Seed Germination in Podocarpus henkelii: An Ultrastructural and Biochemical Study

Biochemical and ultrastructural studies were undertaken on the embryo and female gametophyte of neotonous (recalcitrant) seeds of Podocarpus henkelii over a 9-d period following scarification and incubation on a moist substrate. After 3 days incubation at 25 °C, cells of the root tip were characteri...

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Bibliographic Details
Published in:Annals of botany 1989-11, Vol.64 (5), p.569-579
Main Authors: DODD, M. C., STADEN, J. VAN, SMITH, M. T.
Format: Article
Language:English
Subjects:
Amino acids
Biochemistry
Biological and medical sciences
embryo
Embryos
endosperm
Fatty acids
Fundamental and applied biological sciences. Psychology
Gametophytes
Germination
Germination and dormancy
Lipids
neotonous
overgrown seed
Plant physiology and development
Plant reproduction
Podocarpus henkelii Stapf
recalcitrant
Seeds
Starches
yellow-wood
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Summary:Biochemical and ultrastructural studies were undertaken on the embryo and female gametophyte of neotonous (recalcitrant) seeds of Podocarpus henkelii over a 9-d period following scarification and incubation on a moist substrate. After 3 days incubation at 25 °C, cells of the root tip were characterized at the electron microscope level by increased vacuolation, numerous amyloplasts and lipid mobilization. By d 6 measurable embryonic growth was noted and ultrastructural evidence of synthetic activity was suggested by abundant endoplasmic reticulum (ER), ribosomes and dictyosomes. Fine-structural changes suggestive of reserve mobilization were also observed in the female gametophyte. Biochemical studies indicated a gradual decline in lipid and protein in both the embryo, and female gametophyte, over the 9 d of incubation. A decline in embryonic starch levels contrasted with the increase seen in the female gametophyte at d 6. Small changes in the sugar levels of the female gametophyte contrasted with increases in the embryonic tissues between d 3 and 6, a period coinciding with the first records of germination. The maintenance of high moisture contant and the evidence of metabolic activity obtained from biochemical and ultrastructural observations suggest that, following scarification, the transition between maturation and germination is characterized by a continuation of earlier synthetic activity and reserve interconversions.
ISSN:0305-7364
1095-8290
DOI:10.1093/oxfordjournals.aob.a087878