Acidification of the Medium Associated with Normal and Fusicoccin‐Induced Seed Germination

Lado, P.; Rasi‐Caldogno, Franca; Colombo, Roberta

doi:10.1111/j.1399-3054.1975.tb03853.x

Cited by 58 publications

(16 citation statements)

References 25 publications

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“…This idea is based on the finding that both H+ secretion and K+ uptake are inhibited by ABA along with the inhibition of germination while fusicoccin promotes all three processes in the presence or in the absence of ABA. Whereas the wall loosening action of fusicoccin via H+ secretion seems to be firmly established also in the case of seed germination (1,8,18,20), we feel that the presently available evidence with respect to the causal involvement of ion transport processes in the signal response chain of ABA is not equally conclusive. In preliminary experiments, we were unable to detect any significant H+ secretion by rape embryos normally germinating on water under conditions where fusicoccin induces strong medium acidification and enhances germination.…”

Section: Resultsmentioning

confidence: 73%

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Control of Seed Germination by Abscisic Acid

Schöpfer¹,

Plachy²

1985

Plant Physiol.

144

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The physical mechanism of seed germination and its inhibition by abscisic acid (ABA) in Brassica napus L. was investigated, using volumetric growth (= water uptake) rate (dV/dt), water conductance (L), cell wall extensibility coefficient (m), osmotic pressure (IIi), water potential (*i), turgor pressure (P), and minimum turgor for cell expansion (Y) of the intact embryo as experimental parameters. dV/dt, Hi, and *i were measured directly, while m, P, and Y were derived by calculation. Based on the general equation of hydraulic cell growth IdV/dt = Lm/(L + m) (Al -Y), where All = Hi -II of the external medium; the terms (L m/(L + m) and II -Y were defined as growth coefficient (kG) and growth potential (GP), respectively. Both kG and GP were estimated from curves relating dV/dt (steady state) to I of osmotic test solutions (polyethylene glycol 6000).During the imbibition phase (0-12 hours after sowing), kG remains very small while GP approaches a stable level of about 10 bar. During the subsequent growth phase of the embryo, kG increases about 10-fold. ABA, added before the onset of the growth phase, prevents the rise of kG and lowers GP. These effects are rapidly abolished when germination is induced by removal of ABA. Neither L (as judged from the kinetics of osmotic water efflux) nor the amount of extractable solutes are affected by these changes. Ili and *i remain at a high level in the ABA-treated seed but drop upon induction of germination, and this adds up to a large decrease of P, indicating that water uptake of the germinating embryo is controlled by cell wall loosening rather than by changes of II; or L. ABA inhibits water uptake by preventing cell wall loosening. By calculating Y and m from the growth equation, it is further shown that cell wall loosening during germination comprises both a decrease of Y from about 10 to 0 bar and an at least 10-fold increase of m. ABA-mediated embryo dormancy is caused by a reversible inhibition of both of these changes in cell wall stability.In a previous paper (29), we have provided evidence based on kinetics of water uptake and a factorial analysis that exogenous ABA controls germination of rape seeds by limiting water uptake of the embryo rather than by inhibiting energy* metabolism, protein synthesis, or related processes. It was concluded that ABA and osmotic stress interact at a common point controlling the water relations of the embryo specifically during the growth phase of germination. This phase commences about 12 h after sowing and is characterized by a resumption of rapid water uptake due to active embryo enlargement. In contrast, water uptake during the preceding imbibition phase (O to ,umol 1-' (29). However, a 10-fold higher concentration is needed to maintain the dormant state for longer periods of time.In the present paper, we attempt to localize the site(s) of action of ABA within the physical parameters governing the water relations of the germinating seed. The inhibitory effect of ABA on water uptake has been shown to be both rapidly ind...

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Section: Resultsmentioning

confidence: 73%

“…From the extensive work with radish seeds (1,8,18,20), it has been suggested that germination is controlled by H+-mediated cell wall loosening and K+ accumulation, both contributing to an increase in the capacity for water uptake. ABA is thought to inhibit germination by counteracting these ion fluxes.…”

Section: Resultsmentioning

confidence: 99%

Control of Seed Germination by Abscisic Acid

Schöpfer¹,

Plachy²

1985

Plant Physiol.

144

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Section: Introductionmentioning

confidence: 99%

“…cell elongation and radicle protrusion (4,5,9,15,20). FC2, which is known to stimulate proton extrusion in higher plants (17), breaks the dormancy due to light conditions, high temperature (20), ABA (9,15); it also stimulates the rate of germination (9,15) and counteracts the inhibition of an osmoticum medium (20). The effect of FC is correlated to the stimulation of proton extrusion (15) and potassium uptake capacity (9,20) and to the hyperpolarization ofthe transmembrane electric potential (PD) (2).…”

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confidence: 99%

“…The embryonal axes were excised from the seeds after 2 h imbibition in distilled H20 at OC as described by Chin (6). Ten samples of ten seeds were germinated at 20°C over two sheets of filter paper in 15-cm Petri dishes with 15 Alternatively, the PD measurements were carried out on seeds directly laying over two sheets of filter paper wetted with H20 or 5 AM FC. The system was grounded through a 3 M KCl-agar bridge.…”

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confidence: 99%

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Inhibition by Fusicoccin of Germination of Pea Seeds

Lioi¹,

Petruzzelli²,

Morgutti³

et al. 1984

Plant Physiol.

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Fusicoccin inhibits the germination of pea (Pisum sativum L. cv Progress 9) seeds by decreasing the growth of the embryonal axis and by stimulating the fresh weight increase of the cotyledons. The growth of isolated embryonal axes in the presence of sucrose and KCI is stimulated by fusicoccin. The effect of fusicoccin on the seeds is not counteracted by sucrose and KCI. Fusicoccin promotes preferentially in the cotyledons a hyperpolarization ofthe transmembrane electric potential and an increase in the uptake capacity, suggesting the reinforcement of the sink strength of the cotyledons in comparison with the one of the embryonal axis and therefore the inhibition of translocation from the cotyledons of some substance necessary for the growth of the embryonal axis.In many seeds, the control of dormancy and germination seems to be correlated with the activation, in embryos, of an electrogenic H+/K+ exchange mechanism at the cell membrane level with a subsequent action on the osmotic potential and on the wall plasticity, i.e. cell elongation and radicle protrusion (4,5,9,15,20). FC2, which is known to stimulate proton extrusion in higher plants (17), breaks the dormancy due to light conditions, high temperature (20), ABA (9, 15); it also stimulates the rate of germination (9, 15) and counteracts the inhibition of an osmoticum medium (20). The effect of FC is correlated to the stimulation of proton extrusion (15) and potassium uptake capacity (9,20) and to the hyperpolarization ofthe transmembrane electric potential (PD) (2).Fusicoccin in some cases causes inhibition rather than promotion of seed germination, as reported in dormant Cercis siliquastrum (22) and Atropa belladonna (Lercan and Sponga, unpublished) seeds, and in quiescent Pisum sativum seeds (16).In this work, the inhibitory effect of FC on the germination of Pisum sativum seeds was investigated.MATERIALS AND METHODS Plant Material. Pea (Pisum sativum L. cv Progress 9) seeds were used. The embryonal axes were excised from the seeds after 2 h imbibition in distilled H20 at OC as described by Chin (6). After washing the seeds twice with the same unlabeled solutions at OC, the embryonal axes and the cotyledons were isolated. For K+ uptake, the samples were homogenized with 0.1 N HNO3 and the radioactivity was then measured; for 3-0-MG and phenylalanine uptakes, the samples were homogenized with 10% HC104 and the radioactivity was measured on the acid-soluble fraction. A liquid scintillation counter Beckman LS 7500 was used.Measurement of the Transmembrane Electric Potential. The transmembrane electric potential was measured according to Cocucci et al. (8). Pea seeds, germinated for the desired time with or without FC, were transferred into a lucite cell under continuous flow (about 4 ml min-') ofa thermoregulated (20C) and aerated solution containing 0.2 mm CaSO4, 0.25 (or 1.5) mm K2SO4 ± 5 AM FC, pH 6.5. In about 1 h, the PD values were stabilized. The PD measurements were carried out in different cells from the second to the fourth layer of the p...

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Ultracytochemical and Biochemical Studies of Plasma Membrane Atpase in the Individual Parts of the Mature, Dormant Seed of Pisum Sativum

Pollak

Mogensen

1986

American J of Botany

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The location and activity of a K -ATPase in mature, dormant peas were investigated using two ultracytochemical techniques, as well as biochemical assays of plasma membrane fractions from separate seed parts. Both the Wachstein and Meisel (1957) and the Ernst (1972) cytochemical methods showed plasma membrane-associated reaction product located primarily on the exterior surfaces of the entire pea embryo, except for the stem apex and tip-most cells of the radicle. No plasma membrane-assocated reaction product was found in the seed coat, which typically consists of cells with degenerating protoplasts. Biochemical results showed the highest specific K -ATPase activity in the radicles (775 nmol Pi/mg protein/hr), followed by epicotyls (168 nmol Pi/mg protein/hr) and cotyledons (147 nmol Pi/mg protein/hr). It is proposed that the entire pea embryo may function in the active absorption of nutrients during the initial phases of germination. Additional functions of the enzyme may include cell wall loosening prior to cell elongation, regulation of cytoplasmic pH, and the generation of turgor.

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Acidification of the Medium Associated with Normal and Fusicoccin‐Induced Seed Germination

Cited by 58 publications

References 25 publications

Control of Seed Germination by Abscisic Acid

Control of Seed Germination by Abscisic Acid

Inhibition by Fusicoccin of Germination of Pea Seeds

Ultracytochemical and Biochemical Studies of Plasma Membrane Atpase in the Individual Parts of the Mature, Dormant Seed of Pisum Sativum

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