Bioelectric potential changes in the style of Lilium longiflorum Thunb. after self- and cross-pollination of the stigma

Two different types of bioelectric potential changes have been registered in the style of Lilium longiflorum cv. Arai 5 after different treatments of the stigma. Self-pollination induces a bioelectric potential change different from the potential change induced by cross-pollination. Removal of the stigma or apllication of killed compatible pollen induced a bioelectrical response similar to the potential change recorded after cross-pollination. No bioelectric potential change was recorded after application of pollen of Petunia hybrida, pollen of Haemanthus katherinae, killed self-pollen, or no treatment at all.The mean generation time of the bioelectric potential change was 338 min after the treatment. The translocation velocity varied between 1.2 and 5.4 cm h^-1. Both responses are similar to the potential changes registered in Mimosa pudica after different types of stimulation and to the potential changes generated by the phytochrome in Avena coleoptiles. The translocation of the signals is discussed in relation to the models on the translocation in Mimosa. The relation between the bioelectric potential changes and the incompatibility reaction in Lilium longiflorum is discussed.     

Pistil Receptivity and Pollen Tube Growth in Relation to the Breeding System of Eucalyptus woodwardii (Symphyomyrtus: Myrtaceae)

Pistil structure, stigma receptivity and pollen tube growthwere investigated in relation to seed set of Eucalyptus woodwardii.Self-pollination resulted in reduced capsule retention and seeddevelopment as compared with cross-pollination. The pistil consistedof an ovary with five locules, a long style with a canal extendingfor two-thirds of its length, and a papillate stigma. Therewas no change in style length with time after anthesis, butboth stigma secretion and ability to support pollen germinationand tube growth increased to reach a peak at 7 d. Pollen germinatedon the stigma surface and in the stylar canal, but most tubegrowth occurred intercellularly in the transmitting tissue surroundingthe canal. At the base of the style the pollen tubes split intofive groups following the transmitting tissue strands to theovary. Each group grew through a septum dividing two loculesand entered the placenta. The tubes then emerged from the placentato penetrate the ovules at between 10 and 20 d after pollination.Fewer ovules were penetrated following self- than cross-pollination. Eucalyptus woodwardii Maiden, Lemon-flowered gum, Pistil receptivity, Pollen tube growth, Breeding system, Self-incompatibility     

In vitro protein synthesis with polysomes from unpollinated,cross- and self-pollinated Petunia ovaries

Summary From in-vitro protein synthesis studies it has been shown that in Petunia hybrida (clone W166K, incompatibility genes S₁S₂) the ovary is stimulated to synthesize proteins before the pollentubes reach the ovary. A difference in protein metabolism is detected after self- and cross-pollination. On the basis of this result has been concluded that a signal has to be sent from the stigma or the style towards the ovary which induces the changes in metabolic activity. The signal must be different for cross- and self-pollination.     

Changes in ovarian blood flow and secretion of progesterone and 20 alpha-hydroxypregn-4-en-3-one on day 16 and the morning and afternoon of day 22 of pregnancy in the rat

During late pregnancy in rats, ovarian secretion of progesterone decreases and that of its reduced metabolite, 20 alpha-hydroxypregn-4-en-3-one (20 alpha-OHP), increases. The present study was undertaken to determine whether changes in ovarian blood flow are consistent with changes in progestin secretion. Rats (n = 5 per group) were examined on Day 16, the time of maximal progesterone secretion, and in the morning (AM) and afternoon (PM) of Day 22, the day prior to parturition. Ovarian blood flow was monitored continuously for 60 to 80 min, and serial samples of arterial and ovarian venous blood were obtained at 20-min intervals for determination of ovarian secretion rates of progesterone and 20 alpha-OHP. Ovarian blood flow increased from 0.38 +/- 0.04 ml/min (mean +/- SEM) on Day 16, to 0.77 +/- 0.05 and 0.78 +/- 0.04 ml/min on Day 22 AM and PM, respectively, whereas the secretion of progesterone decreased from 26.9 +/- 4.0 to 4.5 +/- 1.0 and 3.2 +/- 0.3 micrograms/h per ovary. The secretion of 20 alpha-OHP was similar on Day 16 and Day 22 AM (5.6 +/- 1.7 and 5.4 +/- 1.3 micrograms/h per ovary) but then increased to 18.9 +/- 1.2 micrograms/h per ovary by Day 22 PM. Thus the amount of total progestins secreted per unit rate of blood flow relative to that on Day 16 (100%) fell to 15% and 34% on the morning and afternoon of Day 22, respectively. Clearly, the relative changes in ovarian progestin secretion and blood flow in the rat near term to not conform to patterns observed at luteal regression in some other species.(ABSTRACT TRUNCATED AT 250 WORDS)     

Pollination and stigma wounding: same response, different signal?

In Petunia hybrida flowers, both pollination and stigma woundinginduced a transient Increase in ethylene production and hastenedcorolla senescence. Ethylene production by different flowerparts was measured in situ using laser photoacoustic (LPA) spectroscopy.In pollinated flowers, ethylene was exclusively produced bythe stigma/style region whereas wounding of the stigma Inducedethylene production both by the stigma/style region and by theremaining flower parts. In aminoethoxyvinylglycine (AVG)-treatedflowers, subsequent treatment of the unwounded stigma with 1-aminocyclopropane-1-carboxylicacid (ACC) induced ethylene production exclusively by the stigma/styleregion whereas treatment of a previously wounded stigma withACC induced a simultaneous increase in ethylene production bythe stigma/style region and the remaining flower parts. Theseresults suggest that following stigma wounding, either ACC orethylene is involved in inter-organ communication. Followingpollination, the signal is apparently not directly related toethylene. In vivo ACC oxidase activity of most flower parts, includingthe gynoecium, was higher in light than in dark. Light or darkdid not influence the relative contributions of stigma/styleand remaining flower parts to the total pollination, woundingor ACC-induced ethylene production, indicating that ACC is nottranslocated. Both in excised styles and intact flowers, radiolabelledACC and its analogue -aminoisobutyric acid (AIB), applied eitherto an intact or wounded stigma, were largely immobile confirmingthat ACC is not likely to play a role in inter-organ signalling. The results collectively suggest that following stigma wounding,translocation of ethylene may be the signal responsible forinitiation of corolla senescence; following pollination thesignal is not directly related to ethylene. Key words: 1-Aminocyclopropane-1-carboxylic acid (ACC), ethylene, flower senescence, Petunia hybrida, pollination, stigma wounding     

Hormonal status of the pollen-pistil system at the progamic phase of fertilization after compatible and incompatible pollination in Petunia hybrida L.

The hormonal status of the pollen-pistil system in Petunia hybrida L. during the progamic phase of fertilization was investigated. The contents of indolyl-3-acetic acid (IAA), abscisic acid (ABA), and cytokinins, as well as the rate of ethylene production in the pistils and their parts (stigma, style, and ovary) were measured over an 8-h period following compatible and self-incompatible pollination. In both pollinations, the phytohormones were present in various proportions in the stigma, style and ovary: the stigma was the main site of ethylene synthesis and contained 90% of the ABA, while the style contained 80% of the total cytokinin content in the pollinated pistil. Relatively low levels of hormones in the ovary did not influence the hormonal status of the pollen-pistil system. The interaction of the male gametophyte with the stigmatic tissues was accompanied by a 7- to 10-fold increase in ethylene production and a 1.5- to 2.0-fold increase in IAA content in the pollen-pistil system over 0–4 h. Pollen tube growth after self-incompatible pollination, in contrast to compatible pollination, was accompanied by a 3-fold increase in the ABA content in the stigma and style and by a 5-fold higher cytokinin content in the stylar tissues. Thus, the ethylene/ABA status of the stigma may play a role in controlling the processes of adhesion, hydration, and germination of pollen grains during pollination while the auxin/cytokinin status of the style may be involved in controlling pollen tube growth.     

Membrane potential measurements of unfertilized and fertilized Xenopus laevis eggs are affected by damage caused by the electrode

Upon penetration in an unfertilized Xenopus egg bathed in 1/10 Ringer, the voltage recorded by a microelectrode shows an abrupt jump to a negative voltage (Ep) followed by a rapid depolarization to a steady value (Er) (Ep = -39.4 +/- 1.9 mV and Er = -11.5 +/- 0.5 SE, 54 eggs from 9 females). The same is true for fertilized eggs impaled 16-35 min after insemination (Ep = -29.5 +/- 2.1 mV, Er = -11.5 +/- 0.9 mV, SE, 18 eggs from 3 females). The voltage recorded by a second microelectrode inserted into the same egg does not show the transient initial negativity. The stationary level of the membrane potential is close to the diffusion potential calculated from the Goldman equation with equal permeabilities for all the relevant ions. It is concluded that the low resting potentials measured in Xenopus eggs before and after fertilization are largely due to damage caused by the electrode. Using an upper limit of -39 mV for the true membrane potential and correlating the input resistance with the stationary membrane potential, a lower limit of 22 M omega (about 1 M omega cm2) for the membrane resistance can be obtained. Insertion of a microelectrode during the first 3 min after insemination shows a steady positive potential while, at later times (3-16 min post-insemination), a positive peak followed by a repolarization can be observed. This indicates that the measurement of the peak of the fertilization potential is not seriously affected by the electrode penetration while its time course after the first 3 min may be deformed by the presence of a large leakage conductance.     

Pollination-Induced Corolla Wilting in Petunia hybrida Rapid Transfer through the Style of a Wilting-Inducing Substance

Pollination or wounding of the stigma of Petunia hybrida flowers led to the generation of a wilting factor and its transfer to the corolla within 4 hours. This was concluded from the effects of time course removal of whole styles. In this 4-hour period, pollen tubes traversed only a fraction of the total distance to the ovaries. Both pollination and wounding of the stigma immediately resulted in an increase of ethylene evolution. Accelerated wilting, however, occured only when treated styles remained connected with the ovaries, and not when they were detached and left in the flower. A wilting factor was found in eluates collected from the ovarian end of the styles, only in the case of previous pollination or wounding. In such eluates, the level of the ethylene precursor 1-amino-cyclopropane-1-carboxylic acid was below detection.

These observations suggest a material nature of the wilting factor in Petunia flowers, which rapidly passes through the style to the corolla, but which is different from 1-aminocyclopropane-1-carboxylic acid.

     

羽衣甘蓝授粉过程中柱头蛋白质的泛素化

分析自花授粉与异花授粉后的羽衣甘蓝柱头蛋白质泛素化变化的结果表明,自花授粉30min后的柱头蛋白质泛素化水平显著增加,45min时达到峰值;异花授粉的柱头蛋白质泛素化水平没有变化。     

Slow actions of hyperpolarization on sodium channels in the membrane of myelinated nerve.

The mean sodium current, I, and the variance of sodium current fluctuations, var, were measured in myelinated nerve during a depolarization to V = 40 mV applied from the resting potential (VH = 0) or from a hyperpolarizing holding potential VH = -28 mV. From I and var the relative variations in the number N and the conductance gamma of sodium channels following changes of the holding potential were calculated. Hyperpolarizing the membrane from VH = 0 to -28 mV increased N by a factor of 3.7, whereas gamma decreased by a factor of 0.53. These actions of holding potential on sodium channels develop slowly since 500 ms prepulses to 0 or -28 mV do not alter the values of N and gamma.     

The pathway for systemic electrical signal conduction in the wounded tomato plant

The pathway of a systemic electrical signal possibly linking wounding and the systemic synthesis of proteinase inhibitor was investigated in tomato (Lycopersicon esculentumMill. cv. Moneymaker) plants. Heat, causing wounding to a cotyledon, was used to induce both a travelling electrical signal and systemic proteinase inhibitor activity. Intracellular recordings of changes in the membrane potential of different cell types were measured in the petiole of leaf 1, the first true leaf, and impaled cells were identified by injection of fluorescent dye (Lucifer Yellow CH). No difference was found between the membrane potentials of the different cell types; the mean membrane potential of all the cell types was -148 ± 3 mV. Only sieve-tube elements and companion cells produced large (79 ± 3.3 mV) action-potential-like depolarisations following wounding, although smaller (23 ± 1.6 mV) depolarisations were observed in other cell types. It was concluded that the electrical signal possibly linking a wound stimulus in a cotyledon with the induction of systemic proteinase inhibitor synthesis was propagated in the sieve-tube element/companion cell complex.Abbreviations LYCH Lucifer Yellow CH - PI proteinase inhibitor This work was supported by the Biotechnology and Biological Sciences Research Council (UK).     

Structure and development of the stigma, style and ovary of Caesalpinia pulcherrima (L.) Sw., post-anthesis, pre- and post-pollination

The stigma of Caesalpinia pulcherrima is crateriform. The crater continues as a slit-like canal through the style and into the ovary. Both crater and canal are lined by several layers of fusiform and thin-walled cells which are continuous in two narrow regions in the ovary. Postanthesis and before pollination, the middle lamella of cells lining the stigmatic crater and stylar transmitting tissue undergoes dissolution. This occurs in a progression down the style with cells separating partially or wholly from neighbours. Dissolution is initiated at intercellular junctions where wall fibrils loosen and variously-sized and -shaped holes appear. Cytoplasmic changes include increased dictyosome activity, increased rough and smooth endoplasmic reticulum at the periphery of cells and accumulation of electron opaque deposits at the plasma membrane. The crater fills with stigmatic fluid and the diameter of the stylar canal increases. Pollen germinates in the secretion-filled crater, and pollen tubes grow down the style between the cells of the transmitting tissue but do not enter the canal. They emerge at the entrance to the ovary cavity and grow over one or two narrow strips of ovarian transmitting tissue cells which are present throughout the length of the ovary close to the ovules. This ensures that tubes grow in close proximity to the micropyles.     

Maturation of pig oocytes: observations on membrane potential

The membrane-potential changes of pig oocytes during maturation are described. Cumulus-enclosed oocytes have a resting potential of -41.81 +/- 0.60 mV; the removal of cumulus cells caused this potential to drop to -30.95 +/- 0.43 mV. Adding LH to the culture medium did not influence the potential of denuded oocytes but depolarized the potential of cumulus-enclosed oocytes to -32.90 +/- 0.43 mV. FSH did not affect the membrane potential of denuded or cumulus-enclosed oocytes, but significantly reduced the amplitude of the depolarization induced by LH. The effect of gonadotropins on cultured granulosa cells was also investigated. Plated granulosa cells have a resting potential of -45.21 +/- 0.72 mV, similar to that of cumulus-enclosed oocytes. As recorded in cumulus-enclosed oocytes, LH depolarized granulosa cell membrane potential (-30.33 +/- 0.69 mV) and FSH reduced this effect. To evaluate if oocyte maturation in vivo is accompanied by membrane-potential depolarization, follicular growth and oocyte maturation were induced in 6 prepubertal gilts by using an eCG-hCG treatment. Twenty hours after the beginning of oocyte maturation in vivo (induced by hCG), the membrane potential of the oocyte was depolarized to -28.84 +/- 1.01 mV, a value similar to that observed in vitro. These data indicate that both LH and FSH can influence the membrane potential of follicular somatic cells and, consequently, that of the oocyte. The electrical coupling between somatic cell and oocyte may represent a means by which the gonadotropin message is passed to the germinal cell by the somatic compartment.     

Potential difference responses to secretory K+, Na+ and HCO3- changes in secreting and resting states of frog stomach in Cl(-)-free media

The effects of changes in secretory concentrations of K+, Na+ and HCO3- on transmucosal potential difference (PD) and resistance in Cl(-)-free (SO4(2-)) solutions were compared for secreting fundus and resting fundus of Rana pipiens. In the resting fundus experiments, histamine was not present in the nutrient solution and cimetidine was primarily used to obtain acid inhibition. Increase of K+ from 4 to 80 mM, decrease of Na+ from 156 to 15.6 mM and decrease of HCO3- from 25 to 5 mM gave, 10 min after the change, in the secreting fundus delta PD values of 39.7, -11.9 and 3.2 mV, respectively. In the resting fundus, 1.5 to 2 h after the addition of cimetidine, the same changes in secretory ion concentration gave delta PD values of 12.2, -5.6 and 1.5 mV, respectively. Replacement of cimetidine with SCN and without histamine yielded a delta PD somewhat lower than that in cimetidine, namely 9 mV for a K+ change from 4 to 80 mM. Subsequent addition of histamine with SCN present gave a delta PD of about 21 mV. The change in PD was attributed to histamine increasing the secretory membrane area, leading to an increase in K+ conductance. Another possibility is that histamine increases the K+ conductance per se.     

Cold shock and rapid cold-hardening of pharate adult flesh flies (Sarcophaga crassipalpis): effects on behaviour and neuromuscular function following eclosion

Abstract. Little is known about the nature of injury due to cold shock, or its prevention by rapid cold-hardening, in insects. To understand these phenomena better at the system level, physiological and behavioural comparisons were made between control, cold shock injured, and rapidly cold-hardened flesh flies, Sarcophaga crassipalpis Macquart (Diptera, Sarcophagidae). Cold shock impaired the proboscis extension reflex in response to 0.125,0.5 and 1.0 M sucrose solutions. Cold shock-injured flies were unable to groom effectively and spent only 12.5% of the first 5 min following general dust application producing ineffectual leg movements. In contrast, control and rapidly cold-hardened flies exhibited normal grooming behaviour spending 92.4% and 94.1% of the first 5 min following generalized dust application grooming. Cold shock also decreased the mean resting membrane potential of tergotrochanteral muscle fibres from -65.9 mV in control flies to -41.6 m V. Conduction velocities of the three motor neurone populations innervating the tergotrochanteral muscle were all significantly lower in cold-shocked flies than in control or rapidly cold-hardened flies. Finally, cold shock impaired neuromuscular transmission as evidenced by a lack of evoked end plate potentials.     

Gametophyte–Sporophyte Interactions in the Pollen–Pistil System: 4. The Hormonal Status and the Mechanism of Self-Incompatibility

Following 4 and 8 h after self-incompatible pollination of Petunia hybrida plants, ethylene evolution and the contents of IAA, ABA, and cytokinins were measured in pistils and their parts (stigma, style, and ovary). The germination and initial growth of pollen tubes within the initial 4 h of the experiment were accompanied with an almost tenfold increase of the rate of ethylene production by the stigma and a twofold increase of the ABA content in the stigma and style. The inhibition of pollen tube growth in the style tissues during next 4 h coincided with a fivefold increase in the cytokinin content in the style, while high ABA content was maintained in the stigma and style. The authors conclude that phytohormones participate in the mechanism of gametophyte self-incompatibility.     

Effects of carbamylcholine on membrane potential and Na-K pump activity of cultured rat skeletal myotubes

1. We measured changes in resting membrane potential (Em) and Na-K pump activity, assayed by ouabain-sensitive 86Rb uptake, in response to carbamylcholine (CCh) and its continued presence in single rat skeletal myotubes in culture. 2. CCh caused immediate depolarization from control Em (-80 to -85 mV) to near 0 followed by repolarization of varying degrees depending on the age of the culture and temperature of the recording medium; repolarization of Em was most apparent by culture age 8-9 days in vitro (DIV), Em reaching values as high as -60 mV by 5-10 min after peak depolarization at 37 degrees C. 3. Input resistance, which decreased during CCh depolarization, increased only slightly during the initial phase of repolarization and then remained essentially unchanged during the major component of membrane repolarization in the presence of CCh. 4. Ouabain, given before CCh, prevented repolarization of Em and, when given after repolarization had begun, reversed it and caused Em to return to about -7 mV. 5. Na-K pump activity was decreased in myotubes in which Em did not repolarize or did so only slightly, and was increased by over 40-50% in myotubes whose Em repolarized by 40-60 mV, even though CCh was still present in the medium. Inhibition of pump activity in non repolarizing myotubes was related to Na influx, inhibition being reversed to stimulation when CCh was administered to myotubes in Na-free medium. 6. Repeated (three or four times) or prolonged (up to 60-min) administration of CCh to myotubes in which repolarization was hardly expressed (age 6-7 DIV) caused increases both in the amount of repolarization and in 86Rb uptake, both being related to the number or duration of CCh exposures. 7. We conclude that repolarization of Em following CCh-induced depolarization of cultured rat skeletal myotubes depends to a large extent on an increase in activity of the electrogenic Na-K pump.     

Effects of prostaglandins on ovarian blood flow in the bitch

Oestrus and anoestrous mongrel dogs were anaesthetized with chloralose-urethane. In one group, the ovaries were isolated in situ and the effects of a 15-min infusion of PGF-2alpha or PGE-2 on perfusion pressure were measured. In the other group, heated thermocouples were introduced into the stroma of each ovary to measure the changes of local blood flow in response to PGF-2 alpha and PGE-2 infused into the ovarian bursa for 15 min. Intra-arterial infusion of 25.50, 100 or 200 ng PGF-2alpha/kg/min did not affect perfusion pressure; PGE-2 doses of 3.1, 6.2, 12.5 or 25 ng/kg/min caused reductions in proportion to the dose. All doses of PGE-2alpha (50.0, 100 or 200 ng/kg/min) or PGE-2 (25, 50 or 100 ng/kg/min) increased blood flow in the ovarian stroma in proportion to the dose when administered by infusion into the ovarian bursa. There were no differences in the results from oestrous and anoestrous dogs. It is concluded that PGF-2alpha changes intraovarian blood distribution without interfering with the total blood flow while PGE-2 increases both the total and local ovarian blood flow.