron microscopy and energy dispersive X-ray spectrometric microanalysis. Reduced Fe plaque was observed after applying GA₃ to the groups containing added Fe²⁺ (17 and 42 mg•L^-1) and an increasing trend was detected in Mn plaques of the Mn²⁺ (34 and 84 mg•L^-1) added treatments. In contrast, an inhibitor of GA₃, uniconazole, reversed the effects of GA₃. The uptake of Fe or Mn in rice plants was enhanced after GA₃ application and Fe or Mn plaque production. Strong synergetic effects of GA₃ application on Fe plaque production were detected. However, no synergetic effects on Mn plaque production were detected.     

Effect of Gibberellic Acid on Dark and Light Germination at Different Temperatures of Calluna, Ledum andRhododendron Seeds

The aim of the experiments was to study the effects of gibberellic acid (GAs) on the germination of Calluna vulgaris L., Ledum palustre L. and Rhododendron lapponicum (L.) Wahlenb. seeds under different environmental conditions. Under continuous light from white fluorescense tubes (3000 lux), untreated seeds of Calluna were partly dormant at all temperatures studied (9, 15, 21, 27, 27/9, 8/16 hours). Percentage of dormant seeds increased, however, with decreasing temperature, and it varied also from seed lot to seed lot. Untreated seeds of Ledum were dormant in light at 9° and 15°C but not at higher temperatures. Untreated seeds of Rhododendron were completely dormant in light at temperatures from 13° to 24°C. Seeds of all species were completely dormant in darkness both at 15° and 27°C. GA₃ stimulated greatly the germination of all species under all studied environmental conditions. The used concentrations (0.2–3.2 mM) gave nearly 100% germination in most cases. At 9°C the dormancy in some seed lots of Calluna and Ledum was only partly broken by the used concentrations of GA₃.     

Genetic and sexual separation between insect resistant and susceptible Barbarea vulgaris plants in Denmark

Co‐evolution between herbivores and plants is believed to be one of the processes creating Earth’s biodiversity. However, it is difficult to disentangle to what extent diversification is really driven by herbivores or by other historical‐geographical processes like allopatric isolation. In the cruciferous plant Barbarea vulgaris, some Danish individuals are resistant to herbivory by flea beetles (Phyllotreta nemorum), whereas others are not. The flea beetles are, in parallel, either resistant or susceptible to the plants defenses. To understand the historical‐evolutionary framework of these interactions, we tested how genetically divergent resistant and susceptible plants are, using microsatellite markers. To test whether they are reproductively fully compatible, resistant and susceptible plants were grown intermixed in an outdoor experiment, and the paternity of open‐pollinated offspring was determined by analysis of molecular markers. Resistant and susceptible Danish plants were genetically strongly differentiated and produced significantly fewer hybrids than expected from random mating or nearest neighbour mating. Our results suggest that the two types belong to different evolutionary lineages that have been (partly) isolated at some time, during which genetic and reproductive divergence evolved. A parsimonious scenario could be that the two plant types were isolated in different refugia during the previous ice age, from which they migrated into and met in Denmark and possibly neighbouring regions. If so, resistance and susceptibility has for unknown reasons become associated with the different evolutionary lineages.     

Gibberellic Acid and Starch Breakdown in Pea Cotyledons

The stimulation of starch breakdown in the cotyledons of dwarfpea cultivars (Progress No. 9 and Dark Skin Perfection) whentreated with gibberellic acid (GA³) is mediated through theremoval of metabolites by the axis. When applied to excisedcotyledons, GA³ had only a minor effect on starch breakdown,as it did in the cotyledons of a tall pea (cv. Alaska) irrespectiveof whether they were attached to the plant or excised. Enzyme activity appears to be controlled by the level of solublesugars in the cotyledons, and GA³delays the increase in amylolyticactivity in the cotyledons through a direct effect on cotyledonmetabolism.     

Uptake of l-Ascorbate by Intact Spinach Chloroplasts

Uptake of l-[1-¹⁴C]ascorbate by intact ascorbate-free spinach (Spinacia oleracea L. cv Vital^r) chloroplasts has been investigated using the technique of silicone oil filtering. Rates greater than 100 micromoles per milligram chlorophyll per hour (external concentration, 10 millimolar) of ascorbate transport were observed. Ascorbate uptake into the sorbitol-impermeable space (stroma) followed the Michaelis-Menten-type characteristic for substrate saturation. A K_m of 18 to 40 millimolar was determined. Transport of ascorbate across the chloroplast envelope resulted in an equilibrium of the ascorbate concentrations between stroma and medium. A pH optimum of 7.0 to 7.5 and the lack of alkalization of the medium upon ascorbate uptake suggest that only the monovalent ascorbate anion is able to cross the chloroplast envelope. The activation energy of ascorbate uptake was determined to be 65.8 kilojoules (16 kilocalories) per mole (8 to 20°C). Interference of ascorbate transport with substrates of the phosphate or dicarboxylate translocator could not be detected, but didehydroascorbate was a competitive inhibitor. Preloading of chloroplasts with didehydroascorbate resulted in an increase of V_max but did not change the K_m for ascorbate. Millimolar concentrations of the sulfhydryl reagent p-chloromercuriphenyl sulfonate inhibited ascorbate uptake. The data are interpreted in terms of ascorbate uptake into chloroplasts by the mechanism of facilitated diffusion mediated by a specific translocator.