TITLE	Content of adenylate nucleotides and energy charge in the early stage of germination of orthodox and recalcitrant seeds
AUTHOR	Chih-Chang Chao Tree Seed Laboratory, Taiwan Forestry Research Institute, 53 Nan-Hai Road, Taipei, Taiwan, Republic of China Tsan-Piao Lin Tree Seed Laboratory, Taiwan Forestry Research Institute, 53 Nan-Hai Road, Taipei, Taiwan, Republic of China
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ABSTRACT	The content of adenosine phosphates and the energy charges of three species of orthodox seeds, i.e. Phellodendron wilsonii, Michelia compressa, and soybean; three species of recalcitrant seeds, i.e. Podocarpus macrophyllus, Cyclobalanopsis globosa, and Machilus thunbergii; one species of intermediate category, i.e. Neolitsea parvigemma at the early stage of germination were analysed to compare the energy concept established for crop seeds. AMP was the major adenylate in the dry state, and the ATP content in dry orthodox seeds was usually lower than 10 nmol g-1 d.wt resulting in low energy charge values of around 0.20. The highest increase of ATP levels after incubation compared to the level of dry seeds was 167-fold in soybean and 60-fold in Ph. wilsonii. The maximum ATP accumulation coincided with the seed being ready to germinate. A decrease in ATP content was observed after seed germination, and the decline continued throughout the period of radicle emergence. The imbibed dormant seeds of Ph. wilsonii synthesized smaller amounts of ATP than non-dormant ones at the early stage of incubation; the ATP was eventually depleted. The ATP content of recalcitrant seeds, including the intermediate species, ranged from 20 to 220 nmol g-1 d.wt, thereby reflecting energy charge values above 0.6. The ATP levels in the fresh recalcitrant seeds before and after incubation, however, generally remained similar. This suggests that orthodox crop seeds, i.e. soybean synthesize adenosine phosphates extremely efficiently, unlike most of the tree seeds, which are more or less dormant. P. macrophyllus seeds are viviparous and had the highest amount of ATP, ADP and the highest energy charges among the species tested, indicating high metabolic activities in mature seeds. Seeds of C. globosa, another type of recalcitrant seed and N. parvigemma were characterized by low adenylate and energy charges, no significant changes in adenylate in the early stage of incubation, and slow germination. During an artificial drying process, the degradation of adenylates in recalcitrant seeds seemed to continue indefinitely, resulting in lower energy charges. This process must be different from that of orthodox seeds in which AMP is the major adenosine phosphate to accumulate.
KEYWORD	Adenylates; Artificial dehydration; Energy charge; Orthodox; Recalcitrant; Seed germination;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 37 Number 4 October 1996, page 229-237, 9 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China