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Mehrassa Khademi, David S. Koranski, and Joan Peterson

Seeds of Primula acaulis (L.) J. Hill `Dukaat Helderrose' were imbibed for 48 h at 18C, and Maltrin 600 solution was used to separate them into density classes of 1.10, 1.12, 1.14, 1.16, and 1.18 g·cm-3. Seeds were rinsed, air-dried for 48 h at 22C, and germinated at 18C; 80% were separated into density classes between 1.16 and 1.18 g·cm-3. Percentages of germination and high-vigor seedlings were significantly greater for seeds with densities >1.14 g·cm-3. Soluble protein concentration increased with density, whereas insoluble protein concentration was unchanged. Distinct protein groups with estimated molecular weights of ≈50, 33, and 25 kDa were present in the protein profile of nonseparated imbibed seed. These proteins were most abundant at densities ≥1.16 g·cm-3. The 25-kDa protein was present only in higher density seed. Presence of an additional 14-kDa protein was noted in the insoluble protein profile. Certain proteins in the soluble protein fraction maybe used to test for seed vigor.

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Mehrassa Khademi, David S. Koranski, David J. Hannapel, Allen D. Knapp, and Richard J. Gladon

Water uptake by impatiens (Impatiens wallerana Hook. f. cv. Super Elfin Coral) seeds was measured as an increase in fresh weight every 24 hours during 144 hours of germination. Seeds absorbed most of the water required for germination within 3 hours of imbibition and germinated at 60% to 67% moisture on a dry-weight basis. Germination started at 48 hours and was complete by 96 hours at 25C. Water stress of -0.1, -0.2, -0.4, and -0.6 MPa, induced by polyethylene glycol 8000, reduced germination by 13%, 49%, 91%, and 100%, respectively, at 96 hours. Under the same water-stress conditions, increases in fresh weight were inhibited by 53%, 89%, 107%, and 106%, respectively. Three distinct groups of storage proteins were present in dry seed; their estimated molecular weights were 1) 35, 33, and 31 kDa; 2) 26, 23, and 21 kDa; and 3) two bands <14 kDa. Major depletion of storage proteins coincided with the completion of germination. Water potentials that inhibited germination also inhibited degradation of storage proteins. During germination under optimum conditions, the soluble protein fraction increased, coinciding with a decrease in the insoluble fraction.