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Content of Adenosine Phosphates and Adenylate Energy Charge in Germinating Ponderosa Pine Seeds

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Content of Adenosine Phosphates and Adenylate Energy Charge in Germinating Ponderosa Pine Seeds Plant Physiol. (1972) 50, 536-540 Content of Adenosine Phosphates and Adenylate Energy Charge in Germinating Ponderosa Pine Seeds Received for publication May 18, 1972 TE MAY CHING AND KIM K. CHING Crop Science Department and Forest Research Laboratory, Oregon State University, Corvallis, Oregon 97331 ABSTRACT seed germination; (b) whether the gametophyte tissue (food An average of 540 picomoles of total adenosine phosphates storage) has an energy level and energy charge differing from was found in the embryo of mature seeds of ponderosa pine that in the embryo and seedling that may explain their di- (Pinus ponderosa Laws.) and 1140 picomoles in the gameto- vergent metabolic activities; (c) whether a correlation between phyte. Adenylate energy charges were 0.44 and 0.26, respec- the biogenesis of organelles (11) and energy level and energy tively. After stratification, total adenosine phosphates increased charge exists in the gametophytic tissue; and (d) whether co- 7-fold and 6-fold in embryo and gametophyte, respectively, and niferous seeds follow a pattern of energy metabolism during energy charges rose to 0.85 and 0.75. During germination, total germination similar to the angiosperm seeds. adenosine phosphates increased to a 20-fold peak on the 9th day in gametophytic tissue, parallel with the peak of reserve MATERIALS AND METHODS regradation and organellar synthesis, and then decreased. In embryo and seedling, total adenosine phosphates elevated 80- Uniformly large sized ponderosa pine (Pinus ponderosa fold with two distinct oscillating increases of AMP and ADP. Laws.) seeds were selected from a composite, highly viable lot The oscillating increases occurred before the emergence of of collections for 1970. Seeds were soaked in water at room radicle and cotyledons during which the highest mitotic index temperature for 4 hr, stratified at 5 C for 2 weeks, then germi- prevailed in all tissues. Energy charges fluctuated between 0.65 nated on Sponge Rok at a daily cycle of 15 C for 16 hr in the at the rapid cell dividing stage to 0.85 at the fully differentiated dark and 25 C for 8 hr with 1000 ft-c fluorescent light. stage of the seedling, while energy charges remained around Weight, Size, and Water Content Measurements. Four repli- 0.75 in the gametophyte. These data indicated that the content cations of 10 seeds were selected at each of the 12 develop- of adenosine phosphates of germinating seeds reflects growth, mental stages of germination (Table I). After the seedling organogenesis, and morphogenesis, and that a compartmental- length was measured, the seed coat was removed and the ga- ized energy metabolism must exist in dividing and growing metophyte was dissected. Fresh and dry weights (dried at 100 C plant cells. for 24 hr) were determined on gametophytes and embryos or seedlings for each replication. Water content was calculated from the difference of fresh weight and dry weight. Determination of Adenosine Phosphates. Four seeds of the designated stage of germination were dissected into gameto- phyte and embryo or seedling in a moist chamber. The dissec- tion of each seed took less than 10 sec in skilled hands. Each Seed germination requires the synthesis of enzymes and part was quickly extracted by 10 ml of boiling, glass-distilled organelles for catabolic degradation of reserve food in the water for 10 min at 100 C. The extract was cooled in an ice storage tissue and for anabolic building up of cellular constitu- bath, and 0.8 ml of the original (early stages) or diluted (later ents in the seedling (12). Because the synthesis of proteins and stages) extract was incubated at 30 C for 15 min in each of the nucleic acids is the major event in embryonic tissue, ATP is in following mixtures (8). great demand during seed germination (12, 19). ATP was A. For ATP determination, 0.1 ml of reaction buffer con- found to increase very rapidly upon imbibition of lettuce seeds taining 0.5 M N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic under optimum temperature and oxygen conditions (22). The acid (HEPES), pH 7.5, and 0.5 M magnesium acetate and 0.1 content of ATP or adenylate energy supply and energy charge ml of glass-distilled water. (EC = ([ATP] + 12 [ADP])/([ATP] + [ADP] + [AMP])) B. For ADP and ATP determination, 0.1 ml of the reaction often control metabolic activity and growth (1, 8, 22). A good buffer and 0.1 ml of solution containing 20 ,ug of pyruvate example of EC'-controlled metabolism was reported in imbibed kinase (EC 2.7.1.40) (Sigma, crystalline), and 500 nmoles of lettuce seeds. Anaerobiosis induced the activity of adenylate trisodium phosphoenolpyruvate (Calbiochem). kinase that in turn regulated the levels of adenosine phosphates C. For TAP, 0.1 ml of the reaction buffer, and 0.1 ml of to an extremely low EC and thus growth activities of the lettuce solution containing 20 ,ug of pyruvate kinase, 500 nmoles of seeds were limited (4). It would, therefore, be of interest to trisodium phosphoenolpyruvate. and 20 ,.tg of dialyzed (against discern (a) whether the energy level and energy charge are 1 mM phosphate buffer, pH 7.0) adenylate kinase (EC 2.7.4.3) regulating metabolic activities under normal conditions during (Sigma). After incubation, the extracts were either stored at 0 C overnight or assayed immediately by the luciferin-luciferase ' Abbreviations: EC: energy charges; TAP: total adenosine phos- method using an Aminco Chem-Glow photometer (24). The phates. procedure was modified from the St. John's method: two 536 Downloaded from on May 12, 2019 - Published by www.plantphysiol.org Copyright © 1972 American Society of Plant Biologists. All rights reserved. Plant Physiol. Vol. 50, 1972 ATP, ADP, AND AMP IN PINE SEEDS 537 replications of 0.4 ml each of the above mixtures were added meristems were stained in the older seedlings showing localized with 100,ud of firefly lantern extract (Sigma FLE-50; 50 mg of and limited mitotic activity. buffered extract inS ml of water), containing 50 mm potassium arsenate and 20 mm magnesium sulfate, pH 7.4. The instant RESULTS AND DISCUSSION peak height of light emission was used for all three mixtures to avoid endogenous ADP and AMP in the firefly extract inter- The changes in fresh weight, dry weight, and water content fering with the assay of tissue extract, particularly mixtures of the gametophyte and embryo or seedling during the course B and C. The peak height was linear to ATP concentration of of soaking, stratification, and germination are illustrated in 10nM to 10 4LM with the procedure outlined above and the Figure 1 and TableI. These changes are similar to other lots Aminco Chem-Glow photometer. For most batches of the of ponderosa pine seeds (11) and other coniferous tree seeds firefly extracts, a peak height of 20 to 40 equals 1,uM of ATP (10), indicating a normal course of development from an solution or 400 pmoles per 0.4-ml sample. The endogenous embryo enclosed in nutritive gametophyte to an autotrophic ATP in the firefly extract was depleted in the solution at 5 C seedling. Because of the lower (though simulating natural in 16 to 24 hr. Some degradation of the luciferase was observed condition) than usual laboratory germination temperatures during this period, but that did not affect the assay as an excess used, a slower rate of dry weight reduction in the gametophyte of enzyme was used. The step of constant addition of ATP in and a more gradual dry weight increase in the seedling were the original method (24) was not used in this study as the observed than in the previous study (11). quenching effect of various chemicals present in extracts was Energy metabolism is more dynamic in the embryo and minimized by dilution. seedling than in the gametophyte over the whole germination The boiling water extraction method was compared with the period (Fig. 2). In the embryo of mature seed, an average of 60 cold perchloric acid extraction (8) and the boiling ethanol ex- pmoles of ATP, 350 pmoles of ADP, and 130 pmoles of AMP traction (24) in the early stage of this study. The data obtained were found. The 0-day gametophyte contained 60, 480, and by the boiling water method were more reproducible and con- 600 pmoles, respectively. An average energy charge of 0.44 sistently higher than by the other two methods. Stewart and and an ATP concentration of 0.7 mm were found in the em- Guinn (25) also found that hot water extraction resulted in bryo and a lower energy charge of 0.26 and a much lower ATP highest and reproducible ATP quantity from cotton seedlings. concentration of 0.035 mM were observed in the gametophyte Furthermore, the recovery of pure ATP, ADP, and AMP (Fig. 3). A low energy charge is common in quiescent seeds (5, (P-L Biochemicals, Inc.) averaged about 97, 85, and 87% by 22); ponderosa pine appears to be no exception. After 4 hr of the method outlined above. soaking, TAP doubled in the gametophyte, but little change Calculation of the Content of Adenosine Phosphates and was observed in the embryo. This difference is probably at- Energy Charge. Based on the peak height of light intensity pro- tributable to the slowness of water penetration, which resulted duced from the three reaction mixtures, ATP concentrations in a lower degree of hydration in cells of the embryo. At a were read directly from a standard curve of freshly prepared 6.5% water content (Table I), the activation of organelles and ATP solution and the particular batch of enzyme-substrate enzymes in the embryo was clearly limited (12).
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