Embryo growth in mature celery seeds

P. van der Toorn

Research output: Thesisexternal PhD, WU

Abstract

<p>Germination of celery seeds is slow, due to the need for embryo growth before radicle protrusion can occur. Germination rate was correlated with embryo growth rate. Celery seeds with different embryo growth rates were obtained with fluid density separation of a seed lot. Low density seeds germinated faster, due to a larger embryo cell size and a higher embryo cell division rate. It was concluded that the embryo cell size was correlated with the osmotic potential of the true seed. A less negative osmotic potential was caused by the higher air volume and lower pericarp volume in the low density seed. It was argued that the higher embryo cell division rate in low density seeds was partly caused by the higher osmotic potential.<p>During incubation in PEG solutions embryo growth rate in low density seeds was also higher, due to a higher cell division rate. Low density seeds contained more embryo cells after the treatment than high density seeds. It was concluded that the number of embryo cells formed during PEG incubation was partly correlated with the osmotic potential in the true seed.<p>Not only the embryo length was increased after a PEG incubation, but also the embryo growth rate was increased when seeds were subsequently germinated in water. The increase in embryo growth rate was caused by an increase in cell size, most probably due to a positive effect of PEG incubation on embryo cell wall extensibility.<p>Seed density was negatively correlated with seed maturity because during seed ripening on the mother plant the volume of air in the seeds increased. The seed density was not correlated to the umbel position as such, but harvesting of seeds from all umbels at the same time resulted in seeds with different density, due to the different length of the ripening period of the different umbels. Endo-β-mannanase activity, that is part of the hydrolytic activity in the endosperm, was positively correlated with seed maturity During germination the endo-β-mannanase activity increased, but in low density seeds the activity was higher than in high density seeds. The higher hydrolytic activity in low density seeds correlated with the higher embryo cell division rate, both during germination in water and incubation in PEG.<p>The analysis of structural and physiological parameters of different celery cultivars showed that differences in germination rate and the effect of a priming treatment on the germination rate, could be explained by the same mechanisms as in genetically identical but physiologically different seeds. The general effect of seed priming on celery cultivars is a reduction in mean germination time of about 66%.
Original languageEnglish
QualificationDoctor of Philosophy
Awarding Institution
Supervisors/Advisors
  • Karssen, C.M., Promotor
Award date12 Sep 1989
Place of PublicationS.l.
Publisher
Publication statusPublished - 1989

Keywords

  • germination
  • apium graveolens
  • celery
  • apium graveolens var. rapaceum
  • celeriac
  • seed germination
  • seed dormancy
  • plants
  • embryology

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