Light Actions in the Germination of Cocklebur Seeds
1987; Oxford University Press; Volume: 38; Issue: 4 Linguagem: Inglês
10.1093/jxb/38.4.702
ISSN1460-2431
AutoresYohji Esashi, Shuu HASE, Kazuko Kojima,
Tópico(s)Seed Germination and Physiology
ResumoEsashi, Y., Hase, S. and Kojima, K. 1987. Light actions in the germination of cocklebur seeds. V. Effects of ethylene, carbon dioxide and oxygen on germination in relation to light.–J. exp. Bot. 38: 702–710. Effects of ethylene, CO2 and O2 on the germination of after-ripened upper cocklebur (Xanthium pennsylvanicum Wallr.) seeds were examined in relation to pre-irradiation by red (R) or far-red (FR) light In order to remove the pre-existing Pfr, seeds were soaked in the dark for various periods prior to light irradiation and gas treatments. Regardless of light, 0.3 Pa C2H4 promoted germination at 23 °C, but it strongly inhibited germination when applied at 33 °C, the optimal temperature for the germination of this seed. However, delayed application of C2H4 during 33 °C incubation stimulated germination independently of light in a similar manner to that seen at 23 °C. It is, therefore, suggested that the germination-regulating action of C2H4 is completely independent of phytochrome. In contrast, the germination-promoting effect of 3–0 kPa CO2 was pronounced only when the seeds were previously irradiated by R, regardless of temperature, suggesting that CO2 action to promote germination depends upon Pfr. A synergism between CO2 and C2H4 at 23 °C was observed only in the germination of seeds pre-irradiated by R, while at 33 °C an antagonism occurred independently of light. The stimulation of C2H4 production by CO2 was most striking in the cotyledonary tissue pre-irradiated by R. However, the R-dependent enhancement of CO2-stimulated C2H4 production was negated by the subsequent FR and it was not found in the presence of 1-aminocyclopropane-1-carboxylic acid (ACC). Moreover, the R dependency of the germination-promoting CO2 effect disappeared in the presence of C2H4. The R-dependent C2H4 production enhanced by CO2 may thus be involved, at least partially, in some step of conversion from methionine to ACC. The germination-promoting effect of C2H4, but not CO2, was enhanced by O2 enrichment regardless of light. However, the germination-promoting effect of pure O2 itself appeared to depend upon pre-irradiation with R
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