Onset of deoxyribonucleic Acid synthesis in germinating wheat embryos

Germinating wheat embryos (Triticum vulgare var. Florence) synthesize proteins before the onset of DNA synthesis. The onset of DNA replication occurs at about 15 hours of germination and was shown to depend on proteins synthesized before 9 hours of germination with the use of blasticidin S, a specific inhibitor of protein synthesis. A 10-fold increase in the activity of DNA-dependent DNA polymerase was found in extracts derived from germinated embryos, as compared to the activity found in extracts from ungerminated embryos.

Hormones in the Translational Control of Early Germination in Wheat Embryos

Gibberellic and abscisic acid seem to exert their effects on germination by acting in some way at the level of translation. The two hormones may act at different sites.

Naphthoquinone biosynthesis in higher plants. I. Studies on 2-hydroxy-1,4-naphthoquinone in Impatiens balsamina L

The biosynthesis of 2-hydroxy-1,4-naphthoquinone in aerial portions of Impatiens balsamina L. (Balsaminaceae) has been studied. Phenylalanine-U-14C and sodium acetate-1-14C did not label the quinone. Shikimic acid-U-14C, however, was incorporated into the quinone with a dilution of 15.7. The conversion of shikimic acid to ferulic acid in these experiments was accomplished with a dilution of 39.6. GIucose-U-14C was incorporated into the naphthoquinone and ferulic acid molecules with dilutions of 9230 and 29,500 respectively. Administration of an excess of cold p-hydroxybenzoic acid along with labeled shikimic acid resulted in no incorporation of label into the quinone. Degradation of labeled 2-hydroxy-1,4-naphthoquinone yielded phthalic acid with 68.5% of the label originally in the quinone. This agrees well with the theoretical value of 67% calculated on the basis that the shikimic acid ring is incorporated intact into the quinone ring of 2-hydroxy-1,4-naphthoquinone.

THERMOGRAVIMETRY OF THE DEHYDRATION OF Mg(OH)2

The DTG curves for the dehydration of a number of preparations of Mg(OH)2 were determined. Equations necessary to calculate energies of activation and rate constants from these curves were derived on the basis of a two-thirds-order process for dehydration. It was found that the energy of activation was about 5 kcal greater for naturally occurring than for precipitated Mg(OH)2. This was interpreted to mean that there was a difference in the energy levels of the two preparations, and therefore a difference in their apparent solubility products. Differences obtained in the DTG curves for four different preparations of Mg(OH)2 indicated the probability of a series of energy levels for Mg(OH)2.