Vol. 79 No: 4

Title:
Maturity and temperature stratification affect the germination of Styrax japonicus seeds

Authors:
MARK S. ROH, JO-ANN BENTZ, PAUL WANG, ERCHENG LI and MASAJI KOSHIOKA

pp: 645-651

Abstract:
The effect of seed maturity, warm (18°C) or cold (5.5°C) temperature, and gibberellic acid (GA₃) on Styrax japonicus seed germination was investigated. Morphological changes during fruit development were observed using magnetic resonance imaging (MRI) and to correlate changes in germination behaviour with time. Internal structures of fruits were identified using MRI, which showed tissues that contained water with different mobility in early growth stages. In the pericarp, the seed coat, and the endosperm of fruits harvested 17 weeks after anthesis, spin-lattice relaxation time T₁ decreased with maturation of the fruits.This finding indicated the termination of the physiological role of the pericarp due to a loss of free water, and of water that existed in bound form in the endosperm and the cotyledons as seeds became dry. Magnetic resonance images of Styrax japonicus ´Pink Chime` fruits harvested 11 weeks after anthesis showed the formation of cotyledons and endosperm. Fruits were fully developed when harvested 13-15 weeks after anthesis. S. japonicus fruits harvested 12 weeks (1999) and 16 weeks (2000) after anthesis were fully developed and matured, and responded to germination-promoting treatments.To ensure good germination, or higher than 80%, seeds should be harvested 12-16 weeks after anthesis, and should be treated with one month of warm stratification (WS) followed by two months of cold stratification (CS). The maximum percent germination was 98%, after two months of WS followed by three months of CS, which is significantly higher than the percentage previously reported.

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